Sciencemadness Discussion Board - Synthesis of longer chain tertiary alcohols

Initially the mixture is spun up for 20 to 24 hours.

The "Turpentine Oil Hydration using Trichloroacetic Acid as Catalyst" paper abbreviates the catalyst to TCA, so i thought, why not try trichlorocyanuric acid (TCCA) ?

Done.

Trichloroacetic Acid is used there because it's a very strong acid.

Trichloroisocyanuric acid is a very weak acid. This won't work. You might chlorinate that double bond in alpha-pinene somewhat but that's all...

aga - 9-1-2016 at 13:32

Bugger.

Edit:

Wait a sec.

The other paper claims that the presence of a strong acid reduces yields.

Guess we'll see if there's crystals in the morning.

[Edited on 9-1-2016 by aga]

blogfast25 - 9-1-2016 at 15:36

Got a link to the paper with trichloroacetic acid as catalyst?

Without a minimum of H₃O+ the hydration cannot proceed because of that first step: electrophylic attack on that double bond:

... to create that 'wandering' carbonium ion.

Super strong acids are not needed here because we're in the presence of water anyway.

We might have to start thinking about going back to the original plan:

alpha-pinene + glacial acetic acid (GAA) === > alpha-terpineol acetate. Then de-esterify the acetate to get the precious carbinol!

Got any GAA?

[Edited on 10-1-2016 by blogfast25]

aga - 9-1-2016 at 16:01

Can't be bothered trimming the link. Here's the pdf.

Attachment: Ajoct.Vol-1.-Issue-9.-21-26(1).pdf (206kB)
This file has been downloaded 732 times

Likely that the acid catlysis mechanism is far more complex, and the carbonium do-dah is just a part of it.

Edit:

GAA is on hand, maybe 150ml.

More can be made if needed (have a big pot of sodium acetate and lots of conc sulph).

[Edited on 10-1-2016 by aga]

blogfast25 - 9-1-2016 at 17:01

Thanks for the *.pdf. TCA is hard to get and expensive.

I. Likely that the acid catlysis mechanism is far more complex, and the carbonium do-dah is just a part of it.

II. GAA is on hand, maybe 150ml.

I. The mechanism is sound, trust me: it's highly explanatory. But side-reactions do also take place. It's the same mechanism for alpha-terpineol acetate with GAA, BTW...

II. Hold fire with that. ('No stupid moves and no one get hurt, mister!')

Let's formulate a plan ('failing to plan equals planning to fail').

The advantage of GAA is that we can measure it: by... titration! YOUR FAVOURITE method! Talk about 'clouds and silver linings!!!'

[Edited on 10-1-2016 by blogfast25]

aga - 10-1-2016 at 02:40

TCCA gave nothing apart from a slight chlorine smell.

Nicodem - 10-1-2016 at 03:12

Trichloroacetic acid with its pKa of 0.66 is hardly a "very strong acid". It is strong, but still a few million times weaker than HCl (in water).

Trichloroisocyanuric acid is not an acid at all (except by name). That is unless you want to call any electrophile as an acid, which would however make the phrase acid obsolete. (Though sometimes they are called acid if that is their main role in the reaction. For example, I₂ is often called an acid when it is used as a soft acid catalyst.)
The outcome of its reaction with alpha-pinene depends on the solvent used, but in most cases it should give a mixture of products due to the Wagner–Meerwein rearrangements of the reaction intermediates.

aga - 10-1-2016 at 05:52

The data from the 2013 paper in the pdf above states that 88% of the alpha-pinene is converted in 30 minutes @ 70 C with 87% selectivity for alpha-terpineol, when trichloracetic acid is used as the catalyst, with water and acetone as the solvent(s).

Page 99 of "Practical Organic Chemistry, J B Cohen" (available in the SM library)
details the production of chloral hydrate and trichloracetic acid, and it appears that all of the reagents are available.

Would it not be a better plan to synthesise some TCA and follow the 2013 route to alpha-terpineol ?

It seems that chloral hydrate is not a good thing to have lying around.

If it is quickly converted to TCA, can anyone see a downside ?

Edit:

How much terpine do we want at the end of this ?

Working out the figures, to get 8ml of product the process requires 106g of TCA, if the ratios must be held to.

This in turn means making 266g minimum of chloral hydrate.

[Edited on 10-1-2016 by aga]

blogfast25 - 10-1-2016 at 06:31

Very good research, aga.

Let's keep TCA on hold for a minute but it could be useful also with regards to my next post on limonene as a precursor, instead of alpha-pinene.

We need about 10 ml of alpha-terpineol. Bear in mind it's not our end-product!

And then there's limonene...

blogfast25 - 10-1-2016 at 07:03

Limonene is very OTC and very cheap and a known precursor to α-terpineol or its acetate:

(Left: limonene, right: α-terpineol)

The bottom double bond can be hydrated using basically the same methods as used for α-pinene to α-terpineol or its acetate by means of H₂SO₄, TCA, GAA (to the acetate) etc.

An excellent monography on limonene's chemistry can be found here.

In short, there's nothing that can be achieved with α-pinene that can't be achieved with limonene but generally speaking better: more selectively, with fewer by-products and even more selectively (I believe) when the acetate is the target.

One reaction of interest is the electrophylic addition of HCl to limonene in anhydrous conditons (using DCM as solvent), which reportedly yields α-terpineol chloride:

terpineol chloride.gif - 2kB

Which can easily be hydrolysed with NaOH(aq) to α-terpineol.

So, all in all, we still have a few possibilities open to us.

blogfast25 - 10-1-2016 at 07:05

Trichloroacetic acid with its pKa of 0.66 is hardly a "very strong acid". It is strong, but still a few million times weaker than HCl (in water).

Oooopsie. Obviously I hadn't looked up the Ka. Thank you for the correction.

[Edited on 10-1-2016 by blogfast25]

blogfast25 - 10-1-2016 at 07:30

Quote:

Page 99 of "Practical Organic Chemistry, J B Cohen" (available in the SM library) details the production of chloral hydrate and trichloracetic acid, and it appears that all of the reagents are available.

Which gives me:

"Chloral Hydrate, CC13.C Liebig, A?inale7i, 1832, 1, 189; Dumas, Aim. CJiim. Phys. 1834, 56, 123. Chloral hydrate is obtained by the action of chlorine upon ethyl alcohol The solid chloral alcoholate is formed, CC13.CHOH.OC.2H5, which, when decomposed with sulphuric acid, yields chloral, CC13.COH, a liquid which combines with water to form the crystalline hydrate. Properties.—It crystallises in prisms, which dissolve easily in water, alcohol, and liquid hydrocarbons. It has a peculiar smell ; m. p. 57°; b. p. 97*5°. It volatilises on evaporating its aqueous solution. Reactions.—1. Add a few drops of a solution of chloral hydrate to a little ammonio-silver nitrate solution and warm. Metallic silver will be deposited. 2. Add a little caustic soda to a solution of chloral and warm gently. The heat of the hand is sufficient for the purpose. A smell of chloroform is at once apparent, CC13.CH(OH)2 + NaOH = CHCl3 + HCO.ONa + H.>O. Sodium formate remains in solution. 3. Add a few drops of ammonium sulphide solution and warm gently. A brown colouration or precipitate is formed.

Trichloracetic Acid, CC13.CO.OH. Dumas, Compt. rend., 1838, 8, 609 ; Clcrmont, A?in. Chim* Phvs., 1871, (6), 6, 135- 25 grins, chloral hydrate 20 „ fuming nitric acid ; sp. gr. I '5 (see p. 20)."

I couldn't see the end of the TCA synth but 'fuming nitric acid', do you have that?

aga - 10-1-2016 at 08:17

Have made WFNA a couple of times.

Well, i think it was WFNA - it was colourless and fumed when blown on.

Using the last of the 99%+ ethanol (~150ml) in a test of the chlorination step it appears that the yield of solid 'chloral alcoholate' is also quite small.

Smells almost exactly like wart remover.

Best get some more ethanol distilled.

blogfast25 - 10-1-2016 at 08:29

Using the last of the 99%+ ethanol (~150ml) in a test of the chlorination step it appears that the yield of solid 'chloral alcoholate' is also quite small.

Smells almost exactly like wart remover.

Best get some more ethanol distilled.

So you got some solids? Perhaps more chlorine was needed?

blogfast25 - 10-1-2016 at 08:50

An example of (hydro)chlorination, without solvent and with dry HCl:

http://www.orgsyn.org/demo.aspx?prep=CV1P0166

I wonder if this would work for limonene?

aga - 10-1-2016 at 09:40

So you got some solids? Perhaps more chlorine was needed?

Yes. There's a white solid in the filter paper at the moment, drying.

It looks like as much was made as is practicable.

What happens is the the white solid starts to form, then all of the ethanol goes milky, then the solids drop out, leaving a cloudy (yet transparent) layer above.

No matter how much more chlorine was introduced, the transparent layer would not change, and the solid layer would not increase in depth, so it was presumed 'done'.

Wiki says it's soluble in ethanol and water, so the remaining liquid is being left to evaporate away, which might yield more solids.

The fumes certainly impart a slight drunken sensation - trust me, i'm an Expert !

Certainly needs to be done in the fume hood, by someone expendable.

blogfast25 - 10-1-2016 at 10:17

@aga:

Nice!

Could you cut and paste the conversion of the chloral hydrate to TCA for me here? That part of the *.pdf doesn't play for me.

The TCA might also be part recoverable after the hydration.

Someone expendable: get a miniaga!

I'm still not convinced of the rationale behind using TCA instead of e.g. H₂SO₄. Strong acids completely deprotonate in water:

HA(aq) + H₂O(l) === > H₃O+(aq) + A-(aq)

This means the protonating agent (Lewis acid) is H₃O+(aq), not HA.

And that means that two strong acids, say HA₁ and HA₂, are used at the same aqueous concentration they should have roughly the same catalytic effect...

It would make a difference in anhydrous conditions.

'These things are sent to try us'

[Edited on 10-1-2016 by blogfast25]

aga - 10-1-2016 at 11:04

Chloral hydrate is obtained by the action of chlorine upon
ethyl alcohol. The solid chloral alcoholate is formed,
C13.CHOH.OC.2H5, which, when decomposed with sulphuric
acid, yields chloral, CC13.COH, a liquid which combines
with water to form the crystalline hydrate.

...

Trichloracetic Acid, CC13.CO.OH.

...

25 grms, chloral hydrate
20 „ fuming nitric acid ; sp. gr. I '5 (see p. 20).

The chloral hydrate is melted in a distilling flask (250 c.c.) and
the fuming nitric acid added.* The mixture is heated carefully
over a small flame until the reaction sets in. After a few
minutes red fumes are evolved, consisting mainly of nitrogen
tetroxide. The reaction proceeds without the application of
heat, and is complete when, on warming the liquid, nitrous
fumes cease to come off. The product is now distilled ; below
123° excess of nitric acid distils; between 12f and 1940 a.
mixture of trichloracetic acid and a small quantity of nitric acid
pass over, and at 194—1960 nearly pure trichloracetic acid
collects in the receiver and solidifies on cooling. It is advisable
to distil the last fraction with a condenser-tube only. The
fraction boiling at 123—1900 is treated with a fresh quantity of
fuming nitric acid (10 c.c), and the product purified as before.
Yield, 10—15grams.

aga - 10-1-2016 at 11:15

I'm still not convinced of the rationale behind using TCA instead of e.g. H₂SO₄. Strong acids completely deprotonate in water

No idea.

As i said, the mechanism could well be hideously complicated with plenty of intermediates, which would explain why so much acetone is specified, and why Nicodem says :-

The outcome of its reaction with alpha-pinene depends on the solvent used, but in most cases it should give a mixture of products due to the Wagner–Meerwein rearrangements of the reaction intermediates.

Guess that somebody who can understand them takes a look at the Wagner–Meerwein rearrangment(s). I took a peek and can follow the blue line, but no idea why the electrons move as they do.

All i know is that the 3.5 hour and 24 hour processes with sulphuric as catalyst gave next to nothing.

If that 2013 paper is right, there's approx 77% yield (based on pinene) after 30 minutes when TCA is used.

[Edited on 10-1-2016 by aga]

blogfast25 - 10-1-2016 at 12:21

Apart from Wagner–Meerwein rearrangment(s), other common by products like β and γ-terpineol can easily be explained:

If the water attacks the carbonium cation of the type second in the series then we get the beta and/or gamma type isomers. Thus it's a question of creating conditions in which that structure transits to the third kind as quickly as possible, in order to maximise alpha yield.

QC/OC thread to re-start soon, this time on carbanion ions: CH₃- and such like...

[Edited on 10-1-2016 by blogfast25]

aga - 10-1-2016 at 13:20

The catalyst (the acid) is clearly explained in your mechanism, however it can at best be a Summary of the reaction mechanism.

How is the Solvent-dependant product mix explained if the solvent has no part in the reaction ?

Similarly, how can it be that TCA had the highest selectivity for alpha-terpineol compared other tested catalysts if were merely supplying protons ?

The experimental data strongly suggests that Other steps are happening, not just the formation of a wandering carbocation.

Not that i know jack shit really, just seems logical.

aga - 10-1-2016 at 13:40

In this JPL paper

https://www.researchgate.net/publication/231665911_Heterogen...

they say :-

"Acetone was found to be physically absorbed by sulfuric acid without undergoing irreversible reaction below acid concentrations of 87 wt. %"

Above 87 wt % they saw 'condensation products' such as mesityl oxide.

This suggests that the 'simple' mix of acetone and our sulphuric acid catalyst is far from simple.

Why would the acetone react above 87% and not react below 87% ?

Makes no sense unless that system is complex, with the components reacting in an equilibrium, favouring acetone until there are so many protons (or SO₄2-

around that another species is favoured

[Edited on 10-1-2016 by aga]

blogfast25 - 10-1-2016 at 13:54

I. The catalyst (the acid) is clearly explained in your mechanism, however it can at best be a Summary of the reaction mechanism.

II. How is the Solvent-dependant product mix explained if the solvent has no part in the reaction ?

III. Similarly, how can it be that TCA had the highest selectivity for alpha-terpineol compared other tested catalysts if were merely supplying protons ?

IV. The experimental data strongly suggests that Other steps are happening, not just the formation of a wandering carbocation.

I. It also explains why we end up with an alcohol (or an acetate in the case of GAA). What isn't explained is why the carbocation moves. That has to do with the third one being of lowest energy. But I don't know why...

II. Already explained: any OC will tell you that where possible homogeneous catalysis is preferred. That's the role of the acetone: make it all one phase.

III. That is merely a claim by one author. Have you seen his back-to-back comparisons with other catalysts anywhere? He may be right about selectivity but he certainly has not proved it. Has he shown a meta-analysis somewhere?

IV. No dispute. It's already been shown which kind rearrangements and by-products can be expected/explained. Careful not to resort to 'it's magic!' kind of explanations!

[Edited on 10-1-2016 by blogfast25]

blogfast25 - 10-1-2016 at 14:14

In this JPL paper

https://www.researchgate.net/publication/231665911_Heterogen...

they say :-

"Acetone was found to be physically absorbed by sulfuric acid without undergoing irreversible reaction below acid concentrations of 87 wt. %"

Above 87 wt % they saw 'condensation products' such as mesityl oxide.

This suggests that the 'simple' mix of acetone and our sulphuric acid catalyst is far from simple.

Firstly, be careful to quote papers that are very far removed from our actual experimental conditions.

At very high acid concentrations, even acetone become protonatable, but these concentrations are far removed from ours.

No, the main reason for our poor yields is almost certainly further hydration of the terpineol on the second double bond. It's mentioned in most papers related to terpineol synthesis and it happens with TCA catalysis too!

[Edited on 10-1-2016 by blogfast25]

aga - 10-1-2016 at 14:27

Currently a bit lost in contemplating what even H₂SO₄ and H₂O do at the electron/quantum level.

That paper was cited simply to point out that the reaction mechanisms are not Simple, with the reaction of the catalyst and the solvent as an example.

Yes, the 2013 paper categorically shows reduced yield after 30 mins with TCA.

What second double bond ?

Can only see one double bond (resonant) in the pinene or the terpineol.

Can see two in the SO₄2- anion, although likely dislocated and resonant as well.

[Edited on 10-1-2016 by aga]

blogfast25 - 10-1-2016 at 15:09

What second double bond ?

Sorry, by 'second' I meant that the left side double bond in the pinene disappears, then reappears to the right of it when the carbocation moves.

That double bond in the terpineol is also hydratable but less easily than the 'first'. Neither of these bonds is resonant BTW: neither are conjugated!

Quote:

Currently a bit lost in contemplating what even H2SO4 and H2O do at the electron/quantum level.

As long as there's water, the acids completely deprotonate. The H₃O+ is the REAL catalyst.

[Edited on 10-1-2016 by blogfast25]

aga - 10-1-2016 at 15:34

I do not know enough to propose an alternative reaction mechanism.

Logic dictates that it cannot be as simple as your proposed reaction mechanism suggests, simply because the Temperature, Time, Catalyst and the Solvent all have a strong influence on the concentrations of the product species, which implies that they are all Involved in the reaction.

Specifically, external or additive intermediate species form (not just carbocations) which produce alpha-terpineol via a route that involves water, the acid catalyst and the solvent.

TCA as catalyst producing more alpha-terpineol in less time than sulphuric acid is surely evidence of that : they both disassociate, giving protons, yet TCA works better.

blogfast25 - 10-1-2016 at 15:50

TCA as catalyst producing more alpha-terpineol in less time than sulphuric acid is surely evidence of that : they both disassociate, giving protons, yet TCA works better.

We only have the author's assertion for that: no comparison with other catalysts in perfectly comparable conditions has been presented. Nor have I found one elsewhere.

It really is a bit like saying: 'Esso petrol works best' w/o offering a back-to-back comparison with 'Shell', 'Fina' etc etc.

There's no meta-analysis making that claim either. Scientifically the burden of PROOF for such claims MUST be high.

That paper on TCA is actually quite broad in its claims but very poor on detail.

'The Devil is in the detail'

Quote:

Logic dictates that it cannot be as simple as your proposed reaction mechanism suggests, simply because the Temperature, Time, Catalyst and the Solvent all have a strong influence on the concentrations of the product species, which implies that they are all Involved in the reaction.

True but you're using quite a broad definition of 'reaction mechanism' here: a full description of catalysis, activation energy, influence of concentrations etc can of course not be included in a simple qualitative description of changed bonds during the reaction path.

[Edited on 10-1-2016 by blogfast25]

aga - 10-1-2016 at 16:06

We only have the author's assertion for that: no comparison with other catalysts in perfectly comparable conditions has been presented. Nor have I found one elsewhere.

Reference [9] in the 2013 paper is a 2005 $40 article :-

http://www.sciencedirect.com/science/article/pii/S0920586105...

The precis mentions chloroacetic acid and HCl, and might not mention any more than that.

Feck 'em. Forge on and actually make some.

[Edited on 11-1-2016 by aga]

blogfast25 - 10-1-2016 at 16:29

The abstract of that paper:

Quote:

Chloroacetic acid was used as catalyst for the hydration of α-pinene using water as hydroxyl donor, which is soluble in aqueous and organic solvents. The highest selectivity was 95.5 with a conversion of 10%, whereas the higher conversion was 99% with selectivity of 70% after 4 h of reaction at 70 °C. Organo-chlorinated compounds were not found in products as in the case of the use of HCl as catalyst, which indicates that the intermediate carbocation formed after alkene protonation is not susceptible to react with the chloroacetic anion.

Well, that fits perfectly because we know that with HCl, in part terpenyl chloride [and possibly other chlorinated substitutes] is formed which is precisely what we DON'T want. HCl is definitely a bad choice of catalyst here.

And it does indeed suggest that the trichloroacetate anion is far too soft a Lewis base to form an adduct with the carbocation. That's a good thing because it allows water to do that job and form the carbinol.

And 'homogeneous acid catalysis' almost certainly means: with acetone.

[Edited on 11-1-2016 by blogfast25]

blogfast25 - 10-1-2016 at 17:42

The more I look at that paper (TCA, 2013) the less I like it. There are real ABSURDITIES in it.

Quote:

The catalytic tests were performed in a 100-cm3 three-necked-glass reactor with condenser and thermocouple. The reactor was submerged in thermostatic bath with silicone oil and magnetic stirring. In batch experiment, 3.6 mmol of α-pinene, 18 mmol of water and 10 mL of aceton were first placed. After heating to the desired temperature, 32 mol of the trichloroacetic acid catalyst was added. Aliquots were extracted with a micropipette and immediately analyzed with GC.

32 mol of catalyst!!! Of course that's a typo but which is it then: 32 mmol? 3.2 mmol? 32 micromol? We don't know!

Quote:

The formation of these compounds supports the above mentioned, and trichloroacetic acid could promote the water/pinene interaction, so protons at organic phase promote mainly pinene rearrangement isomerization like in the isomerization process of pinene to produce camphene.

Tosh, balderdash and piffle: the system is uniphasic (all one phase: pinene, water, acetone and catalyst), there is no 'organic phase' here. If there was, direct injection of sample into a GC would be very unreliable.

Finally, the yields mentioned aren't real yields, in the sense that no work-up was ever performed. These yields are simply GC values and thus really optimistic.

I think a request for that other paper you mentioned should be made.

=======================

Some more information about acetone as a solvent here to follow later on...

[Edited on 11-1-2016 by blogfast25]

Notes on acetone as a solvent (here)

blogfast25 - 11-1-2016 at 09:25

The need for a solvent has already been explained in terms of homogeneous catalysis being generally preferred.

Why then specifically acetone?

1. The solvent should be inert.
2. The solvent should be miscible with water and the reagents.
3. The solvent should preferably have a low BP.

Three candidates immediately spring to mind: acetone, MeOH and EtOH.

Unfortunately the latter two don't really comply to 1., as both are soft Lewis bases. The Wiki entry on alpha-pinene does indeed mention the formation of terpine ethers in these solvents, by adduct formation with the carbocation.

Other possible candidates would be THF and ether but for obvious reasons acetone is to be preferred.

Acetone does show some reactivity towards water:

Propan-2,2-diol, aka a germinal diol, exists with acetone in equilibrium in a watery solution:

$$K=\frac{[\text{germinal diol}]}{[\text{acetone}]} \approx 10^{-3}$$

So that's about 1 in every 1000 acetone molecules in an acetone/water mixture is present as propan-2,2-diol.

(Source)

[Edited on 11-1-2016 by blogfast25]

aga - 11-1-2016 at 10:49

The more I look at that paper (TCA, 2013) the less I like it. There are real ABSURDITIES in it.
...
32 mol of catalyst!!! Of course that's a typo but which is it then: 32 mmol? 3.2 mmol? 32 micromol? We don't know!
...
Tosh, balderdash and piffle: the system is uniphasic (all one phase: pinene, water, acetone and catalyst), there is no 'organic phase' here. If there was, direct injection of sample into a GC would be very unreliable.

Yes. 32 mol calculated out at something like 5 kilos or similar.

It must be mmol, seeing as it has to fit in a 100ml vessel.
Where the decimal point goes is anyone's guess.

The system isn't really uniphasic - if left unstirred two phases separate in a few seconds.

It does worry me that the three papers found, plus a great many more, could be entirely invented data.

When you think about it, Who would actually bother to test the process in a paper simply on a whim ? 10h stirring time etc - would it be worth it ?

It is quite possible that i simply cannot measure or stir things properly, nor count minutes and hours, but it seems a bit unlikely.

The chloral hydrate synth seems to be working fine by following the procedure found in Cohen, so i can't be ballsing up the other synths that badly.

BTW: there are two RBFs with post-reflux layers in them waiting on any suggestions for an actual (workable) separation process.

blogfast25 - 11-1-2016 at 12:57

I. The system isn't really uniphasic - if left unstirred two phases separate in a few seconds.

II. It does worry me that the three papers found, plus a great many more, could be entirely invented data.

When you think about it, Who would actually bother to test the process in a paper simply on a whim ? 10h stirring time etc - would it be worth it ?

III. It is quite possible that i simply cannot measure or stir things properly, nor count minutes and hours, but it seems a bit unlikely.

BTW: there are two RBFs with post-reflux layers in them waiting on any suggestions for an actual (workable) separation process.

I. Trust me, it is. It's 0.5 g pinene, 0.32 g water, 10 ml acetone and probably 0.52 g TCA. Pinene and TCA are both acetone soluble, that bit of water won't cause problems.

II. I doubt if it's a fake. It's just a poor quality paper. Tons of research have been done on alpha-pinene/limonene to alpha-terpineol.

III. No one's saying anything about 'ballsing things up'. Go higher up and you'll find me and 'ecclectic' trying to make alpha-terpineol from turpentine. We failed. And we NEVER balls anything up!

It could be the turps at fault but it doesn't look like it, see your distillation.

Not sure about those other org. phases. Have they been distilled yet?

aga - 11-1-2016 at 13:28

II, III Exactly.

It is just not that hard to reflux stuff, separate layers or distill, which is why i suspect that the actually useful parts of those experiments were never done, relying instead on GC analysis to claim success.

If it needs a 20m column to separate the stuff, well, it's obviously useful in the understanding of the underlying chemistry, yet pointless if you actually want to make a pot of turpineol juice.

Bought a litre and a half of brandy today to Assist in this research.

There was a mention in the Erowid archive of Hive (or is it the other way around ?) that chloral alcoholate needs distilling with conc sulph to get the chloral, and that the ethanol needs to be rammed with Cl₂ to get a decent yield.

Seems to work pretty well just dripping conc sulph onto the alcoholate, but it may well have volatilsed and buggered off before any water was added

We Will see.

No way this terpineol synth is going to get left behind.

aga - 11-1-2016 at 13:45

While we speculate and wait for darkness and drunken-ness to end, what actually happens when a substance like pinene dissolves in a Non-polar solvent ?

With water and sulphuric acid, the sulphuric spilts to H+ and SO₄2- and the water gets all OH- and H₃O+

What is the actual solvation mechanism for alpha-pinene and acetone ?

Presumably the species produced are reasons why the reaction needs acetone as a solvent.

blogfast25 - 11-1-2016 at 14:06

double post eliminated

[Edited on 11-1-2016 by blogfast25]

blogfast25 - 11-1-2016 at 14:27

Take HCl as a simpler example (monoprotic). As a strong acid it completely deprotonates:

HCl(aq) + H₂O(l) === > H₃O+(aq) + Cl-(aq)

So basically a 1 M HCl solution (for example) becomes a 1 M H₃O+ + 1 M Cl- solution, or:

$$[\mathrm{H_3O^+}]=1\:\mathrm{M}$$

A second equilibrium in water is:

2 H₂O(l) < === > H₃O+(aq) + OH-(aq), with K_W the auto-dissociation constant of water:

$$K_W=[\mathrm{H_3O^+}][\mathrm{OH^-}]=10^{-14}$$

So that in acid conditions:

$$[\mathrm{OH^-}] \approx 0$$

alpha-pinene solvates in solvents like acetone (a polar solvent, BTW) without any such changes: it doesn't 'lose' bits and pieces to the solvent, like acids do. Solvents like THF and diethyl ether would probably work too...

I'm inclined to give up on the old turps and switch to limonene instead. Similar chemistries but more selective.

[Edited on 11-1-2016 by blogfast25]

aga - 11-1-2016 at 14:53

Er, No.

That is ducking the question and avoiding facing the problem head-on.

If they Dissolve and not simply Mix, Acetone and Pinene must React to form a solution containing the two species, and Other intermediate species in some equilibrium.

The JPL paper gives data for acetone and sulphuric acid dissolving or reacting depending on acid concentration, so there's a clue.

I'm currently inclined to think that it is these intermediate species that affect the outcome so much that they need to be at least Known if not Understood.

NOT doing so is the same as saying that H₂SO₄ reacts with pinene forming a carbocation without the acid even dissassociating.

That said, i have a lemon tree with a hell of a lot of lemons on it.

Edit:

I also have a litre and a half of Brandy

[Edited on 11-1-2016 by aga]

blogfast25 - 11-1-2016 at 15:24

I. If they Dissolve and not simply Mix, Acetone and Pinene must React to form a solution containing the two species, and Other intermediate species in some equilibrium.

II. NOT doing so is the same as saying that H₂SO₄ reacts with pinene forming a carbocation without the acid even dissassociating.

III. That said, i have a lemon tree with a hell of a lot of lemons on it.

I. Sigh, sigh and double sigh...

Aga, mixing and dissolving are the same thing here. If you mix two substances that are miscible then by definition they form a solution that is of course by definition a one phase system. That is NOT a reaction though. Dissolving sugar in water (e.g.) is not a reaction. Solvation should not be equated to reaction, even though they have some things in common.

II. Sorry: gibberish to me. In some aprotic solvents and specific strong acids that might even work here. But here we need the water for the OH addition, to get the carbinol.

III. Limonene is too OTC to start steam distilling citrus peels.

Changing precursor is nothing shamefull. But flogging a dead horse is a waste of time...

aga - 12-1-2016 at 02:24

OK. So i need to have a good long stare at dissolution i guess.

Got turps. Not got limonene.

ISTR that it's a major product when pyrolysing old rubber tyres ...

Can't give up just yet - today there are chloral hydrate crystals.

[Edited on 12-1-2016 by aga]

blogfast25 - 12-1-2016 at 07:02

OK. So i need to have a good long stare at dissolution i guess.

Got turps. Not got limonene.

ISTR that it's a major product when pyrolysing old rubber tyres ...

Can't give up just yet - today there are chloral hydrate crystals.

[Edited on 12-1-2016 by aga]

I'll see if I can rustle something up with regards to solvation. It does of course play a part: two same reactions carried out in two different inert solvents often show different reaction rates, so something is going on there.

Why not finish the synth. of the TCA if you can, then try alpha-pinene in GAA with TCA as catalyst? That should give alpha-terpineol acetate (plus cruds).

I've become very pessimistic about this whole endeavour: driving blind without GC/IR makes it very difficult to find that 'sweet spot' of temperature and cooking time.

I was looking (in another thread) at hydrochlorination of limonene with HCl(g) to alpha-terpinyl chloride but the problem is similar: unknown reaction times and by-products.

******************

Oh, and I found a better version of the '2013, TCA' paper, this time as an improved conference paper:

http://psrcentre.org/images/extraimages/13%201212598.pdf

At least the procedure now seems correct. And it does include a direct comparison of TCA and H₂SO₄, showing that TCA works better.

Quote:

The catalytic tests were performed in a 100-cm3 threenecked-glass reactor with condenser and thermocouple. The reactor was submerged in thermostatic bath with silicone oil and magnetic stirring. In batch experiment, 0.25 mol of α-pinene, 0.6 mol of water and 20 mL of aceton were first placed. After heating to the desired temperature (70o C), 0.11 mol of the catalyst was added. Aliquots were extracted with a micropipette and immediately analyzed with GC. Conversion (X %) was defined here as moles of monoterpene converted per 100 moles of monoterpene feed. The selectivities of α-terpineol (S %) were defined as moles of α-terpineol formed per 100 moles of α-pinene converted.

That's 34 g alpha-pinene, 10.8 ml water, 18 g of TCA and 20 ml of acetone.

Fig. 2 shows the selectivity and suggests a reflux time of about 45 minutes to be optimal. Dixit the authors, of course.

In your case the cooled (force cooled if possible to control thermal history better) mixture would have to be neutralised immediately with NaOH to prevent further hydration of any alpha-terpineol formed.

Then add 100 ml of salt brine (saturated NaCl) and shake'n vent several times. Organic phase should separate to the top. Separate and shake'n vent with water. Separate organics and distil off low boilers. May the force be with you!

[Edited on 12-1-2016 by blogfast25]

Nicodem - 12-1-2016 at 09:03

Try stirring a solution of pinenes or limonene in acetic acid in the presence of 1 mol% conc. sulfuric acid. A sulfonic acid such as MsOH and TsOH, or sulfamic acid, would be preferable over sulfuric acid, but the choice depends on availability. Do not overload the acid and follow the reaction by TLC - it should be relatively fast at rt and should give terpinyl acetate as the major product. Going directly to the alcohol is certainly not as trivial and selective.

A synthesis of terpinyl acetate from pinenes and limonene using CAN on silicagel is described in DOI: 10.5650/jos1956.38.553. CAN is quite a common reagent. Alternatively, one could consider ZnCl₂ on silicagel (easily prepared by rotavaping a slurry of silicagel in methanolic ZnCl₂).

blogfast25 - 12-1-2016 at 09:51

@Nicodem:

Thanks. The de-esterification of terpineol acetate won't be easy either though, I imagine.

aga - 12-1-2016 at 13:20

I've become very pessimistic about this whole endeavour: driving blind without GC/IR

The Farce is with us young BlogWalker.

Therefore We cannot fail : Keep the Faith.

Oh, and I found a better version of the '2013, TCA' paper, this time as an improved conference paper:

http://psrcentre.org/images/extraimages/13%201212598.pdf

That's 34 g alpha-pinene, 10.8 ml water, 18 g of TCA and 20 ml of acetone.

Excellent ! Some actual data to work with ! Woohoo !

Nice find.

Try stirring a solution of pinenes or limonene in acetic acid in the presence of 1 mol% conc. sulfuric acid. A sulfonic acid such as MsOH and TsOH, or sulfamic acid, would be preferable over sulfuric acid

Not looked up what MsOH or TsOH are, however there does seem to be an unopened bottle of sulphamic acid on the shelf.

'acetic acid' ?

Does that mean glacial acetic acid or would vinegar do ?

P.S.

The Brandy has almost all gone : it's heading the right way for a whole pile of TCA.

blogfast25 - 12-1-2016 at 14:40

Excellent ! Some actual data to work with ! Woohoo !

Nice find.

Not looked up what MsOH or TsOH are, however there does seem to be an unopened bottle of sulphamic acid on the shelf.

'acetic acid' ?

Does that mean glacial acetic acid or would vinegar do ?

The Brandy has almost all gone : it's heading the right way for a whole pile of TCA.

GAA = pure acetic acid. It's what he meant. Vinegar is only good for fish and chips.

TsOH: ortho-toluenesulphonic acid.

You are the Keith Floyd of amateur OC and the Keith Moon of casual alcoholism!

[Edited on 12-1-2016 by blogfast25]

aga - 13-1-2016 at 15:31

Such Compliments i am certainly unworthy of !

--------------------------------------------------------

Sorry for the delay,
lack of absolute EtOH has eaten a day.

Distilling many litres like mad,
the smell was still Bad.

So distilled it some more,
to even the score.

In went the K₂CO₃, so the water is spent,
Anhydrous it Is, or near 99 percent.

So 200ml was subjected to chlorination,
It has to be said - with some trepidation.

With all in place and gas mask on face.
onto the TCCA went the HCl, apace.

Hubbles and bubbles and Cl₂ around,
it rushed through the EtOH with no precipitate found.

Changing the tack,
the inverted funnel was put back.

Faster and faster the Cl₂ rushed though,
reacting and heating, if only i knew !

Quick ! Quick ! Put in a Bath !
it was so farcical, one could but laugh.

There it remains, the night not yet ended,
no chemistry goes quite how one intended.

[Edited on 13-1-2016 by aga]

blogfast25 - 13-1-2016 at 18:34

You do realise that the penitence for successfully synthing TCA... is a proper write-up?

aga - 14-1-2016 at 11:07

Aw crap. That means i got to do it right, all the way through.

blogfast25 - 14-1-2016 at 12:25

Yeah, but it doesn't have rhyme!

blogfast25 - 15-1-2016 at 19:17

Memory lane: MrHomeScientist and my efforts at alpha-terpineol from turpentine: forgot just how much effort has already gone into this!

http://www.sciencemadness.org/talk/viewthread.php?tid=15171&...

UC235 - 15-1-2016 at 21:52

Wouldn't dumping a grignard (MeMgI or EtMgBr perhaps) into menthone be a rather more straightforward approach to this? Sure, it won't produce alpha-terpineol, but it will produce an 11-carbon (or more) tertiary alcohol with an estimated b.p. of ~220C (for the methyl derivative).

Menthol is fairly cheap and it's conversion to menthone is straightforward and high-yielding. http://www.orgsyn.org/demo.aspx?prep=CV1P0340

[Edited on 16-1-2016 by UC235]

HeYBrO - 15-1-2016 at 23:01

Excellent ! Some actual data to work with ! Woohoo !

Nice find.

Not looked up what MsOH or TsOH are, however there does seem to be an unopened bottle of sulphamic acid on the shelf.

'acetic acid' ?

Does that mean glacial acetic acid or would vinegar do ?

The Brandy has almost all gone : it's heading the right way for a whole pile of TCA.

[Edited on 12-1-2016 by blogfast25]

Nitpik: TsOH is usually encountered as para-toluenesulphonic acid as the ortho won't form easily due to steric hinderance, so i pressume the "p-" is left of for convenience.

UC, i have performed the oxidation of menthol to menthone with jones reagent and had good yields. The procedure is incredibly simple.

[Edited on 16-1-2016 by HeYBrO]

[Edited on 16-1-2016 by HeYBrO]

blogfast25 - 16-1-2016 at 12:34

Quote: Originally posted by UC235

Wouldn't dumping a grignard (MeMgI or EtMgBr perhaps) into menthone be a rather more straightforward approach to this? Sure, it won't produce alpha-terpineol, but it will produce an 11-carbon (or more) tertiary alcohol with an estimated b.p. of ~220C (for the methyl derivative).

Menthol is fairly cheap and it's conversion to menthone is straightforward and high-yielding. http://www.orgsyn.org/demo.aspx?prep=CV1P0340

[Edited on 16-1-2016 by UC235]

I fear 11 (or more) would already be too long, as there's a balance between increased solubility of the K/Na/Mg t-alkoxides and steric hindrance to be struck.

Similarly, I don't think Grignarding isopropylmyristate would yield anything all that useful.

One that could be worth looking at is 2-phenylpropan-2-ol: relatively easy:

benzene > bromobenzene > 2-phenylpropan-2-ol

[Edited on 16-1-2016 by blogfast25]

aga - 16-1-2016 at 13:52

All too complex, especially for me - no bottle labelled 'Grignard' can be seen.

Doubt i could get the apparatus dry enough for a Grignard and i have no idea how they work anyway.

Rebooted the whole TCA thing by er, 'disposing' of the crappy ethanol and Properly distilling more (Vigreux, 1 C differential, done twice) plus making fresh K₃PO₄ to make this batch of ethanol Actually dry.

Simultaneously triple recrystallising some agricultural KNO₃ (+48% K₂O) for the nitric step after chloral hydrate exists in the shed.

Wondering about the N₂O₄ disposal/neutralisation, as plumes of orange/red gas are not generally welcomed.

Bash it into Water seems the obvious idea. Maybe iced ?

[Edited on 16-1-2016 by aga]

blogfast25 - 16-1-2016 at 15:41

All too complex, especially for me - no bottle labelled 'Grignard' can be seen.

Doubt i could get the apparatus dry enough for a Grignard and i have no idea how they work anyway.

Wondering about the N₂O₄ disposal/neutralisation, as plumes of orange/red gas are not generally welcomed.

Bash it into Water seems the obvious idea. Maybe iced ?

Step I: bromobenzene is reacted with an electropositive metal (here Mg) to form an organometallic bromide (aka 'Grignard reagent').

Step II: add acetone (in this case), an adduct is formed.

Step III: adduct is hydrolysed (usually with weak HCl), carbinol is formed. Separate as per usual.

Grignard reagents are very sensitive to water but I do believe some SMers are a bit paranoid about that.

**********

N₂O₄ disposal: yes, water or weak NaOH will absorb it very efficiently. BUT. Oxidations using HNO₃ actually produce NO, NOT NO_2:

NO₃- + 4 H+ + 3 e- === > NO + 2 H₂O

The NO₂ you see is because of spontaneous oxidation of NO by air oxygen:

2 NO + O₂ === > 2 NO₂

So for the NaOH absorption scheme to work there must also be plenty of air oxygen present. Usually that is the case.

blogfast25 - 18-1-2016 at 07:52

A t-alcohol (carbinol) that hasn't been considered so far is:

C5 carbinol.gif - 2kB

1. De-esterify iso-amyl acetate ('banana oil', quite OTC) to get iso-amyl alcohol, aka 3-methylbutan-1-ol (there's a thread on that)

2. Chlorinate iso-amyl alcohol with HCl/anh. ZnCl₂ to 1-chloro-3-methylbutane (iso-amyl chloride).

4. Grignard with Mg and acetone to 2,4-dimethylpentan-2-ol.

aga - 18-1-2016 at 09:45

Maybe. Got to try the turps + TCA route first.

Had to calcine some limestone today as i'd run out of CaO needed to purify the phosphoric acid needed for the tripotassium phosphate needed to dry the ethanol needed for chlorinating to chloral needed to make TCA needed to catalyse the turps to terpineol reaction.

Sorry it's taking so long

Good news is that there's lots of nice clean KNO₃ now for making WFNA for the nitration step.

Edit:

The K₃PO₄ didn't do diddly in drying ethanol as the phosphoric acid and the pot hydroxide were both Lepers (unclean !).

[Edited on 18-1-2016 by aga]

blogfast25 - 18-1-2016 at 10:03

Had to calcine some limestone today as i'd run out of CaO needed to purify the phosphoric acid needed for the tripotassium phosphate needed to dry the ethanol needed for chlorinating to chloral needed to make TCA needed to catalyse the turps to terpineol reaction.

Hmmm... how do you calcine CaCO₃ to CaO? I mean, the process has been used since Roman Times but it does require long calcination times (up to 24 h at 1000 C, IIRW).

Also, if you're looking to dehydrate azeoptropic EtOH then CaO might be your thing: quicklime is indeed used in the production of bio-ethanol, if water-free EtOH is needed.

Quicklime is of course quite easy to get: see building materials. It's also useful to make benzene with, from benzoic acid or sodium benzoate.

[Edited on 18-1-2016 by blogfast25]

aga - 19-1-2016 at 06:46

Hmmm... how do you calcine CaCO₃ to CaO?

Stick lumps of limestone in a fire obviously !

Didn't know that the process took that long - this only ran for about an hour, max.

Top left to bottom right : furnace, raw rocks, rocks in crucible, view thru the lid whilst running, results + remains of copper.

The bit of copper pipe was in there to see if any part of the furnace hit 1000+ C.

The stones are cetainly whiter than before and quite crumbly.

blogfast25 - 19-1-2016 at 06:54

Stick lumps of limestone in a fire obviously !

Didn't know that the process took that long - this only ran for about an hour, max.

The stones are cetainly whiter than before and quite crumbly.

Check progress by means of weight loss, which on completion should be 44 w%.

Also, freshly prepared CaO being a strong alkali it reacts quite violently with water. Apparently 'in Tempus Romanus' slaking the lime with water was not a much envied job!

aga - 24-1-2016 at 08:27

The Chloral synthesis isn't going well at all, hence no progress on the TCA synthesis.

After 3 sessions in the furnace the limestone had reduced to around 48% of the original weight, then used to dry the ethanol.

The result was still not 100% dry, however with no other drying agent on hand, chlorination was attempted, this time for 2 hours.

The outcome was exactly the same as before, with Zero white precipitate.

The Cl₂ must be reacting with the ethanol/water, as the liquid heats up.

I suspect that either the 'chloral alcoholate' dissolves in the water or the reaction takes a different route altogether due to the water.

The only time a precipitate was seen was with anhydrous ethanol prepared with oven-dried tripotassium phosphate, so 120g of that has been made today, this time starting with stoichimetry and calculations instead of a beaker full of hope.

Remarkably the yield is almost exactly the same as the calculated theoretical, so should work as expected.

Unfortunately all the booze seems to have gone, so Shopping & Distilling tomorrow.

[Edited on 24-1-2016 by aga]

blogfast25 - 24-1-2016 at 09:38

Did you mean weight loss was about 48 %?

How much quicklime per volume of EtOH?

Did you crush the quicklime to powder?

What was the contact time?

How did you test EtOH dryness?
<hr>

I also think it might be useful to check the calibration of your refractometer.

Combining data from this page:

http://uk.mt.com/dam/Analytical/Density/DE-PDF/BRIX-Sugar_De...

and this page:

http://www.refractometer.pl/refraction-datasheet-ethanol

I deduce that a solution of 17.5 degrees Brix should give a reading of 44 % ABV on your refractometer.

17.5 degrees Brix = 17.5 g sucrose (white sugar) per 100 ml of pure water.

[Edited on 24-1-2016 by blogfast25]

aga - 24-1-2016 at 11:59

Did you mean weight loss was about 48 %?

How much quicklime per volume of EtOH?

Did you crush the quicklime to powder?

What was the contact time?

How did you test EtOH dryness?
<hr>

I also think it might be useful to check the calibration of your refractometer.
...
I deduce that a solution of 17.5 degrees Brix should give a reading of 44 % ABV on your refractometer.

In the end there was just under 95g of useable CaO from the original 197g of limestone.

Accurate weights are pretty much impossible when the substance is in a charcoal furnace with a makeshift lid on the crucible as bits of charcoal get in, some stone becomes powder, and all have to be discarded.

All of the useable (alleged) CaO was crushed and added to 200ml of ethanol, then left to stand for around 30 mins.

Dryness was tested with KMnO₄ as a quick way to show if the water content was significant.

Had no purple colour appeared (which it did) i'd have diluted the ethanol 1:1 and used the ethanol refractomer rather than the other sucrose refractomer next to it.

With luck there will be dry ethanol after distilling some crude tomorrow, then applying the tripot.

blogfast25 - 24-1-2016 at 13:12

30 minutes seems like a short time to me. Overnight should work well, I think.

aga - 24-1-2016 at 14:19

The dehydrating effect with recently oven-dried tripotassium phosphate is almost instant, also complete (as far as i can tell) so preferred.

Also preferred due to the fact that a white precipitate was only seen when chlorinating tripot-dried ethanol.

Perhaps water in the Cl₂ stream is why that experiment seemed to halt after a few minutes.

Definitely must add a stage to dry the Cl₂ on the next attempt.

Any clues as to what Liquid product ethanol + Cl₂ + H₂O makes instead of a Solid chlorinated ethanol thingy ?

The products of the failed chlorination attempts smell nice, but not like 'musty hay' (thankfully) and are out in a field evaporating away.

blogfast25 - 24-1-2016 at 14:55

Any clues as to what Liquid product ethanol + Cl₂ + H₂O makes instead of a Solid chlorinated ethanol thingy ?

Maybe small amounts of water increases the chloral hydrate's solubility by a lot?

aga - 24-1-2016 at 15:10

As far as the meagre information goes from the paper, you need to get the Solid 'chloral alcoholate' first, then add conc sulphuric acid to that to get the Liquid 'chloral'.

After that, separate, then add equimolar water to get the Chloral Hydrate.

All unexplored territory to me, so i really have no idea.

Chemistry is great fun.

blogfast25 - 24-1-2016 at 15:47

Here's an idea:

If you don't get any crystals, why not try and distil off some of the ethanol? The BPs of azeo EtOH and chloral hydrate are quite different.

The chloral hydrate is very soluble in ethanol, so by distilling some of it off you may reach the solubility limit of the chloral hydrate, then it should crystallise on cooling.

I don't think water impedes the actual synthesis: choral (not hydrate) can also be made from acetaldehyde (the aldehyde of ethanol), Cl₂ an HCl solution. Water doesn't seem to be the problem.

[Edited on 25-1-2016 by blogfast25]

gdflp - 24-1-2016 at 17:43

If you continue to have issues with the synthesis, I would recommend an alternative synthesis that circumvents the need for dry ethanol and chlorine gas. It involves reacting trichloroethylene with a source of hypochlorous acid, such as an acidified hypochlorite, or TCCA/NADCCA which is more convenient. IIRC the reaction takes place at STP and takes a few hours. There is a thread on SM somewhere, as well as a US patent detailing the process.

gdflp - 24-1-2016 at 17:47

Here is thread 1 : http://www.sciencemadness.org/talk/viewthread.php?tid=2535&a...
thread 2 : http://www.sciencemadness.org/talk/viewthread.php?tid=62148
and patent : https://www.google.com/patents/US2759978

blogfast25 - 24-1-2016 at 18:22

Here is thread 1 : http://www.sciencemadness.org/talk/viewthread.php?tid=2535&a...
thread 2 : http://www.sciencemadness.org/talk/viewthread.php?tid=62148
and patent : https://www.google.com/patents/US2759978

Thanks, gdflp!

From the first thread:

Quote: Originally posted by erich_zurich

I talked about synthesis of chloral hydrate from trichloroethylene and hypochlorous acid. I also tried a improved synthesis of chloral hydrate from ethanol, chlorine gas and by utilizing UV light to initiate the free radical chlorination reaction, I will describe both procedures.

Method #2 MY FAVORITE! SEVERAL TIMES FASTER THAN THE ORIGINAL CHLORINATION METHOD!

100 ml of absolute ethyl alcohol is placed in a ice cooled flask with a black light 10cm away from the flask irradiating it with Ultraviolet light. to the flask a bubbler is added to which a current of dry chlorine gas is passed by maintaining the temperature below 10° C. The chlorine is quickly absorbed, and, after a short time, the reaction flask is connected with a reflux condenser. By gently warming of the liquid to 60° C the saturation of the solution is continued with chlorine gas until it is fully absorbed. The chlorination reaction is complete when the solution reaches density of 1.4 g/ml, then the liquid is gently boiled for a short time and allowed to cool after which it is cautiously mixed with an equal volume of concentrated sulfuric acid. During this addition hydrochloric acid and ethyl chloride are evolved. Then the reaction mixture is distilled and the distillate is neutralized with calcium oxide or carbonate and redistilled. Further purification is performed by fractionation. Remaining ethyl chloride with hydrogen chloride distills off first. Between 70° C and 90° C ethyl alcohol passes over, and from 90° C chloral starts to distill. Chloral is a colorless mobile liquid, which boils at 94.5° C. When mixed with about one-fifth of its weight of water, the mixture slowly solidifies to a crystalline mass of chloral hydrate:

That sounds like a modified version of what aga is currently attempting.

Then the chloral (trichloroacetaldehyde) is oxidised with HNO₃ to trichloroacetic acid.

[Edited on 25-1-2016 by blogfast25]

gdflp - 24-1-2016 at 18:48

Thanks, gdflp!

From the first thread:

That sounds like a modified version of what aga is currently attempting.

Then the chloral (trichloroacetaldehyde) is oxidised with HNO₃ to trichloroacetic acid.

Indeed, but I was talking about the first two in that thread. They're much more robust IMO, especially if aga is having issues with the ethanol chlorination.

blogfast25 - 24-1-2016 at 19:02

Indeed, but I was talking about the first two in that thread. They're much more robust IMO, especially if aga is having issues with the ethanol chlorination.

My impression is that his problem is isolation, not the actual formation of the chloral hydrate. Distilling off some unreacted EtOH as water azeotrope could do wonders for the chloral hydrate crystallising out, after some of its solvent has been removed and its concentration increased.

After chlorination, distil at AP to about 90 C overhead. Cool and chill. Collect crystals. :cool:

(hope springs eternal)

What do you think?

[Edited on 25-1-2016 by blogfast25]

gdflp - 24-1-2016 at 19:25

Will chloral hydrate oxidize to trichloroacetic acid? My only concern is that the acetal might inhibit the oxidation. Distilling the hydrate with sulfuric acid might be necessary prior to the oxidation. Other than that, the workup looks fine, just be aware that chloral hydrate has a significant vapor pressure at the BP of erhanol, and some will be carried over.

[Edited on 1-25-2016 by gdflp]

blogfast25 - 24-1-2016 at 19:32

Will chloral hydrate oxidize to trichloroacetic acid? My only concern is that the acetal might inhibit the oxidation. Distilling the hydrate with sulfuric acid might be necessary prior to the oxidation. Other than that, the workup looks fine, just be aware that chloral hydrate has a significant vapor pressure at the BP of erhanol, and some will be carried over.

[Edited on 1-25-2016 by gdflp]

No, I meant the oxidation of chloral (trichloroacetaldehyde) with HNO₃ to trichloroacetic acid. So the conversion of chloral hydrate to chloral (real confusing names!) would definitely still be necessary, with conc. H₂SO₄.

[Edited on 25-1-2016 by blogfast25]

gdflp - 24-1-2016 at 19:36

[rquote=436660&tid=15]

No, I mean oxidation of chloral (trichloroacetaldehyde) with HNO₃ to trichloroacetic acid. So the conversion of chloral hydrate to chloral (real confusing names!) would definitely be necessary, with conc. H₂SO₄.

[Edited on 25-1-2016 by blogfast25]

They certainly are. Sounds like you already thought of that then, so looks good.

blogfast25 - 25-1-2016 at 06:42

There's also this patent on the chlorination of anh. EtOH with Cl₂, in the presence of an immersed 250 W light bulb:

http://www.freepatentsonline.com/2478152.pdf

Chlorination times of about 7 h at 30 C, with HCl evolution starting at 4 h.

I wonder what reaction times were used by aga...

And then there's this (from that patent):

Chloral hydrate patent quote.png - 111kB

So the author claims that in anh. EtOH the reaction is to chloral alcoholate:

2 C₂H₅OH + Cl₂ ===> CCl₃CH(OH)OC₂H₅ + HCl
<hr>

Pfffft... finally got to the bottom of it, I think.

In anh. EtOH the principal reaction appears to be:

2 C₂H₅OH + 2 Cl₂ ===> CCl₃CH(OH)OC₂H₅ + HCl

CCl₃CH(OH)OC₂H₅ = chloral ethanolate (aka chloral alcoholate), MP about 23 C.

On reaction with an excess conc. H₂SO₄, this gives the desired chloral (trichloro acetaldehyde):

CCl₃CH(OH)OC₂H₅ + H₂SO₄ ===> CCl₃CHO + C₂H₅HSO₄ + H₂O

C₂H₅HSO₄ = ethyl hydrogensulphate

Low boiling ethyl chloride, ethanol water azeotrope (and others) can then be distilled off, before the chloral (trichloro acetaldehyde) comes over at 98 C.

See also:

https://docs.google.com/viewer?url=patentimages.storage.goog...

[Edited on 25-1-2016 by blogfast25]

aga - 25-1-2016 at 11:28

Nice work bloggers.

The conclusion i came to after reading up on the Haloform Reaction mechanism is that in the the presence of a Base, then Haloform is what occurs: OH- causes haloform results.

Water is probably acting as a Base in wet ethanol, which is why no solids formed when chlorinating - the wrong products happen, and are (thankfully!) not white solids.

The Time between starting chlorination and the appearance of cloudiness, then obvious solids is not long, just a few tens of minutes, as was seen in the first inverted funnel experiment.

Happily there is around 400ml of 96% ethanol today, after a lot of careful distilliation.

The calculations for the entire series from ethanol to TCCA were awesome.

We need very little dry ethanol to arrive at a useful amount of the TCA catalyst required.

To chlorinate 100g of ethanol, the Cl₂ needed has to come from a quarter of a Kilo of TCCA !

50g dry ethanol will eventually give (if all goes well) more than sufficient TCA for the purpose of making turpineol.

Remember that stuff ?

Vaguely recall it being the original target compound

blogfast25 - 25-1-2016 at 13:09

The Time between starting chlorination and the appearance of cloudiness, then obvious solids is not long, just a few tens of minutes, as was seen in the first inverted funnel experiment.

Vaguely recall it being the original target compound

Well, considering what I've been reading, that sounds like a really short time!

Target compound clearly in sight, no worries.

As regards a reaction mechanism, here's a tentative post hoc candidate.

The chlorination itself is likely to be via free radical mechanism. You can read up on these here:

http://www.chemguide.co.uk/mechanisms/freerad/ch4andcl2.html...

I'm assuming the chlorination proceeds to 1,2,2,2-tetrachloroetan-1-ol, then the remaining alcohol acts as a Lewis base, as shown below:

With water instead of ethanol the adduct would be chloral hydrate, with ethanol chloral alcoholate, as suggested in one of the patents linked to.

The overall stoichiometry is:

2 C₂H₅OH + 4 Cl₂ === > CCl₃CH(OH)OC₂H₅ + 5 HCl

Dehydration with conc. H₂SO₄ yields chloral (trichloroacetaldehyde) and ethyl hydrogensulphate.

[Edited on 25-1-2016 by blogfast25]

aga - 25-1-2016 at 14:43

Well, considering what I've been reading, that sounds like a really short time!

That is what i observed, doing it.

Short, Long, i'm the man with the Chlorine (cheers Bert !).

The proposed reaction mechanism looks Odd.

Firstly, why is the Cl₂ disassociating at all ?
It is Really happy as Cl-Cl.

Is anhydrous ethanol capable of solvating Chlorine ?

blogfast25 - 25-1-2016 at 15:09

Well, considering what I've been reading, that sounds like a really short time!

Free Cl* radicals can be formed by UV photons cleaving the molecules:

$$Cl_2(g) + h\nu \to Cl*(g)$$

The radicals then 'trickle down' the mechanism chain, so you don't really needed masses of them.

So keep the lights on, especially black lights of TL tubes or saver bulbs!

'Happiness' is relative: systems strive to lose Gibbs Free Energy, remember?
<hr>
Oh and properties of chloral alcoholate:

http://www.drugfuture.com/chemdata/chloral-alcoholate.html

MP apparently 47.5 C.

[Edited on 26-1-2016 by blogfast25]

aga - 26-1-2016 at 06:22

The overall stoichiometry is:

2 C₂H₅OH + 4 Cl₂ === > CCl₃CH(OH)OC₂H₅ + 5 HCl

Dehydration with conc. H₂SO₄ yields chloral (trichloroacetaldehyde) and ethyl hydrogensulphate.

Good stuff ! Working out what actually happens has been rather difficult.

For that second reaction i could not get the masses to balance unless 1 molecule of water was also produced.

Here is a spreadsheet with the five reactions calculated out and chained, starting with the required amount of TCA and working backwards.

Attachment: TCA Route Calcs.xlsx (13kB)
This file has been downloaded 577 times

The TCA required is changed in the yellow box at top-right, then the quantities of chemicals used/made is calculated.

An ethanol mass of 200g (= last attempt) would theoretically produce 54g of TCA, requiring a whopping 209 litres of chlorine gas !

That's a lot of bubbles and bubbling time.

This is where the cock-up happened : starting to react stuff before doing the calculations.

15g of TCA might be a safer quantitiy to aim for, although i'm not sure that it would be enough.

Based on the TCA process ratios, 15g TCA would convert 28g of alpha-pinene.

[Edited on 26-1-2016 by aga]

blogfast25 - 26-1-2016 at 07:31

Nice work on the spread sheet! Failing to plan is planning to fail.

This reference confirms the product of chlorination is chloral alcoholate but suggests a different route to the one above.

1. Oxidation of ethanol to ethanal by chorine:

CH₃CH₂OH === > CH₃CHO + 2 H+ + 2 e

Cl₂ + 2 e === > 2 Cl-

2. Formation of hemiacetal:

Reaction of ethanal with ethanol (nucleophilic attack by EtOH on carbonyl carbon):

3. Chlorination of hemiacetal:

Presumably by radical chlorination, the three H on the left C are substituted, because they are the most polarised due to the induction by the O-atoms.

The stoichiometry remains 2 ethanol + 4 chlorine = chloral alcoholate + 5 HCl

Alternatively one could imagine chlorination of the ethanal to chloral (trichloroethanal), with subsequent reaction of the chloral with ethanol to chloral alcoholate.

[Edited on 26-1-2016 by blogfast25]

aga - 26-1-2016 at 09:07

Stoichimetry is all wrong for the Cl₂ generator calculations - my pool shock stuff is Na-DCCA.2H₂O, not TCCA !

Those pesky small-print labels ...

Local version of the spreadsheet altered.

How much Terpineol are we aiming for, so i can work out how much TCA is needed ?

22g TCA requires almost an entire half-kilo jar of Na-DCCA, 1 kilo of 20% HCl (both really cheap here) generating 85.4 litres of Cl₂ (scary) to gas 82g of ethanol.

As for Time, 85.4 litres = 85,400,000 mm3.

If a bubble is about 4mm across, that's approximately a volume of 33.5 mm3/bubble.
At 5 bubbles a second, the total gassing time would be 5.9 days, assuming each bubble is 100% absorbed !

No wonder TCA is expensive.

200ml of azeo ethanol is being dried over some K₂CO₃ that was bought and forgotten about.

The K₃PO₄ produced for the purpose did not work. Not all of it dissolves rapidly in water, so it is Highly contaminated.

blogfast25 - 26-1-2016 at 09:15

How much Terpineol are we aiming for, so i can work out how much TCA is needed ?

Considering we still need to hydrogenate it, I'd say about 10 g. But I wouldn't worry too much about that: try and get whatever is possible, you can always scale-up later.

I still think commercial CaO, thoroughly dried before use and stood overnight in azeo EtOH is the cheapest and best route to anh. EtOH.
<hr>

A 'chlorinator' of this type might work better because of the longer bubble path than an RBF:

Put a strong spotlight on it!

[Edited on 26-1-2016 by blogfast25]

aga - 30-1-2016 at 13:05

Cement !

All this time searching for a local supplier of CaO and there has been a pile of 25kg bags of Cement in the car park !

Major "Doh !" moment just happened.

Will try it in the morning: dry azeo EtOH with Cement.

blogfast25 - 30-1-2016 at 14:06

Cement !

All this time searching for a local supplier of CaO and there has been a pile of 25kg bags of Cement in the car park !

Major "Doh !" moment just happened.

Will try it in the morning: dry azeo EtOH with Cement.

Ooopsie. More a "Dang !" moment, IMHO.

Something got lost in translation?

It does contain CaO: I once made KOH with it.

Probably best trying it in a plastic container?

Expect the cement to contain about 40 w% of active CaO, the rest being tied up as silicates and aluminates.

[Edited on 31-1-2016 by blogfast25]

ScienceHideout - 27-2-2016 at 19:39

Everyone,

Today I successfully ran a Grignard to make 3-methyl-heptan-3-ol. Please see it in prepublications and let me know what you think and if there are any ways I could revise it!

-SH

http://www.sciencemadness.org/talk/viewthread.php?tid=65439#...

Velzee - 24-8-2016 at 17:21