Sciencemadness Discussion Board

Benzyl alcohol, HCl and H2O2 strange oil?

Fantasma4500 - 6-5-2014 at 03:28

in school we recently had to try making benzoic acid from KMnO4 and H2SO4, i understood that the function was an oxidation, not understanding that much about organics
i suggested H2O2 and HCl to be attempted to substitute the KMnO4 and H2SO4

my teacher decided i should try it, at this point i had already tried it at a below 1mL scale at home, realizing it formed some strange substance smelling alike urinal tablets

what happens is that i have mixed up 1:1:1 by volume reagents.. benzyl alcohol, then HCl 36 or 37% then 35% H2O2, my home-concentrated H2O2 i cant tell for sure what concentration is, but im fairly certain its +30%

the reaction starts out very mild..
2 phases forms, the top phase seems to have a high viscosity, some of this manages to drop to the bottom of the test tube, whereafter it starts bubbling slightly, the reaction speeds up and more bubbles forms seemingly from the bottom layer, 3 phases when the bubbling starts
the bubbles goes through a clear middle layer (water?) and up into a cloudy yellowish oily layer as described before - with high viscosity
this SEEMS to be giving off a reaction somehow, as i tried this in a 100mL flask and the reaction didnt really heat up or proceed as expected, its apparently only possible to do if you have it in a test tube so the bubbles can go through the top phase and get absorbed

at one point we observed as much as 5 phases, and it is honestly abit confusing at times to observe this strange reaction

the reaction will exceed in temperature very suddenly, which can be controlled by putting the test tube into a flask of water, the test tube can easily reach +100*C, im supposing i may have had my fingers on +150*C hot glass as i decided to drown the reaction in water when it out of nowhere started really reacting, not having realised it suddenly reacts violently

however, if you let it react enough, at high temperature you will be left with 2 or 3 phases, the third is only a very thin oily layer on the top of the seemingly water, being at top where some strange oily substance can be seen falling to the bottom

when i do this reaction i usually dump the entire thing into water to purify it slightly

it has a high viscosity, its quite clear when it has been left in water for some time, seemingly perfectly insoluble in water and i think it might be that oily substance giving off the urinal tablet alike smell

the oily layer described before i have no idea of what could possibly be at all

however another thing i noted when i did this reaction at home in 9mL amount was that the bubbles seen in the reaction possibly is Cl2, it smells very much alike Cl2 if you can ignore the strong urinal tablet smell, and it reacts with NH3 to give a white smoke, just like Cl2 normally would

i tried taking a drop of the strange oil and heating up on aluminium foil and it decomposes into a decent volume of choking thick fog, doesnt really seem flammable

help with suggesting what this mysterious compound i managed to create would be greatly appreciated, my teacher got somewhat offended for having synthesized a compound he could figure out what was, and i cant see anything at all about this reaction, it seems somewhat that this havent been attempted by anybody before me?

i looked up hypochlorites and found benzyl hypochlorite, but this doesnt seem to be the case either

i could try to test its BP as i have microtubes available for exactly that, but i only have a steel thermometre rated for 120*C max, ill try to dump some into my freezer to see if it solidifies at -17*C

deltaH - 6-5-2014 at 03:52

I have posted a few times on this board about the chlorination of hydroquinone in conc. HCl by adding H2O2. That particular reaction ultimately yields the perchloro product chloranil (tetrachlorobenzoquinone). It is possible that you have a similar thing happening here, i.e. the oxidative chlorination of an aromatic compound in conc. HCl with H2O2. The question is which chloro-derivative is formed and is it selective at all?

You may want to investigate if your oil is benzotrichloride. According to wiki, this oil forms from the radical chlorination of toluene, so it might from from benzyl alcohol. The benzotrichloride is virtually insoluble in water, so it should separate nicely.

Note wiki also reports that benzotrichloride can be hydrolysed to benzoyl chloride, however, how rapidly this occurs is another matter as they report that it is virtually insoluble in water (0.05g/l).

As an aside, a better way to carry out this reaction, learning from the chloranil prep, is not to add all the H2O2 in the beginning which can result in runaway, but rather to heat the acid + aromatic solution to 80C (hot) and clamp a thermometer (gently) in the solution so that it sits well above a rapidly stirring magnet bar. You then add the H2O2 drop wise from a burette and control the addition so that you don't allow it to rise above 95C (this means stopping and waiting for it to cool back down to 80-85C typically before adding a few more drops). This makes sure that the peroxide is consumed rapidly and so there is no major amount present that can accelerate...

[Edited on 6-5-2014 by deltaH]

Fantasma4500 - 6-5-2014 at 04:07

i have an idea that the reaction first takes place when the H2O2 is added, i mix the benzyl alcohol with the HCl and then the H2O2, although this reaction takes long time to start up where it violently bubbles and boils
i dont have any magnetic stirrer, but i could shake it well in a flask, but then i would need large amounts in which could easily get out of control
i get your idea, and i will potentially attempt to react the benzyl alcohol with HCl at 80*C and add H2O2 dropwise, i will however be limited to use a pipette
but keeping it at high temperature with thermometre in until it cannot rise any further in temperature, and then adding H2O2 a little at a time could indicate whether the H2O2 is nessecary for the reaction to proceed

do you have any experiments i could do with the oil that i have now gathered roughly 10mL of to show whether it is part of the same group as of what you managed to create with hydroquinone?

deltaH - 6-5-2014 at 04:16

Yeah I also tried it by chloranil prep by swirling, it does work, just wear good rubber gloves.

As I said, investigate whether you have not made benzotrichloride as this is a likely suspect (sorry I tend to edit texts for a while, you commented to quickly too my post above before I could add this)

OH DEAR, I just read that benzotrichloride is rated category 4 on NFPA health rating, highly toxic!!!! :o:o:o

"4 Very short exposure could cause death or major residual injury (e.g. hydrogen cyanide, phosphine, carbon monoxide, sarin, hydrofluoric acid)"

Please be very cautious about this!

[Edited on 6-5-2014 by deltaH]

Fantasma4500 - 6-5-2014 at 04:22

BENZOYL CHLORIDE?!
damn!! if i really have benzotrichloride, that would be really interesting.. always wanted to play about with benzoyl compounds, and when i bought the benzyl alcohol, as the idiot i am in organic chemistry i mistook it for being benzoyl alcohol

its melting point is -5*C, and i should be able to see whether it is pure benzotrichloride as my freezer reaches as low as -17*C

ill try to see how much i can test it.. ill also attempt to check for solubility of the mysterious substance, should be doable

Fantasma4500 - 6-5-2014 at 04:43

~~sorry for doubly-posting~~
it seems that my material has somehow in a UV proof bottle with screwlid, glass bottle standing away from sun-- managed to change drastically, from last time being impossible to light on fire, and now giving off tonnes of carbon when burnt, with a very acetylene alike flame, it burns quite well and i found it hard to decompose into a thick fog as i did last
in my glass container i have 2 phases -- seemingly
upper layer being slightly foggy but when i try to extract anything from this layer it seems as im sucking away bottom layer?

anyhow, i tried to take sample from the top and sample from the absolute bottom with a 1mL pipette, just a few drops at a time, and they behave the same when held over a flame on a piece of aluminium foil.. burns very nicely!

sadly i cannot at this moment take pictures or video of this burning substance

the fumes doesnt however seem to give off HCl or Cl2 such as
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&...

suggests.. i will try to find its boiling point and its freezing temperature

edit: yes i did see the MSDS of the compound, however it evaporates off extremely slowly, but the toxicity could explain why its smell is so easy to detect

anothe thing.. i did sadly not find any Cl2 or HCl in its decomposition or combustion products?? i tested with ammonia

sealed in test tube + al foil, and then decomposed on al foil and ammonia blown onto it while decomposing

[Edited on 6-5-2014 by Antiswat]

Fantasma4500 - 6-5-2014 at 05:12

as i cleaned up my micropipette sucking the remaining (??) out i realized as i wiped the outside of the pipette that its a splendid solvent.. the markings of 0.1mL and the smaller lines just.. vanished
not sure what those lines were drawn with but they had until today seemed very persistent

Nicodem - 6-5-2014 at 05:37

deltaH, there was no need to ruin this thread with unsubstantiated speculations!

Antiswat, mixing conc. hydrochloric acid with benzyl alcohol rapidly gives benzyl chloride (see Vogel's). Adding hydrogen peroxide is not expected to do anything. You might want to use a scientific approach to evaluate the reaction and obviously check the literature first.

The oxidation of benzyl alcohol or other alcohols with hydrogen peroxide is not trivial and requires catalysts (see the literature examples). For example, you can get excellent yields of either benzaldehyde or benzoic acid from benzyl alcohol oxidation with the corresponding amounts of hydrogen peroxide using 0.5 mol% of a phosphotungstate catalyst (see ARKIVOC 2012 (VIII) 187-197). There are plenty of examples of other catalytic systems in the literature.

Fantasma4500 - 6-5-2014 at 06:23

okay, ill try to go ahead repeating the experiment without H2O2 and wait long enough to determine whether the H2O2 actually plays a role, however i just randomly came by BnCl synthesis video and it seemed to be green aswell as floating ontop and not on the bottom of the reaction vessel

Fantasma4500 - 6-5-2014 at 07:58

equal volumes HCl and benzyl alcohol added together, no phases have formed, only a mixture of the 2
temp. stays at 11*C so far, and has done so for several minutes

10 minutes later 2 phases forms, although they still appear somewhat soluble within each other, still no temperature rise
1 hour later or so a clear bottom phase has formed, ill put it on hotplate in a test tube along with 100 mL beaker with oil to heat it up, however seemingly H2O2 really does some sort of reaction, the mixture is now at around 9.7*C

as i approached the now highly boiling test tube with 7 mL of the mixed phases in it, lightly stoppered off with tissue paper to keep the thermometre still i saw the temperature exceeding 100*C and when it reached 110*C it shot up and all over my stove and also onto my skin, i knew i didnt have much time so i didnt put on gloves to take it off

quickly washed off the liquids that landed on my hands, now im down to approx 2 mL of solution to compare to my previously bottled mysterious oily substance

it acted kind of as when i add H2O2 to it, but the reaction didnt start up by itself, as in the temperature didnt rise by itself

edit: addition

it has a freezing point around -17*C, it can be heated up slightly in your hands to go oily again, the solid is a cloudy white mass

[Edited on 7-5-2014 by Antiswat]

deltaH - 7-5-2014 at 11:00

I missed the edit and such an interesting result it was:D

I do have some questions if I may:
Was you melting point determined with the H2O2 and acid or acid only preparation's crude product?
Also, did the entire amount you froze solidify or was there a small amounts of liquid remaining (slush)?

The melting point of benzyl chloride is much lower (-39C, Wiki), as you probably know. If only part of it froze as a kind of slush, then it was most likely a solution of a higher melting substance dissolved in benzyl chloride.

This higher melting substance could be unreacted benzyl alcohol (-15.2C, Wiki) or something else.

[Edited on 7-5-2014 by deltaH]

Fantasma4500 - 8-5-2014 at 06:18

there was no slush remaining, it was an entirely frozen solid, and i had the .. 0.5mL(?) glass tube standing 20% filled in the freezer for well at least 15 hours in a small rubber stopper

however it was the standard oil, so to call it.. the one where i usually lets it actually run-off, adding all reagents 1:1:1 more or less at once
since then i had mixed 3.5 mL benzyl alcohol and equivalent 37% HCl up
then after nothing happening for some time i decided to heat it up and then i realized whatever i had formed surely was a lachrymator, assuming what i now had was benzyl chloride

i thereafter with about 50% of what i started out with added a small amount of 12% H2O2 and saw no reaction, no temperature rise etc
then i added about twice or 3 times as much as before, of +30% H2O2
still nothing
however as i had it standing beside my screen for several days, still standing the oils have seperated into 3 phases, although the top layer seems to be the bottom layer (colourless - it was part of a runoff on my hotplate running at +100*C, without H2O2 in it!!?)
i suggest the top and bottom layer are related as when i shake the tube gently alot of small spheres flows to the bottom, seemingly shaking off smaller bubbles that has attached themselves to the bottom layer (after adding H2O2 these bubbles are still produced even after several days)

the bubbles carries up and sticks to the bottom layer, not sure if the bottom layer is super slowly decomposing?? but this time its totally colourless .. i suspect this is related to runoff with / without H2O2, which surely indicates that the H2O2 has SOME sort of relation in this reaction

i actually did look up properties of benzyl alcohol, but i can also suggest that its not entirely benzyl alcohol, at least -- because it has this really strange smell to it, which i can only explain as ''urinal tablets''

not sure what benzyl chloride smells like an i should probably get my ass up and try to create a smaller amount of it to see if it smells somewhat the same or has other similar properties

also the phases seperating im thinking could perhaps be because the HCl looses its density as it reacts with the benzyl alcohol (although this seems only to have happened after runoff with/without H2O2 added, benzyl alcohol and HCl needs to be heated as it doesnt apparently create a measurable exothermic reaction)

anyhow, with just a small amount of benzyl chloride within the mixture it seems unreasonable that it could freeze and keep totally solid after being out for at least a few minutes

deltaH - 8-5-2014 at 13:38

Okay, so I think we can safely say that your oil prepared with peroxide is not benzyl chloride then. That should not freeze in a regular chest freezer. I thought your oil might contain some benzyl chloride, but since it froze completely, we can rule out that it was present in significant amounts.

Your 1:1:1 equivolume ratio of reagents is roughly equimolar by chance (+- 20%), so if you chlorinating past just benzyl chloride, you actually have too little HCl there to have good conversion of the starting benzyl alcohol.

Dr.Bob - 8-5-2014 at 18:17

I would agree with Nicodem that benzyl chloride would be the expected product, if you have enough Conc HCl and do the reaction well, then it should work. I have done the same reaction with tBuOH to tBuBr using Conc. HBr. You will need a large excess of HCl in order to drive the reaction to completion.

deltaH - 9-5-2014 at 03:12

Dr.Bob, Antiswat has already proved that his product is not benzyl chloride as his oil freezes completely by -17°C.

*****
Coming back to my theory of oxidative chlorination, I will discuss and reference the basis of my speculations made earlier a little better:

Concentrated hydrogen peroxide mixed with concentrated hydrochloric acid generates chlorine gas when heated. This has already been discussed on the SM thread titled "Hydrochloric acid hydrogen peroxide mix". I quote member kmno4 from that thread:
Quote:
This mixture is not stable and gives off Cl2 gas, sooner or later but it does.
H2O2/HCl mixture is useful chlorinating agent for some purposes.

Quote:
Something to read:
THE PROPERTIES OF PURE HYDROGEN PEROXIDE. IV. ACTION OF THE HALOGENS AND HALOGEN HYDRIDES
O. Maass and P. G. Hiebert
DOI: 10.1021/ja01667a005
But in 'Summary' one can read:
1. Hydrofluoric acid does not decompose hydrogen peroxide but acts as a stabilizer. The other halogen hydrides cause the decomposition of hydrogen peroxide at all concentrations.
For concentrations ~30% of HCl and ~30% H2O2 it gives Cl2, below some concentrations only O2 is liberated.


While it is likely that benzyl alcohol first forms benzyl chloride, it is also likely that it then reacts further by chlorination to form benzal chloride (dichloromethylbenzene), m.p -17 to -15°C (Wiki) as the ability of conc. H2O2 and HCl mixtures to generate chlorine with heating is known AND the Wiki article on benzal (dichloromethylbenzene) chloride mentions that it can arise from the chlorination of benzyl chloride. The article goes on to state that the chlorination sequence can continue even further to also form benzotrichloride, though considering that antiswat has:

(i) used roughly equimolar amounts of reagents,
(ii) reports lachrymatory properties and
(iii) a melting point of -17°C,

he most likely isolated a crude benzal chloride (dichloromethylbenzene) since it would have been limited by the HCl present.

Once again, as I take safety seriously, I feel it is important to note for other readers reading this (antiswat is already aware of this) that benzal chloride (dichloromethylbenzene) is rated Toxic and a category 2B (possible) carcinogen, so if it's presence is suspected, the mixtures should be treated with due caution.

*****
Antiswat, according to Ullmann's, dichloromethylbenzene can be hydrolysed to benzaldehyde, so perhaps you can use this as a basis for a test and try to hydrolyse a tiny amount of your oil (e.g. one drop) in an aqueous solution of sodium hydroxide by mixing with say 50ml 1M NaOH solution until dissolved and then letting it stand for a few hours to hydrolyze fully.

Benzaldehyde has a strong almond smell to it.

[Edited on 9-5-2014 by deltaH]

Dr.Bob - 9-5-2014 at 07:40

Another possibility is that he has some benzyl alcohol left, as it also has a MP of around -16C. The most likely answer is that it is a mixture of several things, and any trace of benzyl chloride would be a lacrymator. I merely agreed that I would expect benzyl chloride to be a product. And it is possible that some benzyl chloride could be chlorinated further, but those chlorination type reactions rarely give a single compound, but rather often give a mixture of no, mono-, di- and tri-chloro compounds. So I am simply saying that I expect that he has a mixture of alcohol, chloride, and other materials. The best way to separate the products there is distillation, but that is not practical on a small scale. And this reaction does not seem a practical way to make benzoic acid.

Fantasma4500 - 10-5-2014 at 05:57

yes.. yes..
ive actually been looking abit around for a really easy route to benzaldehyde.. i have worked with it in school for making silver mirror and also recall it was part of KMnO4, BnOH (benzyl alcohol) and H2SO4

i got a solution of NaOH laying around, not sure about the concentration but im sure its somewhat concentrated, i will try to add a few drops to a solution of this possibly heated up

i will try to react the oil with NaOH ASAP, although im slightly busy with school atm

perhaps i could try to extract or seperate the stuff with acetone and see what properties that would have? but it sounds likely that i still have some BnOH left, i should perhaps try with a greater excess H2O2 and HCl or perhaps try to furthermore react the oil with HCl and H2O2

Fantasma4500 - 21-5-2014 at 04:53

i added about 0.1 mL or 0.2 mL of the oil to a 250 mL flask, then added NaOH solution to it, nothing really happened, and after boiling and diluting it and boiling it again (using excess NaOH, 5mL?) im not sure that i formed benzaldehyde?
benzaldehyde smells quite alot and it shouldnt be hard to detect, but i dont smell it, and if i do then it might just be my imagination..

Electra - 21-5-2014 at 08:17

From experience, only strong oxidizing agents will take benzyl alcohol to benzoic acid, such as KMnO4 and Oxone. In your case, either benzaldehyde was formed or a chlorinated benzyl of some sort as others have stated.

Your mention of the smell of urinal tablets make me think you formed benzaldehyde, which smells sort of cherry/almonish. Though, it is entirely possible you formed a mixture of both. From what I found online, chlorinated benzyl's such as benzyl chloride "have a very unpleasant smell". All of the oxidations of benzyl alcohol involving H2O2 that I have ever found always take it to benzaldehyde....which is probably something you don't want laying around your house.

[Edited on 21-5-2014 by Electra]

deltaH - 21-5-2014 at 10:19

Yes it does smell quiet a lot, very almondish and quiet pleasant, well to me anyway.

Then again, maybe excess hot caustic causes a problem by reacting with the aldehyde.

If you have almond essence in your kitchen, you could always see if adding excess hot caustic to it makes the smell dissapear or not. If it does, then this test of mine would be a bad test :(

It's a very challenging problem to investigate what you have.

Fantasma4500 - 26-5-2014 at 02:40

i tried again today with reacting a more pure sample of this strange oil, i poured some NaOH solution into a test tube in great excess and heated it till it all started bubbling from excess heat
it doesnt seem to change smell at all
also benzaldehyde has a MP of -26*C and again, my sample is frozen SOLID at -17*C

i start with BnOH, and it smells different after the reaction, there is SOME reaction going on
what could i possibly react this with others than NaOH?

PHILOU Zrealone - 28-5-2014 at 11:31

Benzaldehyd is sensitive to air oxydation and turns into benzoic acid.

Exces NaOH turns benzaldehyd into benzoic acid and benzylic alcohol via Cannizaro reaction.

As products for your initial reaction, you may have:
C6H6-CH2Cl
C6H6-CHCl2
C6H6-CCl3
C6H6-CH=O
C6H6-CHCl-OH
C6H6-CO2H
C6H6-CCl=CH-C6H6
C6H6-CCl2-CHCl-C6H6
and if your HCl is technical with traces of Fe also some halogenation into the aromatic ring...

[Edited on 28-5-2014 by PHILOU Zrealone]

Fantasma4500 - 10-6-2014 at 10:57

looks like ill have to have another go at it with NaOH... mhm

thanks for it, ill keep it if i ever get asked what the bottle of ''BzCl'' contains again
i guess i could try to do it concentrated aswell to try making it into benzoic acid, then letting it cool down and precipitate the benzoic acid, just to confirm i havent broken rules of chemistry again