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Rich_Insane
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Hydroquinone Synthesis
Just tell me if my calculations and method is correct. For some reason you can't find a lot of easy, simple syntheses for hydroquinone in literature.
I know that hydroquinone is commercially available, but I feel like doing a short organic syntheses like this sometime.
So we start with 10 g of p-Dichlorobenzene, which I would dissolve in 100 ml of Acetone. To the solution I would stir while adding 5.5 g of NaOH.
Here is my thinking:
10 g is 0.068 mols of p-Dichlorobenzene. I need twice as much NaOH as p-Dichlorobenzene because there are two hydroxyl groups in hydroquinone. This
means I need 0.13606 mols of NaOH which is 5.44 g, which I rounded to 5.5 g.
That's all I do. The theoretical yield is 7.4868 g.
My question is: how would you separate NaCl from the desired product? Both are fairly soluble in water and most solvents one can find. I thought up of
melting the hydroquinone and somehow decanting the hydroquinone somewhere, but I don't know how practical that is. So how would I separate the two? I
also remember from a brief O Chem class that in nucleophilic substitution, sometimes a specific solvent is required. I chose acetone because it is
fairly accessible and is an aprotic polar solvent. Was my decision right?
Thanks,
Rich
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entropy51
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I think nucleophilic displacement of halogen requires high temperatures and pressures, as in the Dow process for the preparation of phenol.
An exception is the presence of a nitro group ortho or para to the halogen, as for example p-chloronitrobenzene to p-nitrophenol, which occurs in
aqueous base, but still at rather high temperature. I think that with a nitro both ortho and para that the reaction is possible in ordinary
glassware.
I think your method is a non-starter. Have you a literature reference that says otherwise?
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Rich_Insane
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Really?
Well, I don't have much lab experience with that, but we always learned that halogens, especially chlorine and bromine, could be displaced by most
nucleophilic substances. Perhaps that only applied to non-cyclic halides. That's a shame, because this would've been easy to do as p-DCB is found as
moth balls and NaOH as lye.
I do not have any literature, and perhaps this is the reason. I did a long search on Google Scholar only to find complex methods that required
cyclohexene and various reagents.
Thanks anyways....
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Picric-A
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Removal of halogen atoms from a aromatic compound does generally require forece-full conditions... Its different to the hydrolysis of aliphatic
compounds which can be removed by simple boiling in dil. NaOH/KOH
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entropy51
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Yes, it is a shame, but there is a paper in JACS, I think it may be posted somewhere here, on reactions of p-dichlorobenzene. You might even be able
to nitrate it to something more interesting. Try searching here, I think the subject has come up before. Someone else might have suggestions for
you.
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Picric-A
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I am afraid p-dichlorobenzene is a fairly useless compound for amateurs.
1,4-Dichloro-2-nitrobenzene is pretty stable, being distillable at 257deg* and not very flammable.
It is hard to make grignards from it, yields of around 30% **are obtained and the products from these also have limited use.
Just keep it till somebody thinks of more interesting uses...
*Source-http://www.chemblink.com/products/89-61-2.htm
** quote from somewhere on this forum... cba to find where
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entropy51
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If for some reason one wanted the dichloroaniline you could reduce the nitro group. Apparently p-dichlorobenzene requires oleum to sulfonate, so
that's not very attractive. It's frustrating to have such a readily available chemical that seems so useless for most things. Anybody else know of
any use for it?
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Rich_Insane
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That's a shame. I chose p-DCB because it was one of those things that are easier for me to obtain,a nd i always wanted to do some organic syntheses.
The problem with the easier stuff - straight chain alkanes (which can readily become alkyl halides which can be converted to all kinds of stuff) is
that the most accessible ones are gas. I hate working with gasses, and I don't have the equipment for it. Those damn aromatic compounds.
I will think of something else up if I can sometime. Just one question. If you exposed Isopropanol to HCl, would you get Isopropyl chloride? I guess I
can go on from there.
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Vogelzang
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You can buy it on ebay.
http://photography.shop.ebay.com/Cameras-Photo-/625/s.html?L...
http://cgi.ebay.com/Hydroquinone-Certified-Photographic-250g...
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vulture
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Acetone is a poor choice as solvent because it will react when using NaOH - aldol condensation.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Magpie
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Rich_Insane here is a thread describing my experiments with making isopropyl bromide which you may find useful.
http://www.sciencemadness.org/talk/viewthread.php?tid=5725#p...
I know that you would just like to do an organic synthesis with OTC materials. But I caution that you really need the proper equipment in place
first: a distillation setup, sep funnel, etc, and a ventilated workspace.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Rich_Insane
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God DAMMIT I thought I could get away with just flasks, beakers, stirring rods, and reagents. Oh well. Back to square one.
I do have an Ahlinn condenser that I obtained in India. It does have a a little grime in it, but that doesn't look like anything a little acetone or
acetic acid could fix. The problem is that I do not have joints, a heating mantle, clamps, and adapters. I don't even know what joint size the
condenser is. I already chipped the portion of the condenser where the adapter goes 
You say that Acetone will react with NaOH.... could that be a syntheses on itself? I understand that an an Aldol condensation joins ketones or so
Wikipedia says (I never got that far in O Chem). So Acetone + NaOH = Acetylacetone?
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entropy51
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Quote: Originally posted by Rich_Insane  | | (Expletive deleted) I thought I could get away with just flasks, beakers, stirring rods, and reagents. ......The problem is that I do not have joints,
a heating mantle, clamps, and adapters. |
You could do some kinds of organic with what you have plus some cork stoppers, glass tubing and something to bend it with. But you do need a stand
and a clamp or two. For the first 20 years that I did home chemistry I had neither jointed glassware nor a heating mantle. I even did brominations
by coating the corks with sodium silicate and letting it dry. You couldn't use them many times but they did work. I used to distill all kinds of
flammables over a flame, but I recommend against it.
My point is, if you don't have the resources for fancy organic chemistry, then do simple organic chemistry. You can make chloroform for example
without much equipment. If you can reflux and you can find oil of wintergreen you can hydrolyze the ester with base and acidify to make salicylic
acid. If you can find benzoic acid or sodium benzoate you can decarboxylate that in a large test tube connected to your condenser with a cork and
glass tube and make benzene. The list of things you could do is probably quite long.
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Rich_Insane
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Well, I may consider pursuing the chloroform. I hate working with it because it evaporates so fast. I have found that Ace Hardware sells both Acetone
and 3 lb bags of Calcium hypochlorite.
Will a standard propane-based torch bend standard glass tubing? I'd think so, but always be sure.
I was thinking of synthesizing some chloroform and perhaps some energetics like ETN. But a lot of the syntheses procedures for chloroform call for
gallon amounts of Acetone and multiple pounds of ice. Not to mention a few pounds of Calcium hypochlorite. Sure, I would love to make that much
chloroform, but I don't have the money to buy all of that equipment or the space to put it in. Any ideas on what I can do with that lone condenser?
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Magpie
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Correct me if I am wrong, but I think that you have not had much experience at the bench in a school setting. That lack of experience is hurting you
in many ways: you don't know what equipment you need, you don't know how to assemble it, you don't know what scale you should be using, or how to
scale down.
This needn't stop progress in home chemistry. You will just have to be very careful and very well prepared. By that I mean lots of reading,
questions, and planning. I'm not trying to be discouraging, so please don't take it that way.
The single most important condition for a successful synthesis is good mixing - Nicodem
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entropy51
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| Quote: | | Any ideas on what I can do with that lone condenser? |
IIRC, it has ground joints, right? You can put a cork (or rubber stopper for some things) in the top joint and connect it to your flask with a glass
elbow for distillations. Harder to put a cork on the bottom for refluxing, though. You can get a condenser without ground joints, which makes them
much cheaper, at places like hms-beagle.com and many other places.
Yes, you can bend glass tubing with a propane torch, if it's not Pyrex. If you have a flame spreader on the torch it makes prettier bends, but you
can do almost as well without one if you practice heating a length of tubing before you bend it. Find some online books with this type of thing in
it.
You needn't start by trying to make a liter of chloroform. Practice on a small scale. Acetone and Ca(OCl)2 can foam out of control unless you have a
feel for how to do it. Magpie has posted a prep on a scale suitable for beginners, but even that scale can go wild and come out of the flask.
Forget the professional ground glass for now. The old fashioned stuff is much cheaper. If you don't have the patience to proceed at a pace you can
afford and handle safely, chemistry is not a good hobby for you. Fancy glass won't really change that.
BTW, have you looked at Woelen's web site? He has some very sophisticted experiments done mostly with relatively simple equipment. Check it out if
you haven't.
[Edited on 10-10-2009 by entropy51]
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JohnWW
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| Quote: Originally posted by Rich_Insane | Well, I may consider pursuing the chloroform. I hate working with it because it evaporates so fast. I have found that Ace Hardware sells both Acetone
and 3 lb bags of Calcium hypochlorite.
Will a standard propane-based torch bend standard glass tubing? I'd think so, but always be sure.
I was thinking of synthesizing some chloroform and perhaps some energetics like ETN. But a lot of the syntheses procedures for chloroform call for
gallon amounts of Acetone and multiple pounds of ice. Not to mention a few pounds of Calcium hypochlorite. |
I recently bought a 10 kg plastic pail of "chloride of lime" (technical-grade calcium hypochlorite) for $NZ5 at a local auction. I was going to use it
as a spray to kill moss and lichen on concrete and overhead glazing. Now I know what to do with it, if I can also find a local hardware store that
sells liters at a time of acetone.
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entropy51
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| Quote: | | Now I know what to do with it |
Honestly JohnWW, are you just now finding that out. There is a thread or ten around here on that.
Hint: KClO3 too!
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Rich_Insane
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Well, I expect more glassware once I get a bit more money. Yea, someone told me that the rxn tends to get out of control even with such large amounts
of ice. But I could do a lot with chloroform if not do reactions. I could use chloroform for extractions or something. It's a good solvent, and it
dissolves lipids.
I do have lab experience -- just not chemistry. I am currently in the process of a project at PSU. Unfortunately it's far more
microbiology/biochemistry than organic chemistry. In fact the only chemistry I'm doing for it right now is figuring out how to extract homogentisate
polymers from microbes -- which I do have a procedure if anyone's interested. My school does not provide such labs, but that's not because they don't
in general, mainly because I'm not in high enough of a grade level yet.
Indeed, it is a ground joint, or so I believe. I didn't spend anything on the condenser. I purchased it for around 5 USD at an Indian Surplus Store --
in India it is fairly easy to obtain reagents and glassware for low prices. It's just that the inside is a bit dirty and in the processing of
transferring it back to USA, I chipped of a small piece at one end.
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Klute
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I wouldn't recommedn buying none-ground joints glassware, they might be cheaper, but they are much more archaic, and you will soon be annoyed by them
when you want to make proper distillation setups, etc. Better start to invest in "real" glassware at the beggining, it might be slower and more
expensive at first, but you won't need to change it in a few years, and it will save you a lot of problems with fittings, cork compatibilty, etc. I
think this old kind of glassware has it place rather in decoration antiques, etc than in a lab, even a home one.
It's like buying a car. Why buy a cheap lousy car as soon as you get your licence, that you will need to repair every so often, and that will cause
you problems every day, while if you wait a few months or so, you can get a decent one that will last you years..
And there nothing more nifty that a beautifully ground glass setup, compared to the "frankestien lab" caricature, with bits and bobs sticking out
everywhere, and that threatens to fall in pieces at any time 
Maybe I'm just too "New-School"..
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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Magpie
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Klute, I completely agree with you. I'm "old school" but the first purchase I made was a 19/22 ground-glass distillation kit. It is the work-horse
of my lab. I paid around $300 for it but they're cheaper on ebay. Start a savings fund and before you know it you'll have one.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Nicodem
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| Quote: Originally posted by Rich_Insane | Really?
Well, I don't have much lab experience with that, but we always learned that halogens, especially chlorine and bromine, could be displaced by most
nucleophilic substances. Perhaps that only applied to non-cyclic halides. That's a shame, because this would've been easy to do as p-DCB is found as
moth balls and NaOH as lye. |
You can not consider a "displacement by nucleophiles" as a single type of a reaction. If you really want to learn organic chemistry you should focus
on reaction mechanisms so that you have a system of learning. Trust me that once you start thinking mechanistically further learning speeds up
exponentially and many confusing things clear up. Without theory you can only have a collection of facts. With theory you have knowledge.
The most classical "displacement by nucleophiles", the one you probably had in mind, is the SN2 reaction. "S" stands for "substitution", "N" is for "nucleophilic" and "2" is for "bimolecular". If you check the mechanism of SN2 you will
soon realize that 1,4-dichlorobenzene or any other aryl chloride simply can not fit in. The mechanism requires that the carbon (or other atom) on
which the substitution occurs is sp3 hybridized while all the carbons in the benzene ring are all sp2 hybridized. That's why the SN2 substitution on
carbon is limited to R-X compounds where R is an alkyl and X is a leaving group (also called nucleofuge).
Now, there are many mechanism that allow a nucleophilic displacement on an aryl halide, just not the SN2. Check the list (not truly complete) at
wikipedia and learn the mechanisms: nucleophilic aromatic substitution.
There was a lot posted about mono- and dinitration of 1,4-dichlorobenzene. From 1,4-dichloro-2-nitrobenzene you can do several transformation. Being
an electron poor aryl halide it is prone toward the addition-elimination (SNAr) nucleophilic substitution, so you can make, for example,
1-alkoxy-4-chloro-2-nitrobenzenes or 4-chloro-2-nitroanilines. You can also reduce it with dithionite to get 2,5-dichloroaniline. There are a lot of
experiments a young amateur can do with 1,4-dichlorobenzene. For example, you could perchlorinate it with trichloroisocyanuric acid in concentrated
sulfuric acid to get haxachlorobenzene. Lots of fascinating chemistry, though a bit hazardous and not for the very beginner.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Rich_Insane
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This was one of the first O Chem reactions I started to understand (the SN2). The problem was that the class I was taking was a summer course that
crammed a whole chapter in a day or two and had a large payload of homework. In the middle of the second term, where we were just finishing Allylic
Systems, i dropped it, but I got a lot of nice basic chemistry.
Is SN2 the one where the Nucleophile slowly sneaks up behind the alkyl halide in the RDS and kicks off the halide? SN1 is the reaction where the
tertiary carbon gives an electron to the halide, causing it to break off and form a carbocation, correct?
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S.C. Wack
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Ha. Not a single on-topic post, way to go. A route that I think would be true to the heart and soul of SM as I see it would be hydrolysis of
acetaminophen, then diazotization, hydrolysis, and isolation. Expensive compared to options such as buying it, and you can't wiggle your nose and get
clean hydroquinone in high yield instantly from acetaminophen, but the graphic still doesn't say "the art and science of amateur shopping". Wouldn't
surprise me if there were details in the arcHive, from ning of course.
Edit: a possible alternative has been mentioned here,
http://www.sciencemadness.org/talk/viewthread.php?tid=8250#p...
keeping in mind that benzoquinone is easy to reduce.
[Edited on 15-10-2009 by S.C. Wack]
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Rich_Insane
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I'm abandoning this topic to create a new one on something far simpler. Probably not gonna be ON topic for a while in this thread.
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