zaltar
Harmless
Posts: 10
Registered: 22-11-2014
Member Is Offline
Mood: sock puppet
|
|
xylene to benzene: HCl + al
I want to de-methylate xylene to toluene
and toluene to benzene. Iv'e have some
source information and tryed to do it
by bubbeling hcl gas (made from salt and
h2so4) and put in some aluminium as the
method discribed. But the reaction of
the aluminium wont start because i think
is anhydrous, because when I add a bit
water the reaction starts and the xylene
mixture starts to stink (:-) assuming
this is benzene.Is it impossible to
dissolve hcl in the xylene mixture ?
Attachment: The Friedel-Crafts reaction Part III.pdf (287kB)
This file has been downloaded 363 times
|
|
|
DraconicAcid
International Hazard
Posts: 4334
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline
Mood: Semi-victorious.
|
|
The paper you cite shows the reaction of alkylbenzenes with anhydrous aluminum chloride. I don't think benzene or xylene will be a good solvent to
try to react HCl with aluminum. If I was to try to make anhydrous aluminum chloride, I think I would try reacting chlorine gas with aluminum in a
solvent such as dichloromethane or chloroform (with a reflux condenser!) or reacting aluminum with anhydrous CuCl2 or FeCl2 in a halogenated version
of the thermite reaction. I'd also hit up a search engine *well* before trying either of these reactions.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
|
|
|
zaltar
Harmless
Posts: 10
Registered: 22-11-2014
Member Is Offline
Mood: sock puppet
|
|
yeah ok, i dont want to use chlorine in my house :-)
|
|
|
CuReUS
National Hazard
Posts: 928
Registered: 9-9-2014
Member Is Offline
Mood: No Mood
|
|
this would be a really bad method ,but if you really want benzene from xylene
why dont you oxidise both the methyl groups to COOH using KMnO4 and then decarboxylate that
also,dealkylation using AlCl3 works best with tert-butyl group
they use tert-butyl to protect the para position and at the end it is removed using AlCl3 
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by CuReUS  | this would be a really bad method ,but if you really want benzene from xylene
why dont you oxidise both the methyl groups to COOH using KMnO4 and then decarboxylate that
also,dealkylation using AlCl3 works best with tert-butyl group
they use tert-butyl to protect the para position and at the end it is removed using AlCl3 |
Neither are practical options for a beginner. Oxidising xylene to phthalic acid with KMnO4 is very skilful. Isolating the phthalic acid isn't easy
either. Nor is decarboxylating it.
FC reactions aren't for the faint of heart and require large amounts of AlCl3.
OP's best bet for benzene is the decarboxylation of sodium benzoate with NaOH, as described in great detail in the relevant OC sticky thread:
http://www.sciencemadness.org/talk/viewthread.php?tid=325
[Edited on 13-12-2014 by blogfast25]
|
|
|
macckone
Dispenser of practical lab wisdom
Posts: 2168
Registered: 1-3-2013
Location: Over a mile high
Member Is Offline
Mood: Electrical
|
|
The oxidation is the hard part. It uses a lot of permanganate.
The decarboxylation is basically the same for benzoic acid
and phthalic/terphthalic acids.
|
|
|
CuReUS
National Hazard
Posts: 928
Registered: 9-9-2014
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by blogfast25 |
Neither are practical options for a beginner. Oxidising xylene to phthalic acid with KMnO4 is very skilful. Isolating the phthalic acid isn't easy
either. Nor is decarboxylating it. |
by it being skillful,are you talking about completely oxidizing both the methyl groups ,instead of only one of them oxidising to COOH
also as you say ,the extraction will be difficult ,as partially oxidized xylene(only one methyl group becomes COOH) would also precipitate out when
you use NaOH
| Quote: | | FC reactions aren't for the faint of heart and require large amounts of AlCl3. |
IIRC F.C reactions are common in undergrad chem course
but i agree that the yields are shitty and require large amounts of catalyst
maybe not as much as we think 
in the mechanism of KMnO4 oxidation of toluene ,benzaldehyde is formed as an intermediate .
benzaldehyde can convert to benzoic acid by air oxidation alone
so if enough KMnO4 was used to convert both the groups to benzaldehdye then it could be left in an open beaker for one week to get the
pthallic acid
(there may be a chance of polymerisation though )
the problem with KMnO4 oxidation is the solubility
you could use a 54.2 w/v acetic acid-water mixture
or you could use methylene chloride
https://books.google.co.in/books?id=bga3xjLVCo0C&pg=PT60...
or another organic solvents
http://chemistry.stackexchange.com/questions/540/what-organi...
|
|
|
zaltar
Harmless
Posts: 10
Registered: 22-11-2014
Member Is Offline
Mood: sock puppet
|
|
but xylene H2 (or H donor) and a cth catalyst such as NiCl2 works ?!!
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
However you look at it, converting something like Xylene to benzene is folly, when sodium benzoate is readily available and can be decarboxylated
fairly easily.
|
|
|
zaltar
Harmless
Posts: 10
Registered: 22-11-2014
Member Is Offline
Mood: sock puppet
|
|
where can you find sodiumbenzoate ,in the grossery store, i mean witch products contains sodiumbenzoate ?
|
|
|
Furboffle
Harmless
Posts: 46
Registered: 15-10-2012
Member Is Offline
Mood: No Mood
|
|
I work part time in grocery store while finishing grad school and I've never seen it or benzoic acid. (I keep an eye out for these types of
products...) though I would recommend checking out your local brewing shop. They usually have a small but nice selection of chemicals, granted they
all pertain to brewing, winemaking, or cheesemaking... I'm not positive that sodium benzoate is typically sold there, but being a food related
chemical I would have high hopes of finding it there. otherwise hit up ebay. its like $6 for a pound.
|
|
|
Mabus
Wiki Master
Posts: 238
Registered: 3-11-2013
Member Is Offline
Mood: Energetic
|
|
Sodium benzoate is sold as a food preservative, usually in small bags. You should look in hypermarkets, in the seasonings section.
|
|
|
Bert
Super Administrator
Posts: 2821
Registered: 12-3-2004
Member Is Offline
Mood: " I think we are all going to die. I think that love is an illusion. We are flawed, my darling".
|
|
Member names zaltar and lyserisc are apparently the same person...
Both profiles have the same birthday, they post from the same IP address while asking similarly ignorant organic chemistry synthesis questions. Quite
like member names phendrol and ewel.
https://www.sciencemadness.org/whisper/viewthread.php?tid=51...
[Edited on 27-12-2014 by Bert]
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
|
|
|
Bert
|
Thread Closed
27-12-2014 at 07:45 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
