Re: ORGLIST: Everybody Digest, Vol 35, Issue 5

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From: A De (ocad$##$mahendra.iacs.res.in)
Date: Fri Jun 08 2007 - 02:24:25 EDT


I do perfectly agree with Dr Pandey. I would prefer ether as solvent. But
what is very very very important that is the rate of addition should be
particularly slow. It may take a couple of trial runs to arrive at the
optimum rate. One note of caution.These bromo compounds are powerful
lachrymators!!!
All the best
Asish

Professor Asish De
Project Investigator
Department of Spectroscopy
Formerly Professor Department of Organic Chemistry
Indian association for the Cultivaion of Science
Jadavpur; Kolkata - 700 032
India
Honorary Secretary,
Royal Society of Chemistry(Eastern India Section)
Tel : +91-33-2473-4971 (Ext : 271)
Fax : +91-33-2473-2805

On Thu, 7 Jun 2007, Anand Pandey wrote:

> Dear Dr. Rajasekharan,
> The bromination of Acetyl group can be done with bromine in
> chloroform/ethers as solvents in the presence/absence of lewis acid as
> catalyst(very little qty). The rate of addition of bromine should be
> very slow. You can also check the cross ref of phenacyl bromide.
> Hope! this will work.
> Regards
> ANAND PANDEY
>
> -----Original Message-----
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> Subject: Everybody Digest, Vol 35, Issue 5
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> Today's Topics:
>
> 1. bromination (kallikat rajasekharan)
> 2. Re: Neutralizing TLC plates? (will jones)
> 3. help (nanjundaswamy swamy marisetty)
> 4. Re: Neutralizing TLC plates? (Ohad Ilovich)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 5 Jun 2007 09:31:09 -0700 (PDT)
> From: kallikat rajasekharan <rajkn_1951$##$yahoo.com>
> Subject: ORGLIST: bromination
> To: orglist <everybody$##$orglist.net>
> Message-ID: <922952.40636.qm$##$web61124.mail.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> Hi all:
>
> I need to brominate the acetyl group of
> 4-acetyl-2,6-di-t-butylphenol
> [3,6-di-t-butyl-4-hydroxyacetophenone]. Tried bromine
> in ether with/without light or AlCl3 and also with
> CuIIBr2 in EtOAc. Only partial bromination. One
> russian patent mentions bromination at 120 oC in
> n-octane under light bulb. Any
> alternatives/suggestions?
> Thanks in advance
>
> KN Rajasekharan PhD
> Prof Chem
> Univ Kerala
>
>
>
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> ------------------------------
>
> Message: 2
> Date: Tue, 05 Jun 2007 17:18:04 +0000
> From: "will jones" <willjones46$##$hotmail.com>
> Subject: Re: ORGLIST: Neutralizing TLC plates?
> To: bvogel95$##$gmail.com, esprcorn$##$hotmail.com
> Cc: everybody$##$orglist.net
> Message-ID: <BAY132-F21CD8E65B3CE14604A824DAE200$##$phx.gbl>
> Content-Type: text/plain; format=flowed
>
> Brandon,
>
> You aren't a relation to the legend Vogel, who wrote the best practical
> organic chemistry book ever are you...?
>
> Will
>
>
>> From: "Brandon M. Vogel" <bvogel95$##$gmail.com>
>> To: Ken Knott <esprcorn$##$hotmail.com>
>> CC: everybody$##$orglist.net
>> Subject: Re: ORGLIST: Neutralizing TLC plates?
>> Date: Wed, 11 Apr 2007 23:12:11 -0400
>>
>> Ken Knott wrote:
>>> I have a compound that I think may be degrading on TLC plates due to
>>> the mild acidity.
>>>
>>> I would appreciate advice on how to neutralize TLC plates prior to
>>> running them. I understand that this can be done with a 1% solution
>>> of TEA in your eluent prior to running the compound? Can anyone
> offer
>>> any suggestions or advice on doing this?
>>>
>>> Also, how might I make myself more certain that I am in fact
>>> witnessing degradation of my compound as a result of running it on
> the
>>> TLC?
>>>
>>> Thanks in advance!
>>>
>>> Ken
>>>
>>>
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>> You may try passivating the TLC plate with hexamethyl disilazane (HMDS)
>> via a vapor treatment. This procedure will methylate the SiO2. Of
>> course, you will also have to functionalize your SiO2 if you run a
> column.
>>
>>
>> Brandon
>
>
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> ------------------------------
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> Message: 3
> Date: 6 Jun 2007 02:51:01 -0000
> From: "nanjundaswamy swamy marisetty" <jrchemist_1999$##$rediffmail.com>
> Subject: ORGLIST: help
> To: everybody$##$orglist.net
> Message-ID: <20070606025101.15133.qmail$##$webmail34.rediffmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear all,
> Please suggest me to reduce picric acid to 2,4,6-triamino phenol
> Thanks in advance,
> H M Nanjundaswamy
> PHI
> Bangalore?
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> Message: 4
> Date: Wed, 6 Jun 2007 07:20:07 +0200
> From: "Ohad Ilovich" <ilovich$##$pob.huji.ac.il>
> Subject: Re: ORGLIST: Neutralizing TLC plates?
> To: <everybody$##$orglist.net>
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>
> Great idea Jason
> I'll have to remember that trick for future use....
> btw i've seen people running the whole TLC with 1% TEA and no just
> washing the silica beforehand with it to keep their materials stable. it
> hampers the TLC visualization in some systems but it does work with acid
> sesitive materials
> Ohad
> ----- Original Message -----
> From: JASON SMITH
> To: everybody$##$orglist.net
> Sent: Tuesday, June 05, 2007 8:54 AM
> Subject: Re: ORGLIST: Neutralizing TLC plates?
>
>
> Stability on silica can be checked by running a 2D TLC:
>
> Using a square silica plate, spot the sample in one corner.
>
> ? Run the plate in one direction (all components of the sample will
> appear in a vertical line of spots).
>
> ? Turn the plate 90 degrees (your "line of spots" should be at the
> bottom) and run the plate again.
>
> ? If the sample is stable to silica, all spots will appear on the
> diagonal.
>
>
> -Jason
>
>
>
>
>
> ------------------------------------------------------------------------
> ------
>
>
> Ken Knott wrote:
> I have a compound that I think may be degrading on TLC plates due to
> the mild acidity.
>
> I would appreciate advice on how to neutralize TLC plates prior to
> running them. I understand that this can be done with a 1% solution of
> TEA in your eluent prior to running the compound? Can anyone offer any
> suggestions or advice on doing this?
>
> Also, how might I make myself more certain that I am in fact
> witnessing degradation of my compound as a result of running it on the
> TLC?
>
> Thanks in advance!
>
> Ken
>
>
> ------------------------------------------------------------------------
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> _______________________________________________
> ORGLIST - Organic Chemistry Mailing List
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> unsubscribe your_orglist_password your_addressYou may try passivating
> the TLC plate with hexamethyl disilazane (HMDS) via a vapor treatment.
> This procedure will methylate the SiO2. Of course, you will also have
> to functionalize your SiO2 if you run a column.
>
>
> Brandon
>
>
> ------------------------------------------------------------------------
> ------
>
>
> _______________________________________________
> ORGLIST - Organic Chemistry Mailing List
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