From: Merlin (medchem$##$home.com)
Date: Wed Apr 28 1999 - 18:40:54 EDT
As promised, I have within my oroginal query as well as six repsonses,
in regards a mention of CH3CN.
These are attached (and hopefully) in order of submission/reply.
They should be readable.
Cheers!
Merlin
Subject: A few queries
Date: Wed, 17 Mar 1999 00:23:39 -0500
From: Merlin <medchem$##$home.com>
Organization: Merlin's Laboratory
To: ACS Medicinal Chemistry Discussion Group <ACSMEDI$##$LISTS.WAYNE.EDU>,
Natural Products Discussion Group <napronet$##$bilkent.edu.tr>,
Organic Chemistry Discussion Group <orgchem$##$gwup.org>,
Organic Chemistry Discussion Group #2 <orglist$##$dq.fct.unl.pt>
Hello there! A few more queries...
1. Is it possible for pyridine to pull of a deuterium atom from a
deuterated cyclohexane (d6 species) if the solution is heated at reflux
for 15-18 hours?
2. Would acetonitrile be a suitable substitute for pyridine to avoid
given the circumstance above?
3. This one is off-the-wall: is there a reaction that involves the
usage of ZnSO4 and 4N BaOH? This came across to me for the separation
of lipids from raw plasma. I'm inclined to believe that it may go by
the name of (or sound like) "Shimogi". Any information concerning this
query would be VERY helpful.
As always, thank you ALL in advance.
Cheers!
--
George D. 'Merlin' McCallion, Research Chemist
Division of Metabolism
The Children's Hospital of Philadelphia
Post Office Box 143
Bala-Cynwyd, PA 19004-0143
Office: 1.215.590.6894
Fax: 1.215.590.3364
Email: medchem$##$home.com
Subject: Re: A few queries
Date: Wed, 17 Mar 1999 01:23:31 -0500 (EST)
From: Vassile$##$AOL.COM
Reply-To: orgchem$##$gwup.org
To: orgchem$##$gwup.org
1) Yes, Although the equilibrium is very unfavorable, There will be
significant exchange after 15-18 hrs. Your cyclohexane will become
protonated
unless of course it's in great excess and then you won't have a problem.
2)acetonitrile is a bit of a weaker base than pyridine but I doubt it would
eliminate the problem.
Best wishes,
Vassil
Subject: Re: A few queries
Date: Wed, 17 Mar 1999 07:54:43 +0100
From: "Le Thanh Giang" <giang.szk$##$chem.bme.hu>
Reply-To: orgchem$##$gwup.org
To: orgchem$##$gwup.org
Dear George D.,
It seems impossible for pyridine to pull of a deuterium atom from
cyclohexane-d6 due to its weak acidity.
Acetonitrile is enough strong acid to exchange hidrogen atom, but you
have to supply proton source.
Best regards.
GLT
Subject: Re: A few queries
Date: Wed, 17 Mar 1999 11:00:36 +0200
From: qogatojo$##$usc.es (Gabriel Tojo)
Reply-To: orgchem$##$gwup.org
To: orgchem$##$gwup.org
>1) Yes, Although the equilibrium is very unfavorable, There will be
>significant exchange after 15-18 hrs. Your cyclohexane will become
protonated
>unless of course it's in great excess and then you won't have a problem.
The pKa of pyridinium is 5.2.
The pKa of cyclohexane is about 50!! In fact, its acidity is so low that
there is no way to measure it in a direct way.
There is a difference of pKa units of about 45. It means that on contact
with pyridine you will have about one deprotonated cyclohexane molecule in
10 to the 45.
We would have about one deprotonated cyclohexane molecule in 10.000.000.000
millions of tons of cyclohexane.
With such an unfavorable equilibrium, I do not see easy kinetics.
The experimental fact must be checked.
Best regards
Gabriel Tojo
Profesor Titular de Quimica Organica
Department of Organic Chemistry
Faculty of Chemistry
Royal University of Santiago de Compostela
E-15706 Santiago de Compostela
SPAIN
Tel +34(9)81/563100 ext. 14244; 989-912733
Fax +34(9)81/595012
Subject: RE: ORGLIST: A few queries
Date: Wed, 17 Mar 1999 8:26:13 -0600
From: CHEMISTRY <GMCHEM$##$VAX1.BEMIDJI.MSUS.EDU>
To: medchem$##$home.com
CC: GMCHEM$##$VAX1.BEMIDJI.MSUS.EDU
You wrote:
>1. Is it possible for pyridine to pull of a deuterium atom from a
deuterated cyclohexane (d6 species) if the solution is heated at reflux
for 15-18 hours?
The only way this would be energetically possible would
be as a photo-reaction. It might work with visible light, if
there were a sensitizer present. Pyridine, like other amines,
is hard to get very dry; hence, water may play a role here.
Commercially-available deuterated solvents are sometimes
impure. I would expect some cyclohexene; have you checked
the solvent by Gc-MS or GC or even UV-spectroscopy?
>2. Would acetonitrile be a suitable substitute for pyridine to avoid
given the circumstance above?
It is hard to tell since you gave so few details about
what you are actually trying to do. Is it possible
a less toxic solvent would do - THF or an alcohol?
Hope this helps,
Gerald Morine
Bemidji State University
gmchem$##$vax1.bemidji.msus.edu
Subject: Re: ORGLIST: A few queries
Date: Tue, 16 Mar 1999 21:25:30 -0500
From: "Dr. Suitcase" <drsuit$##$cdt.infi.net>
Organization: InfiNet
To: medchem$##$home.com
Merlin wrote:
>
> Hello there! A few more queries...
>
> 1. Is it possible for pyridine to pull of a deuterium atom from a
> deuterated cyclohexane (d6 species) if the solution is heated at reflux
> for 15-18 hours?
The equilibrium would be possible, but the rate of exchange would be
vanishlingly small. Just take a look at the pKa for the protons in
cyclohexane and for protonated pyridine!
> 2. Would acetonitrile be a suitable substitute for pyridine to avoid
> given the circumstance above?
The pKa for protonated acetonitrile would be even less than for
pyridine.
> 3. This one is off-the-wall: is there a reaction that involves the
> usage of ZnSO4 and 4N BaOH? This came across to me for the separation
> of lipids from raw plasma. I'm inclined to believe that it may go by
> the name of (or sound like) "Shimogi". Any information concerning this
> query would be VERY helpful.
Never heard of it, but then my training is not exactly in the arena of
biochemistry. Us traditional synthetic organic chemists rarely
encounter "raw plasma", except by accident.
Unless you are talking the kind of "plasma" that high-energy physicists
play in. And I doubt it!!
Good luck in your quest.
The mad scientists rule the chicken koop!
Dr. Suitcase
Subject: Re: ORGLIST: A few queries
Date: Sun, 21 Mar 1999 23:49:42 -0500
From: Merlin <medchem$##$home.com>
Organization: Merlin's Laboratory
To: drsuit$##$cdt.infi.net
"Dr. Suitcase" wrote:
> Never heard of it, but then my training is not exactly in the arena of
> biochemistry. Us traditional synthetic organic chemists rarely
> encounter "raw plasma", except by accident.
My primary work in college has been synthesizing natural products. I
was placed in this line because they were (apparently) looking for a
bench chemist to do wet, analytical work. Funny how these guys couldn't
walk a few hundred feet to UPenn's Chem., Bio., and Med. School. they
have been sitting on this project for a stupid 3 years.
> The mad scientists rule the chicken koop!
Hence why I was given the nickname 'Merlin'
Cheers!
--
George D. 'Merlin' McCallion, Research Chemist
Division of Metabolism
The Children's Hospital of Philadelphia
Post Office Box 143
Bala-Cynwyd, PA 19004-0143
Office: 1.215.590.6894
Fax: 1.215.590.3364
Email: medchem$##$home.com
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