From owner-chemistry@ccl.net Tue Oct 25 18:27:00 2011 From: "Bruce Palfey brupalf~~umich.edu" To: CCL Subject: CCL: o-hydroquinone to o-quinone reaction mechanism Message-Id: <-45744-111025175837-31732-o2me5X82r6JwgOxWqD42tA{}server.ccl.net> X-Original-From: Bruce Palfey Content-Type: multipart/alternative; boundary=Apple-Mail-136--177205704 Date: Tue, 25 Oct 2011 17:58:14 -0400 Mime-Version: 1.0 (Apple Message framework v1084) Sent to CCL by: Bruce Palfey [brupalf(0)umich.edu] --Apple-Mail-136--177205704 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Generally, O2 (a triplet) reacts with singlet organics by an initial = single-electron transfer, forming a solvent-caged superoxide-organic = radical pair. Depending on relative rates of the possible processes, a = second electron transfer, coupled to proton transfer (s) could occur, = giving the oxidized organic and H2O2. Or, the radical intermediate = could couple, forming a peroxide which is protonated to the = hydroperoxide. Depending on the organic moiety (like an o-quinone), = that could eliminate H2O2 leaving the unsaturated organic. Or, the = radical pair could separate by diffusion, and these radicals could = oxidize the reduced organic (SET again) in a chain reaction. Another = link in a chain reaction could be the the reaction of oxidized and = reduced organic to form to radicals - especially possible with quinones. = I don't know if the specifics of what actually occurs have been = addressed for o-quinones; the relative rates of these possible reactions = are likely to depend on the reduction potentials (which will vary with = substituents) and solvent. ciao, Bruce Bruce A. Palfey Associate Professor of Biological Chemistry & Associate Director, Program in Chemical Biology Department of Biological Chemistry University of Michigan Medical School 5220E MSRB III 1150 W. Medical Center Drive Ann Arbor, MI 48109-0606 (734) 615-2452 brupalf*umich.edu http://www.biochem.med.umich.edu/?q=3Dpalfey http://www.chembio.umich.edu/people/palfey.html On Oct 25, 2011, at 5:15 PM, Tapas Kar tapas.kar||usu.edu wrote: >=20 > Sent to CCL by: "Tapas Kar" [tapas.kar()usu.edu] > Hello, >=20 > I am looking for o-hydroquinone to o-quinone reaction mechanism in = O2/H2O. I checked literature but could not found any paper describing = step-by-step reaction mechanism and kinetics. Is there any = theoretical/computation study reported on this reaction? I am interested = to know how this reaction takes place I guess some oxygen based radical = is involved but what kind? Is singlet O2 or triplet O2 facilitated the = reaction?=20 >=20 >=20 > Thanks >=20 > TK >=20 >=20 >=20 > -=3D This is automatically added to each message by the mailing script = =3D- > To recover the email address of the author of the message, please = change>=20>=20>=20 > Subscribe/Unsubscribe:=20>=20>=20 > Job: http://www.ccl.net/jobs=20 > Conferences: = http://server.ccl.net/chemistry/announcements/conferences/ >=20>=20>=20>=20 >=20 >=20 >=20 --Apple-Mail-136--177205704 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii
Bruce A. Palfey
Associate Professor of = Biological Chemistry &
Associate Director, Program in = Chemical Biology
Department of Biological Chemistry
University of = Michigan Medical School
5220E MSRB III
1150 W. Medical Center = Drive
Ann Arbor, MI 48109-0606
(734) 615-2452
brupalf*umich.edu

http://www.biochem.m= ed.umich.edu/?q=3Dpalfey
http://www.chembi= o.umich.edu/people/palfey.html


On = Oct 25, 2011, at 5:15 PM, Tapas Kar tapas.kar||usu.edu wrote:


Sent to CCL by: "Tapas  Kar" = [tapas.kar()usu.edu]
Hello,

I am looking for o-hydroquinone to = o-quinone reaction mechanism in O2/H2O. I checked literature but could = not found any paper describing step-by-step reaction mechanism and = kinetics. Is there any theoretical/computation study reported on this = reaction? I am interested to know how this reaction takes place  I = guess some oxygen based radical is involved but what kind? Is singlet O2 = or triplet O2 facilitated the reaction? =


Thanks

TK



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