Naslov
Formation and Redox Reactions of Some S-N and Se-N Three-electron-bonded Intermediates

Autori
Asmus, Klaus-Dieter ; Bonifačić, Marija

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Book of Abstracts / Glas, R.L. - Flagstaff (AZ) : Northern Arizona University, 2002, 52-52

Skup
20th International Symposium on the Organic Chemistry of Sulfur

Mjesto i datum
Flagstaff (AZ), Sjedinjene Američke Države, 14.07.2002. - 20.07.2002

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
free radicals; redox reactions

Sažetak
Selenomethionine oxide (MetSeO) can be reduced faster and more efficiently than its sulfur analogue, methionine sulfoxide. This has been quantified by time-resolved pulse radiolysis experiments.1 MetSeO reacts with one-electron reductants, such as eaq- (k = 1.2×1010 M-1 s-1), CO2&middot ; - (k= 5.9×108 M&#8211 ; 1 s&#8211 ; 1) and (CH3)2C&middot ; OH (k =3.5×107 M&#8211 ; 1 s&#8211 ; 1) forming a transient selenium-nitrogen coupled zwitterionic radical with the positive charge at an intramolecularly formed Se\N 2s/1s* three-electron bond. The latter is characterized by an optical absorption with lmax 375 nm, and a half-life of about 70 ms. A corresponding transient with a S\N 2s/1s* three-electron can be expected upon reduction of methionineoxide. However, the MetSO reduction is too slow and the follow-up reaction too fast for experimental verification. The Se\N and S\N radical species are, however, easily generated upon &middot ; OH or N3&middot ; radical-induced oxidation of selenomethionine (MetSe) and methionine (MetS), respectively. In contrast to the selenium analogue the S\N radical derived from methionine has only a very short lifetime (t1/2 &#8776 ; 200 ns). The lifetimes of Met(Se\N) and Met(S\N) are controlled by decarboxylation of these species. The three-electron bonded radicals constitute the one-electron redox intermediate between the two oxidation states, MetSeO/MetSO and MetSe/MetS. As shown for a number of S\N transient radicals from various organic sulfides, these species exhibit both reducing as well as oxidizing properties. By comparison, the S\N species are, however, the slightly better oxidants (weaker reductants) than the Se\N species.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA