title: Selenium and sulfur in exchange reactions: a comparative study.
abstract: Cysteamine reduces selenocystamine to form hemiselenocystamine and then cystamine. The rate constants are k(1) = 1.3 × 10(5) M(-1) s(-1); k(-1) = 2.6 × 10(7) M(-1) s(-1); k(2) = 11 M(-1) s(-1); and k(-2) = 1.4 × 10(3) M(-1) s(-1), respectively. Rate constants for reactions of cysteine/selenocystine are similar. Reaction rates of selenium as a nucleophile and as an electrophile are 2-3 and 4 orders of magnitude higher, respectively, than those of sulfur. Sulfides and selenides are comparable as leaving groups.
authors.affiliation: Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, 8093 Zürich, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Steinmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Nauser
authors.forename: Willem H
authors.initials: WH
authors.lastname: Koppenol
mesh_terms: D003538:Cystamine / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000737:chemistry; D003543:Cysteamine / Q000737:chemistry*; D015394:Molecular Structure; D012643:Selenium / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry*
chemical_list: D003543:Cysteamine; D013455:Sulfur; D012643:Selenium; D003538:Cystamine