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selenol
Selenols are organic compounds that contain the functional group with the connectivity C–Se–H. Selenols are sometimes also called selenomercaptans and selenothiols. Selenols are one of the principal classes of organoselenium compounds. The best known member is the amino acid selenocysteine.
==Structure, bonding, properties==
Selenols are structurally similar to thiols, but the C-Se bond is about 8% longer at 196 pm. The C–Se–H angle approaches 90° as it does in hydrogen selenide (H2Se). The bonding involves almost pure p-orbitals on Se, hence the near 90 angles. The Se–H bond energy is weaker than the S–H bond, consequently selenols are easily oxidized and serve as H-atom donors. Also reflecting the relative weakness of bonds to Se, selenols are about 1000x stronger acids than are thiols: the pKa of CH3SeH is 5.2 vs 8.3 for CH3SH. Deprotonation affords the selenolate anion, RSe−, most examples of which are highly nucleophilic and rapidly oxidized by air.〔Wessjohann, L.A.; Schneider, A.; Abbas, M.; Brandt, W. "Selenium in Chemistry and Biochemistry in Comparison to Sulfur" Biol. Chem., Vol. 388, pp. 997–1006, 2007. 〕
The boiling points of selenols tend to be slightly greater than for thiols owing to the increased importance of van der Waals bonding, which is stronger for larger atoms. Volatile selenols have highly offensive odors.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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