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Oxygen versus sulfur: Structure and reactivity of substituted arsine oxides and arsine sulfides
Author(s) -
Orthaber Andreas,
Sax Alexander F.,
Francesconi Kevin A.
Publication year - 2011
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.21950
Subject(s) - arsine , chemistry , reactivity (psychology) , density functional theory , trigonal bipyramidal molecular geometry , computational chemistry , inorganic chemistry , medicinal chemistry , photochemistry , crystallography , catalysis , organic chemistry , crystal structure , medicine , alternative medicine , pathology , phosphine
Although arsenic in its inorganic forms is a well know toxic agent, biotransformations in the environment and in the human body can produce organoarsenic compounds that are generally of much lower toxicity. Foremost among these products is a range of dimethylated arsine oxides and their analogous sulfides, which are crucial to the arsenic detoxification process. We have investigated the formation and interconversion of substituted and unsubstituted arsenicals (R 2 2 As(Z)R 1 , R 2 = CH 3 , R 1 = CH 2 CH 2 OH, CH 2 COOH; Z = S or O) with density functional theory (DFT)/B3LYP. Formation of isomers including a cyclic hydrogen bonded conformer is observed for the ethanol and acetate derivatives. Furthermore, investigating the reaction of arsine oxide with hydrogen sulfide revealed the formation of arsine sulfide via pentacoordinated trigonal bipyramidal intermediates. A tetragonal pyramidal transition state was located enabling exchange of equatorial and axial positions in the trigonal bipyramidal species. The reaction was proven exothermic for all studied substituents (Δ E rxn −50 to −80 kJ/mol). This fundamental study shows that H 2 S easily leads to the formation of thio‐organoarsenicals. Conversion of arsine sulfides into their corresponding arsine oxides is experimentally accomplished with hydrogen peroxide, which could also be rationalized by means of ab initio calculations showing high exothermicity (Δ E rxn ca. −550 kJ/mol). Reactions are considered at different levels of theory (i.e., DFT, second and fourth order Møller–Plesset (MP) perturbation theory) including two solvation models for DFT, which show good agreement for resulting geometries and reaction energies. Hence, the widely used B3LYP/6‐31G** combination is a suitable method for the description of molecular organoarsenicals. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011