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Density functional theory calculations were employed to quantify the effect of hydrogen bonding interactions in the reactions involving cleavage of dichalcogenides in cystines and selenocystines. The computed gas phase reaction has a multistep mechanism involving hydrogen bond transfers from one heteroatom to another across the reaction coordinate along with the anionic charge transfer from the nucleophile to the product. The solution phase mechanism, however, is simple SN2 irrespective of the nature of the reaction centre or hydrogen bonding interaction at the reaction site, or the nucleophile. When compared to similar reactions without any hydrogen bonding interactions at the reaction centre, these were found to be very facile both in gas phase as well as in aqueous solution. |
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