| Abstract
| - Proton abstraction from acetaldehyde by the first- andsecond-row hydride anions NH2-,OH-, F-,SiH3-,PH2-, and SH- have beeninvestigated with ab initio quantum mechanical calculationsup to the MP2/6-31+G**//HF/6-31+G* and MP2/6-311+G**//MP2/6-31+G* level.Progress of energies, geometric variables,and charge distributions along the reaction coordinate have beeninvestigated by employing the intrinsic reactioncoordinate method. These computations revealed that protonabstractions occur in three essentially separatesteps. The main difference between the first- and second-rowhydrides is that the carbon, which donatesproton in the reaction, changes hybridization from sp3 tosp2 later in the reaction coordinate in the case ofthefirst-row systems. Consequently, the flow of negative charge fromthe CH2 to CHO end of the developingenolate anion is retarded more in the case of the first-row hydrides.The results showed that the protonabstractions by the first-row hydride anions have more imbalancedtransition states than the second-row hydrideanions.
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