Showing papers by "Kwang S. Kim published in 1981"
TL;DR: In this paper, a systematic theoretical study of the ion isomerization H{sub 2}CO{sup +} {yields} HCOH{sup+} has been carried out at the double zeta basis set self-consistent field level.
Abstract: Motivated by the recent experiments of Berkowitz, a systematic theoretical study of the ion isomerization H{sub 2}CO{sup +} {yields} HCOH{sup +} has been carried out. Structures and vibrational frequencies for H{sub 2}CO{sup +}, the transition state, and the cis and trans isomers of HCOH{sup +} have been determined at the double zeta basis set self-consistent-field (SCF) level of theory. Equilibrium geometries were also predicted from SCF theory using a double zeta plus polarization (DZ+P) basis set. Final energetics were pinned down using DZ+P configuration interaction, involving a total of 16,290 configurations. The most reliable theoretical results suggest that trans-HCOH{sup +} lies 5.5 kcal above H{sub 2}CO{sup +}. Zero-point vibrational energy corrections do not change this H{sub 2}CO{sup +}-HCOH{sup +} separation. Similarly cis-HCOH{sup +} is predicted to lie 4.1 kcal above the trans isomer, and the barrier to rotation between the two HCOH{sup +} isomers is -18 kcal. The barrier to H{sub 2}CO{sup +} {yields} HCOH{sup +} rearrangement is predicted to be 49.0 kcal, or 44.4 kcal after correction for zero-point vibrational energies is made. The relationship between this cationic 1,2-hydrogen shift and the corresponding neutral rearrangement is discussed in terms of qualitative molecular orbital theory.
35 citations
TL;DR: In this article, a systematic theoretical study of the ion isomerization H{sub 2}CO{sup +} {yields} HCOH{sup+} has been carried out at the double zeta basis set self-consistent field level.
Abstract: Motivated by the recent experiments of Berkowitz, a systematic theoretical study of the ion isomerization H{sub 2}CO{sup +} {yields} HCOH{sup +} has been carried out. Structures and vibrational frequencies for H{sub 2}CO{sup +}, the transition state, and the cis and trans isomers of HCOH{sup +} have been determined at the double zeta basis set self-consistent-field (SCF) level of theory. Equilibrium geometries were also predicted from SCF theory using a double zeta plus polarization (DZ+P) basis set. Final energetics were pinned down using DZ+P configuration interaction, involving a total of 16,290 configurations. The most reliable theoretical results suggest that trans-HCOH{sup +} lies 5.5 kcal above H{sub 2}CO{sup +}. Zero-point vibrational energy corrections do not change this H{sub 2}CO{sup +}-HCOH{sup +} separation. Similarly cis-HCOH{sup +} is predicted to lie 4.1 kcal above the trans isomer, and the barrier to rotation between the two HCOH{sup +} isomers is -18 kcal. The barrier to H{sub 2}CO{sup +} {yields} HCOH{sup +} rearrangement is predicted to be 49.0 kcal, or 44.4 kcal after correction for zero-point vibrational energies is made. The relationship between this cationic 1,2-hydrogen shift and the corresponding neutral rearrangement is discussed in terms of qualitative molecular orbital theory.