Formation of Van Der Waals Complexes in Concerted Unimolecular Elimination Processes. (9th April 2012)

• Record Type: Journal Article
• Authors: Dubnikova, Faina; Lifshitz, Assa
• Other Names: Koster A. M. Academic Editor.; Sasaki S. Academic Editor.
• Is Part Of: ISRN physical chemistry. Volume 2012(2012)
• Publication Date: 2012-04-09
• Subjects: Chemistry, Physical and theoretical -- Periodicals; Chemistry, Physical and theoretical; 35.10 physical chemistry: general; Periodicals; Electronic journals; 541
• DOI: 10.5402/2012/431367
• Languages: English
• ISSNs: 2090-7761

Abstract

Abstract : Potential energy surfaces for three unimolecular elimination reactions: ( CH 3 ) 3 C – OH → ( CH 3 ) 3 = C = CH 2 + H 2 O, CH 3 – CF 3 → CH 2 = CF 2 + HF, and CH 3 – CH 2 – CH 2 C 1 → CH 3 – CH = CH 2 + HC 1 were calculated using a variety of quantum chemical methods. It was shown that, in all the three cases, the transition state in the first step of the reaction leads to the production of the complex intermediates based on van der Waals interactions. In addition to the fact that the three complexes appear as intermediates on the potential energy surfaces, which means that they are not free entities, the entropy values of the two elimination products are far above those of the complexes due to their additional Sackur-Tetrode entropy. Moreover, the three vibrational frequencies of the H2 O group in the (CH3 )3 COH complex and the H–Cl and H–F stretch frequencies in CH3 CF3 and CH3 CH2 CH2 Cl are quite different (see the various tables). The energy levels of the complexes were found to be below those of the corresponding decomposition products. Rate constants for the elimination processes were calculated from the potential energy surfaces using transition-state theory and were compared to available experimental data.