C-13 NMR relaxation study of molecular motions in tetraphenyltin and tetra(p-tolyl)tin in solution

MUN, LO KONG (2005) C-13 NMR relaxation study of molecular motions in tetraphenyltin and tetra(p-tolyl)tin in solution. Journal of Physical Chemistry A, 109.

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Abstract

The Woessner approach is applied to the 13C relaxation data for tetraphenyltin (1) and tetra(p-tolyl)tin (2) in CDCl3 solution over the temperature range 5-42oC to obtain correlation times for roatational motions and hence the activation barriers. Quantum mechanical computations were carried out to obtain the rotational energy barriers for comparsons. For 2 the relaxation data indicate (1) slower ring rotation than 1, (2) highly hindered internal rotation of the methyl group . IR and chemical shift data support the hypothesis of hyperconjugation of the methyl correclated with interaction between the pi-electrons and the 5d orbitals of the tin in the (p-tolyl)Sn mioety to account for the hindrances to the rotations of the ring and the methyl. The activation barrier for the tolyl group rotation is found to be much higher than that for thephenyl rotation. However, the Woessner approach yields an anomalously high barrier for the methyl rotation. An explanation based on correlated rotations of the tolyl ring and the methyl is offered.

Item Type: Article
Uncontrolled Keywords: NMR, relaxation study
Subjects: Q Science
Depositing User: MR. ADNAN YAHYA
Date Deposited: 17 Apr 2015
Last Modified: 17 Apr 2015
URI: http://repository.um.edu.my/id/eprint/99183

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