Molecular Structure of 9-Chloromethyl-1,4-dimethoxytriptycene and Its Implications for the Presence of O···CH2C1 Interactions

Publisher Website
Google Scholar
Abstract
Changing the substituent at the 4-position of 9-chloromethyl-1-methoxytriptycene shows that the nitro group increases the sc conformation whereas the methoxyl group favors the ap conformation in a relative sense, as judged from the 1H NMR spectra at low temperatures. Examination of rotational barriers, solvent effects, and thermodynamic parameters has not been able to distinguish three possibilities, O···CH2Cl interactions, head-to-tail arrangement of two dipoles, and van der Waals repulsions as a main cause for the observed population change. X-Ray crystallographic analyses of the title compound and related ones suggest that in the crystalline state the 1-methoxyl group in the title compound takes an anomalous conformation in which the group is nonplanar with the benzeno bridge. This feature was not observed in 1,4-dimethoxy-9-methyltriptycene. This structural feature is attibuted to the presence of O···CH2Cl interactions in the title compound and eliminates the van der Waals repulsion and the head-to-tail arrangement of two dipoles from being the main cause that favors the ap form.

This publication has 20 references indexed in Scilit: