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Crystal and molecular structures of dimesitylketene and bis(3,5‐dibromo‐2,4,6‐trimethylphenyl)ketene. Intrinsic torsional angles and buttressing effects in 1,1‐dimesitylvinyl propellers
Author(s) -
Biali Silvio E.,
Gozin Michael,
Rappoport Zvi
Publication year - 1989
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610020310
Subject(s) - chemistry , ketene , allene , molecule , aryl , crystal (programming language) , propeller , crystallography , crystal structure , stereochemistry , molecular mechanics , computational chemistry , medicinal chemistry , organic chemistry , alkyl , marine engineering , computer science , engineering , programming language , catalysis
The crystal and molecular structures of dimesitylketene (1) and bis(3,5‐dibromo‐2,4,6‐trimethylphenyl)ketene (2), the first free ketenes to be studied by X‐ray diffraction, have been determined. The molecules of 1 and 2 have crystallographic C 1 and C 2 symmetry, respectively, and exist in a propeller conformation. Molecular mechanics calculations of 1 and 2 using a modification of Allinger's new allene parameters reproduce satisfactorily the structural parameters of the ketenes. The torsional angles of the aryl rings in 1 and 2 are similar ( ca. 50°) and are regarded as ‘intrinsic’ values for a 1,1‐dimesitylvinyl propeller. From the similarity in aryl torsional angles in 1 and 2 it is concluded that the buttressing effects in 2 (if any) are not markedly manifested in the structural parameters of 2 .