Infrared spectra and theoretical study of the conformations of substituted benzoylketene-S,S-acetals

摘要

The C=O stretching frequencies of substituted benzoylketene-S,S-dimethylacetals (1a–1o) and benzoylketene-S,S-ethyleneacetals (2a–2m) were measured in CHCl3and CCl4and correlated with theHammettsubstituent constants. The correlations were split into two different and well separated lines for compounds containing electron donor and electron acceptor substituents, which were assigned tos-transands-cisquasiplanar conformations. The correlations of carbonyl stretching frequencies with C=O bond orders and oxygen atom charge densities calculated using the semiempirical AM1 method reveal similar results consistent with assignments of structures1and2to two quasiplanar conformations. The preparation of some new benzoylketene-S,S-acetals is reported as w