Sir:Solvolysis studies' and PRDDO calculations2 both show that cyano groups destabilize an a cation less than a p cation. This (17) Sir: Numerous calculations of the energy spacing separating the lowest singlet and triplet states of carbenes have been reported.'In contrast, almost no quantitative experimental information is available concerning the dynamics of interconversion or the energetic separation of the triplet and singlet states of carbenes, although many investigations of the products arising selectively from one of the two spin states have appeared. From competition experiments and kinetic analysis of the reactions of diphenylcarbene (DPC), it has been suggested that singlet diphenylcarbene (1) (a) Harrison, J. F.; Liedtke, R. C.; Liebman, J. F.
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