Absolute proton affinity and basicity of the carbenes CH2, CF2, CCl2, C(OH)2, FCOH, CPh2 and fluorenylidene

Abstract

Ab initio molecular orbital calculations were performed in order to determine the absolute proton affinity and basicity of some carbenes. For the species CH 2 , CF 2 , CCl 2 C(OH) 2 , and FCOH, the G2(MP2) method was utilized, and we have obtained the values 207.0, 177.4, 209.6, 217.3 and 199.9 kcal mol -1 , respectively, for the absolute proton affinities. For CPh 2 and fluorenylidene the calculation was performed at the HF/DZ+(P)//HF/DZ and MP2/DZ//HF/DZ levels of theory. For CPh 2 we have obtained an absolute proton affinity of 275.0 kcal mol -1 and, for fluorenylidene, the value is 272.4 kcal mol -1 . The implication of these results for the carbene reaction mechanism with OH groups is discussed.