An ab initio study of the [C2H5O-] potential energy surface and the fragmentation pathways of the ethoxide anion

The [C2H5O-] potential energy surface has been investigated with a modified Gaussian-2 methodology, the C2++ approximation. Eight stable [C2H5O-] isom ers have been found on the surface: CH3CH2O- (1-), W-CH3CHOH- (2(-)), Y-CH3 CHOH- (3(-)), Y-CH2OCH3- (4(-)), W-CH2OCH3- (5(-)), ZE-CH2CH2OH-(6(-)), EE- CH2CH2OH- (7(-)), and EZ-CH2CH2OH- (8(-)). Among these isomers, 1- is the m ost stable thermodynamically. The calculated G2++ heats of formation for th e isomeric anions are in very good accord with the available experimental d ata. Also studied with the same ab initio method are the various rearrangem ents among the eight isomers and the fragmentation pathways of 1(-). Among the reactions involving 1(-), the fragmentation process 1(-) --> H-2 + CH2C HO- has the least barrier. This result is in total agreement with the exper imental collision activated dissociation and infrared multiple photon induc ed elimination studies of the ethoxide anion.