Ionization and Dissociation of Formate Esters by Electron Impact

The mass spectra of methyl formate-d, ethyl formate-d, and isopropyl formate-d are compared with the mass spectra of the undeuterated compounds. By use of the deuterium labelling and appearance potential studies the dissociation reactions leading to a number of the oxygen-containing ions have been elucidated. The proton affinity of formic acid is estimated to be 157 kcal/mole from the appearance potential of the HC(OH) 2 + ion in the mass spectra of ethyl formate and isopropyl formate.