Main characters of the potential energy surface of brocarbenoids H2CMBr(M=Na,K) have been studied by RHF/3-21G^* gradient method. Three equilibrium structures and two isomerization transition states are located. The electron correlation energies have been calculated at the second-order (MP2) perturbation theory and harmonic vibrational frequencies have also been executed. Energies of the equilibrium states are in the order of 1 (three-membered ring form)<3(p-complex)<2(σ-complex). 1 is predicted to be the form in which H2C MBr exists and takes part in reactions. The Mulliken populations and zero-point energies are also given.

Key words: STABILITY, CARBENE, AB INITIO CALCULATION, STRUCTURE, GEOMETRICAL ISOMERISM