Analytical gradient optimizations were carried out using Gaussian 92 program at MP2/6-31+G^* level for equilibrium structures and transition states of CH~2=C(OH)Na. Four structures were reported. Structure 1 with a deflection three-member ring is the most stable one, and will be dominant in existence. Structure 4 is the reaction intermediate for H~2C=C(OH)Na to serve as acyl anion equivalent. When H~2C=C(OH)Na reacts as a carbenoid, it will have a transition state like structure 2. Compared with CH~2=C(OH)Li, CH~2=C(OH)Na is easier to serve as acyl anion equivalent, but more difficult to react as carbenoid.

Key words: ACYL GROUP, ANION, CARBENOID, AB INITIO CALCULATION, ISOMERIZATION, CONFIGURATION, REVERSE, POLARITY, NUCLEOPHILIC REACTION