The hydrogen abstraction reaction CH2O+H→CHO+H2 was studied using ab initio calculation theory. The geometries of the reactants, transition state and products were optimized at QCISD/6-311G^** level. The forward and reverse reaction potential bariers were found to be 35.4 kJ/mol and 98.8 kJ/mol respetively. By analyzing the changes of the generalized normal -mode vibrational frequencies along the IRC, it was found that the C—H bond breaking and the H—H bond forming took place simultaneously. There is a reactive vibrational normal- mode which leads to the reaction process form the reactants to the products. At temperature ranging from 300 to 3 000K, the calculated forward and reverse reaction rate constants are consistent with the experimental values.

Key words: FORMALDEHYDE, AB INITIO CALCULATION, TRANSITION STATE THEORY, REACTION RATE CONSTANT