In the molecule CH3COOH acetic acid , the central atom is the carbon atom in the carboxyl group COOH . To determine the hybridization of this carbon atom, we need to consider its electron domains.The central carbon atom in the COOH group is bonded to three other atoms: one oxygen atom in a double bond, one oxygen atom in a single bond, and one hydrogen atom in a single bond. This gives the central carbon atom a total of three electron domains.According to the VSEPR theory, three electron domains correspond to sp2 hybridization. Therefore, the hybridization of the central carbon atom in the molecule CH3COOH is sp2.