Singlet and triplet free energy surfaces for the reactions of C atom (P-3 and D-1) with CH2O are studied computationally to evaluate the excited singlet (B-1(1)) methylene formation from deoxygenation of CH2O by C (D-1) atom as suggested by Shevlin et al. Carbon atoms can react by addition to the oxygen lone pair or to the C=O double bond on both the triplet and singlet surfaces. Triplet C (P-3) atoms will deoxygenate to give CO plus CH2 (B-3(1)) as the major products, while singlet C (D-1) reactions will form ketene and CO plus CH2 ((1)A(1)). No definitive evidence of the formation of excited singlet ( 1B1) methylene was found on the singlet free energy surface. A conical intersection between the (1)A' and (1)A'' surfaces located near an exit channel may play a role in product formation. The suggested 1B1 state of methylene may form via the (1)A'' surface only if dynamic effects are important. In an effort to interpret experimental observation of products trapped by (Z)-2-butene, formation of cis- and trans-1,2-dimethylcyclopropane is studied computationally. The results suggests that "hot" ketene may react with (Z)-2-butene nonstereospecifically.