HEAT OF FORMATION OF CH2OH AND D0(H-CH2OH)

The appearance potential (AP) of CH2OH+ from CH3OH has been reexamined by photoionization mass spectrometry, using higher resolution, better statistics, and a more extensive analysis. The result, AP(CH2-OH+/CH3OH) = 11.649 +/- 0.003 eV, when combined with IP(CH2OH) = 7.549 +/- 0.006 eV, yields D0(H-CH2OH) = 395.6 +/- 0.6 kJ/mol. Other quantities which can be derived from this value include D298, DELTAH(f)-degrees (CH2OH) at 0 and 298 K and the proton affinity of CH2O. A prior thermochemically deduced value for DELTAH(f)degrees 298 (CH2OH) is corrected, utilizing a hindered rotor in calculating S-degrees298(CH2OH). The revised value, DELTAH(f)degrees 298 (CH2OH) = -12.2 +/- 1.7 kJ/mol, still differs from the present value, -16.6 +/- 0.9 kJ/mol, but a recent high-quality ab initio calculation is in good agreement with the present result.