Erratum : Ionization energy of methylene revisited : improved values for the enthalpy of formation of CH{sub 2} and the bond dissociation Energy of CH{3} via simultaneous solution of the local thermochemical network

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 1999-01, Vol.103A (1999)
• Main Authors: Ruscic, B., Litorja, M., Asher, R., Chemistry
• Format: Article
• Language: English
• Subjects: DATA; DISSOCIATION ENERGY; FORMATION HEAT; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IONIZATION POTENTIAL; METHYLENE RADICALS; THERMODYNAMICS
• ISSN: 1089-5639; 1520-5215

The appearance energy of the CH{sub 2}{sup +} fragment from CH{sub 2}CO has been carefully remeasured and fitted by a model curve, producing EA{sub 0}(CH{sub 2}{sup +}/CH{sub 2}CO) = 13.743 {+-} 0.005 eV. This value can be sequentially propagated through selected thermochemical cycles to yield individual values for El(CH{sub 2}), D{sub 0}(H-CH{sub 2}), {Delta}H{sup o}{sub f 0}(CH{sub 2}CO). A set of values with a statistically larger weight is produced by analyzing a local thermochemical network, which combines the present measurement with thirteen other experimental determinations from the literature and encompasses the enthalpies of formation of CH{sub 3}, CH{sub 3}{sup +}, CH{sub 2}, CH{sub 2}{sup +}, and CH{sub 2}CO. The recommended simultaneously adjusted thermochemical values are: {Delta}H{sup o}{sub f 0}(CH{sub 3}) = 35.86 {+-} 0.07 kcal/mol (35.05 {+-} 0.07 kcal/mol at 298 K), {Delta}H{sup o}{sub f 0}(CH{sub 3}{sup +}) = 262.73 {+-} 0.06 kcal/mol (261.83 {+-} 0.06 kcal/mol at 298 K), {Delta}H{sup o}{sub f 0}(CH{sub 2}) = 93.18 {+-} 0.20 kcal/mol (93.31 {+-} 0.20 kcal/mol at 298 K), {Delta}H{sup o}{sub f 0}(CH{sub 2}{sup +}) = 332.92 {+-} 0.19 kcal/mol (333.04 {+-} 0.19 kcal/mol at 298 K), {Delta}H{sup o}{sub f 0}(CH{sub 2}CO) = -11.10 {+-} 0.21 kcal/mol (-11.85 {+-} 0.21 kcal/mol at 298 K), as well as D{sub 0}(H{sub 3}C-H) = 103.42 {+-} 0.03 kcal/mol (104.99 {+-} 0.03 kcal/mol at 298 K), D{sub 0}(H{sub 2}C-H) = 108.95 {+-} 0.20 kcal/mol (110.35 {+-} 0.20 kcal/mol at 298 K), D{sub 0}(H{sub 2}C{double_bond}CO) = 77.08 {+-} 0.02 kcal/mol (78.73 {+-} 0.02 kcal/mol at 298 K), El(CH{sub 3}) = 9.3830 {+-} 0.0005 eV, and El(CH{sub 2}) = 10.3962 {+-} 0.0036 eV. These values are in excellent agreement with current and several previous experimental measurements. The recommended enthalpy of formation of CH{sub 2} implies that the reaction of singlet methylene with water is essentially thermoneutral (to within {+-}0.2 kcal/mol) at 0 and 298 K, and slightly endothermic (0.5 {+-} 0.2 kcal/mol) at 1000 K.