Portal de Periódicos da CAPES

Thermokinetic Determination of Gas-Phase Basicities. Application to Ketene, Methylketene, and Formaldimine

1996; American Chemical Society; Volume: 100; Issue: 41 Linguagem: Inglês

10.1021/jp960761h

1541-5740

Guy Bouchoux, Jean‐Yves Salpin,

Phase Equilibria and Thermodynamics

Rate constants have been determined for proton transfer reactions of the type [MH]+ + B ⇆ M + [BH]+, where M is ketene, methylketene, and formaldimine and B is a reference base. A quantitative relationship between the rate constant and the free energy (or enthalpy) of the reaction allows the determination of the gas-phase basicity, GB, (or proton affinity, PA) of M. This thermokinetic method gives results comparable to that obtained from equilibrium constant measurements. The values derived for ketene, methylketene, and formaldimine follow: GB(ketene) = 788 ± 3 kJ/mol, PA(ketene) = 817 ± 3 kJ/mol; GB(methylketene) = 809 ± 3 kJ/mol, PA(methylketene) = 842 ± 3 kJ/mol; GB(formaldimine) = 830 ± 3 kJ/mol and PA(formaldimine) = 860 ± 5 kJ/mol. Heats of formation of methylketene and of formaldimine that may be deduced from a combination of these results with literature data are as follows: ΔHf°300 (CH3CHCO) = −97 ± 5 kJ/mol and ΔHf°300 (CH2NH) = 75 ± 5 kJ/mol.