Open AccessThe thermal decomposition of acetaldehyde and the existence of different activated states
Publication year - 1933
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1933.0102
Subject(s) - acetaldehyde , chemistry , thermal decomposition , kinetics , thermodynamics , decomposition , homogeneous , atmospheric temperature range , thermal , first order , ethanol , mathematics , physics , organic chemistry , classical mechanics
Homogeneous thermal gas reactions were at one time tacitly assumed to possess a definite order, unimolecular and bimolecular reactions, for example, being sharply distinguished. The kinetics of the decomposition of acetalde hyde, CH3 CHO = CH4 + CO, over the pressure range of 100 to 400 mm. were found to satisfy the criterion of a bimolecular reaction, namely, that the reciprocal of the time for half change (1/t 1/2 ) )plotted against the initial pressure (p 0 ) gave a straight line inclined to the axes. The line, however, did not pass through the origin, as may be seen in fig. 1 of the present paper. This indicated the presence of some first order reaction, the nature of which was not determined. Subsequently, in accordance with the collision theory of activation and deactivation, it was shown that certain reactions, sometimes called quasiummolecular, change their order from the second at low pressures to the first at high pressures. This apparently was the reverse of the behaviour shown by acetaldehyde.