Gas-phase kinetics of elimination reactions of pentane-2,4-dione derivatives. Part ii [1]. Thermolysis of derivatives and analogues of 3-phenylhydrazonopentane-2,4-dione
作者:Nouria A. Al-Awadi、Mohamed H. Elnagdi、Hanan A. Al-Awadhi、Osman M. E. El-Dusouqui
DOI:10.1002/(sici)1097-4601(1998)30:7<457::aid-kin1>3.0.co;2-r
日期:——
Six analogues and derivatives (1-6) of 3-phenylhydrazonopentane-2.4-dione (7) were subjected to gas-phase thermolysis. The Arrhenius log A (s(-1)) and Ea (kJ mol(-1)) of the analogues (1-5) are, respectively: 10.42 and 140.8 for 1-cyano-1-phenyl-hydrazonopropanone (1), 11.19 and 135.4 for 1-cyano-1-(p-nitrophenylhydrazono)-propanone (2), 10.68 and 144.9 for l-cyano-1-(p-methoxyphenylhydrazono)propanone (3), 11.76 and 137.8 for 1-cyano-3-phenyl-1-phenylhydrazonopropanone (4), and 11.29 and 145.9 for 1-cyano-1-phenylhydrazonobutanone (5). The corresponding values for ethyl 3-oxo-2-phenylhydrazonobutanoate (6) are 11.90 s(-1) and 141.3 kJ mol(-1). The rates of reaction at 600 K are compared with those of the title diketone (7) and of pentane-2,4-dione (8) and rationalized in terms of a plausible elimination pathway involving a semiconcerted six-membered transition state. (C) 1998 John Wiley & Sons, Inc.