Kinetics and mechanism of thermal gas-phase elimination of α-substituted carboxylic acids: role of relative basicity of α-substituents and acidity of incipient proton
✍ Scribed by Nouria A. Al-Awadi; Kamini Kaul; Osman M. E. El-Dusouqui
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 62 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0894-3230
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✦ Synopsis
2-Phenoxypropanoic acid together with five of its aryl derivatives, its phenylthio and its Nphenylamino analogues were pyrolyzed at 494-566 K. The reactions were homogeneous, polar and free from catalytic and radical pathways, and obeyed a first-order rate equation. The limits of the Arrhenius log A (s À1 ) and E (kJ mol À1 ) values obtained for these reactions averaged 11.98 AE 1.71 and 158.1 AE 17.4, respectively. Analysis of the pyrolysates showed the elimination products to be carbon monoxide, acetaldehyde and the corresponding phenol, thiophenol or aniline compounds. The pyrolysis of 2-phenoxy-and 2-(N-phenylamino)-1-propanol was also investigated over the temperature range 638-792 K. The kinetic results and products analysis lend support to a reaction pathway involving a five-membered cyclic polar transition state.