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Kinetics and mechanism of reaction of p-methoxystyrene and tetracyanoethylene. II. Effect of pressure

✍ Scribed by Y. Uosaki; M. Nakahara; J. Osugi

Publisher
John Wiley and Sons
Year
1983
Tongue
English
Weight
433 KB
Volume
15
Category
Article
ISSN
0538-8066

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✦ Synopsis

The reaction of p-methoxystyrene and TCNE is studied in 50% CHC13-50% CCll ( v h ) a t 25OC a t high pressures up to 1000 bar by following the disappearance of the absorbance a t 600 nm due to the EDA complex. By using the mixed solvent, equations required for the high-pressure kinetics are simplified. The volume of activation is -42 to -46 cmJ/mol for the 1,4-~ycloaddition and -55 cmJ/mol for the 1,2-cycloaddition. The activation volume for the 1,4-cycloreversion is assumed to be -8 to -12 cm3/mol based on a previous study on a similar system. The rate of the cycloreversion process is affected by solvent polarity. The rate of the 1,2-cycloaddition is influenced by solvent more significantly than that of the 1,4-cycloaddition. It is concluded that the transition state is polar in both cycloadditions and that its zwitterionic character is much stronger in the 1,2-cycloaddition.

📜 SIMILAR VOLUMES

Kinetics and mechanism of reaction of p-
Kinetics and mechanism of reaction of p-methoxystyrene and tetracyanoethylene. I. Evidence for competitive 1,2- and 1,4-cycloadditions
✍ Y. Uosaki; M. Nakahara; J. Osugi 📂 Article 📅 1982 🏛 John Wiley and Sons 🌐 English ⚖ 470 KB

## Abstract Time‐resolved absorption spectra for a reaction mixture of __p__‐methoxystyrene and tetracyanoethylene (TCNE) are found to have a band maximum at 325 nm which is assigned to the 1,4‐cycloadduct. The reaction in chloroform at 15, 20, and 25°C is followed by the charge‐transfer band at 60