Issue 0, 1978

Hg(63P1) photosensitization of 3-methylbut-1-ene. Part 2.—Intersystem crossing and cyclisation of the 2-methylbuta-1,3-diyl biradical

Abstract

Hg(63P1) photosensitization of 3-methylbut-1-ene (3MB) yields, among other products, trans- and cis-1,2-dimethylcyclopropane, in a strongly pressure dependent ratio, ranging from 1.37 at 2.5 Torr to 3.44 at 789.2 Torr. This observation is interpreted in terms of a mechanism involving intersystem crossing and ring closure of both vibrationally excited and thermalised triplet 2-methylbuta-1,3-diyl (MBD13) biradicals, produced by a 5pp hydrogen migration in excited triplet 3MB. Quantitative analysis of the data allows a value for the intersystem crossing rate constant for 3(MBD13)* to be obtained, together with the ratio of dimethylcyclopropanes formed from thermalised MBD13. Addition of oxygen to the reaction system considerably simplifies the observed product spectrum and enables lower limit estimates of the rate constants for intersystem crossing and cyclisation of thermalised triplet and singlet MBD13 respectively, to be derived. The results are compared to those obtained in other systems, and their relevance to the implications of thermochemical and quantum chemical analyses of the energetics of propa-1,3-diyl biradicals discussed.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans. 1, 1978,74, 277-287

Hg(63P1) photosensitization of 3-methylbut-1-ene. Part 2.—Intersystem crossing and cyclisation of the 2-methylbuta-1,3-diyl biradical

D. C. Montague, J. Chem. Soc., Faraday Trans. 1, 1978, 74, 277 DOI: 10.1039/F19787400277

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements