8025
Verbalis facilitated this work. We thank Drs. J. E. williams, R. c. ~ i ~ and~G. J. h Gleicher ~ ~ for, their contributions in the Of Our analysis programs. We especially wish to express Our gratitude to Professor K. Mislow, Professor S . Lifson, professor N. L. ~ l l i D~ ~ 0. ~, ~E ~ ~ , and ~D ~ A. .~ 'Omdiscussions and Warshel for ments.
Supplementary Material Available. A listing of calculated Cartesian coordinates will appear following these pages in the microfilm edition of this volume of the journal. Photocopies of the supplementary material from this paper only or microfiche (105 X 148 mm, 20x reduction, negatives) containing all of the supplementary material for the papers in this issue may be obtained from the Journals ~ , Department, American Chemical Society, 1155 16th St., N.W., Washington, D. C. 20036. Remit check or money order for $3.00 for photocopy or $2.00 for microfiche, referring to code number JACS-73-8005.-
Substituent Effects on U-P Conjugation. The Absence of r-Electron Transmission through Cyclopropane R i n g P R. S . Brown and T.G.Traylor" Contribution from the Department of Chemistry, University of California, San Diego, La Jolla, Calqornia 92037. Received March 3, 1973 Abstract: Charge-transfer frequencies of acceptor complexes with 2-methoxy-1-phenylcyclopropaneand similar
compounds have been used to show that a 1,2-substituted cyclopropane does not transmit a-electron density from an electron-rich to an electron-deficient T center in the manner of a ir bond. The rapid solvolysis of 2-methoxycyclopropylcarbinyl p-nitrobenzoate is interpreted as resulting from distortional stabilization in the form of fragmentation.
T
here is an enormous literature demonstrating that the strained cyclopropane ring acts as a simple Pelectron donor in a manner similar to that of ethylene. 3-7
write u-P conjugated forms of such strained, primary cations.
3 1
2
Recent evidence shows that other strained rings behave similarly, as illustrated below for the very strained homocubane group.ga The charge-transfer frequencies
If this u-P delocalization in 2 and 3 behaves like P-P delocalization in 1, then we might reasonably expect conjugation through the strained ring as in 5. This has been called P - - ~ - PconjugationSbor through-bond interaction7b(n, m,r = 0 to 2). U
U
hv
--*
M
TCNE
e
o
