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Journal of the Mexican Chemical Society
versión impresa ISSN 1870-249X
J. Mex. Chem. Soc vol.53 no.3 Ciudad de México jul./sep. 2009
Article
Allylic ProtonProton Coupling in Stereodefined Alkylidenecyclobutanes and Alkylidenecycopentanes*
William F. Bailey1* and Timo V. Ovaska2*
1 Department of Chemistry, The University of Connecticut, Storrs, Connecticut 062693060, USA.*Responsible author: William.Bailey@uconn.edu
2 Department of Chemistry, Connecticut College, New London, Connecticut 063204196, USA.*Responsible author: tvova@conncoll.edu
Received June 28, 2009
Accepted August 14, 2009
Abstract
Analysis of the 1H NMR spectra of eight stereodefined alkylidenecycloalkanes allows determination of the magnitude of allylic coupling in these compounds. In contrast to the trend normally observed, the magnitude of transoidallylic coupling was found to be invariably greater by ~0.5 Hz than the cisoidallylic coupling. The larger transoidallylic coupling may be attributed to the slightly smaller dihedral angle relating allylic =CCH plane with the C=CC plane in the Eisomers.
Keywords: Proton NMR, Allylic Coupling, Alkylidenecycloalkanes.
Resumen
El análisis de los espectros de RMN protónica de ocho alquilidéncicloalcanos estereoisoméricos permite determinar la magnitud de los acoplamientos alílicos en estos compuestos. En contraste con la tendencia normal, la magnitud de los acoplamientos en segmentos alílicos transoides es siempre mayor que la encontrada en sistemas alílicos cisoides, por aproximadamente 0.5 Hz. Los valores mas grandes en las constantes de acoplamiento para los sistemas transoides pudiera explicarse con base en el ángulo diedro existente entre el plano alílico =CCH y el plano en el segmento C=CC presente en los isómeros E, que es ligeramente mas pequeño.
Keywords: RMN de protones, acoplamientos alílicos, alquilidéncicloalcanos.
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Acknowledgment
This work was supported by the Connecticut Department of Economic Development. We thank the editorial board of this journal, and particularly Prof. Eusebio Juaristi, for arranging this memorial issue dedicated to Ernest Eliel.
References
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*Dedicated to Professor Ernest L. Eliel: a giant in the field of stereochemistry and to us a mentor and friend to whom much is owed for his generous support and encouragement.