LOW RESOLUTION MICROWAVE SPECTROSCOPIC STUDIES OF ALLYL ESTERS
Loading...
Date
1977
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
Low resolution microwave spectra of allyl cyanoformate and chloroformate display a-type band series associated with four conformational forms designated EG, CG, CG^{\prime} and IG. The band series are characterized by $B + $C values of 1838.1(3), 2019.8(3), 2188.0(7), and 2069(2) MHz, respectively, for allyl cyanoformate and 1834.5(3) (1799.5(5), $^{37}Cl)$, 2015(1) (1988(1), $^{37}C1)$, 2213(2) and 2081(2) MHz, respectively, for allyl chloro-formate. Allyl fluoroformate displays band series from four rotamers designated EG, ES, CG and IG having B + C values of 2406(1), 2764(1), 3075(5), and 2815(5) MHz, respectively. Allyl formate displays one band series having a B + C value of 3298(3) attributed to an EG conformer. Each E conformer is consistent with a syn-anti $[\tau_{1}(OCOC) = O^\circ, \tau_{2}$ (COCC) $= 180.^\circ]$ heavy atom planar structure and each C species is consistent with a syn-gauche $[\tau_{1} (OCOC) = 0^\circ, \tau_{2}$ (COCC) $\sim 90^\circ]$ structure. The I conformers are consistent with a gauche-gauche $[\tau_{1}$ (OCOC) $\sim 90^\circ \tau_{2}$ (COCC) $\sim 240^\circ]$ structure. The ES conformer of allyl fluoroformate has the vinyl group syn-eclipsed with the C-O bond, $[\tau_{3}(OCCC) = 0^\circ]$. Rotational constants of all other conformers are consistent with structures having the vinyl group eclipsed with a methylene C-H bond, $[\tau_{3} (OCCC) = 120^\circ]$. E and C conformers are of nearly equal energy in each case. I conformers are approximately 2-3 kcal/mole higher in energy. These results parallel previous findings for ethyl, propargyl and n-propyl esters, demonstrating that the potential functions for internal rotation of primary esters are similar.""
Description
Author Institution: Department of Chemistry and Institute of Materials Science, The University of Connecticut Storrs