BAND SHAPE OF ESTER CARBONYL IN SOLUTION.

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1989

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Ohio State University

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In solid solutions of large molecules of biological interest such as chlorophylls' and proteins, the infrared spectra show large structureless bands. These characteristics are due to overlapping bands. To separate the components in the massive abaorptions it is necessary to know the band shapes and bandwidths of the functional group involved in the absorption. We have used methyl acetate in a $CCl_{4}$ solution as a model system for the ester band of solid chlorophyll. The spectra at several concentrations were obtained and merged to obtain a spectrum free of noise. Essentially a single band with an isotope satellite band were obtained, The bandwidth and band shape ratio (Lorentz index over the sum of Lorentz and Gauss indices) of the principal band are $12.6 cm^{-1}$ and 0.77, respectively. The band could not be entirely fit with a gaussian, lorentzian, or product function and signified the presence of weak side components. To retrieve these components we used the Fourier self-deconvolution technique to determine the number of components and locate their positions after which a simulation of the spectrum was performed. By this way we have identified several carbonyl components that we have assigned to different conformers of the molecule. The integrated intensity of the components was used to determine the relative concentration of the conformers.

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$^{1}$ C. Chapados, Photochem. Photobiol. 47, 115-132 (1988)
Author Institution: D\'{e}partenent de chimie-biologie, Universit\'{e} du Qu\'{e}bec \`{a} Trois-Rivi\`{e}res

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