OBSERVATIONS ON THE EFFECTS OF HYDROGEN BONDING ON THE INFRARED SPECTRA OF ALCOHOLS BETWEEN $6 \mu$ AND $20 \mu$
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Date
1952
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Ohio State University
Abstract
The major portion of all previous work on hydrogen bonding in alcohols has been devoted to studying the changes in their OH stretching vibrations near $3 \mu$ and $1.5 \mu$ as the proportion of monomer molecules is altered by varying the concentration of the alcohol in a suitable solvent such as $CCl_{4}$. In order to clarify the nature of the hydrogen bond, it is essential that the facts be established about the changes in other vibrations caused by hydrogen bonding and especially in the OH deformation vibrations. A systematic study has therefore been made of the spectra of various series of alcohols in the range between $6 \mu$ and $20 \mu$ using the well-known effects in the $3 \mu$ regions as a guide in choosing suitable concentrations. It is not easy to summarise the results which are complex and seem to depend on the nature of the alcohol (primary or secondary) and on the position of substituents in the hydrocarbon part of the molecule. Certain results, however, are common to certain series of alcohols. Thus all n-primary alcohols exhibit bands near $7.1 \mu, 7.5 \mu, 9 \mu$ and $15.4 \mu$ which weaken markedly on dilution, while a new band (presumably due to the monomer form) appears in the neighbourhood of $8.2 \mu$. The ``association'' band centered near $15.4 \mu$ is extremely wide and diffuse, closely resembling the $3 \mu$ association band. The association bands at $7.1 \mu$ and $7.5 \mu$ are also rather broad but the one near $9 \mu$ is relatively sharp. The $8.2 \mu$ monomer band is extremely variable in position but it may be remarked that in secondary and branched primary alcohols, a second monomer band appears (in addition to this variable one) near $9.3 \mu$, which is much more constant in position. Observations have also been made on the corresponding effects in some deuterated alcohols. Possible interpretations of all of these results will be discussed.
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Author Institution: Randall Laboratory of Physics, University of Michigan