Investigations of infra-red spectra-absorption of some hydroxy compounds in the region of 3 μ

Abstract

It has been realized by several investigators that with some exceptions compounds containing the hydroxyl group have a sharp absorption band close to 2.75 μ , and frequently another much wider band about 3 μ . Erreta and Mollet (1936, 1937) and Erreta (1937) have shown that the latter is an "association" band which diminishes on dilution in a non-polar solvent, or by raising the temperature, when the association complexes split up and the hydroxyl band at 2.75 μ becomes more pronounced. (Compare also Barchewitz (1937) and Freymann (1937). In the present investigations of the infra-red absorption spectra of certain hydroxyl compounds in the 3 μ region we have made observation of the effect of the structure of the molecule on both the above-mentioned bands, as well as on the CH vibration bands. The OH bands in the region about 1.4-1.6 μ have been investigated by Wulf and his co-workers (1935, 1936) for the most part with solutions of about 0.01 mol./l/ in which the association band had practically disappeared.

Investigations of infra-red spectra. Determination of C-H frequencies (~3000 cm. -1 ) in paraffins and olefins, with some observations on “polythenes”

“…The frequency shift between vapour and liquid in the region of 3000 cm.-1 is ~ 10 cm.-1, but the difference between carbon tetrachloride solution and liquid is only ~ 3 cm.-1 (cf. Fox and Martin 1938). A comparison of our infra-red frequencies with the Raman data shows that there are four " coincidences" in the region of 3000 cm.-1 for each isomer, the agreement being slightly better for the trans (maximum difference 10 cm.-1) than for the cis isomer (maximum difference 14 cm.-1).…”

“…Two CH frequencies are found at 3092 and 2977 cm.-1, due to the unsymmetrical and symmetrical modes of vibration, respectively (cf. Fox and Martin 1938), while the single CH frequency of the group ^)CH occurs about mid way between these, e.g. 3023 cm.-1 in cyclohexene (band 1, figure 6).…”

“…The apparatus and general technique have been described previously (Fox andMartin 1937,1938). All the compounds were examined in solution in carbon tetrachloride a t room temperature (20-24° C), but owing to low solubility some measurements with the polythenes were made a t tem peratures up to 50° C. The apparatus used for these measurements was th a t constructed by us for investigations on water a t different temperatures, and an account of this work is in the Press.…”

“…In many cases the final absorption curves obtained by plotting k against the wave-length or frequency were rather complex, and to assess fairly the bands, as regards position and intensity, it was necessary to resort to graphical separation (e.g. Fox andMartin 1938, 1939). The integrated area of a band is approximately l-4//cmax ) w h e re/ is the half-width of the band in cm.-1, as shown previously (1938).…”

On the Origin of the 3.3 μm Unidentified Infrared Emission Feature

“…The first identification of these bands as due to vibrations of molecules were provided by mechanical models with empirical force constants (Fox & Martin 1937, 1938, 1939, 1940. These interpretations were later confirmed by quantum mechanical ab initio electronic structure calculations (Hehre et al 1986).…”