171. The vibrational spectra of esters and ketones

Abstract

elation of strong bands found in related series suggests assignments of some of the frequencies t o vibrations of particular parts of the nuclear frameworks, which may be useful in disentangling the spectra of complex molecules containing these groupings. The results are also useful in suggesting key bands for infra-red analysis of mixtures of these compounds, or for the detection of impurities.THE use of infra-red spectra for both analysis and structural diagnosis demands the measurement of the spectra of many compounds differing in type over a wide spectral range. By this means, characteristic differences may be found giving key absorption bands for analysis, but a t the same time the comparison of spectra of related compounds may lead to an assignment of vibration frequencies which are characteristic of particular types of nuclear skeleton. Such data can only be applied successfully in the study of complex or macromolecules if measurements are first made, for purposes of reference, on relatively simple molecules, where the assignment of frequencies can be made with conviction. Compilations of this kind have been published recently, and some important correlations obtained (Barnes, Liddel, and Williams, Ind. Eng. Chenz. A naE., 1943, 15, 8 3 ; Thompson and Torkington, Proc. Roy. SOC., 1945, A , 184,3; '1'rans. Faraday SOG., 1945,41, 246).In connexion with the elucidation of the vibrational spectra of some polymers containing ester groupings, we have measured the spectra of many esters and ketones between 2 p and 20 p. Some of the results are collected here, and the spectra are discussed briefly from the standpoint of molecular structure. A complete correlation of the infra-red absorption frequencies with the corresponding Kaman intervals would a t present become unwieldy, and will therefore be deferred until the most important features can be disentangled from the much larger number of molecules under examination.A few were prepared in this laboratory. I n many cases two or more samples of the same compound were examined, the identity of the spectra serving as a check on purity. Benzophenone was measured as a solid film on rocksalt; the remainder were measured as liquids in an absorption cell made by separating plates of rock-salt by a washer about 0.08 mm. thick. The spectrometers have already been described (Thompson and Whiffen, this vol., p. 268).The spectra are shown as charts, Figs. 1-7, in which bands are shown as lines of varying intensity covering the spectral range 500-1750 wave numbers. The disadvantage of this form of representation is that it does not reveal the relative breadths of the bands, and the intensities can only be regarded as approximate, but itThe vibrational spectra *of a number of ketones and esters have been measured between 5-20 p.The compounds employed were usually commercial products, purified by fractionation.

Reaction of Aldoses and Ketoses With Lead Tetraacetate

“…Two moles of oxidant were consumed within three minutes and oxidation proceeded subsequently a t a markedly slower rate reaching a value of 2.1 moles in one hour; the rapidity of the reaction may be contrasted with the relatively slow oxidation rates of polyols (12) and glycosides (13). The product of the initial rapid oxidation, isolated as a sirup in yield, was strongly reducing, very soluble in ethyl acetate, and i t absorbed strongly in the infrared region a t about 1170 cm.-I, characteristic of formate esters (31). In agreement with the latter result two moles of formic acid were liberated when the compound was hydrolyzed with acid or alkali.…”

“…The infrared absorption spectrum showed very strong absorption at 1725 cm.? and at 1170 cm.-1, characteristic of formate esters (31). A sample of the oil (7.4 mgm.)…”

Mechanisms of H2 generation for metal doped Al16M (M = Mg and Bi) clusters in water

“…In addition, the natural bond orbital (NBO) [27] and the Hirshfeld charge [28] analysis have been carried out to understand the interaction mechanism between Al 16 M (M ¼ Al, Mg and Bi) clusters and water. The highest energy occupied molecular orbital (HOMO) and the lowest energy unoccupied molecular orbital (LUMO) were adopted for predicting the adsorption and dissociation of H 2 O.…”

Theoretical and vibrational spectral investigation of sodium salt of acenocoumarol

“…[19] NBO calculations [20] were performed using NBO 3.1 program as implemented in the Gaussian 98 package at the DFT/B3LYP level in order to understand various second-order interactions between the filled orbitals of one subsystem and vacant orbitals of another subsystem, which is a measure of the intermolecular delocalization or hyperconjugation. The hyperconjugative interaction energy was deduced from the second-order perturbation approach:…”