Raman carbonyl stretch

P. G. Puranik. J, Chem. Phys. 26, 601 (1957). Raman carbonyl stretch of esters, pure and in phenol, alcohols. 

Infrared Intensities of Metal Carbonyl Stretching Vibrations, 10, 199 Infrared and Raman Studies of w-Complexes, 1, 239 Insertion Reactions of Compounds of Metals and Metalloids, 5, 225 Insertion Reactions of Transition Metal-Carbon o-Bonded Compounds I Carbon Monoxide Insertion, 11, 88... 

The carbonyl stretching frequency of both the keto and enol tautomers can be recognized in the vibrational spectrum of pentane-2,4-dione. The enol has v(C=0) at 1618cm" , generally the dominant peak in the spectrum and more intense than the in- and out-of-phase v(C=0) stretching modes of the keto form, which are found at 1727 and 1707 cm" , respectively. These are identified by their Raman counterparts at 1719 cm" (polarized) and 1697 cm" (depolarized) (Ernstbrunner, 1970). The ratio of absorbances of the enol and the out-of-phase keto bands in the ir was used as an early method of analysis of the keto/enol equilibrium in different solvents (Le Fevre and Welsh, 1949). 

Ultraviolet spectra of benzoic acid in sulphuric acid solutions, published by Hosoya and Nagakura (1961), show a considerable medium effect on the spectrum of the unprotonated acid, but a much smaller one in concentrated acid. The former is probably connected with a hydrogen-bonding interaction of benzoic acid with sulphuric acid which is believed to be responsible for a peculiarity in the activity coefficient behaviour of unprotonated benzoic acid in these solutions (see Liler, 1971, pp. 62 and 129). The absence of a pronounced medium effect on the spectra in >85% acid is consistent with dominant carbonyl oxygen protonation. In accordance with this, Raman spectra show the disappearance in concentrated sulphuric acid of the carbonyl stretching vibration at 1650 cm (Hosoya and Nagakura, 1961). Molecular orbital calculations on the structure of the carbonyl protonated benzoic acid have also been carried out (Hosoya and Nagakura, 1964). 

The resonance Raman spectrum of a similar complex has been reported, that of a ternary complex of LADH, NADH and 4-(7V 7V-dimethylamino)benzaldehyde (DABA) with the disappearance of the carbonyl stretching frequency of the DABA at 1664 cm-1 also indicating strongly that inner sphere complexation of the substrate occurs, the zinc withdrawing electron density from the aldehyde oxygen forming a zinc-oxygen coordinate bond.1397... 

A more serious objection is that the evidence for an anhydride intermediate is based upon observation of a transient phase during the hydrolysis of an ester intermediate under cryoenzymological conditions, i.e. at low temperature and in the presence of an organic cosolvent (Makinen et al., 1979). No evidence was obtained by these workers as to the molecular nature of the transient, but subsequently Hoffman et al. (1983) examined the system by multichannel resonance Raman spectroscopy. The characteristic carbonyl stretching frequency of an anhydride should have been detected by their experiments, but was not. Kuo and Makinen (1985), however, re-... 

The group VI compounds M(CO)4(DAB) were first prepared by Tom Dieck and his coworkers in the 1960s and their strong solvatochromism arising from the antiparallel dipole of the excited state was reported shortly thereafter. Resonance Raman studies established the relationship between the MLCT absorption and several molecular vibrations, most notably the carbonyl stretching frequencies. The resonance Raman spectra of this class of compounds has been reviewed. Vlcek has published a detailed review of the photophysics and photochemistry of the group VI diimine compounds. ... 

Before it is possible to interpret on a rigorous basis the behavior of the carbonyl stretching frequencies of a series of isostructural and isoelectronic complexes complete vibrational analyses are necessary. However, it is only within the last few years that far-infrared 137) and laser Raman 84) spectrometers have become available generally. Hence, in the general absence of the data they have provided, earlier complete analyses were limited to the spectra of simple metal carbonyls (for which such information was available). Even for these complexes, the number of force constants exceeds the number of observable frequencies, and model force fields had to be used. Since Urey-Bradley type force fields proved to be unsuitable for carbonyl complexes 86,105, 106), Jones 80-82) developed a resonance interaction valence force field which reduced the number of force constants by interrelating several on the basis of orbital overlap. This approach is not readily adaptable to less symmetrical substituted carbonyl complexes. Alternative models had, therefore, to be investigated. 

The carboxylic acid carbonyl frequency is shifted to lower frequency by 1 to 6 percent in carboxylic acid dimers, which is much less than the relative shifts of The mechanical splitting of the symmetric and antisymmetric carbonyl stretching modes is evident in the difference between the Raman and IR spectra of formic acid. Of course the average of these two is of interest, but often only one is measured. 

Spektroskopiya 2, 160-4 (1957). Raman H bond effect on carbonyl stretch, acetophenone, phenols, solutions in dioxane, acetone, et ... 

Raman H bonding of acetic acid and mixtures with H2O, phenol, etc., carbonyl stretch. 

Raman carbonyl, C—G stretch, effect of H bonding, acetone with alcohols. 

Ph. Traynard. Bull. soc. chim. France 1947, 316-21. Raman acetic acid dimer by carbonyl stretch, AH dimerization. 

COCIF possesses C symmetry (see Appendix A4), and the fundamental vibrational modes, their symmetry and activity are illustrated in Fig. 16.4, for a general COXY molecule. Thus, the planar COCIF molecule has six normal modes of vibration, all of which are infrared and Raman active. to r belong to the A irreducible representation, and >>g belongs to A". The p, mode corresponds to the carbonyl stretching frequency, r j is often described as... 

A C n.m.r. study of the fluxional behaviour of the stereochemically non-rigid acetylenic carbonyl complex Co4(CO)ioC2(C6H5)2 has shown the exchange process to be a three-step and not two-step process as previously reported. Intensity and depolarization ratios have been measured from a Raman solution spectrum of Hg[Co(CO)4]2 and the carbonyl stretching force fields have been calculated. 

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