Conformations of some αβ-unsaturated carbonyl compounds. Part I. Infrared spectra of acraldehyde, crotonaldehyde, methyl vinyl ketone, and ethylideneacetone

Abstract

Infrared spectra of acraldehyde, crotonaldehyde, methyl vinyl ketone, and ethylideneacetone in solution and vapour states are reported. Band intensity measurements at temperatures between -1 10" and 200" are interpreted in terms of conformational equilibrium between the s-trans and non-trans forms of the ketones. The additional enthalpy ( A H ) of the non-trans forms are : Methyl vinyl ketone EthylideneacetoneSolution in CS, Vapour 461 f 23 cal. mole-' 565 f 52 cal. mole-l 51 3 f 52 cal. mole-1 585 f 46 cal. mole-1No evidence is found for more than one form of the aldehydes and the rotational structure of vibrational bands of both acraldehyde and crotonaldehyde suggest these exist in the s-trans conformation. Vibrational assignments are provided for the various conformations detected in these compounds.AN understanding of factors responsible for the stability of particular conformations is important because different conformers may have different physical and chemical properties. assign bands in the i.r. and Raman spectra of methyl vinyl ketone (R1 = H, R2 = CH,) and ethylideneacetone

Vibrational analysis of (E,E)-2,4-hexadienal, (E,E,E)-2,4,6-octatrienal, and (E,E,E)-3-methyl-2,4,6-octatrienal

“…Regio~z 3100-2700 em-' Most assignments in this region are similar to those already given for (E,E)-2,4-hexadiene (4). However, a 2808-cm-' band, which does not occur in (E,E)-2,4-hexadiene spectra, is assigned to the aldehydic CH stretching mode (v CHa) (12)(13)(14)(15)(16)(17). Another rather strong band at 2734 cm-' corresponds to the overtone of the deformation mode of the same CH group (2 6 CHa), in Fermi resonance with the v CHa (12)(13)(14)(15)(16)(17)(18)(19).…”

Improved chemoselective hydrogenation of crotonaldehyde over bimetallic AuAg/SBA-15 catalyst

“…5(g) [50]. As introducing CRAL vapor into IR cell containing pure SBA-15 wafer pre-treated with H 2 at 623 K, two characteristic bands at 1725 and 1711 cm À1 attributed to m(C@O) of unabsorbed or physicallyabsorbed CRAL molecule emerge and gradually diminish under continuous evacuation (Fig.…”

Infrared spectroscopy and conformation of alkyl vinyl ketone monomer

“…The ratio of populations (s-cis/s-trans) increased with the bulkiness of the alkyl group (E:).2 Kossanyi3 reported that v C=O bands in all the AVK's and Y C=C bands in a'few AVK's were measured in pairs. Bowles et al 4 reported that v C-C, 6 CH=CH out of plane and 6 CH2 out of plane in the MVK were assigned with the two conformations. Katritzky et al5 reported the relation between the population of the conformations and the absorption coefficients of the v C=C bands ( A C=C) by assuming the A C=C value of the propenal and t-BuVK.…”