Spectroscopic studies of rotational isomerism in β-halogenopropionitriles

Abstract

The infrared and Raman spectra of p-fluoro-, p-chloro-, p-bromo-, and p-iodo-propionitrile have been obtained over the complete fundamental vibrational frequency range. Solid-state i.r. spectra have also been measured. The results show that each of these compounds exists as an equilibrium mixture of gauche and trans isomers. In all cases the gauche isomer is the more stable form in the liquid phase. Enthalpy differences have been determined for the chloro-, bromo-, and iodo-derivatives. A vibrational frequency assignment has been made for each of the isomers and this has been tested by application of the sum rules.1 ,~-DISUBSTITUTED ethanes usually exist as mixtures of two energetically favoured isomers, the trans and gauche forms. A recent i.r. spectroscopic investigation has shown that this is the case for liquid P-chloro-, P-broino-, and 8-iodo-propionitrile. The present work has extended the i.r. frequency range studied to include the entire range where fundamental vibrations might be observed. Raman data have also been obtained for the first time. p-Fluoropropionitrile, for which no previous spec troscopic result was available, has also been studied.The present investigation, which partially overlaps E. Wyn-Jones and W. J. Orville-Thomas, J . Chem. SOC. ( A ) ,

Solute−Solvent Interactions in Liquid Noble Gases As Probed by the Conformational Equilibrium of Some 1,2-Disubstituted Ethanes

“…Vapor Phase. From the vibrational spectra, 17,33 the trans form has been determined to be the more stable in the gas phase while in the pure liquid phase the gauche form is the preferred conformer. A problem with the literature values for ∆H°of 1-chloro-2-fluoroethane has been pointed out by Wiberg et al 15 Therefore, the enthalpy difference in the vapor phase was redetermined.…”

Microwave Spectrum and Conformational Composition of 3-Fluoropropionitrile (FCH2CH2CN)

“…No experimental conformational studies of gaseous FCH 2 CH 2 CN are available, but the compound in the liquid and solid states has been subject to an infrared and Raman study more than half a century ago . No attempt was made in this study to measure the enthalpy difference of the two conformers in the liquid phase, but a value close to zero was estimated, although the synclinal form appeared to be the more stable conformer. B3LYP/6-311+G(d,p) and M05-2X/6-311+G(d,p) calculations both predicted 2.7 kJ/mol for this energy difference of 3-fluoropropionitrile with sc as the high energy form.…”

Hydrogen Bonding in Monomers and Dimers of 2-Aminoethanol

“…2-Aminoethanol (AE) or monoethanolamine has been the subject of numerous experimental, − theoretical, − and combined studies , for the past 30 years. Although a relatively simple molecule, the AE moiety is an important constituent of some biologically relevant molecules such as phospholipids (as the headgroup of phosphatidylethanolamine).…”