Conformation-Sensitive Isolated C−D Stretching Vibrations in Alkoxyl Chains

Abstract

The isolated C-D stretching vibrations have been studied for a number of selectively monodeuterated species of tetrahydropyran, methyl ethyl ether, methyl propyl ether, methyl butyl ether, methyl hexyl ether, and cyclohexane, and the dependence of the C-D stretching wavenumbers on the conformation of the CO-C(D)-CC, OC-C(D)-CC, and CC-C(D)-CC structures of the alkoxyl chain has been examined. The infrared spectra of three monodeuterated species of tetrahydropyran with a chair form gave definitive evidence for the conformational dependence of the C-D stretching wavenumbers. The observed wavenumbers of the C-D stretching vibrations for the monodeuterated compounds studied are correlated linearly to the C-D bond lengths calculated by the ab initio MO method using the basis set with polarization functions. The dependence of the C-D stretching wavenumbers on the conformational disposition of the C-D bond in the CO-C(D)-CC structure is more significant than that of the C-D bond in the OC-C(D)-CC or CC-C(D)-CC structure. For the CO-C(D)-CC structure, the stretching wavenumbers of the C-D bond trans to the DC-OC and DC-CC bonds are higher by about 90 cm -1 than those of the C-D bond gauche to the same bonds. C-D stretching vibrational spectroscopy has been shown to be one of the advantageous methods for determining the conformation of alkyl chains, which may contain any heterogenous atoms.

A Combined Raman and Deuterium NMR Spectroscopic Study on the Molecular and Phase Structure of a Nonionic Surfactant C12E5−Water System

“…Our previous studies 20,21 have shown that the wavenumbers of isolated C−D stretching vibrations of selectively monodeuterated alkyl chains depend on the conformation around the C−C bonds in the vicinity of the C−D bond. This conformational dependence of the C−D stretching wavenumbers is correlated directly to the lengths of the C−D bonds and their force constants. , The isolated C−D stretching vibrations can therefore be used to determine the local conformation of the C−C bonds in alkyl chains, supplemented by the data afforded by quantum chemical calculations.…”

“…In this work, the relevant data of structural and spectroscopic properties were obtained by performing density functional calculations at the B3LYP/6-311+G(d,p) level on hexyl methyl ether and heptane as model compounds for C 12 E 5 . In Table , the calculated results of the C−D bond lengths and the diagonal force constants, Raman scattering activities, and wavenumbers of the C−D stretching vibrations for the relevant conformations of the model compounds are given together with their observed wavenumbers. , …”

“…d Unscaled wavenumbers. e The observed wavenumbers for CH 3 O−CHD−CH 2 CH 2 CH 2 CH 2 CH 3 , CH 3 OCH 2 −CHD−CH 2 CH 2 CH 2 CH 3 , and CH 3 OCH 2 CH 2 CH 2 −CHD−CH 2 CH 3 are taken from ref , and those for CH 3 CH 2 CH 2 −CHD−CH 2 CH 2 CH 3 are actually the observed wavenumbers for CH 3 CH 2 CH 2 −CHD−CH 2 CH 3 (hexane-3- d 1 ) taken from ref .…”

“…The conformation of surfactant molecules in the aggregated structures has been studied in most cases by vibrational spectroscopy, that is, infrared spectroscopy and Raman spectroscopy, since the properties of molecular vibrations, in particular the wavenumbers , of vibrations, are highly sensitive to the conformational state of the molecule. , Actually, in a series of Raman studies of melting transitions of phospholipids, Peticolas et al have discussed conformations of alkyl chains using C−H and C−D stretching vibrations. − In our previous work, − we have proposed and utilized a method of analyzing wavenumbers of isolated C−D stretching vibrations to determine the conformation of a specified site of the molecular chain. Using a number of monodeuterated species in which one of the hydrogen atoms at different positions in the chain is selectively substituted by deuterium, we can eventually determine the conformational state of the whole chain.…”

Blue Shift of the Isolated CD Stretching Band of CH2DOH in Water Induced by Changes in the Hydrogen-Bonding Pattern

“…CH 2 DOH was prepared by a similar synthetic route described previously. , The purity of the sample was determined to be over 99% by gas chromatography.…”