Infra-red studies and thermodynamics of hydrogen bonding in ethylene glycol monoalkyl ethers. Evidence for a ten membered ring dimer

Abstract

An i.r. study in the hydroxyl stretching region of three monoalkyl (methyl, ethyl and butyl) ethers of ethylene glycol in CCI4 solutions (concentrations up to 0.1 mol dm-3) has been carried out over the temperature range 298-338 K. Apparent integrated intensities of the bands at -3635, -3600 and -3475 cm-' of the free, intramolecularly and intermolecularly bonded OH groups have been measured and used to evaluate the equilibria between the monomeric and associated species. Various possible structures including open and cyclic dimers, trimers and tetramers for the associated species absorbing at -3475 cm-' have been considered. A cyclic ten-membered ring dimer involving the ether oxygens in hydrogen bonding satisfactorily explains the observed results. Various thermodynamic quantities such as K, AH", AGO and AS" in the three way equilibrium involving free monomer, intramolecularly bonded monomer and the cyclic ten membered ring dimer have been evaluated. The values of intra-and inter-molecuIar hydrogen bond strengths as calculated from the respective AH" values are -14.1 kJ mol-' and -28.2 kJ mol-' respectively.Intramolecular hydrogen bonding in P-substituted ethanols XCH2CH20H, where X is a proton accepting group such as C1, NH2, OCH, etc., is well known 1 -1 7 and in very dilute solutions, such compounds 9 9-1 exist as equilibrium mixtures of nonhydrogen bonded free forms and intramolecularly hydrogen bonded gauche conformers. The intermolecular association of such compounds is particularly interesting in view of the presence of the additional proton acceptor X, which can lead to different types of self-associated species not possible in simple alcohols. For simple alcohols, the first associated species absorbing at -3500 cm-l are usually considered to be linear and/or cyclic dimers.

Aerogels from Chitosan Solutions in Ionic Liquids

“…The values of these activation parameters are very similar to those that are observed during the formation of hydrogen bonds [40,41,42]. Their magnitudes coincide with the chemical nature of hydrogen bonding.…”

Ir spectra and conformational behavior of N‐acetyl‐(glycine, L‐alanine, L‐leucine)‐N′‐methylamides in chloroform

“…The integrated absorption intensities were determined by measuring the band areas and applying the necessary correction^'^ as described earlier. 16 The band separation was done either using a graphical method or a computer programme adopted before?…”

Dielectric relaxation study of aqueous 2-ethoxyethanol using time domain reflectometry technique

“…Aqueous solutions of EE have a wide range of chemical, biological, pharmaceutical, industrial and condensed matter physics applications because EE and water molecules have the H-bond sites and they can enter into intra and intermolecular hydrogen bonding giving rise to different conformations [1]. In dynamic equilibrium monoalkylethers of ethylene glycol may exists in Gauche anti conformation [2][3].…”

“…Different techniques have been used to investigate the dielectric, thermodynamic and optical properties of monoalkylethers of ethylene glycol in pure as well as mixed solvents [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. These properties were attributed as existence of inter and intra molecular hydrogen bonding in EE.…”