A site-specific and multielement approach to the determination of liquid-vapor isotope fractionation parameters: the case of alcohols

• Published in: Journal of physical chemistry (1952) Vol. 94; no. 21; pp. 8303 - 8309
• Main Authors: Moussa, Issam, Naulet, Norbert, Martin, Maryvonne L, Martin, G. J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.10.1990
• Subjects: 400202 - Isotope Effects, Isotope Exchange, & Isotope Separation; ALCOHOLS; Applied sciences; CARBON ISOTOPES; Chemical engineering; Crystallization, leaching, miscellaneous separations; DATA; ETHANOL; Exact sciences and technology; EXPERIMENTAL DATA; FRACTIONATION; HYDROXY COMPOUNDS; INFORMATION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ISOTOPE EFFECTS; ISOTOPE RATIO; ISOTOPES; MASS SPECTROSCOPY; NUMERICAL DATA; ORGANIC COMPOUNDS; SEPARATION PROCESSES; SPECTROSCOPY; Distillation; Oxygen Isotopes; Isotope separation; Ethanol; Carbon Isotopes; Liquid vapor equilibrium; Alcohol; Evaporation; Hydrogen Isotopes; Experimental study; Phase equilibrium; Methanol
• ISSN: 0022-3654; 1541-5740
• DOI: 10.1021/j100384a056

Isotope fractionation phenomena occurring at the natural abundance level in the course of liquid-vapor transformation have been investigated by using the SNIF-NMR method (site-specific natural isotope fractionation studied by NMR) which has a unique capability of providing simultaneous access to fractionation parameters associated with different molecular isotopomers. This new approach has been combined with the determination of overall carbon and hydrogen fractionation effects by isotope ratio mass spectrometry (IRMS). The results of distillation and evaporation experiments of alcohols performed in technical conditions of practical interest have been analyzed according to the Rayleigh-type model. In order to check the performance of the column, unit fractionation factors were measured beforehand for water and for the hydroxylic sites of methanol and ethanol for which liquid-vapor equilibrium constants were already known. Inverse isotope effects are determined in distillation experiments for the overall carbon isotope ratio and for the site-specific hydrogen isotope ratios associated with the methyl and methylene sites of methanol and ethanol. In contrast, normal isotope effects are produced by distillation for the hydroxylic sites and by evaporation for all the isotopic ratios.