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Spectroscopic investigation of alkylcarbonic acid formation and dissociation in CO2-expanded alcohols / John L. Gohres in Industrial & engineering chemistry research, Vol. 48 N°3 (Février 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°3 (Février 2009) . - p. 1302–1306 Titre : Spectroscopic investigation of alkylcarbonic acid formation and dissociation in CO2-expanded alcohols Type de document : texte imprimé Auteurs : John L. Gohres, Auteur ; Andrew T. Marin, Auteur ; Jie Lu, Auteur Année de publication : 2009 Article en page(s) : p. 1302–1306 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Acids  Alkylcarbonic  acid Résumé : We show a technique to measure alkylcarbonic acid (ACA) formation and dissociation constants in CO2-expanded methanol, ethanol, and benzyl alcohol at 25 °C. In these systems, CO2 reacts with alcohols to form an in situ, self-neutralizing acid that exists under CO2 pressure. UV/vis spectroscopy is a noninvasive method to assay proton concentration, and the resulting values of this proton concentration yield effective equilibrium constants, the product of the formation, and dissociation constants. To separate the acid dissociation constant from the formation equilibrium constant, we employ a method using mass balances. From this, we find that methylcarbonic acid has a pKa of 5.7 and the relative ACA strengths are methyl > ethyl > benzyl. This work provides key parameters to design processes and expanded solvents that fully exploit the environmental and processing benefits of ACAs. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8011227 [article] Spectroscopic investigation of alkylcarbonic acid formation and dissociation in CO2-expanded alcohols [texte imprimé] / John L. Gohres, Auteur ; Andrew T. Marin, Auteur ; Jie Lu, Auteur . - 2009 . - p. 1302–1306. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°3 (Février 2009) . - p. 1302–1306 Mots-clés : Acids  Alkylcarbonic  acid Résumé : We show a technique to measure alkylcarbonic acid (ACA) formation and dissociation constants in CO2-expanded methanol, ethanol, and benzyl alcohol at 25 °C. In these systems, CO2 reacts with alcohols to form an in situ, self-neutralizing acid that exists under CO2 pressure. UV/vis spectroscopy is a noninvasive method to assay proton concentration, and the resulting values of this proton concentration yield effective equilibrium constants, the product of the formation, and dissociation constants. To separate the acid dissociation constant from the formation equilibrium constant, we employ a method using mass balances. From this, we find that methylcarbonic acid has a pKa of 5.7 and the relative ACA strengths are methyl > ethyl > benzyl. This work provides key parameters to design processes and expanded solvents that fully exploit the environmental and processing benefits of ACAs. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8011227