Item – Theses Canada

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OCLC number
30068894
Author
Chen, Qing Feng,1964-
Title
The gas phase basicities and proton affinities of alkanediols
Degree
M. Sc. -- Queen's University, 1992
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, 1993.
Description
2 microfiches.
Notes
University Microfilms order no. UMI00379814.
Includes bibliographical references.
Abstract
A pulsed electron beam high pressure mass spectrometer (PHPMS) was used to study the thermodynamics of the gas phase ion molecule reactions of alkanediols. The ion chemistries in a methane buffer gas of 1,2-ethanediol ($\rm{C\sb2 H\sb6 O\sb2}$). 1,3-propanediol (C$\rm{\sb3 H\sb8 O\sb2}$) and 1,4-butanediol (C$\rm{\sb4 H\sb{10} O\sb2}$) were studied at ion source temperatures of 300-630 K and pressure in the ion source from 2 to 5 torr. Standard enthalpy and entropy changes have been determined from the temperature coefficients of the equilibrium constants for the reaction: Diol + BH$\sp{+}\longleftrightarrow$ DiolH$\sp{+}$ + B, where B is a suitable reference base. The extraordinarily large entropy changes for protonation of 1,3 and 1,4 diols ($\approx$ 17 col/mol K) and very large proton affinities ($\approx$ 30 kcal/mol higher than that of methanol (182 kcal)) show that, upon protonation, cyclization occurs. There is no thermodynamic evidence for such a structure for protonated 1,2-ethanediol although poor data was obtained for this diol. The proton affinities obtained from equilibrium measurements of 1,3-propanediol and 1,4-butanediol are significantly higher than previously reported results obtained from the study of collisional assisted dissociation of mixed proton-bound dimers. (Abstract shortened by UMI.)
Subject
Alkanediols.
Mass spectrometry.
Ions.
Molecules.
Ionized gases.
Spectrométrie de masse.
Ions.
Molécules.
Gaz ionisés.
ISBN
0315763507
9780315763500