Item – Theses Canada

​
OCLC number
46520456
Author
Chen, Qing Feng,1964-
Title
The construction and operation of a small flowing afterglow for the study of the reactions of trimethylsilylium with alkylamines.
Degree
Ph. D. -- Queen's University at Kingston, 1996
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, 1997.
Description
3 microfiches.
Notes
Includes bibliographical references.
Abstract
A miniature version of a Flowing Afterglow (FA) has been designed to carry out studies of ion-molecule reactions in the gas phase. It has been successfully built, tested, calibrated and instrumental corrections have been determined experimentally. It is equipped with an Extrel quadrupole mass filter for the separation of ions resulting from reactions. Total gas pressures of 0.6 to 1.2 Torr in the flow tube are used at room temperature. The new design is able to operate using an 80 m$\sp3$/hour Edwards High Vacuum Roots pump, whereas usual designs using wider bore tubes call for 200 m$\sp3$/hour pumping speed. The new design can accommodate further additions to the system so that future modifications can be made without new construction of major parts. The performance of the FA was assessed by measurements of the rate constant for a previously measured proton transfer reaction of t-C$\rm\sb4H\sb9\sp+$ with NH$\sb3.$ Seven association reactions between the trimethysilylium ion, $\rm Me\sb3Si\sp+,$ and acetone and several alkylamines (Me$\rm\sb3Si\sp+$ + amine $\to$ $\rm Me\sb3Si\sp+\cdot$amine) have been studied at room temperature. The measured rate constants (10$\sp{-9}$ cm$\sp3$ molecule$\rm\sp{-1}s\sp{-1})$ together with the standard deviations of multiple (12) determinations for each reaction are: CH$\rm\sb3COCH\sb3,$ 1.92 $\pm$ 0.03; NH$\sb3,\ 1.53\pm0.09$; $\rm CH\sb3NH\sb2,\ 1.19\pm0.02$; $\rm C\sb2H\sb5NH\sb2,\ 1.13\pm0.10$; (CH$\rm\sb3)\sb2NH,\ 0.90\pm0.05$; $\rm(CH\sb3)\sb3N,\ 0.61\pm0.04$; $\rm(C\sb2H\sb5)\sb3N,\ 0.36\pm0.02.$ Comparisons are made with the rate constants calculated from the Average-Dipole-Orientation (ADO) ion-molecule collision theory. The measured rate constants for acetone and ammonia are close to the collision limit but decrease with increasing number of alkyl groups on nitrogen. Additional measurements were made to explore the pressure dependence of the rate constants for the association reactions, and all were found to be independent of pressure. Six exchange reactions between different Me$\rm\sb3Si\sp+\cdot$ amine adducts $\rm(Me\sb3Si\sp+\cdot amine\sb1+amine\sb2\to Me\sb3Si\sp+\cdot amine\sb2+amine\sb1)$ were also investigated. The measured results: $\rm amine\sb1/amine\sb2,$ rate constant and standard deviation $\rm(10\sp{-10}\ cm\sp3\ molecule\sp{-1}s\sp{-1})$ from multiple determinations are: $\rm NH\sb3/CH\sb3NH\sb2,\ 6.2\pm0.3$; $\rm NH\sb3/(CH\sb3)\sb2NH,\ 5.4\pm0.2$; $\rm CH\sb3NH\sb2/(CH\sb3)\sb2NH,\ 5.1\pm0.3$; $\rm CH\sb3NH\sb2/(CH\sb3)\sb3N,\ 4.1\pm0.2$; $\rm(CH\sb3)\sb2NH/(CH\sb3)\sb3N,\ 24\pm0.1.$ For $\rm NH\sb3/(CH\sb3)\sb3N,$ very little adduct formation occurred. It was suggested by a proton transfer reaction for which the rate constant was measured as: $\rm9.9\pm0.6\times10\sp{-10}\ cm\sp3\ molecule\sp{-1}s\sp{-1}.$ For both association and exchange reactions, the experimental values of the rate constants demonstrate a significant steric inhibition with increase in the number of the alkyl groups on nitrogen.
ISBN
0612152375
9780612152373