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Title: Chemical reaction dynamics in solution in chlorinated solvents
Author: Abou-Chahine , Fawzi
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2013
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This thesis investigates chemical reaction dynamics in solution in chlorinated solvents on ultrafast timescales. Ultraviolet (UV) photolysis of the chlorinated solvents at 266 nm produces Cl atoms, which react with 2,3-dimethylbut-2-cne (DMB). Experimental studies of this reaction address the question of how the energetic pathways and fundamental mechanisms of an isolated (i.e. gas phase) reaction change when it is occurs in the more condensed phase of a liquid environment. The data analysis and proposed reactive pathways are informed by the comparable reactions of Cl with propene in the gas phase and Cl with n-pentane in the condensed phase. A key observation is that - 15 - 30 % the Hel product of the reaction of Cl atoms with DMB is formed vibrationally hot (in v= I). This deduction is reinforced by separate measurements of the lifetime of vibrationally excited HCl in neat solvents, determined using infra-red (lR) pump and IR probe spectroscopy. These studies prompted a more complete study of the consequences of UV photoexcitation of the chlorinated solvents, and extensions to photochemical behaviour of solutions of 1,5- hexadiene (Hex) in CC14 and CDC13. Strong transient absorption bands centred around 330 nm and 500 nm were observed following 266-nm excitation of CC14, and a kinetic analysis supports assignment of these bands to CI-CC14 complexes and an isomeric form of the solvent, CI-CICC12, respectively. Similar assignments are made in the case of CD Ch. The loss of CI-CCI4 complexes, and thus the rates of decay of the transient absorption features, is accelerated upon addition of Hex to CCI4, because of reaction of Cl-CC14 with the Hex solute. Transient IR spectra obtained [or solutions of Hex in CCI4 and in CDCI) show evidence for formation of Hex cations following 2-phoLon excitation of the solvent. The assignments of the IR bands to the cations, instead of a range of other possible transient intermediates, are supported by computational calculations, at the B3L YP/6-31 G/2df,p level of theory.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available