title: Vibrationally quantum-state-specific reaction dynamics of H atom abstraction by CN radical in solution.
abstract: Solvent collisions can often mask initial disposition of energy to the products of solution-phase chemical reactions. Here, we show with transient infrared absorption spectra obtained with picosecond time resolution that the nascent HCN products of reaction of CN radicals with cyclohexane in chlorinated organic solvents exhibit preferential excitation of one quantum of the C-H stretching mode and up to two quanta of the bending mode. On time scales of approximately 100 to 300 picoseconds, the HCN products undergo relaxation to the vibrational ground state by coupling to the solvent bath. Comparison with reactions of CN radicals with alkanes in the gas phase, known to produce HCN with greater C-H stretch and bending mode excitation (up to two and approximately six quanta, respectively), indicates partial damping of the nascent product vibrational motion by the solvent. The transient infrared spectra therefore probe solvent-induced modifications to the reaction free energy surface and chemical dynamics.
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol, UK.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Greaves
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Rose
authors.forename: Thomas A A
authors.initials: TA
authors.lastname: Oliver
authors.forename: David R
authors.initials: DR
authors.lastname: Glowacki
authors.forename: Michael N R
authors.initials: MN
authors.lastname: Ashfold
authors.forename: Jeremy N
authors.initials: JN
authors.lastname: Harvey
authors.forename: Ian P
authors.initials: IP
authors.lastname: Clark
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Greetham
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Parker
authors.forename: Michael
authors.initials: M
authors.lastname: Towrie
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Orr-Ewing
mesh_terms: D055598:Chemical Phenomena; D003510:Cyclohexanes / Q000737:chemistry*; D005609:Free Radicals; D006859:Hydrogen / Q000737:chemistry*; D006856:Hydrogen Cyanide / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D012996:Solutions; D012997:Solvents / Q000737:chemistry; D013055:Spectrophotometry, Infrared
chemical_list: D003510:Cyclohexanes; D005609:Free Radicals; D012996:Solutions; D012997:Solvents; D006856:Hydrogen Cyanide; C506365:Cyclohexane; D006859:Hydrogen