Ultraviolet photodissociation and thermochemistry of CH/sub 2/BrCH/sub 2/I, CF/sub 2/BrCF/sub 2/I, and CF/sub 2/ICF/sub 2/I
Using photofragment translational spectroscopy, we have monitored the dissociation of CH/sub 2/BrCH/sub 2/I at 248, 266, and 308 nm, and CF/sub 2/BrCF/sub 2/I and CF/sub 2/ICF/sub 2/I at 308 nm. The primary fragments are I(/sup 2/P/sub 3//sub ///sub 2/) and I(/sup 2/P/sub 1//sub ///sub 2/) and the corresponding haloethyl radicals. The I(/sup 2/P/sub 3//sub ///sub 2/) contribution decreases upon fluorination, but it is dominant for CH/sub 2/BrCH/sub 2/I at 308 nm. The electronic absorption dipole lies roughly along the C--I bond axis in every case. Stable CF/sub 2/CF/sub 2/Br and CF/sub 2/CF/sub 2/I radicals can be readily generated through photodissociation of the parent compounds, while stable CH/sub 2/CH/sub 2/Br could not be unambiguously observed. Upper limits to the reaction enthalpy at 0 K for CF/sub 2/ICF/sub 2/Br(I)..-->..C/sub 2/F/sub 4/+I+Br(I) are 75 +- 1(59 +- 1) kcal/mol. The TOF spectra and related data suggest that there is a barrier to decomposition for CF/sub 2/CF/sub 2/I..-->..C/sub 2/F/sub 4/+I that exceeds the C--I bond energy in the radical.
- Research Organization:
- Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory and Department of Chemistry, University of California, Berkeley, California 94720
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6259854
- Journal Information:
- J. Chem. Phys.; (United States), Vol. 90:11
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BROMINATED ALIPHATIC HYDROCARBONS
DISSOCIATION HEAT
PHOTOLYSIS
FLUORINATED ALIPHATIC HYDROCARBONS
IODINATED ALIPHATIC HYDROCARBONS
CHEMICAL BONDS
ULTRAVIOLET RADIATION
CHEMICAL REACTIONS
DECOMPOSITION
ELECTROMAGNETIC RADIATION
ENTHALPY
HALOGENATED ALIPHATIC HYDROCARBONS
ORGANIC BROMINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC FLUORINE COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHYSICAL PROPERTIES
RADIATIONS
REACTION HEAT
THERMODYNAMIC PROPERTIES
400500* - Photochemistry