Photodissociation of 1,2-chloroiodoethane at 248 and 266 nm: The enthalpy of formation of CH/sub 2/ClCH/sub 2/I

Journal Article · Wed Aug 15 00:00:00 EDT 1984 · J. Chem. Phys.; (United States)

OSTI ID:6672190

Minton, T K; Felder, P; Brudzynski, R J; Lee, Y T

The technique of photofragmentation translational spectroscopy has been utilized to study the photodissociation of CH/sub 2/ClCH/sub 2/I at excitation wavelengths of 248 and 266 nm. The primary photofragments are C/sub 2/H/sub 4/Cl and either I*(/sup 2/P/sub 1//sub ///sub 2/) or I(/sup 2/P/sub 3//sub ///sub 2/). A fraction of the chloroethyl radical product contains enough internal excitation after the primary process to undergo secondary dissociation into C/sub 2/H/sub 4/ and Cl. By observing the threshold for this secondary process, the reaction enthalpy for CH/sub 2/ClCH/sub 2/I..-->..C/sub 2/H/sub 4/+Cl+I was determined, which leads to: ..delta..H/sup 0//sub f/,0 (CH/sub 2/ClCH/sub 2/I) = -7.8 +- 1 kcal/mol. The c. m. translational energy distribution of the photofragments was derived for both the I* and I channels, yielding I*/I branching ratios of 1.5 at 248 nm and 3 at 266 nm. The translational energy distribution also revealed that about 50% of the excess energy went into translation. The angular distributions of dissociation products with respect to the laser polarization indicate that the primary photodissociation process for the ground and excited state iodine channels at both wavelengths proceeds via a parallel transition, i.e., the transition moment must be nearly parallel to the C--I bond.

• Research Organization: Materials and Molecular Research Division, Lawrence Berkeley Laboratory and Department of Chemistry, University of California, Berkeley, California 94720
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6672190
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 81:4; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500 -- Photochemistry
42 ENGINEERING
420300* -- Engineering-- Lasers-- (-1989)
ANGULAR DISTRIBUTION
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
DECOMPOSITION
DISSOCIATION
DISTRIBUTION
ELEMENTS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
ENTHALPY
EXCITED STATES
FORMATION HEAT
GAS LASERS
HALOGENATED ALIPHATIC HYDROCARBONS
HALOGENS
IODINATED ALIPHATIC HYDROCARBONS
IODINE
LASERS
NONMETALS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PHYSICAL PROPERTIES
REACTION HEAT
THERMODYNAMIC PROPERTIES