Dynamics of endoergic substitution reactions. I. Br+chlorinated aromatic compounds

Journal Article · Tue Nov 15 00:00:00 EST 1988 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.455439· OSTI ID:6774146

Robinson, G N; Continetti, R E; Lee, Y T

The endoergic substitution reactions Br+R--Cl..-->..Cl+R--Br (R = o-, m-, and p-CH/sub 3/C/sub 6/H/sub 4/, C/sub 6/H/sub 5/, C/sub 6/F/sub 5/; ..delta..H/sup 0/approx. =15 kcal/mol) have been studied using the crossed molecular beams method in the collision energy (E/sub c/ ) range 20--35 kcal/mol. The CH/sub 3/C/sub 6/H/sub 4/Br and C/sub 6/F/sub 5/Br products were found to be mostly forward scattered with respect to the incident Br beam indicating that the lifetimes of the Br--R--Cl collision complexes are short compared to their rotational periods. The product translational energy distributions and excitation functions for these reactions are well reproduced by statistical calculations that assume that only a few vibrational modes in the collision complexes participate in intramolecular energy redistribution prior to Cl elimination. Ring substituents are found to affect both the extent of energy redistribution in the complexes and the probability of Br addition. For example, no substitution product was observed with m-CH/sub 3/C/sub 6/H/sub 4/Cl or C/sub 6/H/sub 5/Cl. The relative magnitudes of the cross sections are explained in terms of possible features of the potential energy surfaces along their reaction coordinates.

• Research Organization: Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory and Department of Chemistry, University of California, Berkeley, California 94720
• OSTI ID: 6774146
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 89:10; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
640304 -- Atomic
Molecular & Chemical Physics-- Collision Phenomena
74 ATOMIC AND MOLECULAR PHYSICS
AROMATICS
BEAMS
BROMINE
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINATED AROMATIC HYDROCARBONS
CROSS SECTIONS
ELEMENTS
EXCITATION FUNCTIONS
FUNCTIONS
HALOGENATED AROMATIC HYDROCARBONS
HALOGENS
KINETICS
MOLECULAR BEAMS
NONMETALS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RADICALS
REACTION KINETICS