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Gas-phase aromatic substitution by positive bromine ions from /sup 80m/Br(IT)/sup 80/Br: a study of linear free energy relationship

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00451a031· OSTI ID:7311237

Mono- and disubstituted benzenes have been brominated by /sup 80/Br/sup +/ in the gas phase following the isomeric transition /sup 80m/Br(IT)/sup 80/Br. The ratios of rates, derived from product ratios, give linear sigma rho plots using sigma/sup +/ parameters with rho/sup +/ = - 0.9. Inductive and resonance effects were separated to obtain rho/sub I/sup m/ = -0.78, rho/sub I//sup p/ = - 0.80, rho/sub R/sup m/ = -0.20 and rho/sub R/sup p/ = -1.03. An extension of these results led to a quantitative analysis of additive influences of the substituents in the p-dichlorobenzene molecule. Following the empirical formula log p/sub f/sup Me/ = c log (p/sub f/sup Me/m/sub f/sup Me/) in the toluene system, a correlation between the experimental results and the theory is given by the expression c = sigma/sub p//sup +//(sigma/sub p//sup +/ - sigma/sub m//sup +/). The fact that our results of the electrophilic substitution by /sup 80/Br/sup +/ follow the ''classical'' reactivity-selectivity relationship seems to be a good proof for the validity of a linear free energy relationship for extremely reactive electrophilic species like unsolvated ions in the gas phase. Obviously the naked ions follow a similar mechanism as solvated ions and there is no need for establishing a new reaction model for the gas-phase aromatic substitution.

Research Organization:
Kernforschungsanlage, Juelich GmbH, Ger.
OSTI ID:
7311237
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 99:9; ISSN JACSA
Country of Publication:
United States
Language:
English

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Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400701* -- Radiochemistry & Nuclear Chemistry-- Hot-Atom Chemistry
AROMATICS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
BROMINATION
BROMINE 80
BROMINE ISOTOPES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
ELECTRON CAPTURE RADIOISOTOPES
HALOGENATION
HOT ATOM CHEMISTRY
HOURS LIVING RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
ISOTOPES
KINETICS
MINUTES LIVING RADIOISOTOPES
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
RADIOCHEMISTRY
RADIOISOTOPES
REACTION KINETICS