Halogen-substituted benzen

Inasmuch as the conjugation properties of a double bond and a benzene ring are closely similar,11 we expect for the halogen substituted benzenes interatomic distances similar to those for the halogen ethylenes. De Laszlo12 has reported the values C-Cl = 1.69 A., C-Br = 1.88 A., and C-I = 2.05 A., corresponding to 14., 6, and 10% double bond character, respectively.15... 

The alkylation of halogen-substituted benzenes such as fluorobenzene and dichlorobenzenes with other (dichloroalkyl)silanes in the presence of aluminum chloride catalyst afforded isomeric mixtures of the corresponding (dihalogen-substituted phenyl)alkylsilanes in moderate yields (Eq. (13)). These results are summarized in Table Xll. 

A similar result was also found for halogen-substituted benzenes as... 

The effect of fluorine, chlorine, or bromine as a substituent is unique in that the ring is deactivated, but the entering electrophile is directed to the ortho and para positions. This can be explained by an unusual competition between resonance and inductive effects. In the starting material, halogen-substituted benzenes are deactivated more strongly by the inductive effect than they are activated by the resonance effect. However, in the intermediate carbocation, halogens stabilize the positive charge by resonance more than they destabilize it by the inductive effect. 

Warne, M.S., Osbom, D., Lindon, J.C. and Nicholson, J.K. (1999b). Quantitative Stmcture-Toxicity Relationships for Halogenated Substituted-Benzenes to Vibrio fischeri. Using Atom-Based Semi-Empirical Molecular-Orbital Descriptors. Chemosphere, 38,3357-3382. 

The ultra-violet absorption maxima of p-halogen substituted benzene... 

Given the name (or structural diagram) of an alkyl- or halogen-substituted benzene compound, write the stmctural diagram (or name). 

The range of possible shifts of the NQR frequencies is reduced to 10-20% when only one class of compound is studied. In this case the shifts are determined by the surroundings and donor-acceptor properties of the substituents. For example, for halogen substituted benzenes, the changes of the frequencies for the C-Cl bonds are about 9% for C-Br bonds 12% and for C-I bonds 18%. 

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