3- Chloro-4-bromotoluene

Stock and Baker2 5 9 measured the relative rates of chlorination of a number of halogenated aromatics in acetic acid containing 20.8 M H20 and 1.2 M HC1 at 25 °C and the values of the second-order rate coefficients (103Ar2) are as follows p-xylene (11,450), benzene (4.98), fluorobenzene (3.68), chlorobenzene (0.489), bromobenzene (0.362), 2-chlorotoluene (3.43), 3-chlorotoluene (191), 4-chloro-toluene (2.47), 4-fluorotoluene (9.70), 4-bromotoluene (2.47). Increasing the concentration of the aromatic, however, caused, in some cases, a decrease in the rate coefficients thus an increase in the concentration of chlorobenzene from 0.1 M to 0.2 M caused a 20 % decrease in rate coefficient, whereas with 4-chloro-and 4-bromo-toluene, no such change was observed. 

The following couples were tested p-chlorobenzonitrile/p-chloro-acetophenone, p-chloroacetophenone/p-chlorodiphenyl, p-chlorodiphenyl /chlorobenzene, p-chlorodiphenyl/p-chlorofluorobenzene, chlorobenzene /p-chlorotoluene, chlorobenzene/p-chloroanisole, p-chloroacetophenone/ methyl ester of m-chlorobenzoic acid, chlorobenzene/m-chlorotoluene, p-chlorodiphenylether/p-chlorotoluene, m-chlorodiphenylether/chloroben-zene, m-chlorodiphenylether/p-chlorotoluene, chlorobenzene/methyl ester of m-chlorobenzoic acid, chlorobenzene/p-bromoanisole, p-bromoaceto-phenone / p-chlorobenzonitrile, p-bromobenzonitrile / p-chloroacetophe-none, bromobenzene/p-chlorodiphenyl, m-bromotoluene/chlorobenzene, and p-chlorodiphenyl/p-bromotoluene. 

The reaction of o-, m- and/ -bromotoluenes with Bu3SnLi in THF gave the substitution product. However, cme-substitution products were found with /7-chloro- and />-fluoro-toluenes, indicating that a benzyne mechanism operates. In the presence of Li metal, the yield of the ipso substitution products increased. These results suggest that the reaction, at least partially, occurs by a radical mechanism218. 

Thus, whereas Ph3Sn ions do not react in the dark with/7-chloro- and/7-bromotoluenes, /7-dichlorobenzene, 1-chloronaphthalene and 2-chloroquinoline, showing that there is no HME reaction, good yields of substitution products (62-80%) were obtained under irradiation (equation 114). 

For the preparation of chlorides or bromides, the diazonium salt is decomposed with a solution of cuprous chloride or bromide in the corresponding halogen acid (Sandmeyer reaction). It is possible to prepare the aryl bromide from the diazonium chloride or sulfate. A variation Involves the use of copper powder and a mineral acid for the decomposition step (Gattermann reaction). Both procedures are illustrated by the syntheses of the isomeric bromotoluenes and chlorotoluenes. The usual conditions of the Sandmeyer reaction fail in the preparation of the chloro- and bromo-phenanthrenes. However, these compounds can be successfully obtained by the interaction of the diazonium compound with mercuric and potassium halides (Schwechten procedure). Another procedure for formation of aryl bromides involves treatment of the amine hydrobromide with nitrogen trioxide in the presence of excess 40% hydro-bromic acid. The Intermediate diazonium perbromide is then decomposed by heat. ... 

The spectra of the intermediate transients formed in the reaction of OH with dichloro- and dibromo-benzenes and chloro- and bromo-toluenes exhibited absorption maxima around 325-330 nm with both ortho- and w to-isomers of dichlorobenzenes, dibromobenzenes, and bromotoluenes (Fig. 6). The transients were assigned to the isomeric OH adducts formed from the addition of OH to the benzene ring. A blue shift was observed in the absorption maximum of -bromotoluene (315 nm) when compared to its ortho- and meta-isomers which have maxima at 330 nm. Such a behavior was also seen in the absorption spectra of OH adducts of 0- and w-chlorotoluenes (325-330 nm) and w-xylenes (326-328 nm) as compared to their... 

Apply this test to benzyl bromide (a-bromotoluene), bromobenzene, and 2-chloro-2-methylpropane (ferf-butyl chloride). 

The host Ni(4-mepy)4(NCS)2 If forms isomorphous 1 1 inclusion compounds with many monocyclic aromatic guests. In continuing attempts to determine the basis for the selectivity shown by towards pairs of such guests, distribution data between solid and liquid phases were reported for seven ternary systems at room temperature. These consist of -xylene, and each of the following in turn -bromotoluene, -chlorotoluene, -fluorotoluene, -dichlorobenzene, 4-meth-ylpyridine and benzene, as well as the system I — -chloro-toluene— -dichlorobenzene, The results, as well as those already published, were reviewed. 

Ethyl oxalate Isocaproic acid a,a-Dichlorotoluene Benzoic acid a-Bromotoluene m-Bromotoluene o-Bromotoluene p-Bromotoluene a-Chloro toluene... 

Not every reaction that might pass through arynes always does it. All ortho-, meta-, and para-isomers of fluoro-, chloro-, and bromotoluene produce with TMEDA-activated phenyllithium isomeric mixtures of methylbiphenyls, the proportions of which are halogen-invariant and are in accordance with the intermediacy of 3-methyl- or 4-methyl-1,2-didehydrobenzene, respectively. In contrast, each one of the three iodotoluene gives a sole isomer that has conserved the regiochemistry of its precursor. Similarly, the treatment of or/Ao-fluoroanisole with 2,6-dimethoxyphenyllithium cleanly furnishes the weto-coupled 2, 3,4 -trimethoxybiphenyl-2-yllithium. However,... 

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