Halogenation product mixtures

Reactions other than those of the nucleophilic reactivity of alkyl sulfates iavolve reactions with hydrocarbons, thermal degradation, sulfonation, halogenation of the alkyl groups, and reduction of the sulfate groups. Aromatic hydrocarbons, eg, benzene and naphthalene, react with alkyl sulfates when cataly2ed by aluminum chloride to give Fhedel-Crafts-type alkylation product mixtures (59). Isobutane is readily alkylated by a dipropyl sulfate mixture from the reaction of propylene ia propane with sulfuric acid (60). 

In a very recent study, it has been demonstrated116 that zinc 5,15-bis(3,5-di-tert-butylphenyl)-porphyrin (13) without any activating halogen atoms at the chromophore can be directly linked in a very simple oxidative coupling reaction with silver(I) hexafluorophosphate to a mixture of porphyrin dimers, trimers and tetramers. The separation of the product mixture was achieved by gel-permeation chromatography based on the molecular weights of the oligomers. The dimer when re-exposed to the same reaction conditions yielded 25% of the tetramer.116... 

It was suggested that halogenation-dehalogenation with diaryltellurium derivatives is an equilibrium process since, at identical concentrations, debromination of erythro-l, 2-dibromo-l,2-diphenylethane with diaryItellurides andbromination of trani-stilbene with dibromodiarylteUurides gives identical product mixtures. 

The composition of the product mixture will depend on the relative rates of formation of the isomeric enols, provided that the halogenation step is not a reversible reaction. Barring any serious steric effects that influence the rate of reaction, the more rapidly formed enol generally is the more thermodynamically stable enol. 

In other substitution reactions, such as halogenation, the reactivity determinations are necessarily based on the quantitative analysis of product mixtures. The results can often be dubious, especially if individual site reactivities show a wide spread. Protodedeuteration is not subject to this limitation because the reactivities of individual positions are determined in separate experiments. 

In general, the reaction of aromatic amines with sources of a positive halogen (chlorine) proceeds to give mixtures of ring-halogenated products (equation 19). 

As noted previously, the electrophilic halogenation of phosphonate carbanions often suffers from competing transmetallation reactions, which generate product mixtures containing mono-, di-, and... 

This is a substitution reaction, as a hydrogen atom on the carbon is substituted for a Cl or Br atom. A mixture of halogenated products is usually obtained if further substitution reactions can take place. 

Eq. (25)] produced a mixture of trans and cis products 105 and 106. It appears that halogenated products are formed in olefin cyclizations only in those systems where proton elimination from the intermediate carbonium ion is relatively slow. 

In the presence of large (not catalytic) amounts of various halogen-containing compounds of transition metals, including Rh, and Co, methylmagnesium-halide reagents and PhC=CPh form (after hydrolysis) product mixtures that include an addition product, PhCH=C(CH3)Ph . The extent to which precursors of this product contain bonds from carbon to Mg rather than to another metal is not certain, however. 

---