Bromination of aromatic hydrocarbons

The bromination of aromatic hydrocarbons can occur either in a side chain or on the ring, depending on conditions. In the presence of sunlight aLkylben2enes are brominated predominately in the side chain (24). 

Whereas pure NBS effects side chain bromination of aromatic hydrocarbons, aged material effects bromination of aromatic ring. 

Whereas pure NBS effects side-chain bromination of aromatic hydrocarbons, aged material effects bromination of the aromatic ring. The responsible impurity can be removed by pumping out at 0.5 mm. over phosphorus pentoxide for 4 hrs. Caution Explosions have been reported in reactions of NBS. ... 

Aromatic bromides. McKillop, Bromley, and Taylor1 have described a new, simple, general procedure for bromination of aromatic hydrocarbons using thallium triacetate and bromine (CC14). The reaction is remarkable in that a single monobromo product is obtained. Note, however, that the combination of thallium triacetate and chlorine or iodine leads to isomeric mixtures. The method is particularly useful in the case of aromatics that are sensitive to bromine. 

With respect to solid-supported reactions, it can be observed that the structure of the support can be altered during the sonochemical reaction. In a non-catalytic reaction that is beyond the scope of this chapter, the bromination of aromatic hydrocarbons using cupric bromide on neutral alumina, author showed that both the particle size of AI2O3 and its morphology have been changed after the preparation step using ultrasound. An optimum level of ultrasound power... 

Impurities can sometimes be removed by conversion to derivatives under conditions where the major component does not react or reacts much more slowly. For example, normal (straight-chain) paraffins can be freed from unsaturated and branched-chain components by taking advantage of the greater reactivity of the latter with chlorosulfonic acid or bromine. Similarly, the preferential nitration of aromatic hydrocarbons can be used to remove e.g. benzene or toluene from cyclohexane by shaking for several hours with a mixture of concentrated nitric acid (25%), sulfuric acid (58%), and water (17%). 

Horii Y, Ok G, Ohura T, Kannan K (2008) Occurrence and profiles of chlorinated and brominated polycyclic aromatic hydrocarbons in waste incinerators. Environ Sci Technol 42(6) 1904—1909. doi 10.1021/es703001f... 

Horii Y, Khim JS, Higley EB, Giesy JP, Ohura T, Kannan K (2009) Relative potencies of individual chlorinated and brominated polycyclic aromatic hydrocarbons for induction of aryl hydrocarbon receptor-mediated responses. Environ Sci Technol 43(6) 2159-2165. doi 10.102 l/es8030402... 

SCHEME 185. Chlorination and bromination of aromatic amines, hydrocarbons and naphthols with in situ generated active halogen... 

The direct halogenation of aromatic hydrocarbons in the laboratory is feasible. Chlorination or bromination of benzene gives one monohalogen, CoHisX, and by proper control of temperature and concentration of the halogen, the formation of dihalogen com-poimds, C6H4X2, can be kept at a minimum ... 

Under the preparation of brombenzene it has already been mentioned that by the action of chlorine or bromine on aromatic hydrocarbons containing aliphatic side-chains, different products are formed,... 

Two methods are used to determine bromine index of aromatic hydrocarbons which contain trace amounts of olefins and are substantially free of materials lighter than isobutane and have distillation end-point lower than 288 C. The meteods measure trace amounts of unsaturations in materials which have a bromine index below 500. 

ASTM D 5776-98. Standard method for bromine index of aromatic hydrocarbons by electrometric titration. 

Horii, Y., Khim, J.S., Higley, E.B., Giesy, J.P., Ohura, T., Kannan, K., 2009. Relative Potencies of Individual Chlorinated and Brominated Polycyclic Aromatic Hydrocarbons for Induction of Aryl Hydrocarbon Receptor-Mediated Responses. Environ Sci Technol 43, 2159-2165. 

The sulfoxidation of aromatic hydrocarbons has been extensively studied, but work on the sulfoxidation of saturated hydrocarbons to alkanesulfonic acids remains at a less satisfactory level. The Strecker reaction using alkyl halides, preferably alkyl bromides, and alkali metal or ammonium sulfides, is commonly used for the synthesis of alkanesulfonic adds [153]. Another procedure, the oxidation of thiols with bromine in the presence of water or hydrogen peroxide and acetic acid, has been... 

---