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One prominent application of synthetic organobromine compounds is the use of polybrominated diphenyl ethers as fire-retardants, and in fact fire-retardant manufacture is currently the major industrial use of the element bromine. A variety of minor organobromine compounds are found in nature, but none are biosynthesized or required by mammals.
Bromine monofluoride in ethanol readily leads to the monobromination of the aromatic compounds PhX (para-bromination occurs for X = Me, Bu t, OMe, Br; meta-bromination occurs for the deactivating X = –CO 2 Et, –CHO, –NO 2); this is due to heterolytic fission of the Br–F bond, leading to rapid electrophilic bromination by Br +. [4]
The major product of the addition reaction will be the one formed from the more stable intermediate. Therefore, the major product of the addition of HX (where X is some atom more electronegative than H) to an alkene has the hydrogen atom in the less substituted position and X in the more substituted position.
These methods work best when the bromide product is stable to hydrolysis; otherwise, the possibilities include high-temperature oxidative bromination of the element with bromine or hydrogen bromide, high-temperature bromination of a metal oxide or other halide by bromine, a volatile metal bromide, carbon tetrabromide, or an organic bromide.
The NBS product precipitates and can be collected by filtration. [1] Crude NBS gives better yield in the Wohl–Ziegler reaction. In other cases, impure NBS (slightly yellow in color) may give unreliable results. It can be purified by recrystallization from 90 to 95 °C water (10 g of NBS for 100 mL of water). [2]
A halogen addition reaction is a simple organic reaction where a halogen molecule is added to the carbon–carbon double bond of an alkene functional group. [1]The general chemical formula of the halogen addition reaction is:
Bromination favors the reactants because it is an endothermic reaction, which means that the reactants are lower in energy than the products. [11] Since the transition state is hard to observe, the postulate of bromination helps to picture the “late” transition state (see the representation of the "late" transition state).
The latter occurs faster, and is the major product. The experimental relative chlorination rates at primary, secondary, and tertiary positions match the corresponding radical species' stability: tertiary (5) > secondary (3.8) > primary (1). Thus any single chlorination step slightly favors substitution at the carbon already most substituted.