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The preparation of EtBr stands as a model for the synthesis of bromoalkanes in general. It is usually prepared by the addition of hydrogen bromide to ethene: H 2 C=CH 2 + HBr → H 3 C-CH 2 Br. Bromoethane is inexpensive and would rarely be prepared in the laboratory.
Ethane can react with the halogens, especially chlorine and bromine, by free-radical halogenation. This reaction proceeds through the propagation of the ethyl radical: [36] Cl 2 → 2 Cl• C 2 H 6 • + Cl• → C 2 H 5 • + HCl C 2 H 5 • + Cl 2 → C 2 H 5 Cl + Cl• Cl• + C 2 H 6 → C 2 H 5 • + HCl
As it attacks and forms a bond with one of the carbons, the bond between the first bromine atom and the other carbon atoms breaks, leaving each carbon atom with a halogen substituent. In this way the two halogens add in an anti addition fashion, and when the alkene is part of a cycle the dibromide adopts the trans configuration .
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula C 2 H 4 or H 2 C=CH 2. It is a colourless, flammable gas with a faint "sweet and musky " odour when pure. [ 7 ] It is the simplest alkene (a hydrocarbon with carbon–carbon double bonds ).
The bromine test can also be used as an indication of the degree of unsaturation for unsaturated hydrocarbons. Bromine number is defined as gram of bromine able to react with 100g of product. [18] Similar as hydrogenation, the halogenation of bromine is also depend on the number of π bond. A higher bromine number indicates higher degree of ...
These bromine atoms add to an alkene at the most accessible site, to give a bromoalkyl radical, with the radical on the more substituted carbon. That radical then abstracts a hydrogen atom from another HBr molecule to regenerate the monatomic bromine and continue the reaction. [3]: 758
The silver salt 1 reacts with bromine to form the acyl hypohalite intermediate 2. Formation of the diradical pair 3 allows for radical decarboxylation to form the diradical pair 4, which recombines to form the organic halide 5. The trend in the yield of the resulting halide is primary > secondary > tertiary. [2] [3]
Depending on the substrate double bond, addition can have different effects on the molecule. After addition to a straight-chain alkene such as ethene (C 2 H 4), the resulting alkane will rapidly and freely rotate around its single sigma bond under normal conditions (i.e. room temperature). Thus whether substituents are added to the same side ...