Search results
Results from the WOW.Com Content Network
Halogenation of saturated hydrocarbons is a substitution reaction. The reaction typically involves free radical pathways. The regiochemistry of the halogenation of alkanes is largely determined by the relative weakness of the C–H bonds. This trend is reflected by the faster reaction at tertiary and secondary positions.
The initial step of the halogenation of aromatic compounds differs from that of the halogenation of alkenes in that alkenes do not require a catalyst to enhance the electrophilicity of the halogen. The formation of the arenium ion results in the temporary loss of aromaticity , which has a higher activation energy compared to halonium ion ...
The general chemical formula of the halogen addition reaction is: C=C + X 2 → X−C−C−X (X represents the halogens bromine or chlorine, and in this case, a solvent could be CH 2 Cl 2 or CCl 4). The product is a vicinal dihalide. This type of reaction is a halogenation and an electrophilic addition.
The classical example of this is bromination (any halogenation) of alkenes. [5] An anti addition reaction results in a trans-isomer of the products, as the substituents are on opposite faces of the bond. Depending on the substrate double bond, addition can have different effects on the molecule.
A classic example of perceived RSP found in older organic chemistry textbooks concerns the free radical halogenation of simple alkanes. Whereas the relatively unreactive bromine reacts with 2-methylbutane predominantly to 2-bromo-2-methylbutane, the reaction with much more reactive chlorine results in a mixture of all four regioisomers.
For alkylbenzene derivatives, e.g. toluene, the alkyl positions tend to be halogenated by free radical conditions, whereas ring halogenation is favored in the presence of Lewis acids. [6] The decolouration of bromine water by electron-rich arenes is used in the bromine test. Reaction between benzene and halogen to form an halogenobenzene
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).
Toluene (/ ˈ t ɒ l. j u iː n /), also known as toluol (/ ˈ t ɒ l. j u. ɒ l , - ɔː l , - oʊ l / ), is a substituted aromatic hydrocarbon [ 15 ] with the chemical formula C 6 H 5 CH 3 , often abbreviated as PhCH 3 , where Ph stands for the phenyl group.