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In chemistry, the haloform reaction (also referred to as the Lieben haloform reaction) is a chemical reaction in which a haloform (CHX 3, where X is a halogen) is produced by the exhaustive halogenation of an acetyl group (R−C(=O)CH 3, where R can be either a hydrogen atom, an alkyl or an aryl group), in the presence of a base.
Trihalomethanes with all the same halogen atoms are called haloforms. Many trihalomethanes find uses in industry as solvents or refrigerants . Some THMs are also environmental pollutants , and a few are considered carcinogenic .
Bromoform was discovered in 1832 by Löwig who distilled a mixture of bromal and potassium hydroxide, as analogous to preparation of chloroform from chloral. [5]Bromoform can be prepared by the haloform reaction using acetone and sodium hypobromite, by the electrolysis of potassium bromide in ethanol, or by treating chloroform with aluminium bromide.
It is a hydrofluorocarbon as well as being a part of the haloforms, a class of compounds with the formula CHX 3 (X = halogen) with C 3v symmetry. Fluoroform is used in diverse applications in organic synthesis. It is not an ozone depleter but is a greenhouse gas. [2]
Several thousand complex halocarbons are known to be produced mainly by marine species. Although chlorine compounds are the majority of the discovered compounds, bromides, iodides and fluorides have also been found in nature. Tyrian purple is a bromide and is produced by certain sea snails. Thyroxine is secreted by the thyroid gland and is an ...
In acidic solution, usually only one alpha hydrogen is replaced by a halogen, as each successive halogenation is slower than the first. The halogen decreases the basicity of the carbonyl oxygen, thus making protonation less favorable. However, in basic solutions, successive halogenation is more rapid due to inductive electron withdrawal by the ...
Halomethane compounds are derivatives of methane (CH 4) with one or more of the hydrogen atoms replaced with halogen atoms (F, Cl, Br, or I). Halomethanes are both naturally occurring, especially in marine environments, and human-made, most notably as refrigerants, solvents, propellants, and fumigants.
Square planar tetrahalides are known for Pd(II), Pt(II), and Au(III). Examples with 2- and 3-coordination are common for Au(I), Cu(I), and Ag(I). Due to the presence of filled p π orbitals, halide ligands on transition metals are able to reinforce π-backbonding onto a π-acid. They are also known to labilize cis-ligands. [2] [3]