Alcoholysis
The alcoholysis is the cleavage of a chemical compound by reaction with an alcohol . In the process, a hydrogen atom is formally transferred to one "split piece", the remaining alcoholate is bound to the other split piece. Alcoholysis falls under the umbrella term “ solvolysis ” - a nucleophilic substitution in which the solvent itself is the nucleophile .
Reaction examples
Example of the acid-catalyzed transesterification of a natural triglyceride (above) in fats and oils. The fatty acid residue marked blue is saturated, the green marked is single, the red marked triple unsaturated . In the equilibrium reaction, glycerine is split off and FAME (below), a mixture of fatty acid methyl esters (biodiesel), in the example three different ones, is produced.
- The alcoholysis of carboxylic acid anhydrides produces esters and a carboxylic acid.
- A carboxylic acid halide reacts with an alcohol to form an ester and hydrogen halide . The reaction of alcohols with carboxylic acid chlorides in the presence of an alkali lye is known as the Schotten-Baumann method , with the halide of the alkali metal (e.g. sodium chloride ) being formed as a by-product .
- The corresponding esters can be obtained analogously from inorganic acid halides; so phosphorus oxychloride gives phosphoric acid esters and hydrogen chloride.
- The alcoholysis of carboxylic acid esters results in an equilibrium mixture of both possible esters and alcohols. This reaction can be catalyzed by acids or bases. In most cases, a is ester of a low molecular weight alcohol in an ester of a higher molecular weight alcohol is converted, wherein the low molecular weight alcohol wird.- by distillation from the reaction mixture away reversal has industrial significance: fats (Glycerinester of fatty acids ) - for example, rapeseed oil - are by acidic or basic catalysis converted into fatty acid methyl ester ( biodiesel ) and glycerine in the presence of methanol .
- The alcoholysis of alkyl halides , alkyl sulfonates or alkyl sulfates produces ethers . Usually, however, alcoholates ( Williamson ether synthesis ) are used instead of the corresponding alcohols because of their higher nucleophilicity .
See also
Individual evidence
- ^ Siegfried Hauptmann : Organic Chemistry , 2nd reviewed edition, VEB Deutscher Verlag für Grundstoffindindustrie, Leipzig, 1985, p. 419, ISBN 3-342-00280-8 .