Diketene

4-methylene -2-oxetanone

Flammable, highly reactive, colorless liquid with a pungent odor

Liquid

1.09 g · cm -3

-7 ° C

127 ° C.

10 hPa ( 20 ° C)

Decomposes in water

1.4379 (20 ° C)

Attention

-233.1 KJ / mol

Template: Infobox chemical / molecular formula search available

Diketene is the common name of the chemical compound 4-methylene -2-oxetanone from the group of lactones.

Production and representation

Diketene is prepared by dimerization of ketene. The dimerization runs at room temperature spontaneously.

Properties

Diketene is highly reactive, colorless liquid, which is caused by dimerization of the ketene at room temperature and has a tendency to spontaneous polymerization. By heating it can be again converted into ketene.

Also alkylated ketenes dimerize readily to the corresponding substituted diketenes.

Diketene reacts readily with alcohols and amines to derivatives of acetoacetic acid.

Use

Diketene with two alkyl chains (so-called " Ketenwachs " ) is used in the manufacture of paper for sizing ( water repellency ) of paper, to improve the printability. In addition to the rosin resins with approximately 60% share of world consumption also known as alkyl ketene dimers (AKD ) are called long-chain diketenes with 16 % share of the most important synthetic paper sizes and are usually used in concentrations of 0.15 %, ie 1.5 kg of solid AKD / t of paper used. The production of AKD is accomplished by chlorination of long chain fatty acids - such as stearic acid - by chlorinating agents such as thionyl chloride to give the corresponding acid chlorides and subsequent elimination of HCl with amines - for example, triethylamine - in toluene or other solvents.

Diketene also serves as an intermediate in the preparation of pharmaceuticals, insecticides, and dyes. And it is to the substituted phenyl hydrazines as analgesics now largely obsolete Pyrazolones. With methylamine diketene reacts to Methylacetoacetamid which is chlorinated with sulfuryl chloride and reacted with trimethyl phosphite to the highly toxic ( especially bees ) insecticide monocrotophos. Diketene reacts with substituted aromatic amines to acetoacetanilides ( Arylide ), which are important precursors for usually yellow, orange or red azo dyes and azo pigments.

Exemplary of the synthesis of arylidene by reaction of diketene with the aromatic amine is

Aromatic diazonium coupling with arylidene the formation of azo dyes, such as Brilliant Yellow ( Pigment Yellow 74).

The industrial synthesis of the sweetener acesulfame-K is based on the reaction of diketene with sulfamic acid, and cyclization using SO3

Safety

The vapors of 4- methylene-2 ​​-oxetanone can form (33 ° C, ignition temperature 275 ° C flash point) with air to form an explosive mixture.