Diketene
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Names | |||
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Preferred IUPAC name
4-Methylideneoxetan-2-one | |||
Other names
γ-Methylenepropiolactone
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Identifiers | |||
3D model (
JSmol ) |
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ChemSpider | |||
ECHA InfoCard
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100.010.562 | ||
EC Number |
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PubChem CID
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RTECS number
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UNII | |||
UN number | 2521 | ||
CompTox Dashboard (EPA)
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Properties | |||
C4H4O2 | |||
Molar mass | 84.074 g·mol−1 | ||
Density | 1.09 g cm−3 | ||
Melting point | −7 °C (19 °F; 266 K) | ||
Boiling point | 127 °C (261 °F; 400 K) | ||
Viscosity | 0.88 mPa.s | ||
Hazards | |||
GHS labelling: | |||
Danger | |||
H226, H301, H302, H315, H318, H330, H331, H332, H335 | |||
P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P280, P284, P301+P310, P301+P312, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P311, P312, P320, P321, P330, P332+P313, P362, P370+P378, P403+P233, P403+P235, P405, P501 | |||
Flash point | 33 °C (91 °F; 306 K) | ||
275 | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Diketene is an
Production
Diketene is produced on commercial scale by dimerization of ketene.[2]
Reactions
Heating or irradiation with UV light[3] regenerates the ketene monomer:
Alkylated ketenes also dimerize with ease and form substituted diketenes.
Diketene readily hydrolyzes in water forming acetoacetic acid. Its half-life in water is approximately 45 min. a 25 °C at 2 < pH < 7.[4]
Certain diketenes with two aliphatic chains, such as alkyl ketene dimers (AKDs), are used industrially to improve hydrophobicity in paper.
At one time acetic anhydride was prepared by the reaction of ketene with acetic acid:[5]
Acetoacetylation
Diketene also reacts with alcohols and amines to the corresponding acetoacetic acid derivatives. The process is sometimes called acetoacetylation. An example is the reaction with 2-aminoindane:[6]
Diketene is an important industrial intermediate used for the production of acetoacetate esters and amides as well as substituted 1-phenyl-3-methylpyrazolones. The latter are used in the manufacture of dyestuffs and pigments.[7] A typical reaction is:
These acetoacetamides are precursors to arylide yellow and diarylide pigments.[8]
Use
Diketenes with two alkyl chains are used in the manufacture of paper for sizing of paper in order to improve their printability (by hydrophobization). Besides the rosin resins with about 60% share of world consumption, long chain diketenes called alkylketene dimers (AKD) are with 16% share the most important synthetic paper sizes, they are usually used in concentrations of 0.15%, meaning 1.5 kg solid AKD/t paper.
The preparation of AKD is carried out by chlorination of long chain fatty acids (such as stearic acid, using chlorinating agents such as thionyl chloride) to give the corresponding acid chlorides and subsequent elimination of HCl by amines (for example triethylamine) in toluene or other solvents:[9]
Furthermore, diketenes are used as
Exemplary for the synthesis of arylides by the reaction of diketenes with aromatic amines is:
Aromatic diazonium coupling with arylides to form azo dyes, such as Pigment Yellow 74:
The industrial synthesis of the sweetener acesulfam-K is based on the reaction of diketene with sulfamic acid and cyclization by sulfur trioxide (SO3).[10]
Safety
Despite its high reactivity as an
References
- ^ Beilstein E III/IV 17: 4297.
- ISBN 978-3-527-30385-4.
- PMID 22273010.
- doi:10.1002/poc.1483.
- ]
- PMID 17999519.
- ^ Ashford's Dictionary of Industrial Chemicals, Third Edition, 2011, pages 3241-2.
- ISBN 978-3527306732.
- ^ Wolf S. Schultz: Sizing Agents in Fine Paper[permanent dead link] Retrieved 1 March 2012.
- ^ EP 0218076 Process for the preparation of the non-toxic salts of 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-on-2,2-dioxide.
- PMID 18759502.