Diketene

Diketene is an organic compound with the molecular formula C4H4O2, also written as (CH2CO)2[1]. It is formed by the dimerization of ketene, H2C=C=O, and is a member of the oxetane family. Diketene is a colorless liquid used as a reagent in organic chemistry.

Production and Reactions

Diketene is produced commercially by the dimerization of ketene[1]. It can be converted back into ketene through heating or UV light irradiation[1]. Diketene readily hydrolyzes in water to form acetoacetic acid, with a half-life of approximately 45 minutes at 25°C and pH between 2 and 7[1]. It also reacts with alcohols and amines to form acetoacetic acid derivatives, a process known as acetoacetylation[1].

Use

Diketene is an important industrial intermediate used in the production of acetoacetate esters and amides, as well as substituted 1-phenyl-3-methylpyrazolones[1]. These pyrazolones are used in the manufacture of dyestuffs and pigments. Diketenes with two alkyl chains, known as alkyl ketene dimers (AKDs), are used in the paper industry to improve hydrophobicity and printability[1]. They are also used as intermediates in the manufacture of pharmaceuticals, insecticides, and dyes[1].

Safety

Diketene is a flammable and reactive chemical, posing a dangerous fire and explosion hazard[2]. It is a DOT Poison Inhalation Hazard (PIH) and can affect health when inhaled, causing irritation to the skin, eyes, nose, throat, and lungs[2]. Prolonged contact can cause redness and drying of the skin. Despite its high reactivity, diketene is not considered a carcinogen, possibly due to the instability of its DNA adducts[1].

Handling and Emergency Procedures

When handling diketene, it is essential to follow proper safety protocols to minimize exposure risks[2]. In case of spills or leaks, the area should be evacuated, ignition sources removed, and the spill covered with an activated charcoal adsorbent before disposal[2]. The CDC's National Institute for Occupational Safety and Health (NIOSH) has established an Immediately Dangerous to Life or Health (IDLH) value for diketene, which is 7.6 ppm[3][5]. This value is based on the rat BMCL05 of 181 ppm for lethality in a 1-hour exposure[3][5].

Citations:

[1] https://en.wikipedia.org/wiki/Diketene

[2] https://nj.gov/health/eoh/rtkweb/documents/fs/0732.pdf

[3] https://www.cdc.gov/niosh/docs/2017-108/default.html

[4] https://www.sigmaaldrich.com/US/en/product/aldrich/422363

[5] https://www.cdc.gov/niosh/docs/2017-108/pdfs/2017-108.pdf