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Ketene
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Ketene
In organic chemistry, a ketene is an organic compound of the form RR'C=C=O, where R and R' are two arbitrary monovalent chemical groups (or two separate substitution sites in the same molecule). The name may also refer to the specific compound ethenone H2C=C=O, the simplest ketene.
Although they are highly useful, most ketenes are unstable. When used as reagents in a chemical procedure, they are typically generated when needed, and consumed as soon as (or while) they are produced.
Ketenes were first studied as a class by Hermann Staudinger before 1905.
Ketenes were systematically investigated by Hermann Staudinger in 1905 in the form of diphenylketene (conversion of -chlorodiphenyl acetyl chloride with zinc). Staudinger was inspired by the first examples of reactive organic intermediates and stable radicals discovered by Moses Gomberg in 1900 (compounds with triphenylmethyl group).
Ketenes are highly electrophilic at the carbon atom bonded with the heteroatom, due to its sp character. Ketenes can be formed with different heteroatoms bonded to the sp carbon atom, such as O, S or Se, respectively called ketenes, thioketenes and selenoketenes.
Ethenone, the simplest ketene, has different experimental lengths for each of its double bonds; the C=O bond is 1.160 Å and the C=C bond is 1.314 Å. The angle between the two H atoms is 121.5°, similar to the theoretically ideal angle in alkenes between sp2 carbon atoms and H substituents.
Ketenes are unstable and cannot be stored. Absent nucleophiles with which to react, they dimerise (see § Reactions).
Ethenone is produced on a commercial scale by thermal dehydration of acetic acid. Substituted ketenes can be prepared from acyl chlorides by an elimination reaction in which HCl is lost:
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Ketene
In organic chemistry, a ketene is an organic compound of the form RR'C=C=O, where R and R' are two arbitrary monovalent chemical groups (or two separate substitution sites in the same molecule). The name may also refer to the specific compound ethenone H2C=C=O, the simplest ketene.
Although they are highly useful, most ketenes are unstable. When used as reagents in a chemical procedure, they are typically generated when needed, and consumed as soon as (or while) they are produced.
Ketenes were first studied as a class by Hermann Staudinger before 1905.
Ketenes were systematically investigated by Hermann Staudinger in 1905 in the form of diphenylketene (conversion of -chlorodiphenyl acetyl chloride with zinc). Staudinger was inspired by the first examples of reactive organic intermediates and stable radicals discovered by Moses Gomberg in 1900 (compounds with triphenylmethyl group).
Ketenes are highly electrophilic at the carbon atom bonded with the heteroatom, due to its sp character. Ketenes can be formed with different heteroatoms bonded to the sp carbon atom, such as O, S or Se, respectively called ketenes, thioketenes and selenoketenes.
Ethenone, the simplest ketene, has different experimental lengths for each of its double bonds; the C=O bond is 1.160 Å and the C=C bond is 1.314 Å. The angle between the two H atoms is 121.5°, similar to the theoretically ideal angle in alkenes between sp2 carbon atoms and H substituents.
Ketenes are unstable and cannot be stored. Absent nucleophiles with which to react, they dimerise (see § Reactions).
Ethenone is produced on a commercial scale by thermal dehydration of acetic acid. Substituted ketenes can be prepared from acyl chlorides by an elimination reaction in which HCl is lost:
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