OXIMES, in organic chemistry, compounds containing the grouping > C: N OH, derived from aldehydes and ketones by condensing them with hydroxylamine.
Beckmann, Ber., 1886, 1 9, p. 9 8 9; 188 7, 20, p. 2580), yielding as final products an acid-amide or anilide, thus: RC(:N OH)R'-RC(OH) :NR' ---> As regards the constitution of the oximes, two possibilities exist, namely >C: NOH, or > C' ?, and the first of these is presumably correct, since on alkylation and subsequent hydrolysis an alkyl hydroxylamine of the type NH 2 OR is obtained, and consequently it is to be presumed that in the alkylated oxime, the alkyl group is attached to oxygen, and the oxime itself therefore contains the hydroxyl group. It is to be noted that the oximes of aromatic aldehydes and of unsymmetrical aromatic ketones frequently exist in isomeric forms. This isomerism is explained by the HantzschWerner hypothesis (Ber., 1890, 23, p. II) in which the assumption is made that the three valencies of the nitrogen atom do not lie in the same plane.
Benzophenone oxime, CeHSC (:NOH)C 6 H 5, exists only in one modification which melts at 140° C.; whereas the unsymmetrical benzophenones each yield two oximes.
Wallach (Ann., 1900, 312, p. 171) has shown that the saturated cyclic ketones yield oximes which by an application of the Beckmann reaction are converted into isoximes, and these latter on hydrolysis with dilute mineral acids are transformed into acyclic amino-acids; thus from cyclohexanone, e-amidocaproic acid (e-leucine) may be obtained: CH2" C NOH C CH 2 CH 2 7: ?12?CH2 CH2 NH /CH2 CH2 C02H CH2', An ingenious application of the fact that oximes easily lose the elements of water and form nitriles was used by A.
Both oximes and hydrazones, on boiling with dilute acid, regenerate the parent aldehyde.
The oximes permit the reverse change, i.e.
Wallach, Ber., 1881, 14, P. 421); by the action of reducing agents on nitroparaffins; by the action of zinc and hydrochloric acid on aldehyde ammonias (German Patent 73,812); by the reduction of the phenylhydrazones and oximes of aldehydes and ketones with sodium amalgam in the presence of alcohol and sodium acetate (J.
According to Hantzsch the isomeric diazo hydroxides are structurally identical, and the differences in behaviour are due to stereo-chemica l relations, the isomerism being comparable with that of the oximes.
With aldehydes and ketones it forms oximes.
Thus with hydroxylamine aldehydes yield aldoximes, R CH: N OH, and ketones, ketoximes, R 2 C: N OH (see Oximes), while phenyl hydrazine gives phenylhydrazones, R 2 C:N NH C 6 H 5 (see Hydrazones).
The isomerism of the oximes of unsymmetrical ketones is explained in the same manner, and their configuration is determined by an application of the Beckmann transformation (see Ber., 1891, 24, p. 1 3); thus: R C R' - R C(OH): NR'-->R Conhr'(R' and OH, " syn ").
Benzophenone oxime, CeHSC (:NOH)C 6 H 5, exists only in one modification which melts at 140Ã‚° C.; whereas the unsymmetrical benzophenones each yield two oximes.
The latter readily undergo the " Beckmann " transformation on treatment with acid chlorides, yielding substituted acid amides, RR' C:NOH -› RC(NR') OH - R CO NHR' (see OxIMES, also A.
With phenylhydrazine it forms a hydrazone, and with hydroxylamine an oxime, which exists in one form only; if, however, one of the phenyl groups in the oxime be substituted in any way then two stereo-isomeric oximes are produced (cf.
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