Oximes


Hydroxylamine condenses with the carbonyl group of an aldehyde or ketone to form an oxime  [c.223]

Since hydroxylamine is usually available only in the form of its salts, e.g., the hydrochloride or sulphate, the aqueous solution of these salts is treated with sodium acetate or hydroxide to liberate the base before treatment with the aldehyde or ketone. Most oximes are weakly amphoteric in character, and may dissolve in aqueous sodium hydroxide as the sodium salt, from which they can be liberated by the addition of a weak acid, e.g., acetic acid.  [c.93]

Impure aldehydes and ketones are sometimes purified by conversion into the corresponding oximes, and the latter after recrystallisation are then hydrolysed by boiling with dilute sulphuric acid  [c.93]

Note. The sodium hydroxide must be accurately weighed out, for an excess will dissolve the oxime as the sodium derivative.)  [c.94]

Hydrolysis of Acetoxime. Place about i g. of the recrystallised oxime in a small distilling-flask (50 ml.), add 10 ml. of dilute HjSO, and heat gently until about half the solution has distilled over. Test [a] the aqueous distillate for acetone by the iodoform reaction (p.346), b) the residual solution in the distilling-flask for hydroxylamine by  [c.94]

Place 80 g, of hydroxylamine sulphate (or 68-5 g. of the hydrochloride), 25 g. of hydrated sodium acetate, and 100 ml. of water in a 500 ml. flask fitted with a stirrer and a reflux water-condenser, and heat the stirred solution to 55-60°. Run in 35 g (42 nil,) of -hexyl methyl ketone, and continue the heating and vigorous stirring for ij hours. (The mixture can conveniently be set aside overnight after this stage.) Extract the oily oxime from the cold mixture twice with ether. Wash the united ethereal extract once with a small quantity of water, and dry it with sodium sulphate. Then distil off the ether from the filtered extract, preferably using a distillation flask of type shown in Fig. 41 (p. 65) and of ca, 50 ml, capacity, the extract being run in as fast as the ether distils, and then fractionally distil the oxime at water-pump pressure. Collect the liquid ketoxime, b.p. 110-111713 mm. Yield, 30-32 g.  [c.225]

Place 25 g. (29 ml.) of the oxime and 100 ml. of ethanol in the flask, and heat the stirred solution under reflux on a boiling  [c.225]

Chill the concentrated solution of the amine hydrochloride in ice-water, and then cautiously with stirring add an excess of 20% aqueous sodium hydroxide solution to liberate the amine. Pour the mixture into a separating-funnel, and rinse out the flask or basin with ether into the funnel. Extract the mixture twice with ether (2 X25 ml.). Dry the united ether extracts over flake or powdered sodium hydroxide, preferably overnight. Distil the dry filtered extract from an apparatus similar to that used for the oxime when the ether has been removed, distil the amine slowly under water-pump pressure, using a capillary tube having a soda-lime guard - tube to ensure that only dry air free from carbon dioxide passes through the liquid. Collect the amine, b.p. 59-61°/12 mm. at atmospheric pressure it has b.p. 163-164°. Yield, 18 g.  [c.226]

The oximes of ketones when treated with various acidic reagents undergo the Beckmann Rearrangement, whereby, e.g., the OH group in the oxime (I) can be regarded as undergoing a tram exchange with the group R, followed by back migration of the H atom, to give the substituted acid amide (II). This process  [c.227]

Cyclohexanone oxime. Add 20 g. (21 ml.) of cyclohexanone to a solution of 17 g. of hydroxylamine hydrochloride in 40 ml. of water, and cool the mixture in ice-water. Add a solution of 13 g. of anhydrous sodium carbonate in 40 ml. of water slowly to the mixture, stirring the latter with a 100° thermometer, and maintaining the temperature of the mixture at 20-25° meanwhile. The oxime rapidly separates. Stir the complete mixture at intervals, and after 10 minutes filter the oxime at the pump, drain thoroughly and dry it in a (vacuum) desiccator. Yield of crude oxime, 20 g. Recrystallise from petroleum (b.p. 100-120 ) and dry over paraffin wax (p. 19). Yield of pure oxime, 16 g., m.p. 88°.  [c.228]

Beckmann Rearrangement. Prepare the 85% sulphuric acid by adding 50 ml. of the concentrated acid cautiously to 10 ml. of water, stirring the mixture meanwhile, and then cool the diluted acid in ice-water. Place 16 ml. of the cold acid in a 500 ml. beaker, add 8 g, of the pure oxime, and warm the mixture cautiously until effervescence begins, and then at once remove the heat. A vigorous reaction occurs, and is soon complete. Repeat this operation with another 8 g. of the oxime in a second beaker the reaction is too vigorous to be carried out with larger quantities.  [c.228]

Form phenylhydrazones, 2,4-dinitrophenylhydrazones and semicarbazones. (Many oximes are too soluble for ready isolation.)  [c.341]

B) Oximes. Dissolve i g. of the quinone in 5 ml. of glacial acetic acid. Dissolve i g. of hydroxylamine hydrochloride in 10 ml. of 10% aqueous sodium acetate solution and shake the mixture for 5 minutes. Cool, filter off the dioxime and recrystallise from ethanol. (M.ps., p. 549.)  [c.372]

Colour U.p. Oxime M.p. Semi-car ba zone M.p.  [c.547]

M.ps. of oximes and semicarbazones are those of the di-derivatives, except those marked which are mono-derivatives.  [c.547]

CgH,3N, PhCH2CH(CH3)NH2. Colourless liquid, b.p. 200 C (decomp.). It is prepared by the reduction of phenylacetone oxime. It is a  [c.32]

Usually prepared by the action of NaCN on benzaldehyde in dilute alcohol. It is oxidized by nitric acid to benzil, and reduced by sodium amalgam to hydrobenzoin PhCHOHCHOHPh by tin amalgam and hydrochloric acid to des-oxybenzoin, PhCH2COPh and by zinc amalgam to stilbene PhCH = CHPh. It gives an oxime, phenylhydrazone and ethanoyl derivative. The a-oxime is used under the name cupron for the estimation of copper and molybdenum.  [c.56]

Various chemical tricks are possible. Zinc ores are not well floated with xanthates, but a pretreatment with dilute copper sulfate rectifies the situation by electrodepositing a thin layer of copper on the mineral particles (note Ref. 83 for complexities). Chelating agents such as oximes may be used instead of xanthates [84]. Treatment of an ore containing a mixture of iron, zinc, and lead minerals with dilute cyanide solution will inhibit adsorption of the collector on the first two, but not on the last. In this case, cyanide is called a depressant. Depressants are also used to inhibit the undesired coflotation of talc, sulfate, graphite, and so on organic polymers have been useful [85]. STM and AFM studies of galena (PbS) surfaces show the formation of 0.3-0.6-nm pits during the surface chemical reactions controlling flotation [86].  [c.477]

Both aldehydes and ketones usually condense readily with free hydroxyl-amine, HONHj, to give crystalline oximes  [c.93]

The oxime is freely soluble in water and in most organic liquids. Recrystallise the crude dry product from a minimum of 60-80 petrol or (less suitably) cyclohexane for this purpose first determine approximately, by means of a small-scale test-tube experiment, the minimum proportion of the hot solvent required to dissolve the oxime from about 0-5 g. of the crude material. Then place the bulk of the crude product in a small (100 ml.) round-bottomed or conical flask fitted with a reflux water-condenser, add the required amount of the solvent and boil the mixture on a water-bath. Then turn out the gas, and quickly filter the hot mixture through a fluted filter-paper into a conical flask the sodium chloride remains on the filter, whilst the filtrate on cooling in ice-water deposits the acetoxime as colourless crystals. These, when filtered anddried (either by pressing between drying-paper or by placing in an atmospheric desiccator) have m.p. 60 . Acetoxime sublimes rather readily when exposed to the air, and rapidly when warmed or when placed in a vacuum. Hence the necessity for an atmospheric desiccator for drying purposes.  [c.94]

Aldehydes and ketones may be converted into the corresponding primary amines by reduction of their oximes or hydrazones (p. 93). A method of more limited application, known as the Leuckart Reaction, consists of heating the carbonyl compound with ammonium formate, whereby the formyLamino derivative is formed, and can be readily hydrolysed by acids to the amine. Thus acetophenone gives the i-phenylethylformamide, which without isolation can be hydrolysed to i-phenylethylamine.  [c.223]

Unite the two reaction-mixtures and cool in ice-salt add 40 g. of crushed ice to the mixture, and stir it mechanically whilst slowly adding 25% aqueous potassium hydroxide solution (about 200 ml.) until the mixture is faintly alkaline to phenol-phthalein ensure that the temperature does not rise above 20° during this operation. A considerable amount of potassium sulphate crystallises from the mixture. Filter the latter at the pump, and wash the residual sulphate on the filter with 30 ml. of chloroform. Run the filtrate and washings into a separating-funnel, run off the chloroform, and extract the aqueous layer three times with chloroform, using 30 ml. on each occasion. Dry the united chloroform extracts with sodium sulphate, filter, and distil off the chloroform, finally distilling the residual caprolactam at water-pump pressure. It distils at 140-142°/ 5 mm., and solidifies in the receiver. Yield, 10 g. from 16 g. of oxime. The caprolactam, m.p. 68-70°, may be recrystallised from petroleum n An—onA nKtainerl iic rnlnurleQQ nlateQ m n An—  [c.228]

Acetophenone similarly gives an oxime, CHjCCgHjlCtNOH, of m.p. 59° owing to its lower m.p. and its greater solubility in most liquids, it is not as suitable as the phenylhydrazone for characterising the ketone. Its chief use is for the preparation of 1-phenyl-ethylamine, CHjCCgHslCHNHj, which can be readily obtained by the reduction of the oxime or by the Leuckart reaction (p. 223), and which can then be resolved by d-tartaric acid and /-malic acid into optically active forms. The optically active amine is frequently used in turn for the resolution of racemic acids.  [c.258]

Aldehydes and ketones may frequently be identified by their semicarbazones, obtained by direct condensation with semicarbazide (or amino-urea), NH,NHCONH a compound which is a monacidic base and usually available as its monohydrochloride, NHjCONHNH, HCl. Semicarbazones are particularly useful for identification of con jounds (such as acetophenone) of which the oxime is too soluble to be readily isolated and the phenylhydrazone is unstable moreover, the high nitrogen content of semicarbazones enables very small quantities to be accurately analysed and so identified. The general conditions for the formation of semicarbazones are very similar to those for oximes and phenylhydrazones (pp. 93, 229) the free base must of course be liberated from its salts by the addition of sodium acetate.  [c.258]


See pages that mention the term Oximes : [c.53]    [c.53]    [c.57]    [c.78]    [c.131]    [c.139]    [c.183]    [c.212]    [c.226]    [c.231]    [c.233]    [c.280]    [c.293]    [c.404]    [c.148]    [c.196]    [c.232]    [c.93]    [c.127]    [c.224]    [c.227]    [c.229]    [c.345]   
See chapters in:

Hydrogenation methods  -> Oximes


Textbook on organic chemistry (1974) -- [ c.341 , c.343 , c.345 , c.348 , c.721 , c.1075 ]

Carey organic chemistry (0) -- [ c.727 ]

Protective groups in organic synthesis (1991) -- [ c.0 ]

Organic chemistry (0) -- [ c.727 ]

Hydrogenation methods (1985) -- [ c.94 , c.95 , c.96 , c.97 , c.98 , c.99 , c.100 ]