Oximes addition

Treatment of benzaldehyde oxime ether (166) with butyllithium (pentane/-10 C) demonstrates the complexity of the reaction (Scheme 32) as the desired alkoxyamine (167 R = Bu) is accompanied by other oxime-derived side products" (entry 1, Table 12). Selectivity is reagent/solvent dependent as allyl Grignard (ether)," allylzinc bromide (THF)," and butyllithium (THF)" treatment produce predominantly amine (171 R = allyl) (the Beckmann rearrangement derived product), alkoxyamine (167 R = allyl) (the oxime addition product) and ketone (169 R = Bu) (the nitrile-derived pro ct), respectively (entries 2-4, Table 12). 

Using this pulse sequence to estimate the nature of derivatization of Suwannee River fulvic acid with N-enriched hydroxylamine to leam more about the carbonyl functionality of fulvic acid, Thom et al.(76) obtained signals for the primary products as oximes. Additional signals of secondary products arising from Beckmann rearrangements of the initial oxime derivatives were identified as nitriles, secondary amides and lactams. The bands assigned to hydroxamic acid result from a reaction of esters with NH2OH and are evidence for the presence of esters in the fulvic acid. 

Among aldehydes, acetaldehyde is quite reactive. This reaction makes it possible to distinguish methyl ketones from methylcarbinols (both classes of substances give a positive iodoform reaction). As the reaction is carried out in an alkaline medium, certain substances are hydrolyzed and their products then give a positive test. Such substances are, for example, geminal dihalo derivatives (1,1-dichloroethane, 2,2-dibromopropane, 2,2-dibromo-but e) and certain methyl derivatives (oximes, addition compounds with hydrogen sulfite). 

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. 

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. 

Oximes, hydrazines and semicarbazones. The hydrolysis products of these compounds, t.e., aldehydes and ketones, may be sensitive to alkali (this is particularly so for aldehydes) it is best, therefore, to conduct the hydrolysis with strong mineral acid. After hydrolysis the aldehyde or ketone may be isolated by distillation with steam, extraction with ether or, if a solid, by filtration, and then identified. The acid solution may be examined for hydroxylamine or hydrazine or semicarbazide substituted hydrazines of the aromatic series are precipitated as oils or solids upon the addition of alkali. 

A sodium stannite solution was prepared by addition of aqueous sodium hydroxide (2.5 mol, lOOg) to aqueous stannous chloride (0.25 mol, 56g). The initially formed precipitate redissolved to form a clear solution. This solution was gradually added to a solution of 16.3g (0.1 mol) phenyl-2-nitropropene in THF at room temperature. A slightly exothermic reaction ensued, and the reaction mixture was stirred for 30 min, a saturated sodium chloride solution was added, and the solution was extracted with ether and the pooled extracts were evaporated under vacuum to give essentially pure P2P oxime in 80% yield. 

A"-Octadienylatiori, rather than 0-octadienylation, of aldehyde oximes takes place to give the nitrone 37 as an intermediate, which undergoes 1.3-dipolar addition to butadiene, yielding the isoxazolidine 38[39],... 

Nevertheless, storage hardening can be effectively inhibited by the addition of a reagent such as hydroxylamine, which produces an oxime via a... 

Citral readily forms acetals by acid-catalyzed addition of alcohols or by the use of trialkoxyorthoformates. Citral dimethyl acetal [7549-37-3] is stable under alkaline conditions, whereas citral is not. Neryl and geranyl nitriles can be made by oximation of citral and dehydration of the intermediate oxime. For instance, geranonitrile [31983-27-4] is made as follows ... 

Dutch State Mines (Stamicarbon). Vapor-phase, catalytic hydrogenation of phenol to cyclohexanone over palladium on alumina, Hcensed by Stamicarbon, the engineering subsidiary of DSM, gives a 95% yield at high conversion plus an additional 3% by dehydrogenation of coproduct cyclohexanol over a copper catalyst. Cyclohexane oxidation, an alternative route to cyclohexanone, is used in the United States and in Asia by DSM. A cyclohexane vapor-cloud explosion occurred in 1975 at a co-owned DSM plant in Flixborough, UK (12) the plant was rebuilt but later closed. In addition to the conventional Raschig process for hydroxylamine, DSM has developed a hydroxylamine phosphate—oxime (HPO) process for cyclohexanone oxime no by-product ammonium sulfate is produced. Catalytic ammonia oxidation is followed by absorption of NO in a buffered aqueous phosphoric acid... 

Acid treatment or thermolysis of aziridinyl phenyl ketone oxime generated a 2-isoxazoline (74JAP(K)74i 17462), while treatment of a diphenylcyclopropene (486) with NOCl generated a 2-isoxazoline in contrast to dialkylcyclopropene (487) which produced addition across the double bond (Scheme 126) (73MI41605). 

Diphenylthiirene 1-oxide reacts with hydroxylamine to give the oxime of benzyl phenyl ketone (79JA390). The reaction probably occurs by addition to the carbon-carbon double bond followed by loss of sulfur monoxide (Scheme 80). Dimethylamine adds to the double bond of 2,3-diphenylthiirene 1,1-dioxide with loss of sulfur dioxide (Scheme 81) (75JOC3189). Azide ion gives seven products, one of which involves cleavage of the carbon-carbon bond of an intermediate cycloadduct (Scheme 81) (80JOC2604). 

Ketones are more stable to oxidation than aldehydes and can be purified from oxidisable impurities by refluxing with potassium permanganate until the colour persists, followed by shaking with sodium carbonate (to remove acidic impurities) and distilling. Traces of water can be removed with type 4A Linde molecular sieves. Ketones which are solids can be purified by crystallisation from alcohol, toluene, or petroleum ether, and are usually sufficiently volatile for sublimation in vacuum. Ketones can be further purified via their bisulfite, semicarbazone or oxime derivatives (vide supra). The bisulfite addition compounds are formed only by aldehydes and methyl ketones but they are readily hydrolysed in dilute acid or alkali. 

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