Benzaldoximes

In a 250 ml. conical flask mix a solution of 14 g. of sodium hydroxide in 40 ml. of water and 21 g. (20 ml.) of pure benzaldehyde (Section IV,115). Add 15 g. of hydroxylamine hydrochloride in small portions, and shake the mixture continually (mechanical stirring may be employed with advantage). Some heat is developed and the benzaldehyde eventually disappears. Upon cooling, a crystalline mass of the sodium derivative separates out. Add sufficient water to form a clear solution, and pass carbon dioxide into the solution until saturated. A colourless emulsion of the a- or syn-a.ldoxime separates. Extract the oxime with ether, dry the extract over anhydrous magnesium or sodium sulphate, and remove the ether on a water bath. Distil the residue under diminished pressure (Fig. II, 20, 1). Collect the pure sj/n-benzaldoxime (a-benzald-oxime) at 122-124°/12 mm. this gradually solidifies on coohng in ice and melts at 35°. The yield is 12 g. 

P-Benzilmonoxime. Boil 10 g. of the pure a-monoxime for 15 minutes with 1 g. of dried animal charcoal in a quantity of pure benzene just sufficient to dissolve the a-monoxime at the boiling point. Filter off the charcoal and allow the filtrate to stand. The p-monoxime -f 0-5 CgH, crystallises slowly on cooling a further crop can be obtained by evapora tion of the mother liquid. An excellent yield of the p-monoxime, m.p. 112°, is obtained. The pure S-oxime causes no colour change with aqueous - alcoholic copper acetate solution if it is contaminated with the a-oxinie, a greenisli colour is produced. 

CfiHs CHO 4- NH. OH.HCl 4- 2NaOH = QdbCII.NONa 4- NaCl CjHgCH NONa 4- CO, 4- ILO = CuH Cri NOII 4- NaPICOj. 

Reaction —Dissolve a small quantity of the n-o ime in a few diops of acetic anhydride, waim if necessary, and cool quickly by adding a little ice. Add to the clear solution solid sodium carbonate and a little caustic soda solution. The solution becomes clear on shaking or warming. 

The fi-compound is dissolved in 50 c c. pure dry ether, and dry hydiogen chloride is passed in with constant shaking to prevent the delivery tube from becoming blocked. Colourless crystals of the hydrochloride of the /3-o ime separate and aie filtered and washed with dry ether and then placed in a separating funnel and covered with a layer of ether. A. concentrated solution of sodium carbonate is gradually added with constant shaking until no further effervescence is observed. Sodium chloride is precipitated and the /3-oxime dissolves in the ether. The ether extract is sepaiated, dehydrated over sodium sulphate, and the ether remoi ed as rapidly as possible at the ordinary temperature by evaporation in vacuo. The residue crystallises, and when pressed on a porous plate leaves a mass of small silky needles, m. p. 126—130A It may be re- 

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Benzaldehyde reacts with hydroxylamine in the presence of excess of sodium hydroxide to 3deld an oxime of low m.p. (a- or. gjM-benzaldoxime) which is stable to alkah, but is rapidly rearranged by acids to give an isomeric oxime of higha m.p. ( 3- or < i/r-benzaldoxlme) ... 

Benzaldoxime.—The various steps in the preparation of the /3-oxime must be earned out continuously, and it is therefore necessary to be provided beforehand with about 300 c.c. of pure anhydrous ether. 

Attempts to prepare hydroxybiphenyl derivative 19 by treatment of tetranitro derivative 18 with sodium benzaldoxime led to a mixture of the required phenol 19 and dibenzofuran 20 (Eq. 5) (82JCS(P1)2299). 

Ponzio Reaction. The formation of phenyl-dinit romethane from benzaldoxime by oxidation with nitrogen dioxide in eth (Refs 1 2) CH=NOH CH(N02)2... 

Bei der Reduktion an Quecksilber von Benzaldoxim zvtN-Benzyl-hydroxylamin wird in Phosphatpuffer-Losung bei 0° gearbeitet6. 

Oximes can be alkylated by alkyl halides or sulfates. N-Alkylation is a side reaction, yielding a nitrone. " The relative yield of oxime ether and nitrone depends on the nature of the reagents, including the configuration of the oxime, and on the reaction conditions. For example, anri-benzaldoximes give nitrones, while the syn isomers give oxime ethers. " ... 

C15H19N5O 56976-47-7) see Pildralazine benzaldehyde semicarbazone (C,H,N30 1574-10-3) see Azimilide hydrochloride benzaldoxime... 

Aryl-5-cyano-2-isoxazolines, possessing liquid crystal properties (smectic phases A or E) have been synthesized, 1,3-dipolar cycloaddition of nitrile oxides to acrylonitrile being the key step (532). For example, nitrile 462 has been obtained in 66% yield from substituted benzaldoxime and acrylonitrile via in situ generated nitrile oxides. 

The reaction of Z-2-furaldoximes (134) with oxirane affords in good yield N-(2- hydroxy ethyl)-a-2-furylnitrone (135) the product of TV-alkylation. E-benzaldoxime, predominantly gives the O-alkylation product (136), whereas its Z -isomer leads to a mixture with an insignificant amount of TV-alkylation product (138) (Scheme 2.50) (304). 

Interaction of Mannich base methyliodides (148, R = Ph, 2-Thenyl) with anti -benzaldoxime gives dinitrones (149) (Scheme 2.53) (307). 

The examples of compounds showing geometrical isomerism and having >C=N- structure are afforded by the oximes of aldehydes and ketones. Benzaldoxime, prepared by the action of hydroxy-lamine or benzaldehyde exists in the two forms. 

The conversion of benzaldoxime [157] into benzonitrile and benzamide by catalytic amounts of potassium halides and cyanide has also been attributed to proton abstraction by the anion (Rasmussen, 1977). Nucleophilic addition was thought to be unlikely, since the anion reactivities in (26) in acetonitrile with... 

The pKi, values of a series of para- and meffl-substituted benzaldoximes and phenyl methyl ketoximes, ArCR=NOH (R=H, Me), have been measured in DMSO. The aldoximes exhibit pK. = 20.05 + 3.21ap. The homolytic bond dissociation energy of the O-H bond has been estimated as 88.3 (aldoximes) and 89.2kcal mol" (ketoximes) by relating the pK to the oxidation potential of the conjugate base (i.e. ox for ArCR=NO- ArCR=NO ). 

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