Benzaldehyde from benzylidene chloride

Dry chlorine is led into 50 g. of boiling toluene until its weight has increased by 40 g., and the boiling point has risen to 187° the operation is carried out in the same way as described for the preparation of benzyl chloride (p. 100). We are merely concerned with a continuation of this same reaction. 

The crude benzylidene chloride so obtained is boiled for four hours in a round-bottomed flask under an efficient reflux condenser with 500 c.c. of water and 150 g. of precipitated calcium carbonate 

1 The procedure here described was worked out in the chemical laboratory of the University of Gottingen. 

The residue in the flask is then filtered at the pump while hot, and the filtrate is strongly acidified with concentrated hydrochloric acid. When the acid filtrate is cooled the by-product of the reaction, benzoic acid, separates in glistening plates. These are filtered with suction, and recrystallised from boiling water. Melting point 121°. Benzoic acid is somewhat volatile with steam. 

The distillate from the steam distillation is twice shaken with not too much ether, and the ethereal extract, if necessary after concentration, is transferred to a wide-mouthed bottle, into which technical sodium bisulphite solution is poured in small portions with stirring (a glass rod is used) so that the aldehyde addition compound formed sets to a thick paste. The bottle is then stoppered and vigorously shaken the stopper is removed from time to time until all the benzaldehyde has entered into combination. (Odour ) The paste is now filtered with suction, and the solid on the funnel, after washing with ether, is at once decomposed by mixing it with an excess of sodium carbonate solution the liberated aldehyde is removed without delay by steam distillation. The distillate is extracted with ether, the extract is dried over a little calcium chloride, the ether is removed by distillation, and the benzaldehyde which remains is likewise distilled. Boiling point 179°. Yield 35-40 g. (70 per cent of the theoretical). 

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Vargha186 obtained a l,6-dibenzoyl-2,3,4,5-dibenzylidene-D-sorbitol from both 1,6-dibenzoyl-D-sorbitol and l,6-dibenzoyl-2,4-benzylidene-D-sorbitol, by treatment with benzaldehyde and zinc chloride. The crystalline dibenzylidene-D-sorbitol (m. p. 208°) which was derived by debenzoylation of Vargha s product was termed 2,4 3,5-dibenzylidene-D-sorbitol by Haworth, Gregory and Wiggins,133 but we feel that additional information should be furnished before the 2,3 4,5- and 2,5 3,4-structures are finally eliminated. 

Wood and coworkers isolated 1,2 3,5-di-0-benzylidene-a-D-gluco-furanose in 16% yield from the system D-glucose-benzaldehyde-zinc chloride-acetic acid. On the other hand, without acetic acid, the mixtime... 

Methods for preparation of dichlorides from aldehydes or ketones do not differ in principle from those for acid chlorides. The reaction is exemplified by the preparation of benzylidene dichloride from benzaldehyde, this product being difficult to obtain pure by direct chlorination of toluene. 

In the simplest form of the Abramov reaction, the phosphorus-containing reactant is hypophosphorous acid (phosphinic acid) or an ester thereof, and in the reactions between the acid and formaldehyde or benzaldehyde the initial product is the phosphinic acid 144 (R = H or Ph.). However, the reaction can proceed further to give the bis(l-hydroxyalkyl)phosphinic acid (145 R = H or Ph) the latter (R = Ph) reacts readily with yet more benzaldehyde to give its benzylidene derivative, 5-hydroxy-2,4,6-triphenyl-1,3,5-dioxaphosphorinane 5-oxide (146 R = Ph). When acted on by a second mole of cyclohexanone in the presence of acetyl chloride, (l-hydroxycyclohexyl)phosphinic acid (147) gives the novel phosphinic chloride 148, characterized as the free acid 149 following ready hydrolysis A reaction between a phosphinic acid (150) and a second (non-identical) carbonyl compound leads to an unsymmetrical phosphinic acid (151). Esters of symmetrical 1, r-dihydroxy-substituted phosphinic acids are preparable from hypophosphite esters, H2P(0)0R ". ... 

Materials. 4-vinylbenzyl chloride, 4-(dimethylamino)pyridine (DMAP), 2,2-bis(hydroxymethyl) prpionic acid (bisMPA), benzaldehyde dimethyl acetal, p-toluene sulfonic acid-monohydride ( TSAOH), and n-butyl lithium (2.5M) were purchased from Sigma-Aldrich. Benzylidene-2,2-bis(oxymethyl)propionic acid and its anhydride were prepared following a literature procedure (2SJ. Dichloromethane (DCM) was distilled under nitrogen from calcium hydride immediately prior to use. Tetrahydrofuran (THF) was distilled under nitrogen from sodium/benzophenone immediately prior to use. All other reagents were commercially obtained and used without further purification. 

Dilute sodium hydroxide was used as a condensing ent by J. G. Schmidt and the method was applied by Claisen and collaborators to the s3mthesis (Claisen reaction) of aromatic ketonic esters, e.g. benzylidene acetone and di-benzylidene acetone from benzaldehyde and acetone. An alternative method was the use of an aromatic aldehyde or ketone with acetoacetic ester in presence of hydrogen chloride. Benzoylacetic ester, CgHgCO CHe-COOCoHs, was obtained by condensing benzoic and acetic esters in presence of sodium ethoxide, and j8-diketones by condensing ketones and acid esters, e.g. acetyl-acetone CHaCO-CHaCOCHg."... 

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