Benzaldehyde mandelic acid from

ADDITION OF HYDROGEN CYANIDE TO AN ALDEHYDE. MANDELIC ACID FROM BENZALDEHYDE... 

The group in Kunming have reported a synthetic approach to aqueous solution of NaOH under the influence of ultrasound [59]. 

Mandelic acid is a -hydroxyl phenyl acetic acid. Mandelic acid and its derivatives are very useful in medicinal chemistry some of them have been used in pharmaceutical applications. A few methods have been developed to synthesize mandelic acid and even optically pure mandelic acid. Shown here is the general method for the preparation of mandelic acid from benzaldehyde and sodium cyanide. 

Mandelic acid, which has the formula CgH5CH(OH)COOH, can be isolated from bitter almonds (called mandel in German). It is sometimes used in medicine to treat urinary infections. Devise a two-step synthesis of mandelic acid from benzaldehyde, using the latter s cyanohydrin (see Sec. 9.10) as an intermediate. 

Substituted mandelic acids are key compounds in the synthesis of vanillin from phenols. However, the KIE observed during the oxidative degradation of mandelic acid into benzaldehyde is extremely dependent on the experimental conditions. 

Figure 11.13 The synthesis of enantiomer-ically pure (S)-mandelic acid from ben-zaldehyde in the presence of a triple CLEA [73]. Conversion benzaldehyde )), (S)-mandelonitrile ( ), (S)-mandelic acid (O , enantiomeric excess), (S)-mandelic amide...

Sosedov, O., Matzer, K., Burger, S., Kiziak, C., Baum, S., Altenbuchner, J., Chmura, A., van Rantwijk, F., and Stolz, A. (2009) Construction of recombinant Escherichia coli catalysts which simultaneously express an (S)-oxynitrilase and different nitrilase variants for the synthesis of (S)-mandelic acid and (S)-mandelic amide from benzaldehyde and cyanide. Adv. Synth. Catal., 351, 1531-1538. 

It is important to mix the mandelonitrile with hydrochloric acid immediately it has been separated from the water. Standing results in rapid conversion to the acetal of benzaldehyde and mandelonitrile C(H,CH[OCH(CN)C H,] and/or the iso-nitrile the yield of mandelic acid will, in consequence, be reduced. 

Mandelic acid is best prepared by the hydrolysis of mandeloni-trile with hydrochloric acid. The mandelonitrile has been prepared from amygdalin, by the action of hydrocyanic acid on benzaldehyde, and by the action of sodium or potassium cyanide on the sodium bisulfite addition product of benzaldehyde. ... 

Figure 8.12 Conversion of benzaldehyde into enantiomerically pure (S)-mandelic acid by the sequential addition of HCN catalyzed by the (.S )-selective oxynitrilase from Manihot esculenta (MeHnL), and subsequent hydrolysis of the resultant (5)-mandelonitrile by the nitrilase from Pseudomonas fluorescens ECB 191 (PfNLase)...

Mandelic acid has been prepared by hydrolysis of mandeloni-trile (prepared in turn from benzaldehyde and hydrogen cyanide or from benzaldehyde, sodium bisulfite, and sodium cyanide) 3 by action of water at 180° upon trichloromethylphenylcarbinol by action of potassium carbonate upon a heated mixture of benzaldehyde and chloroform 7 by action of warm, dilute alkali upon dibromoacetophenone 8 and by action of warm, dilute sodium hydroxide upon phenylglyoxal. ... 

There are a few data in the literature to suggest that the hydrolysis of aliphatic nitriles occurs in mammals, but only as a minor or even undetectable pathway in competition with oxidative denitrilation. For example, benzyl cyanide (11.80, Fig. 11.12) undergoes cytochrome P450 catalyzed hydroxy-lation to mandelonitrile (11.81), from which cyanide and benzaldehyde are produced, the latter being oxidized to benzoic acid (11.83) [118]. However, a careful metabolic study of mandelonitrile has shown that, in the rat, this pathway accounts for ca. 90% and not 100% of the dose [122], Only ca. 10% of orally administered benzyl cyanide was converted to mandelic acid (11.82, Fig. 11.12) by hydrolysis of the CN group. 

The cyanohydrin synthesis of a-hydroxy acids is very often carried out without isolation or purification of the cyanohydrins. The various techniques for the preparation of the cyanohydrins are discussed elsewhere (method 390). Hydrolysis to the a-hydroxy acids is usually effected by heating with concentrated hydrochloric acid. Excellent directions are given for mandelic acid (52% over-all from benzaldehyde), a-methyl-a-hydroxybutyric acid (65% from methyl ethyl ketone), and eighteen dialkyl- and alkylphenyl-glycolic acids (60-80%). Sodium hydroxide solution is used in the preparation of /S-hydroxypropionic acid from the /S-hydroxy nitrile (80%). ... 

Mandellic Acid.—Mandellic acid is phenyl glycolic acid, CeHs— CH(OH)—COOH, phenyl hydroxy acetic acid. This constitution is proven by its synthesis from benzaldehyde by condensation with hydrogen cyanide and the hydrolysis of the resulting nitrile. 

Production of Benzaldehyde from Benzoyl Formate or Mandelic Acid... 

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