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benzaldehyde

Product name benzaldehyde
Synonyms benzoic aldehyde
phenylmethanal
GOST no data
CAS 100-52-7

Benzaldehyde is a colorless liquid with a pleasant bitter almond-like odor. It turns yellow upon storage on air and light. Benzaldehyde is only slightly soluble in water (0.6% wt at 20°C), but readily soluble in ethanol, diethyl ether, benzene, toluene and most organic solvents. It forms azeotropes with o-cresol (23% wt of benzaldehyde, bp 192°C), benzyl chloride (54% and 177.9°C), phenol (46% and 185.6°C).

Being oxidized, benzaldehyde is readily converted into unpleasant smelling benzoic acid. Hydrogenation results in benzyl alcohol. Being treated with alkali solution benzaldehyde undergo disproportionation to give benzyl alcohol and benzoic acid (Cannizzaro reaction):

2C6H5CHO --> C6H5CH2OH + C6H5COOH

Like aliphatic aldehydes, benzaldehyde reacts with hydrogen cyanide resulting in racemic mandelic acid nitrile, which is subsequently hydrolysed to a racemic mixture of mandelic acid:

C6H5CHO + HCN --> C6H5CH(OH)CN
C6H5CH(OH)CN + 2H2O --> C6H5CH(OH)COOH + NH3


Benzaldehyde gives condensation products - triphenylmethane derivatives reacting with phenols and tertiary aromatic amines. Catalytical condensation with acetic anhydride results in cinnamic acid (Perkin reaction):

C6H5CHO + (CH3C(O))2O --> C6H5CH=CHCOOH + CH3COOH

Electrophilic substitution in aromatic ring occurs mainly in meta-positions.

Benzaldehyde is the primary component of bitter almond oil extract, and can be extracted from a number of other natural sources in which it occurs, such as apricot, cherry, and laurel leaves, peach seeds. All these plants contain significant amounts of glycoside amygdalin, which, being hydrolysed results in benzaldehyde, hydrogen cyanide and two molecules of glucose.

Production.

Benzoic aldehyde is prepared commercially:

  • by catalytical toluene oxidation in the presence of vanadium, chromium, molibdenum, tungsten or thorium oxides;
  • by catalytical oxidation of benzyl alcohol;
  • by C6H5CHCl2 hydrolysis;
  • by benzene carbonylation in the presence of hydrogen chloride HCl and aluminium chloride AlCl3 (Gatterman-Koch reaction);

    Uses.

  • as a commercial food flavourant and fragnance (almond flavour);
  • as an industrial solvent;
  • as an intermediate compound in making a number of fragnances, such as cinnamic acid, cinnamic anhydride, benzyl benzoate, benzaldehyde acetals, jasmine aldehyde and others;
  • as a starting material in preparation dyes (e.g. aniline and triphenyl methane);
  • as an intermediate in pharmaceuticals syntheses;

  • Manufacturer(s) no data
    Chemical structure of benzaldehyde

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