Everything about Benzaldehyde totally explained
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Benzaldehyde (C
6H
5CHO) is a chemical compound consisting of a
benzene ring with an
aldehyde substituent. It is the simplest representative of the
aromatic aldehydes and one of the most industrially used members of this family of compounds. At room temperature it's a colorless liquid with a characteristic and pleasant
almond-like
odor: benzaldehyde is an important component of the scent of almonds, hence its typical odor. It 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 and, in a
glycoside combined form (
amygdalin), in certain
nuts and
kernels. Currently benzaldehyde is primarily made from
toluene by a number of different processes.
Production
Benzaldehyde can be obtained by many processes. Currently liquid phase
chlorination or
oxidation of
toluene are among the most used processes. There are also a number of discontinued applications such as partial oxidation of
benzyl alcohol,
alkali treating of
benzal chloride and reaction between benzene and
carbon monoxide.
Reactions
On oxidation, benzaldehyde is converted into the odorless
benzoic acid.
Benzyl alcohol can be formed from benzaldehyde by means of
hydrogenation or by treating the compound with alcoholic
potassium hydroxide thus undergoing a simultaneous oxidation and
reduction which result in the production of
potassium benzoate and benzyl alcohol. Reaction of benzaldehyde with anhydrous
sodium acetate and
acetic anhydride yields
cinnamic acid, while alcoholic
potassium cyanide can be used to
catalyze the condensation of benzaldehyde to
benzoin.
Benzaldehyde can also undergo
disproportionation in concentrated alkali (
Cannizzaro's reaction): one molecule of the aldehyde is reduced to the corresponding alcohol and another molecule is simultaneously oxidized to the salt of a
carboxylic acid. The speed of this reaction depends on the substituents present in the aromatic ring.
Uses
While it's commonly employed as a commercial food
flavourant (
almond flavour) or industrial
solvent, benzaldehyde is used chiefly in the synthesis of other organic compounds, ranging from pharmaceuticals to plastic additives. It is also an important intermediate for the processing of perfume and flavouring compounds and in the preparation of certain
aniline dyes.
The synthesis of
mandelic acid starts from benzaldehyde:
First
hydrocyanic acid is added to benzaldehyde and the resulting mandelic acid
nitrile is subsequently
hydrolysed to a
racemic mixture of
mandelic acid. (The scheme above depicts only one of the two formed
enantiomers).
Glaciologists LaChapelle and Stillman reported in 1966 that benzaldeyde and
N-heptaldehyde inhibit the recrystallization of snow and therefore the formation of
depth hoar. This treatment may prevent avalanches caused by unstable depth hoar layers. However, the chemicals are not in widespread use because they damage vegetation and contaminate water supplies.
Biology
Almonds,
apricots,
apples and
cherry kernels, contain significant amounts of
amygdalin. This
glycoside breaks up under enzyme catalysis into benzaldehyde,
hydrocyanic acid and two molecules of
glucose.
Further Information
Get more info on 'Benzaldehyde'.
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