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Benzaldehyde (also called
Benzenecarbonal) is the simplest representative of the aromatic
aldehydes. It is a colorless liquid aldehyde with a characteristic almond
odor. It boils at 180°C, is soluble in ethanol, but is insoluble in
water. Benzaldehyde is formed by partial oxidation of benzyl alcohol and
readily oxidized to benzoic acid and is converted to addition products by
hydrocyanic acid or sodium bisulfite. It is also prepared by oxidation of
toluene or benzyl chloride or by treating benzal chloride with an alkali,
e.g., sodium hydroxide. Benzaldehyde is the first step in the synthesis
for fragrances. It undergoes simultaneous oxidation and reduction with
alcoholic potassium hydroxide, giving potassium benzoate and benzyl
alcohol. It is converted to benzoin with alcoholic potassium cyanide,
with anhydrous sodium acetate and acetic anhydride, giving cinnamic acid.
Benzaldehyde and its derivatives are used chiefly in the synthesis of
other organic compounds, ranging from pharmaceuticals to plastic
additives. They are important intermediate for the processing of perfume
and flavoring compounds and in the preparation of certain aniline dyes.
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