Benzaldehyde. Benzaldehyde (C 6 H 5 CHO) is a chemical compound consisting of a benzene ring with an aldehyde substituent . It is the simplest representative of aromatic aldehydes and one of the most industrially used members of this family of compounds.
Summary
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- 1 Features
- 2 Obtaining
- 3 Use
- 4 Sources
characteristics
Melting point: – 26 ºC Boiling point: 179 ºC Density: 1,046 It is a colorless liquid, which is sometimes called artificial almond oil or bitter almond oil, due to its characteristic seed odor. Benzaldehyde is slightly soluble in water, although it is miscible in alcohol or ether in all proportions. In the presence of air, benzaldehyde rapidly oxidizes to benzoic acid (C 6 H 5 COOH).
Obtaining
Commercially, benzaldehyde can be produced:
- heating benzal chloride (C 6H 5 CHCl 2 ) with calcium hydroxide [Ca (OH) 2 ]:
- heating calcium benzoate and calcium formate or:
- boiling amygdalin glucoside or bitter almonds in dilute acid.
Benzaldehyde is made in two grades: technical and refined. The technical grade is mostly used as an intermediate raw material in the synthesis of other chemical compounds, such as benzyl benzoate (C 6 H 5 COOCH 2 C 6 H 5 ), cinnamic aldehyde (C 6 H 5 CH = CHCHO), and certain dyes. Most of the technical grade is obtained through the direct oxidation in the vapor phase of toluene (C 6 H 5 CH 3), although a certain amount is obtained by chlorination of toluene to benzal chloride, followed by alkaline or acid hydrolysis. To be used in perfumery or as a flavoring, the refined, chlorine-free grade is required, which is produced economically by direct phase oxidation of toluene in the vapor phase, using air at 500 ºC. Relatively high yields have been obtained in this reaction, using a catalyst mixture composed of 93% uranium and 7% molybdenum . The oxidation is usually carried out in the liquid phase using manganese dioxide (MnO 2 ) / sulfuric acid (H 2 SO 4 ) at 40 ºC.
Use
Benzaldehyde is used as a flavoring material, as well as to obtain cinnamic acid (C 6 H 5 CH = CHCOOH), green malachite dye, and as an ingredient in the production of pharmaceuticals and as an intermediate in many chemical syntheses. Bisphenol A is obtained by reacting phenol (C 6 H 5 OH) with acetone (CH 3 COCH 3) in the presence of an acid catalyst. The reaction temperature is maintained at 50 ° C (120 ° F) for about 8-12 hours. A slurry of bisphenol A will form, which is neutralized and distilled to remove excess phenol: Bisphenol A is used for the production of epoxy and polycarbonate resins.
