Benzaldehyde
C₇H₆O,PhCHO. Colourless refractive liquid with almond-likeodour. b.p 180°C. It occurs in nature as part of the glucoside, amygdatin. Manufactured from toluene, either by vapour phase air oxidation over a catalyst, or by chlorination to benzal chloride followed by hydrolysis with boiling water.
It is readily oxidized by air to benzoic acid. With aqueous KOH gives benzyl alcohol and benzoic acid. Gives. addition products with hydrogen cyanide and sodium hydrogen sulphite.
Its chief importance is as a source of cinnamic acid by condensation with sodium ethanoate and ethanoic anhydride and as a source of triphenylmethane dyestuffs by condensation with pyrogallol, dimethylaniline, etc. It is also used in the manufacture of perfumes.

Benzedrine.
A trade name for a brand o amphetamine.

Benzene.
A colourless liquid hydrocarbon, C₆H₆; r.d; m.p. 5.5°C; b.p.80.1°C. It is now made from gasoline from petroleum by catalytic reforming (formerly obtained from coal tar.) Benzene is the archetypal aromatic compound. It has an unsaturated molecule, yet will not readily undergo additional reactions. On the other hand, it does undergo substitution reactions in which hydrogen atoms are replaced by other atoms or groups. This behaviour occurs because of delocalization of r-electrons over the benzene ring, and all the C.C bonds in benzene are equivalent and intermediate in length between single and double bonds.