The benzoic acid which is monobasic carbonic aromatic acid has a chemical formula C6H5COOH. Its appearance – badly soluble colourless crystals in water. It is well soluble in some organic matter, easily is exposed to sublimation. In what ways it is possible to receive benzoic acid?
Instruction
1. The main raw materials for synthesis of this substance – the toluene (it is methyl benzene) having chemical formula C6H5CH3. During various reactions, its methyl group (CH3) by oxidation turns into carboxyl (SOON). General scheme of reactions such: 2C6H5CH3 + 3O2 = 2C6H5COOH + 2H2O
2. In vitro, oxidation of toluene is made either permanganate of potassium (KMnO4), or compounds of chrome extremely by oxidations (for example, chromic CrO3 anhydride, potassium to two-chromate K2Cr2O7), that is substances which easily decay with formation of oxygen. In the industry the oxidation is made by pure oxygen with participation of manganese or cobalt catalysts.
3. Benzoic acid in laboratories can be received also in other ways. For example, from a brombenzol (C6H5Br), with use of "Grinyar's reactant" - the difficult complex connection consisting from alkyl - (or aril-) halogenide and an ion of magnesium. The final stage of this reaction (at addition of hydrochloric acid) goes thus: C6H5CO2MgBr + HCl = C6H5COOH + MgBrCl
4. Also benzoic acid is received by method of hydroxylation of benzoic alcohol. Reaction goes on such mechanism (it is represented in strongly simplified look): 2C6H5COH (benzaldehyde) + IT - = C6H5COH (benzylic alcohol) + C6H5COOH (benzoic acid). It carries the name "Kannizzaro's Reaction", in honor of the chemist who for the first time carried out and who described it. In a different way it is called: "Reaction of disproportionation of aldehydes".