Michael Gibson, M. The name derived from gum benzoin , which was for a long time the only source for benzoic acid. This weak acid and its salts are used as a food preservative. Benzoic acid is an important precursor for the synthesis of many other organic substances. Benzoic acid was discovered in the 16th century. In Salkowski discovered the antifungal abilities of benzoic acid, which were used for a long time in the preservation of benzoate containing fruits.
Benzoic acid is produced commercially by partial oxidation of toluene with oxygen. The process is catalyzed by cobalt or manganese naphthenates. The process uses cheap raw materials, proceeds in high yield, and is considered environmentally green. The first industrial process involved the reaction of benzotrichloride trichloromethyl benzene with calcium hydroxide in water, using iron or iron salts as catalyst.
The resulting calcium benzoate is converted to benzoic acid with hydrochloric acid. The product contains significant amounts of chlorinated benzoic acid derivatives.
For this reason, benzoic acid for human consumption was obtained by dry distillation of gum benzoin. Food-grade benzoic acid is now produced synthetically. Alkyl substituted benzene derivatives give benzoic acid with the stoichiometric oxidants potassium permanganate , chromium trioxide , nitric acid. Benzoic acid and its salts are used as a food preservative, represented by the E-numbers E , E , E , and E Benzoic acid inhibits the growth of mold , yeast [5] and some bacteria.
It is either added directly or created from reactions with its sodium , potassium , or calcium salt. The mechanism starts with the absorption of benzoic acid in to the cell. The efficacy of benzoic acid and benzoate is thus dependent on the pH of the food. Typical levels of use for benzoic acid as a preservative in food are between 0. Foods in which benzoic acid may be used and maximum levels for its application are laid down in international food law.
Concern has been expressed that benzoic acid and its salts may react with ascorbic acid vitamin C in some soft drinks, forming small quantities of benzene. Benzoic acid is a constituent of Whitfield Ointment which is used for the treatment of fungal skin diseases such as tinea, ringworm , and athlete's foot.
Benzoic acid is purified by recrystallisation of the crude product. This involves dissolving the material and allowing it to recrystallize or re-solidify , leaving any impurities in solution and allowing the pure material to be isolated from the solution. Benzoic acid occurs naturally free and bound as benzoic acid esters in many plant and animal species. Appreciable amounts have been found in most berries around 0. Ripe fruits of several Vaccinium species e.
Benzoic acid is also formed in apples after infection with the fungus Nectria galligena. Among animals, benzoic acid has been identified primarily in omnivorous or phytophageous species, e. Benzoic acid is present as part of hippuric acid N-Benzoylglycine in urine of mammals , especially herbivores Gr. Humans produce about 0.
Reactions of benzoic acid can occur at either the aromatic ring or the carboxylic group :. Electrophilic aromatic substitution reaction will take place mainly in 3-position to the electron-withdrawing carboxylic group. Products Related molecules Quiz! References Don't forget to take the quizz!
History Sodium benzoate is the sodium salt of benzoic acid. In acidic conditions the sodium is replaced by a hydrogen and benzoic acid is formed. Hence when put in alkaline conditions e. Institutional Repository. JavaScript is disabled for your browser. Some features of this site may not work without it. Date: Abstract: The acid juice of apples and various other fruits was employed for preparing different medicines before any attempt was made to isolate the acid itself.
Free benzoic acid, however, obtained by subliming benzoin, was discovered and minutely discussed by the French physician, Blaise de Vigenial toward the end of the sixteenth century.
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