12-3+Recommendation+of+Benzoic+Acid

Home Preview Next

Recommendation of Benzoic Acid 

Food preservative
Benzoic acid and its salts are used as a food [|preservative], represented by the [|E-numbers] [|E210], [|E211], [|E212], and [|E213]. Benzoic acid inhibits the growth of [|mold], [|yeast][|[8]] 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. If the intracellular [|pH] changes to 5 or lower, the [|anaerobic fermentation] of [|glucose] through [|phosphofructokinase] is decreased by 95%. The efficacy of benzoic acid and benzoate is thus dependent on the pH of the food.[|[9]] Acidic food and beverage like [|fruit juice] ([|citric acid]), sparkling drinks ([|carbon dioxide]), [|soft drinks] ([|phosphoric acid]), [|pickles] ([|vinegar]) or other acidified food are preserved with benzoic acid and benzoates. Typical levels of use for benzoic acid as a preservative in food are between 0.05 – 0.1%. Foods in which benzoic acid may be used and maximum levels for its application are laid down in international food law.[|[10]][|[11]] 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].[|[12]] See also: [|Benzene in soft drinks] Benzoic acid is a constituent of [|Whitfield's Ointment] which is used for the treatment of fungal skin diseases such as tinea, [|ringworm], and [|athlete's foot]. [|[13]][|[14]] As the principal component of [|Benzoin resin], benzoic acid is also a major ingredient in both [|Tincture of Benzoin] and [|Friar's Balsam]. Such products have a long history of use as topical [|antiseptics] and inhalant [|decongestants].

Biology and health effects
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 0.05%). Ripe fruits of several [|Vaccinium] species (e.g., [|cranberry], V. vitis idaea; [|bilberry], V. macrocarpon) contain as much as 0.03-0.13% free benzoic acid. 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.g., in viscera and muscles of the [|ptarmigan] (Lagopus mutus) as well as in gland secretions of male [|muskoxen] (Ovibos moschatus) or Asian bull elephants ([|Elephas maximus]).[|[15]] [|Gum benzoin] contains up to 20% of benzoic acid and 40% benzoic acid esters.[|[16]] Benzoic acid is present as part of [|hippuric acid] (N-Benzoylglycine) in [|urine] of [|mammals], especially [|herbivores] (Gr. hippos = horse; ouron = urine). Humans produce about 0.44 g/L [|hippuric acid] per day in their urine, and if the person is exposed to [|toluene] or benzoic acid it can rise above that level.[|[17]] For humans, the WHO's International Programme on Chemical Safety (IPCS) suggests a provisional tolerable intake would be 5 mg/kg body weight per day.[|[15]] [|Cats] have a significantly lower tolerance against benzoic acid and its [|salts] than [|rats] and [|mice]. Lethal dose for cats can be as low as 300 mg/kg body weight.[|[18]] The oral [|LD50] for rats is 3040 mg/kg, for mice it is 1940–2263 mg/kg.[|[15]] In [|Taipei], Taiwan, a city health survey in 2010 found 30% of tested dried and pickled food products failed a test having too much benzoic acid, which is known to affect the liver and kidney[|[19]], along with more serious issues like excessive [|cyclamate].

Chemistry
Reactions of benzoic acid can occur at either the [|aromatic ring] or the [|carboxyl group]:

Aromatic ring
 [|Electrophilic aromatic substitution] reaction will take place mainly in 3-position due to the [|electron-withdrawing] [|carboxylic group]; i.e. benzoic acid is [|meta directing]. The second substitution reaction (on the right) is slower because the first nitro group is deactivating.[|[20]] Conversely, if an activating group (electron-donating) was introduced (e.g., alkyl), a second substitution reaction would occur more readily than the first and the disubstituted product might not accumulate to a significant extent.

Carboxyl group
All the reactions mentioned for [|carboxylic acids] are also possible for benzoic acid.
 * Benzoic acid [|esters] are the product of the acid catalysed reaction with [|alcohols].
 * Benzoic acid [|amides] are more easily available by using activated acid derivatives (such as [|benzoyl chloride]) or by coupling reagents used in [|peptide synthesis] like [|DCC] and [|DMAP].
 * The more active benzoic [|anhydride] is formed by dehydration using [|acetic anhydride] or [|phosphorus pentoxide].
 * Highly reactive acid derivatives such as [|acid halides] are easily obtained by mixing with [|halogenation] agents like [|phosphorus chlorides] or [|thionyl chloride].
 * <span style="color: #008000; font-family: 'Lucida Console',Monaco,monospace; font-size: 120%;">[|Orthoesters] can be obtained by the reaction of alcohols under acidic water free conditions with [|benzonitrile].
 * <span style="color: #008000; font-family: 'Lucida Console',Monaco,monospace; font-size: 120%;">Reduction to [|benzaldehyde] and [|benzyl alcohol] is possible using [|DIBAL-H], [|LiAlH4] or [|sodium borohydride].
 * <span style="color: #008000; font-family: 'Lucida Console',Monaco,monospace; font-size: 120%;">The copper catalysed [|decarboxylation] of [|benzoate] to benzene may be effected by heating in [|quinoline]. Also, Hunsdiecker decarboxylation can be achieved by forming the silver salt and heating.