Acetic acid

Description

Acetic acid is a colourless liquid or crystal with a sour, vinegar-like odour and is one of the simplest carboxylic acids and is an extensively used chemical reagent. It is the principal component of vinegars and pyroligneous acid. As one of the earliest flavoring agents, Vinegars are used extensively in preparing salad dressing and mayonnaise, sour and sweet pickles and numerous sauces and catsups.

Chemical properties

Acetic acid, also known as ethanoic acid, is a colorless liquid with a pungent, vinegar-like odor and the chemical formula CH3COOH. It is the main component of vinegar and is used as a food additive, in household cleaners, and for the production of dyes, pharmaceuticals, and other chemicals. 

History

Vinegar is a dilute aqueous solution of acetic acid. The use of vinegar is well documented in ancient history, dating back at least 10,000 years. Egyptians used vinegar as an antibiotic and made apple vinegar. Babylonians produced vinegar from wine for use in medicines and as a preservative as early as 5000 b.c.e. Hippocrates (ca. 460–377 b.c.e.), known as the “father of medicine,” used vinegar as an antiseptic and in remedies for numerous conditions including fever, constipation, ulcers, and pleurisy.

The Uses of Acetic acid

Acetic acid is an important industrial chemical. It is used in the manufacture ofcellulose acetate, acetate rayon, and variousacetate and acetyl compounds; as a solventfor gums, oils, and resins; as a food preservative in printing and dyeing; and in organicsynthesis. Acetic acid is used as table vinegar, as preservative and as an intermediate in the chemical industry, e.g. acetate fibers, acetates, acetonitrile, pharmaceuticals, fragrances, softening agents, dyes (indigo) etc.

Indications

Used to treat infections in the ear canal.

Background

Acetic acid is a product of the oxidation of ethanol and of the destructive distillation of wood. It is used locally, occasionally internally, as a counterirritant and also as a reagent. (Stedman, 26th ed) Acetic acid otic (for the ear) is an antibiotic that treats infections caused by bacteria or fungus.

Definition

ChEBI: Acetic acid is a simple monocarboxylic acid containing two carbons. It has a role as a protic solvent, a food acidity regulator, an antimicrobial food preservative and a Daphnia magna metabolite. It is a conjugate acid of an acetate.

Production Methods

Acetic acid is used in numerous industrial chemical preparations and the large-scale productionof acetic acid takes place through several processes. The main method of preparation ismethanol carbonylation. In this process, methanol reacts with carbon monoxide to give aceticacid:
CH₃OH_(l) + CO_(g) → CH₃COOH_(aq).
Because the reaction requires high pressures (200atmospheres), this method was not used until the 1960s, when the development of specialcatalysts allowed the reaction to proceed at lower pressures. A methanol carbonylation proceduredeveloped by Monsanto bears the company’s name. The second most common methodto synthesize acetic acid is by the catalytic oxidation of acetaldehyde:
2 CH₃CHO_(l) + O_2(g) →2 CH₃COOH_(aq).
Butane may also be oxidized to acetic acid according to the reaction:
2 C₄H_10(l) +5O_2(g) → 4 CH₃COOH_(aq) + 2H₂O_(l).
This reaction was a major source of acetic acid beforethe Monsanto process. It is carried out at a temperature of approximately 150°C and 50 atmospheres pressure.

brand name

Vosol (Carter-Wallace).

Aroma threshold values

Aroma characteristics at 1.0%: sour pungent, cider vinegar, slightly malty with a brown nuance.

Taste threshold values

Taste characteristics at 15 ppm: sour, acidic tangy.

Reactivity Profile

Acetic acid reacts exothermically with chemical bases. Subject to oxidation (with heating) by strong oxidizing agents. Dissolution in water moderates the chemical reactivity of acetic acid, A 5% solution of acetic acid is ordinary vinegar. Acetic acid forms explosive mixtures with p-xylene and air.

Health Hazard

Glacial acetic acid is a highly corrosive liquid. Contact with the eyes can produce mild to moderate irritation in humans. Contact with the skin may produce burns. Ingestion of this acid may cause corrosion of the mouth and gastrointestinal tract. The acute toxic effects are vomiting, diarrhea, ulceration, or bleeding from intestines and circulatory collapse. Death may occur from a high dose (20–30 mL), and toxic effects in humans may be felt from ingestion of 0.1–0.2 mL. An oral LD50 value in rats is 3530 mg/kg (Smyth 1956).
Glacial acetic acid is toxic to humans andanimals by inhalation and skin contact. Inhumans, exposure to 1000 ppm for a fewminutes may cause eye and respiratory tractirritation. Rabbits died from 4-hour exposureto a concentration of 16,000 ppm in air.

Flammability and Explosibility

Acetic acid is a combustible substance (NFPA rating = 2). Heating can release vapors that can be ignited. Vapors or gases may travel considerable distances to ignition source and "flash back." Acetic acid vapor forms explosive mixtures with air at concentrations of 4 to 16% (by volume). Carbon dioxide or dry chemical extinguishers should be used for acetic acid fires.

Toxicity

Dilute acetic acid solutions containing up to 10% w/w of acetic acid have been used topically following jellyfish stings.Dilute acetic acid solutions containing up to 5% w/w of acetic acid have also been applied topically to treat wounds and burns infected with Pseudomonas aeruginosa.
The lowest lethal oral dose of glacial acetic acid in humans is reported to be 1470 mg/kg.The lowest lethal concentration on inhalation in humans is reported to be 816 ppm.Humans, are, however, estimated to consume approximately 1 g/day of acetic acid from the diet.
LD₅₀ (mouse, IV): 0.525 g/kg
LD₅₀ (rabbit, skin): 1.06 g/kg
LD₅₀ (rat, oral): 3.31 g/kg

Storage

Acetic acid should be used only in areas free of ignition sources, and quantities greater than 1 liter should be stored in tightly sealed metal containers in areas separate from oxidizers.

Incompatibilities

Acetic acid reacts with alkaline substances.

Waste Disposal

Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber. All federal, state, and local environmental regulations must be observed