Acetic Acid
DESCRIPTION:
Otec-ac (acetic acid otic solution, USP) is a solution of acetic acid (2%), in a propylene glycol vehicle .The empirical formula for acetic acid is CH3COOH, with a molecular weight of 60.05.
Acetic acid is available as a nonaqueous otic solution buffered at pH 3 for use in the external ear canal.
CLINICAL PHARMACOLOGY:
Acetic acid is anti-bacterial and anti-fungal; propylene glycol is hydrophilic and provides a low surface tension; benzethonium chloride is a surface active agent that promotes contact of the solution with tissues.
INDICATIONS AND USAGE:
For the treatment of superficial infections of the external auditory canal caused by organisms susceptible to the action of the antimicrobial.
CONTRAINDICATIONS:
Hypersensitivity to acetic acid or any of the ingredients. Perforated tympanic membrane is frequently considered a contraindication to the use of any medication in the external ear canal.
WARNINGS:
Discontinue promptly it sensitization or irritation occurs.
PRECAUTIONS:
Transient stinging or burning may be noted occasionally when the solution is first instilled into the acutely inflamed ear.
ADVERSE REACTIONS:
Stinging or burning may be noted occasionally; local irritation has occurred very rarely.
DOSAGE AND ADMINISTRATION:
Carefully remove all cerumen and debris to allow acetic acid to contact infected surfaces directly. To promote continuous contact, insert a wick saturated with acetic acid into the ear canal; the wick may also be saturated after insertion. Instruct the patient to keep the wick in for at least 24 hours and to keep it most by adding 3 to 5 drops of acetic acid every 4 to 6 hours. The wick may be removed after 24 hours but the patient should continue to instill 5 drops of acetic acid 3 or 4 times daily thereafter, for as long as indicated.
Store at room temperature; avoid excessive heat. Keep container tightly closed.
Glacial acetic acid is a trivial name for water-free acetic acid.
Usually acetic acid containing usually less than 1 percent of water
Glacial acetic acid is anhydrous form of acetic acid in which it exists in dimmer form. It's known as Glacial because on freezing it forms needle shape crystals.
Acetic acid, systematically named ethanoic acid, is an organic compound with the chemical formula CH3CO2H (also written as CH3COOH). It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar (apart from water), and has a distinctive sour taste and pungent smell. It is mainly produced as a precursor to polyvinylacetate and cellulose acetate. Although it is classified as a weak acid, concentrated acetic acid is corrosive, and attacks the skin.
Acetic acid is one of the simplest carboxylic acids. It is an important chemical reagent and industrial chemical, mainly used in the production of cellulose acetate mainly for photographic film and polyvinyl acetate for wood glue, as well as synthetic fibres and fabrics. In households, diluted acetic acid is often used in descaling agents. In the food industry, acetic acid is used under the food additive code E260 as an acidity regulator and as a condiment. As a food additive it is approved for usage in the EU,[6] USA[7] and Australia and New Zealand.[8]
The global demand of acetic acid is around 6.5 million tonnes per year (Mt/a), of which approximately 1.5 Mt/a is met by recycling; the remainder is manufactured from petrochemical feedstock.[9] As a chemical reagent, biological sources of acetic acid are of interest but generally uncompetitive. Vinegar is dilute acetic acid, often produced by fermentation.
Because of this release of the proton (H+), acetic acid has acidic character. Acetic acid is a weak monoprotic acid. In aqueous solution, it has a pKa value of 4.75. Its conjugate base is acetate (CH3COO?). A 1.0 M solution (about the concentration of domestic vinegar) has a pH of 2.4, indicating that merely 0.4% of the acetic acid molecules are dissociated.
Solvent properties
Liquid acetic acid is a hydrophilic (polar) protic solvent, similar to ethanol and water. With a moderate relative static permittivity (dielectric constant) of 6.2, it dissolves not only polar compounds such as inorganic salts and sugars, but also non-polar compounds such as oils and elements such as sulfur and iodine. It readily mixes with other polar and non-polar solvents such as water, chloroform, and hexane. With higher alkanes (starting with octane), acetic acid is not completely miscible anymore, and its miscibility continues to decline with longer n-alkanes.[20] This dissolving property and miscibility of acetic acid makes it a widely used industrial chemical. Its solvent properties are mainly of value in the production of dimethyl terephthalate.[9]
Biochemistry
At physiological pHs, acetic acid is usually fully ionized to acetate. In biochemistry, acetate and acetic acid are equivalent.
The acetyl group, derived from acetic acid, is fundamental to all forms of life. When bound to coenzyme A, it is central to the metabolism of carbohydrates and fats. Unlike longer-chain carboxylic acids (the fatty acids), acetic acid does not occur in natural triglycerides. However, the artificial triglyceride triacetin (glycerine triacetate) is a common food additive and is found in cosmetics and topical medicines.
Acetic acid is produced and excreted by acetic acid bacteria, notable ones being the Acetobacter genus and Clostridium acetobutylicum. These bacteria are found universally in foodstuffs, water, and soil, and acetic acid is produced naturally as fruits and other foods spoil. Acetic acid is also a component of the vaginal lubrication of humans and other primates, where it appears to serve as a mild antibacterial agent.[
Vinegar
Vinegar is typically 4-18% acetic acid by mass. Vinegar is used directly as a condiment, and in the pickling of vegetables and other foods. Table vinegar tends to be more diluted (4% to 8% acetic acid), while commercial food pickling, in general, employs solutions that are more concentrated. The amount of acetic acid used as vinegar on a worldwide scale is not large, but is by far the oldest and best-known application.
Use as solvent
Glacial acetic acid is an excellent polar protic solvent, as noted above. It is frequently used as a solvent for recrystallization to purify organic compounds. Acetic acid is used as a solvent in the production of terephthalic acid (TPA), the raw material for polyethylene terephthalate (PET). In 2006, about 20% of acetic acid is used for TPA production.[23]
Acetic acid is often used as a solvent for reactions involving carbocations, such as Friedel-Crafts alkylation. For example, one stage in the commercial manufacture of synthetic camphor involves a Wagner-Meerwein rearrangement of camphene to isobornyl acetate; here acetic acid acts both as a solvent and as a nucleophile to trap the rearranged carbocation. Acetic acid is the solvent of choice when reducing an aryl nitro-group to aniline using palladium-on-carbon.
Glacial acetic acid is used in analytical chemistry for the estimation of weakly alkaline substances such as organic amides. Glacial acetic acid is a much weaker base than water, so the amide behaves as a strong base in this medium. It then can be titrated using a solution in glacial acetic acid of a very strong acid, such as perchloric acid.
Niche applications
Dilute solutions of acetic acids are also used as a stop bath during the development of photographic films, and in descaling agents to remove limescale from taps and kettles. In the clinical laboratory dilute acetic acid lyse red blood cells in order to facilitate microscopic examination.
The acidity is also used for treating the sting of the box jellyfish by disabling the stinging cells of the jellyfish, preventing serious injury or death if applied immediately, and for treating outer ear infections in people in preparations such as Vosol. In this manner, acetic acid is used as a spray-on preservative for livestock silage, to discourage bacterial and fungal growth. Glacial acetic acid is also used as a wart and verruca remover.
Organic or inorganic salts are produced from acetic acid, including:
" Sodium acetate, used in the textile industry and as a food preservative (E262).
" Copper(II) acetate, used as a pigment and a fungicide.
" Aluminium acetate and iron(II) acetate-used as mordants for dyes.
" Palladium(II) acetate, used as a catalyst for organic coupling reactions such as the Heck reaction.
" Silver acetate, used as a pesticide.
Substituted acetic acids produced include:
" Monochloroacetic acid (MCA), dichloroacetic acid (considered a by-product), and trichloroacetic acid. MCA is used in the manufacture of indigo dye.
" Bromoacetic acid, which is esterified to produce the reagent ethyl bromoacetate.
" Trifluoroacetic acid, which is a common reagent in organic synthesis.
Amounts of acetic acid used in these other applications together (apart from TPA) account for another 5-10% of acetic acid use worldwide. These applications are, however, not expected to grow as much as TPA production.[23] Diluted acetic acid is also used in physical therapy to break up nodules of scar tissue via iontophoresis.
Safety
Concentrated acetic acid is corrosive to skin and must, therefore, be handled with appropriate care, since it can cause skin burns, permanent eye damage, and irritation to the mucous membranes. These burns or blisters may not appear until hours after exposure. Latex gloves offer no protection, so specially resistant gloves, such as those made of nitrile rubber, are worn when handling the compound. Concentrated acetic acid can be ignited with difficulty in the laboratory. It becomes a flammable risk if the ambient temperature exceeds 39 Β°C (102 Β°F), and can form explosive mixtures with air above this temperature (explosive limits: 5.4-16%).
Solutions at more than 25% acetic acid are handled in a fume hood because of the pungent, corrosive vapour. Dilute acetic acid, in the form of vinegar, is harmless. However, ingestion of stronger solutions is dangerous to human and animal life. It can cause severe damage to the digestive system, and a potentially lethal change in the acidity of the blood.
Due to incompatibilities, it is recommended to keep acetic acid away from chromic acid, ethylene glycol, nitric acid, perchloric acid, permanganates, peroxides and hydroxyls.