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. Acetic acid has wide application as a laboratory reagent, in the production of cellulose acetate mainly for photographic film and polyvinyl acetate for wood glue, synthetic fibres, and fabric materials. Acetic acid has also been of large use as a descaling agent and acidity regulator in food industries.

Chemical Properties

Acetic acid, CH3COOH, is a colorless, volatile liquid at ambient temperatures. The pure compound, glacial acetic acid, owes its name to its ice-like crystalline appearance at 15.6°C. As generally supplied, acetic acid is a 6 N aqueous solution (about 36%) or a 1 N solution (about 6%). These or other dilutions are used in adding appropriate amounts of acetic acid to foods. Acetic acid is the characteristic acid of vinegar, its concentration ranging from 3.5 to 5.6%. Acetic acid and acetates are present in most plants and animal tissues in small but detectable amounts. They are normal metabolic intermediates, are produced by such bacterial species as Acetobacter and can be synthesized completely from carbon dioxide by such microorganisms as Clostridium thermoaceticum. The rat forms acetate at the rate of 1% of its body weight per day.

As a colorless liquid with a strong, pungent, characteristic vinegar odor, it is useful in butter, cheese, grape and fruit flavors. Very little pure acetic acid as such is used in foods, although it is classified by FDA as a GRAS material. Consequently, it may be employed in products that are not covered by Definitions and Standards of Identity. Acetic acid is the principal component of vinegars and pyroligneous acid. In the form of vinegar, more than 27 million lb were added to food in 1986, with approximately equal amounts used as acidulants and flavoring agents. In fact, acetic acid (as vinegar) was 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. They are also used in the curing of meat and in the canning of certain vegetables. In the manufacture of mayonnaise, the addition of a portion of acetic acid (vinegar) to the salt- or sugar-yolk reduces the heat resistance of Salmonella. Water binding compositions of sausages often include acetic acid or its sodium salt, while calcium acetate is used to preserve the texture of sliced, canned vegetables.

Physical properties

Acetic acid is a weak carboxylic acid with a pungent odor that exists as a liquid at room temperature. It was probably the first acid to be produced in large quantities. The name acetic comes from acetum, which is the Latin word for “sour” and relates to the fact that acetic acid is responsible for the bitter taste of fermented juices.

Occurrence

Reported found in vinegar, bergamot, cornmint oil, bitter orange oil, lemon petitgrain, various dairy products

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. Oxymel, which was an ancient remedy for coughs, was made by mixing honey and vinegar. A story recorded by the Roman writer Pliny the Elder (ca. 23–79 c.e.) describes how Cleopatra, in an attempt to stage the most expensive meal ever, dissolved pearls from an earring in vinegar wine and drank the solution to win a wager.

Uses

Acetic acid is an important industrial chemical. The reaction of acetic acid with hydroxyl containing compounds, especially alcohols, results in the formation of acetate esters. The largest use of acetic acid is in the production of vinyl acetate . Vinyl acetate can be produced through the reaction of acetylene and acetic acid. It is also produced from ethylene and acetic acid. Vinyl acetate is polymerized into polyvinyl acetate (PVA), which is used in the production of fibers, films, adhesives, and latex paints.
Cellulose acetate, which is used in textiles and photographic film, is produced by reacting cellulose with acetic acid and acetic anhydride in the presence of sulfuric acid. Other esters of acetic acid, such as ethyl acetate and propyl acetate, are used in a variety of applications.
Acetic acid is used to produce the plastic polyethylene terephthalate (PET) . Acetic acid is used to produce pharmaceuticals.

Uses

Acetic acid occurs in vinegar. It is producedin the destructive distillation of wood. Itfinds extensive application in the chemicalindustry. 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.

Uses

Glacial Acetic Acid is an acidulant that is a clear, colorless liquid which has an acid taste when diluted with water. It is 99.5% or higher in purity and crystallizes at 17°c. It is used in salad dressings in a diluted form to provide the required acetic acid. It is used as a preservative, acidulant, and flavoring agent. It is also termed acetic acid, glacial.

Uses

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. Product Data Sheet

Uses

manufacture of various acetates, acetyl compounds, cellulose acetate, acetate rayon, plastics and rubber in tanning; as laundry sour; printing calico and dyeing silk; as acidulant and preservative in foods; solvent for gums, resins, volatile oils and many other substances. Widely used in commercial organic syntheses. Pharmaceutic aid (acidifier).

Production Methods

Alchemists used distillation to concentrate acetic acid to high purities. Pure acetic acid isoften called glacial acetic acid because it freezes slightly below room temperature at 16.7°C(62°F). When bottles of pure acetic acid froze in cold laboratories, snowlike crystals formedon the bottles; thus the term glacial became associated with pure acetic acid. Acetic acidand vinegar were prepared naturally until the 19th century. In 1845, the German ChemistHermann Kolbe (1818–1884) successfully synthesized acetic acid from carbon disulfide (CS₂). Kolbe’s work helped to establish the field of organic synthesis and dispelled the idea of vitalism. Vitalism was the principle that a vital force associated with life was responsible for all organic substances.
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.

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.

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.

General Description

A colorless aqueous solution. Smells like vinegar. Density 8.8 lb / gal. Corrosive to metals and tissue.

Air & Water Reactions

Dilution with water releases some heat.

Reactivity Profile

ACETIC ACID, [AQUEOUS SOLUTION] 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 (Shraer, B.I. 1970. Khim. Prom. 46(10):747-750.).

Hazard

Corrosive; exposure of small amounts can severely erode the lining of the gastrointestinal tract; may cause vomiting, diarrhea, bloody feces and urine; cardiovascular failure and death.

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.

Agricultural Uses

Herbicide, Fungicide, Microbiocide; Metabolite, Veterinary Medicine: A herbicide used to control grasses, woody plants and broad-leaf weeds on hard surface and in areas where crops are not normally grown; as a veterinary medicine.

Pharmaceutical Applications

Glacial and diluted acetic acid solutions are widely used as acidifying agents in a variety of pharmaceutical formulations and food preparations. Acetic acid is used in pharmaceutical products as a buffer system when combined with an acetate salt such as sodium acetate. Acetic acid is also claimed to have some antibacterial and antifungal properties.

Trade name

ACETUM®; ACI-JEL®; ECOCLEAR®; NATURAL WEED SPRAY® No. One; VOSOL®

Safety Profile

A human poison by an unspecified route. Moderately toxic by various routes. A severe eye and skin irritant. Can cause burns, lachrymation, and conjunctivitis. Human systemic effects by ingestion: changes in the esophagus, ulceration, or bleeding from the small and large intestines. Human systemic irritant effects and mucous membrane irritant. Experimental reproductive effects. Mutation data reported. A common air contaminant. A flammable liquid. A fire and explosion hazard when exposed to heat or flame; can react vigorously with oxidizing materials. To fight fire, use CO2, dry chemical, alcohol foam, foam and mist. When heated to decomposition it emits irritating fumes. Potentially explosive reaction with 5azidotetrazole, bromine pentafluoride, chromium trioxide, hydrogen peroxide, potassium permanganate, sodium peroxide, and phosphorus trichloride. Potentially violent reactions with acetaldehyde and acetic anhydride. Ignites on contact with potassium tert-butoxide. Incompatible with chromic acid, nitric acid, 2-amino-ethanol, NH4NO3, ClF3, chlorosulfonic acid, (O3 + diallyl methyl carbinol), ethplenediamine, ethylene imine, (HNO3 + acetone), oleum, HClO4, permanganates, P(OCN)3, KOH, NaOH, xylene

Safety

Acetic acid is widely used in pharmaceutical applications primarily to adjust the pH of formulations and is thus generally regarded as relatively nontoxic and nonirritant. However, glacial acetic acid or solutions containing over 50% w/w acetic acid in water or organic solvents are considered corrosive and can cause damage to skin, eyes, nose, and mouth. If swallowed glacial acetic acid causes severe gastric irritation similar to that caused by hydrochloric acid.
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

Synthesis

From the destructive distillation of wood from acetylene and water and from acetaldehyde by subsequent oxidation with air. Pure acetic acid is produced commercially by a number of different processes. As dilute solutions, it is obtained from alcohol by the “Quick-Vinegar Process.” Smaller quantities are obtained from the pyroligneous acid liquors acquired in the destructive distillation of hard wood. It is manufactured synthetically in high yields by the oxidation of acetaldehyde and of butane, and as the reaction product of methanol and carbon monoxide
Vinegars are produced from cider, grapes (or wine), sucrose, glucose or malt by successive alcoholic and acetous fermentations. In the United States, the use of the term “vinegar,” without qualifying adjectives, implies only cider vinegar. Although a 4 to 8% solution of pure acetic acid would have the same taste characteristics as cider vinegar, it could not qualify as a vinegar, since it would lack other readily detectable components characteristic of cider vinegar. In Great Britain, malt vinegar is specified. On the European continent, wine vinegar is the most common variety

Potential Exposure

Acetic acid is widely used as a chemical feedstock for the production of vinyl plastics, acetic anhydride, acetone, acetanilide, acetyl chloride, ethyl alcohol, ketene, methyl ethyl ketone, acetate esters, and cellulose acetates. It is also used alone in the dye, rubber, pharmaceutical, food preserving, textile, and laundry industries. It is utilized, too; in the manufacture of Paris green, white lead, tint rinse, photographic chemicals, stain removers, insecticides, and plastics.

Carcinogenicity

Acetic acid is a very weak tumor promoter in a multistage mouse skin model for chemical carcinogenesis, but was very effective in enhancing cancer development when applied during the progression phase of the model. Female SENCAR mice were initiated with a topical application of 7,12-dimethylbenzanthracene and 2 weeks later were promoted with 12-O-tetradecanoylphorbol- 13-acetate, twice weekly for 16 weeks. Topical treatment with acetic acid started 4 weeks later (40 mg glacial acetic acid in 200mL acetone, twice weekly) and continued for 30 weeks. Before treatment with acetic acid, each group of mice had approximately the same number of papillomas at the exposure site. After 30 weeks of treatment, mice treated with acetic acid had a 55% greater conversion of skin papillomas to carcinomas than vehicle-treated mice. Selective cytotoxicity to certain cells within the papilloma and a compensatory increase in cell proliferation were considered the most probable mechanism.

Source

Present in domestic sewage effluent at concentrations ranging from 2.5 to 36 mg/L (quoted, Verschueren, 1983). A liquid swine manure sample collected from a waste storage basin contained acetic acid at a concentration of 639.9 mg/L (Zahn et al., 1997). Acetic acid was identified as a constituent in a variety of composted organic wastes. Detectable concentrations were reported in 18 of 21 composts extracted with water. Concentrations ranged from 0.14 mmol/kg in a wood shaving + poultry cattle manure to 18.97 mmol/kg in fresh dairy manure. The overall average concentration was 4.45 mmol/kg (Baziramakenga and Simard, 1998).
Acetic acid was formed when acetaldehyde in the presence of oxygen was subjected to continuous irradiation (λ >2200 ?) at room temperature (Johnston and Heicklen, 1964).
Acetic acid occurs naturally in many plant species including Merrill flowers (Telosma cordata), in which it was detected at a concentration of 2,610 ppm (Furukawa et al., 1993). In addition, acetic acid was detected in cacao seeds (1,520 to 7,100 ppm), celery, blackwood, blueberry juice (0.7 ppm), pineapples, licorice roots (2 ppm), grapes (1,500 to 2,000 ppm), onion bulbs, oats, horse chestnuts, coriander, ginseng, hot peppers, linseed (3,105 to 3,853 ppm), ambrette, and chocolate vines (Duke, 1992).
Identified as an oxidative degradation product in the headspace of a used engine oil (10–30W) after 4,080 miles (Levermore et al., 2001).

Environmental Fate

Biological. Near Wilmington, NC, organic wastes containing acetic acid (representing 52.6% of total dissolved organic carbon) were injected into an aquifer containing saline water to a depth of approximately 1,000 feet below ground surface. The generation of gaseous components (hydrogen, nitrogen, hydrogen sulfide, carbon dioxide, and methane) suggests acetic acid and possibly other waste constituents, were anaerobically degraded by microorganisms (Leenheer et al., 1976).
Plant. Based on data collected during a 2-h fumigation period, EC50 values for alfalfa, soybean, wheat, tobacco, and corn were 7.8, 20.1, 23.3, 41.2, and 50.1 mg/m³, respectively (Thompson et al., 1979).
Photolytic. A photooxidation half-life of 26.7 d was based on an experimentally determined rate constant of 6 x 10^-13 cm³/molecule?sec at 25 °C for the vapor-phase reaction of acetic acid with OH radicals in air (Atkinson, 1985). In an aqueous solution, the rate constant for the reaction of acetic acid with OH radicals was determined to be 2.70 x 10^-17 cm³/molecule?sec (Dagaut et al., 1988).
Chemical/Physical. Ozonolysis of acetic acid in distilled water at 25 °C yielded glyoxylic acid which oxidized readily to oxalic acid before undergoing additional oxidation producing carbon dioxide. Ozonolysis accompanied by UV irradiation enhanced the removal of acetic acid (Kuo et al., 1977).

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.

Shipping

UN2789 Acetic acid, glacial or Acetic acid solution, with .80 % acid, by mass, hazard class: 8; labels: 8-Corrosive material, 3-flammable liquid. UN2790 acetic acid solution, not ,50% but not .80% acid, by mass, hazard class: 8; labels: 8-Corrosive material; acetic acid solution, with .10% and ,50%, by mass, hazard class: 8; labels: 8-Corrosive material

Purification Methods

Usual impurities are traces of acetaldehyde and other oxidisable substances and water. (Glacial acetic acid is very hygroscopic. The presence of 0.1% water lowers its m by 0.2o.) Purify it by adding some acetic anhydride to react with water present, heat it for 1hour to just below boiling in the presence of 2g CrO3 per 100mL and then fractionally distil it [Orton & Bradfield J Chem Soc 960 1924, Orton & Bradfield J Chem Soc 983 1927]. Instead of CrO3, use 2-5% (w/w) of KMnO4, and boil under reflux for 2-6hours. Traces of water have been removed by refluxing with tetraacetyl diborate (prepared by warming 1 part of boric acid with 5 parts (w/w) of acetic anhydride at 60o, cooling, and filtering off, followed by distillation [Eichelberger & La Mer J Am Chem Soc 55 3633 1933]. Refluxing with acetic anhydride in the presence of 0.2g % of 2-naphthalenesulfonic acid as catalyst has also been used [Orton & Bradfield J Chem Soc 983 1927]. Other suitable drying agents include anhydrous CuSO4 and chromium triacetate: P2O5 converts some acetic acid to the anhydride. Azeotropic removal of water by distillation with thiophene-free *benzene or with butyl acetate has been used [Birdwhistell & Griswold J Am Chem Soc 77 873 1955]. An alternative purification uses fractional freezing. [Beilstein 2 H 96, 2 IV 94.] Rapid procedure: Add 5% acetic anhydride, and 2% of CrO3. Reflux and fractionally distil.

Toxicity evaluation

Acetic acid is present throughout nature as a normal metabolite of both plants and animals. Acetic acid may also be released to the environment in a variety of waste effuents, in emissions from combustion processes, and in exhaust from gasoline and diesel engines. If released to air, a vapor pressure of 15.7 mmHg at 25 °C indicates acetic acid should exist solely as a vapor in the ambient atmosphere. Vapor-phase acetic acid will be degraded in the atmosphere by reaction with photochemically produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 22 days. Physical removal of vapor-phase acetic acid from the atmosphere occurs via wet deposition processes based on the miscibility of this compound in water. In acetate form, acetic acid has also been detected in atmospheric particulate material. If released to soil, acetic acid is expected to have very high to moderate mobility based upon measured Koc values, using near-shore marine sediments, ranging from 6.5 to 228. No detectable sorption was measured for acetic acid using two different soil samples and one lake sediment. Volatilization from moist soil surfaces is not expected to be an important fate process based upon a measured Henry’s law constant of 1×10-9 atmm3 mol-1. Volatilization from dry soil surfaces may occur based upon the vapor pressure of this compound. Biodegradation in both soil and water is expected to be rapid; a large number of biological screening studies has determined that acetic acid biodegrades readily under both aerobic and anaerobic conditions. Volatilization from water surfaces is not expected to be an important fate process based on its measured Henry’s law constant. An estimated bacterial colony foraging (BCF) of <1 suggests that the potential for bioconcentration in aquatic organisms is low.

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

Regulatory Status

GRAS listed. Accepted as a food additive in Europe. Included in the FDA Inactive Ingredients Database (injections, nasal, ophthalmic, and oral preparations). Included in parenteral and nonparenteral preparations licensed in the UK.