Peracetic acid

Peracetic acid
IUPAC name	Ethaneperoxoic acid
Other names	Peroxyacetic acid Acetic peroxide Acetyl hydroperoxide Proxitane
Identifiers
Abbreviations	PAA
CAS number	[79-21-0]
RTECS number	SD8750000
SMILES	CC(=O)OO
Properties
Molecular formula	C2H4O3
Molar mass	76.05
Appearance	Colourless liquid
Density	1.13 g/ml (liquid)
Melting point	0.1 °C
Boiling point	105 °C
Acidity (pKa)	8.20
Viscosity	3.280 cP
Hazards
EU classification	O, C, N
S-phrases	(1/2-)-3/7-14-36/37/39-45-61
NFPA 704	2 3 4 OX
Flash point	40.5 °C
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references

Peracetic acid (peroxyacetic acid, or PAA), is a organic compound with the formula CH3CO₃H. This organic peroxide is a colorless liquid with a characteristic acrid odor reminiscent of acetic acid. It can be highly corrosive.

Peracetic acid is a much weaker acid than the parent acetic acid, with a pK_a of 8.2.

Production

Peracetic acid arises upon treatment of acetic acid with hydrogen peroxide, the equilibrium constant being 0.37 at room temperature:

H₂O₂ + CH₃CO²H CH₃CO₃H + H₂O

Alternatively, acetyl chloride and acetic anhydride can be used to generate products with lower water content.

Peracetic acid is produced by continuously feeding acetic acid and hydrogen peroxide into an aqueous reaction medium containing a sulfuric acid catalyst. The reaction is allowed to continue for up to ten days in order to achieve high yields of product according to the following equation.^[1]

Peracetic acid production

Peracetic acid is always sold in solution with acetic acid and hydrogen peroxide to maintain the stability of the chemical. The concentration of the acid as the active ingredient can vary, and usually depends on its application. Additional methods of preparation involve the oxidation of acetaldehyde or alternatively as an end product of the reaction of acetic anhydride, hydrogen peroxide, and sulfuric acid. Another method involves the reaction of tetraacetylethylenediamine (TAED) in the presence of an alkaline hydrogen peroxide solution.^[1] PAA is also formed naturally in the environment through a series of photochemical reactions involving formaldehyde and photo-oxidant radicals.^[2]

Uses

Synthesis of other compounds

The main use of peracetic acid is for the industrial synthesis of epoxides. It transfer an oxygen atom to double bonds, e.g. in ethene and propene, to form epoxides and alcohols. It can also be used in producing synthetic glycerol from propene, and is used in nylon manufacturing.^[3]

Antimicrobial agent

Peracetic acid is an ideal antimicrobial agent due to its high oxidising potential. It is broadly effective against microorganisms and is not deactivated by catalase and peroxidase, the enzymes that break down hydrogen peroxide. It also breaks down food to safe and environmentally friendly residues (acetic acid and hydrogen peroxide), and therefore can be used in non-rinse applications. It can be used over a wide temperature range (0-40 °C), wide pH range (3.0-7.5), in clean-in-place (CIP) processes, in hard water conditions, and is not affected by protein residues.

Mechanism of action

Peracetic acid kills microorganisms by oxidation and subsequent disruption of their cell membrane, via the hydroxyl radical (OH·). As diffusion is slower than the half-life of the radical, it will react with any oxidizable compound in its vicinity. It can damage virtually all types of macromolecules associated with a microorganism: carbohydrates, nucleic acids (mutations), lipids (lipid peroxidation) and amino acids (e.g. conversion of Phe to m-Tyr and o-Tyr). This ultimately leads to cell lysis and true microbial death.

Application

The United States Environmental Protection Agency‎‎ first registered peracetic acid as an antimicrobial in 1985 for indoor use on hard surfaces. Use sites include agricultural premises, food establishments, medical facilities, and home bathrooms. Peracetic acid is also registered for use in dairy/cheese processing plants, on food processing equipment and in pasteurizers in breweries, wineries, and beverage plants.^[4] It is also applied for the disinfection of medical supplies, to prevent bio film formation in pulp industries, and as a water purifier and disinfectant. Peracetic acid can be used as a cooling tower water disinfect where it prevents bio film formation and effectively controls Legionella bacteria.

Bleaching agent

Peracetic acid can be used as a bleaching agent especially for Kraft pulp. It is used at weakly acidic pH and relatively low temperature. It is a relative efficient and selective bleaching agent, and it is often used as an alternative to chlorine dioxide and elemental chlorine in totally chlorine free bleaching sequences (TCF). It is however relatively expensive, and is difficult to store due to its high reactivity. This has limited its use. It is efficient in removing hexenuronic acid, and its one-letter code is T.

Fowl Sanitizer

Peracetic acid is extremely effective for sanitizing fowl carcasses without affecting the skin or the flesh of the bird carcass by applying direct to the meat. In particular, paracetic acid is applying to a fowl that has been killed, plucked and eviscerated by contacting the fowl with an aqueous paracetic acid solution and maintaining that contact to a time sufficient to sanitize the fowl. [1]

See also

• Disinfection
• Hydroxyl
• Organic peroxide
• Peroxy acid

References