Acetic Acid

Acetic Acid (CH3COOH)

Acetic acid, having the formula CH3COOH, is a chemical substance. A methyl group is connected to a carboxyl functional group in this carboxylic acid. The IUPAC name for acetic acid is ethanoic acid, and its chemical formula is C2H2O. Vinegar is a solution of acetic acid in water that contains between 5 and 20 percent volume of ethanoic acid. The acetic acid found in it is responsible for its pungent odour and sour flavour.

A solution of acetic acid that has not been diluted is frequently referred to as glacial acetic acid. It forms crystals that resemble ice at temperatures below 16.6 degrees Celsius. As a polar, protic solvent, it has an extensive range of applications. In analytical chemistry, glacial acetic acid is commonly used to measure weakly alkaline compounds.

Structure of  Acetic acid-CH₃COOH

• In the solid state of acetic acid, a chain of molecules can be observed in which individual molecules are joined to one another via hydrogen bonds.
• Dimers of ethanoic acid can be found in the vapour phase at temperatures close to 120 °C.
• When ethanoic acid is present in a diluted solution, its dimers can be discovered in the liquid state.
• Solvents that increase hydrogen bonding have a detrimental effect on these dimers.
• The chemical formula for acetic acid is CH3(C=O)OH or CH3CO2H.

The structure of acetic acid is represented in the diagram below.

Properties of  Acetic acid-CH₃COOH

CH3COOH	Acetic Acid
Molecular weight/molar mass of CH3COOH	60.052 g/mol
Density of Acetamide	1.05 g/cm³
Boiling Point of Acetamide	118 °C
Melting Point of Acetamide	16.6 °C

Physical Properties of Acetic Acid

It may be surprising to learn that ethanoic acid, despite its reputation as a relatively weak acid, may cause serious damage to human skin when in its concentrated form.

Below are some general features of acetic acid.

• Ethanoic acid is a seemingly colourless liquid with a strong odour.
• At standard temperature and pressure, the melting and boiling temperatures of ethanoic acid are 289K and 390K, respectively.
• The molar mass of acetic acid is 60,052 grammes per mole, and its liquid density is 1.049 grammes per cubic centimetre.
• The carboxyl functional group of ethanoic acid can result in the ionisation of the molecule, as shown by the following reaction: CH3COOH CH3COO– + H+
• The release of the proton, as stated by the equilibrium reaction above, is the underlying source of acetic acid’s acidic nature.
• In a water solution, the acid dissociation constant (pKa) of ethanoic acid is 4.76.
• Acetate is the conjugate base of acetic acid; its formula is CH3COO–.
• The pH of a 1.0M concentration of ethanoic acid is 2.4, indicating that it does not dissociate entirely.
• In its liquid state, acetic acid is a polar, protic, dielectric solvent with a dielectric constant of 6.2.

The binding of acetic acid to coenzyme A is crucial to the metabolism of carbohydrates and lipids in a variety of organisms. Typically, this chemical is created through the interaction of methanol with carbon monoxide (carbonylation of methanol).

Chemical Properties of Acetic Acid

Acetic acid has chemical reactions that are consistent with those of other carboxylic acids. When heated above 440 degrees Celsius, this molecule breaks down into methane and carbon dioxide, or water and ethenone, as shown in the following chemical formulae.

CH₃COOH + Heat → CO₂ + CH₄

CH₃COOH + Heat → H₂C=C=O + H₂O

Magnesium, zinc, and iron are susceptible to corrosion when exposed to acetic acid. The outcome of these reactions is the creation of acetate salts.

2CH₃COOH + Mg → Mg(CH₃COO)₂ (magnesium acetate) + H₂

According to the aforementioned chemical equation, the reaction between ethanoic acid and magnesium results in the creation of magnesium acetate and hydrogen gas.

As described below, acetic acid interacts with alkalis to generate acetate salts.

CH₃COOH + KOH → CH₃COOK + H₂O

This substance also generates acetate salts by combining them with carbonates (along with carbon dioxide and water). Examples of these responses include:

2CH₃COOH + Na₂CO₃ (sodium carbonate) → 2CH₃COONa + CO₂ + H₂O

CH₃COOH + NaHCO₃ (sodium bicarbonate) → CH₃COONa + CO₂ + H₂O

Preparation of  Acetic acid-CH₃COOH

Methanol carbonylation

Most acetic acid is created through the carbonylation of methanol. According to the following equation, methanol and carbon monoxide react in this procedure to make acetic acid:

The procedure consists of three phases and uses iodomethane as an intermediate. Metal carbonyl is required as a catalyst for carbonylation (step 2).

1. CH₃OH + HI → CH₃I + H₂O
2. CH₃I + CO → CH₃COI
3. CH₃COI + H₂O → CH₃COOH + HI

For the carbonylation of methanol, two related methods exist: the rhodium-catalyzed Monsanto process and the iridium-catalyzed Cativa process.

The latter technique, which is greener and more efficient, has generally replaced the earlier, frequently in the same manufacturing facilities.

Both processes require catalytic amounts of water, but the Cativa process requires less, therefore the water-gas shift reaction is inhibited and fewer byproducts are produced.

Ethylene oxidation

The Wacker process can be used to produce acetaldehyde from ethylene, which is subsequently oxidised as described above.

C₂H₄ + O₂ → CH₃CO₂H

Anaerobic fermentation

Species of anaerobic bacteria, such as Clostridium or Acetobacterium, can metabolise carbohydrates directly into acetic acid without producing ethanol as an intermediary. The overall chemical reaction carried out by these microorganisms can be depicted as follows:

C₆H₁₂O₆ → 3 CH₃COOH

These acetogenic bacteria generate acetic acid from one-carbon molecules, such as methanol, carbon monoxide, or a carbon dioxide and hydrogen mixture:

2 CO₂ + 4 H₂ → CH₃COOH + 2 H₂O

This capacity of Clostridium to directly metabolise sugars or to create acetic acid from less expensive inputs suggests that these bacteria could make acetic acid more efficiently than ethanol-oxidizing bacteria such as Acetobacter.

Uses of Acetic Acid

Ethanoic acid is a crucial chemical molecule for human existence. Below are some significant applications of acetic acid.

• Due to its antimicrobial properties, acetic acid is used as an antiseptic.
• Utilizing ethanoic acid in the production of rayon fibre.
• By directly injecting acetic acid into the tumour, acetic acid has been utilised to treat cancer.
• As the primary component of vinegar, it is used to pickle a variety of vegetables.
• Rubber production requires the usage of ethanoic acid.
• It is also utilised in the production of perfumes.
• It is commonly employed in the manufacture of VAM (vinyl acetate monomer).
• The result of the condensation reaction between two molecules of acetic acid is acetic anhydride.

Acetic Acid as a Solvent

• CH3COOH is a hydrophile (it rapidly dissolves in water) and a polar, protic solvent in its liquid state. In this way, a mixture of acetic acid and water is comparable to a mixture of ethanol and water.
• Also miscible with hexane, chloroform, and many oils is acetic acid. It does not, however, create miscible mixes with long-chain alkanes (such as octane).
• Acetic acid is a crucial industrial solvent due to its excellent solvent characteristics and its ability to generate miscible mixes with both polar and non-polar chemicals.
• It is commonly employed in the commercial synthesis of dimethyl terephthalate (DMT).

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