What Is Acetate Definition Formation Reactions and Uses in Chemistry
Most of us are familiar with vinegar, it is a common kitchen ingredient having a sour taste. Vinegar is an aqueous solution of acetic acid (IUPAC name: ethanoic acid), with the chemical formula CH3COOH. When the acid loses a proton, the anion of the acetic acid is termed an ‘acetate anion’. When the acetate anion combines with a cation, the compound is called an ‘acetate’. The simplest acetate is hydrogen acetate, which is another name for acetic acid.
a) Acetic Acid b) Acetate Anion
Acetate is the conjugate base of acetic acid. The acetate ion is commonly abbreviated as AcO- or -OAc. Acetic acid is a weak acid which dissociates in water to release a proton and an acetate ion at a pH of 5.5 or above. Acetate chemical formula is CH3COO-
CH3COOH + H2O ⇌ CH3COO- + H3O+
A very well-known reaction of vinegar (acetic acid) and baking soda (sodium bicarbonate) produces an acetate ester (sodium acetate). This mixture is often used for cleaning purposes.
CH3COOH + NaHCO3 → CH3COONa + CO2 + H2O
In human biology, acetate is one of the most common building blocks for biosynthesis, such as fatty acid synthesis. It is a common anion found in Biology.
Table: Properties of Acetate Ion
Acetate Structure
Acetate contains one methyl group(-CH3) which is bonded with a carbonyl carbon. The carbonyl group is connected to another oxygen with a negative charge along with the methyl group.
Acetate Anion
The methyl carbon is sp3 hybridised and has a tetrahedral geometry; the connected carbonyl carbon is sp2 hybridised that is doubly bonded to neutral oxygen and singly bonded to a negatively charged oxygen. However, both the oxygen is equivalent due to the delocalization of electrons through resonance.
Hybridisation Sates of Acetate Anion
The negative charge over one oxygen shifts to form a double bond with the carbonyl carbon, while the existing double bond dissolves and the electron cloud is pushed over the other oxygen atom with the accumulation of negative charge. This delocalization results in equal distribution of the negative charge on both the oxygen atoms of the acetate anion.
Delocalisation of Negative Charge by Resonance
Acetate Esters
In Organic Chemistry, acetate esters are the esters of acetic acid, where the acetate anion combines with an organyl group (R). Acetate esters are generally represented as CH3COOR. These esters are generally fragrant liquids with low toxicity and are lipophilic and, sometimes, volatile.
Acetate Ester
Acetate Biochemistry
Acetate is broken down in nature by fermentation carried out by methanogenic archaea. The microbe catalyses the dismutation of acetic acid, which is a disproportion reaction; a single electron from carbonyl (e- donor) of the carboxylic acid is transferred to the methyl group (e- acceptor), releasing methane and carbon dioxide.
CH3COO- + H+ → CH4 + CO2
Acetate is produced by gut bacteria by fermentation. It is also derived from diet and generated from various tissues like the intestine and liver. Deacylation reaction produces acetate in all cells. The acetates, in order to be utilised, are converted into acetyl coenzyme A (acetyl-CoA).
Acetyl-coenzyme A is converted into acetate while producing ATP (the energy currency) during substrate-level phosphorylation in E.Coli.
Acetyl-CoA + phosphate → acetyl-phosphate + CoA
Acetyl-phosphate + ADP → acetate + ATP
Acetyl CoA is involved in lipid, protein and carbohydrate metabolism. In the citric acid cycle, it delivers the acetyl group that leads to the production of energy.
Uses of Acetate
Acetate is used largely in the production of vinyl acetate, a precursor to polyvinyl alcohol used as a component of paints.
‘Acetate’ is often used as a substituent for cellulose acetate, which is produced using acetic acid. Cellulose acetate is used in the production of fibres.
Variety of industrial solvents are acetates, such as methyl acetate, ethyl acetate, isopropyl acetate and butyl acetate (used as a fragrance in food products).
Interesting Facts
Acetates have been found to have immunomodulatory properties, affecting innate immune response to pathogenic bacteria.
Most of the acetic acid produced annually (about 5 billion kilograms) is consumed in the production of acetates.
Key Features
‘Acetate’ refers to the compound containing the acetate anion and another cation.
Chemical formula of acetate anion is C2H3O2- or CH3COO-.
Acetic acid is the simplest acetate. Hydrogen cation and the acetate anion combine to form hydrogen acetate (acetic acid: CH3COOH)
Acetate is utilised in the form of acetyl CoA in biological systems. It is used in various metabolism to yield energy, and in biosynthesis, it serves as a common building block.
FAQs on Acetate Ion Structure Formula and Chemical Properties
1. What is acetate in chemistry?
The acetate ion is the conjugate base of acetic acid with the chemical formula CH3COO− (also written as C2H3O2−).
- It is formed when acetic acid (CH3COOH) loses a proton (H+).
- It contains a carboxylate group (–COO−).
- Acetate commonly forms salts such as sodium acetate (CH3COONa).
2. What is the formula and charge of the acetate ion?
The formula of the acetate ion is CH3COO−, and it carries a −1 charge.
- It consists of two carbon atoms, three hydrogen atoms, and two oxygen atoms.
- The negative charge is delocalized over the two oxygen atoms due to resonance.
- Alternative formula: C2H3O2−.
3. How is the acetate ion formed from acetic acid?
The acetate ion is formed when acetic acid donates a proton (H+) in an acid–base reaction.
- Ionization in water:
- Acetic acid acts as a weak acid.
- Acetate is its conjugate base.
4. Is acetate an acid or a base?
The acetate ion (CH3COO−) is a weak base because it is the conjugate base of acetic acid.
- It can accept a proton to reform acetic acid.
- In water, it undergoes hydrolysis:
- This reaction produces OH−, making the solution slightly basic.
5. What is the difference between acetic acid and acetate?
The key difference is that acetic acid (CH3COOH) is a weak acid, while acetate (CH3COO−) is its conjugate base.
- Acetic acid contains a replaceable acidic hydrogen.
- Acetate lacks this hydrogen and carries a −1 charge.
- Acetic acid lowers pH; acetate can raise pH slightly.
6. What are common examples of acetate salts?
Common acetate salts are ionic compounds containing the CH3COO− ion combined with a metal cation.
- Sodium acetate (CH3COONa)
- Potassium acetate (CH3COOK)
- Calcium acetate [Ca(CH3COO)2]
- Lead(II) acetate [Pb(CH3COO)2]
7. What is the molar mass of the acetate ion?
The molar mass of the acetate ion (C2H3O2−) is approximately 59.04 g/mol.
- Carbon: 2 × 12.01 = 24.02 g/mol
- Hydrogen: 3 × 1.008 = 3.024 g/mol
- Oxygen: 2 × 16.00 = 32.00 g/mol
- Total ≈ 59.04 g/mol
8. Why is acetate important in buffer solutions?
Acetate is important in buffer solutions because the acetic acid–acetate pair resists changes in pH.
- A buffer contains a weak acid (CH3COOH) and its conjugate base (CH3COO−).
- Added acid is neutralized by acetate.
- Added base is neutralized by acetic acid.
9. What is the structure and bonding in the acetate ion?
The acetate ion has a resonance-stabilized carboxylate structure where the negative charge is delocalized over two oxygen atoms.
- Two equivalent resonance forms can be drawn.
- The C–O bonds in the –COO− group have equal bond lengths.
- The central carbon is sp2-hybridized and trigonal planar.
10. How do you write the balanced reaction for the formation of sodium acetate?
Sodium acetate is formed by the neutralization of acetic acid with sodium hydroxide in a 1:1 ratio.
- Balanced equation:
- This is an acid–base neutralization reaction.
- One mole of acid reacts with one mole of base.
