What is Trichloroacetic Acid Definition Formula Preparation and Uses
What is Trichloroacetic Acid?
Trichloroacetic acid is an organic compound in which three hydrogen atoms of the methyl group of acetic acid get replaced by chlorine atoms. It is a white crystalline solid. It is also known as TCA, TCAA or trichloro ethanoic acid. But its systematic IUPAC name is trichloroacetic acid. As the name suggests, it's an analogue of acetic acid. It is a strong acid which is widely used in clinical chemical and biochemistry. Specially its salts and esters are very famous for their usage in cosmetics. Its salts and esters are called trichloroacetates.
In 1839, French Chemist Jean – Baptiste Dumas discovered trichloroacetic acid. It is also called aceto - caustin. Its discovery gave a noticeable example to the theory of organic radicals and valances. This theory was based on the facts which were contrary to the beliefs of Swedish Chemist Jons Jakob Berzelius. Thus, Jean – Baptiste Dumas was the first chemist who criticized or questioned the results of the electro – chemical research of Jons Jakob Berzelius. Before the discoveries made by Dumas, results of electro – chemical research by Jons Jakob Berzelius were widely accepted at that time. It started a long debate between Jons Jakob Berzelius and Jean – Baptiste Dumas.
Formula of Trichloroacetic Acid
Structure of Trichloroacetic Acid
It is an organic covalent compound which is formed by the displacement of hydrogen atoms of acetic acid by chlorine atoms. The carbon atom which is bonded with O, OH and CCl3 group is sp2 hybridized and the carbon atom which is bonded to three chlorine atoms and COOH group is sp3 hybridized.
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Trichloroacetic acid (CCl3COOH)
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3D – Structure of trichloroacetic acid
Properties of Trichloroacetic Acid
Physical and chemical properties of trichloroacetic acid - Properties of trichloroacetic acid are listed below –
Its molar mass is 163.38 g/mol.
It is a white or colorless crystalline solid.
It has a sharp pungent smell.
Its density is 1.63 g.cm-3.
Its melting point is 58 ℃.
Its boiling point is 197 ℃.
It is soluble in water.
It is acidic in nature. Its pH is 1.2.
It turns blue litmus paper into red.
Its pKa value is 0.66.
It is a stable compound with a flash point over 93 ℃.
It is not reactive with water.
It is corrosive in nature like other strong acids.
Its dipole moment is 3.23 D.
It reacts with protein.
Preparation of Trichloroacetic Acid
It is produced by the reaction of chlorine gas on acetic acid in presence of a catalyst. Reaction is given below –
CH3COOH + 3Cl2 🡪 CCl3COOH + 3HCl
It can also be produced by the reaction of trichloroacetaldehyde with oxygen or by the oxidation of trichloroacetaldehyde.
Uses of Trichloroacetic Acid
Due to its stable and strong acidic nature, trichloroacetic acid is used in many fields to fulfill various purposes. Its few applications are listed below –
It is widely used in clinical chemistry in the preparation of formulations.
In biochemistry, it is used for precipitation of macromolecules. For example, it can precipitate proteins, DNA and RNA.
It is used in the chemical peels and tattoo removal.
It is used in cosmetics.
It is used on the skin for chemoablation of warts.
In diluted form it can be used on the genital warts as well.
It can be used even during pregnancy for skin infections.
Its sodium salt was used as an herbicide till the 1980s.
Effects of Trichloroacetic Acid on Health And Environment
Trichloroacetic acid is a strong acid. So, it is a corrosive compound. Its overuse on skin can cause skin damage. Its short exposure can cause serious temporary or long - lasting injuries. It can be lethal for rats when taken 5000 mg/kg. It is harmful for the environment as well.
Trichloroacetic Acid: Summary in Tabular Form
FAQs on Trichloroacetic Acid Structure Properties and Reactions
1. What is trichloroacetic acid?
Trichloroacetic acid (TCA) is a strong organic carboxylic acid with the molecular formula CCl3COOH and systematic name 2,2,2-trichloroethanoic acid. It is derived from acetic acid by replacing three hydrogen atoms of the methyl group with chlorine atoms. Key features include:
- Colorless crystalline solid at room temperature
- Highly soluble in water due to its polar –COOH group
- Much stronger acid than acetic acid because of the electron-withdrawing effect of three chlorine atoms
It is widely used in organic synthesis, protein precipitation, and dermatological chemical peels.
2. What is the chemical formula and structure of trichloroacetic acid?
The chemical formula of trichloroacetic acid is CCl3COOH, and its structure consists of a trichloromethyl group attached to a carboxyl group. Structurally, it can be written as:
- CCl3–COOH
- Expanded form: Cl3C–C(=O)–OH
The molecule contains:
- One carboxylic acid functional group (–COOH)
- Three chlorine atoms bonded to the same carbon (–CCl3)
The strong –I (inductive) effect of chlorine increases its acidity compared to acetic acid.
3. Why is trichloroacetic acid stronger than acetic acid?
Trichloroacetic acid is stronger than acetic acid because the three chlorine atoms exert a strong electron-withdrawing inductive effect (–I effect) that stabilizes the conjugate base. When TCA ionizes:
CCl3COOH(aq) ⇌ CCl3COO-(aq) + H+(aq)
- The CCl3 group pulls electron density away from the –COO- ion
- This stabilizes the negative charge on the conjugate base
- Greater stabilization means greater acidity
As a result, trichloroacetic acid has a much lower pKa (~0.7) than acetic acid (~4.76).
4. Is trichloroacetic acid a strong or weak acid?
Trichloroacetic acid is classified as a strong organic acid but not a strong mineral acid like HCl or H2SO4. It partially ionizes in water but to a much greater extent than most carboxylic acids. In aqueous solution:
CCl3COOH(aq) ⇌ CCl3COO-(aq) + H+(aq)
- pKa ≈ 0.7
- Much stronger than typical weak acids like acetic acid
- Still does not ionize 100%, so it is not a strong acid in the Arrhenius sense
5. How is trichloroacetic acid prepared?
Trichloroacetic acid is commonly prepared by chlorination of acetic acid in the presence of a catalyst. The reaction replaces three hydrogen atoms in the methyl group with chlorine:
CH3COOH + 3Cl2 → CCl3COOH + 3HCl
- Occurs via free-radical halogenation
- Requires heat or UV light
- Progressive substitution forms mono-, di-, then trichloroacetic acid
Careful control ensures full substitution to obtain trichloroacetic acid as the final product.
6. What are the main uses of trichloroacetic acid?
Trichloroacetic acid is used in organic synthesis, protein precipitation, and dermatology. Its strong acidity and denaturing properties make it valuable in several fields:
- Protein precipitation in biochemistry labs
- Chemical peels in dermatology to remove damaged skin layers
- Intermediate in organic synthesis
- Analytical chemistry reagent
Its corrosive nature requires careful handling under laboratory safety guidelines.
7. What happens when trichloroacetic acid reacts with a base?
When trichloroacetic acid reacts with a base, it undergoes a neutralization reaction to form a trichloroacetate salt and water. For example, with sodium hydroxide:
CCl3COOH(aq) + NaOH(aq) → CCl3COONa(aq) + H2O(l)
- Acid donates H+
- Base provides OH-
- Forms sodium trichloroacetate and water
This is a typical acid–base neutralization reaction.
8. What is the molar mass of trichloroacetic acid?
The molar mass of trichloroacetic acid (CCl3COOH) is approximately 163.4 g/mol. It is calculated as:
- Carbon (2 × 12.01) = 24.02 g/mol
- Chlorine (3 × 35.45) = 106.35 g/mol
- Hydrogen (1 × 1.01) = 1.01 g/mol
- Oxygen (2 × 16.00) = 32.00 g/mol
Total ≈ 163.38 g/mol, commonly rounded to 163.4 g/mol for calculations in stoichiometry.
9. What is the conjugate base of trichloroacetic acid?
The conjugate base of trichloroacetic acid is the trichloroacetate ion, CCl3COO-. It forms when the acid donates a proton:
CCl3COOH ⇌ CCl3COO- + H+
- Negative charge is delocalized over the two oxygen atoms
- Further stabilized by the electron-withdrawing CCl3 group
This stabilization explains the relatively high acidity of trichloroacetic acid.
10. What safety precautions should be taken when handling trichloroacetic acid?
Trichloroacetic acid is corrosive and should be handled with proper personal protective equipment (PPE). Key safety precautions include:
- Wear gloves, goggles, and lab coat
- Handle in a fume hood to avoid inhalation
- Avoid skin and eye contact due to its corrosive nature
- Store in tightly sealed containers away from bases and reactive metals
In case of contact, rinse immediately with plenty of water and seek medical attention if necessary.
