You must have seen in movies; someone puts a soaked chloroform rag to another person’s face, and they pass out immediately. This is because Chloroform has a robust anaesthetic effect on a person’s body. Chloroform is a trichloro derivative of methane first discovered in \(1831\) by Liebig. Simpson found its anaesthetic properties in \(1848.\) The Chloroform formula is represented as ({\text{CHC}}{{\text{l}}_3}.)

The structure of Chloroform is achieved by substituting three chlorine atoms in place of three hydrogen atoms in a methane molecule. In this article, we will provide detailed information on the chloroform formula. Scroll down to learn more!

Choloroform Formula: Overview

Chloroform is made of five atoms that include one carbon \(\left({\text{C}} \right)\) atom, one hydrogen \(\left({\text{H}} \right)\) atom, and three chlorine \(\left({\text{Cl}} \right)\) atoms. Hence, its chemical formula is \({\text{CHC}}{{\text{l}}_3}.\) It resembles the structure of methane.

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Molar Mass

The molar mass of Chloroform,\({\text{CHC}}{{\text{l}}_3} = \left( {{\text{Atomic}}\,{\text{mass}}\,{\text{of}}\,{\text{Carbon}}} \right) + \left( {{\text{Atomic}}\,{\text{mass}}\,{\text{of}}\,{\text{hydrogen}}} \right) + 3\left({{\text{Atomic}}\,{\text{mass}}\,{\text{of}}\,{\text{Chlorine}}} \right)\)
\( = \left({12.01} \right) + \left({1.007} \right) + 3\left({35.453} \right) = 119.38\,{\text{g}}/{\text{mol}}\)
Hence, one mole of Chloroform weighs \(119.38\,{\text{grams}}.\)

Hybridisation

Hybridisation is the process in which two or more atomic orbitals with similar energy levels mix to form new hybrid orbitals.

Chloroform has only one carbon atom bonded to one hydrogen atom and three chlorine atoms.

Steric number of carbon atom is \( = \) Number of atoms attached \( + \) Lone pairs \( = 4 + 0 = 4 = \left({1{\text{s}} + 3{\text{p}}} \right)\)
Thus, the carbon atom in \({\text{CHC}}{{\text{l}}_3}\) is \({\text{s}}{{\text{p}}^3}\) hybridised.
The ground state of Carbon has two electrons in its \(2{\text{s}}\) orbital and \(1\) electron each in \(2{\text{Px}}\) and \(2{\text{Py}}\) orbital. The \(2{\text{Pz}}\) orbital is empty. However, in its excited state, one paired electron from the \(2{\text{s}}\) orbital jumps to occupy the empty \(2{\text{Pz}}\) orbital.
Hence, there are four orbitals, \(2{\text{s}},2{\text{Px}},2{\text{Py}},\) and \({\text{2Pz}},\) singly paired orbitals that readily accept electrons from other atoms. This overlapping of atomic orbitals results in \({\text{s}}{{\text{p}}^3}\) hybridisation. The presence of these four \({\text{s}}{{\text{p}}^3}\) hybrid orbitals makes Carbon tetravalent in nature.

Molecular Geometry

The shape and geometry of a molecule can be determined by the VSEPR theory or the Valence shell electron pair repulsion theory.

According to the theory, the shape of any compound depends largely and solely on the Number of bonding and lone pairs of electrons around the central atom. The compound takes up a shape that makes it the most stable and has the least repulsion between different bonds.

If a central atom has four bonded atoms and no lone pair on it, then the general formula for it is \({\text{A}}{{\text{X}}_4},\) and the geometry of that molecule will be tetrahedral.
Therefore, \({\text{CHC}}{{\text{l}}_3}\) molecular geometry is tetrahedral as it has four bonded atoms and no lone pair on it with \({\text{s}}{{\text{p}}^3}\) hybridisation.

Bond Angle

Chloroform consists of four atoms bonded to a carbon atom. The carbon atom in Chloroform is \({\text{s}}{{\text{p}}^3}\) hybridised. Hence, it resembles the structure of methane, i.e. tetrahedral. The four hybrid orbitals in Chloroform repel each other and get placed at the corners of a tetrahedron to minimise the force of repulsion between them. Ideally bond angle should be \({109^ \circ }28’\) but due to higher electronic repulsion between chlorine-chlorine atoms, \({\rm{Cl}} – {\rm{C}} – {\rm{Cl}}\) bond angle become greater than \({109^ \circ }28’\) and this results in \({\text{H}} – {\text{C}} – {\text{Cl}}\) bond angle to be less than \({109^ \circ }28′.\)

Dipole Moment

\({\text{CHC}}{{\text{l}}_3}\) is polar due to its tetrahedral molecular structure and the difference between the electronegativity of \({\text{C,H}}\) and \({\text{Cl}}\) atoms. Chlorine atoms are more electronegative than carbon and hydrogen and lie at three vertices of the pyramid and pull the negative charge to its direction, making it a polar molecule with a dipole in the direction of \({\text{Cl}}\) atoms. It has a net dipole moment of \(1.15\,{\text{D}}.\) The molecule is not symmetric, so dipole moments along these bonds cannot cancel each other, making this molecule polar.
A molecule having tetrahedral geometry is nonpolar in nature, but this condition is valid only when all atoms in the molecule is the same, like \({\text{CC}}{{\text{l}}_4}\) has four chlorine atoms and that make four similar \({\text{C-Cl}}\) bonds which cause a non-polar nature of it.
But in the case of \({\text{CHC}}{{\text{l}}_3},\) two different atoms present(hydrogen and chlorine) make different bonds and create some dipole moment which makes this molecule polar.

Lewis Structure

Lewis structure is a \(2 – {\text{D}}\) representation of all the bonding and nonbonding electron pairs of different atoms in a compound.
Total no. of valence electrons of \({\text{CHC}}{{\text{l}}_3}, = \) Valence electrons of Carbon \( + \) Valence electrons of Hydrogen \( + \) Valence electrons of Chlorine \( = 4 + 1 + \left({3*7} \right)\)
Total no. of valence electrons of \({\text{CHC}}{{\text{l}}_3} = 4 + 1 + 21 = 26\)
Chloroform \(\left({{\text{CHC}}{{\text{l}}_3}} \right)\) has \(26\) valence electrons.
Out of all carbon, hydrogen, and chlorine atoms, carbon is the highest valency atom, and hence we will place it in the central position. Chlorine is the most electronegative atom and occupies terminal positions. And the \(26\) valence electrons are distributed as shown below

The carbon atom is sharing four electrons with three chlorine atoms and a hydrogen atom. As the carbon atom needs four electrons to complete its octet, all the valency is satisfied, and it now has eight electrons in its valence shell. Similarly, hydrogen completes its duplet, and the three chlorine atoms also complete their octets.

Skeletal Structure

A chloroform molecule has the typical structure of a methane molecule, where three hydrogen atoms have been substituted by three chlorine atoms.

Preparation of Chloroform

1. From bleaching powder. Chlorine obtained by the reaction of water with bleaching powder oxidises ethyl alcohol to form acetaldehyde.

\({\text{CaOC}}{{\text{l}}_2} + {{\text{H}}_2}{\text{O}} \to {\text{Ca}}{\left({{\text{OH}}} \right)_2} + {\text{C}}{{\text{l}}_2}\)
\({\text{C}}{{\text{H}}_3}{\text{C}}{{\text{H}}_2}{\text{OH}} + {\text{C}}{{\text{l}}_2} \to {\text{C}}{{\text{H}}_3}{\text{CHO}} + 2{\text{HCl}}\)

Acetaldehyde obtained in the above reaction reacts with chlorine to form trichloro-aldehyde (chloral).

\({\text{C}}{{\text{H}}_3}{\text{CHO}} + 3{\text{C}}{{\text{l}}_2} \to {\text{CC}}{{\text{l}}_3}{\text{CHO}} + 3{\text{HCl}}\)

Chloral so formed reacts with calcium hydroxide to form Chloroform.

2. Reaction of ethyl alcohol with chlorine in \({\text{NaOH}}\) solution.
\({\text{C}}{{\text{H}}_3}{\text{C}}{{\text{H}}_2}{\text{OH}} + 4{\text{C}}{{\text{l}}_2} + 6{\text{NaOH}} \to {\text{CHC}}{{\text{l}}_3} + {\text{HCOONa}} + 5{\text{NaCl}} + 5{{\text{H}}_2}{\text{O}}\)
3. Reaction of acetaldehyde with chlorine in \({\text{NaOH}}\) solution.
\({\text{C}}{{\text{H}}_3}{\text{CHO}} + 3{\text{C}}{{\text{l}}_2} + 4{\text{NaOH}} \to {\text{CHC}}{{\text{l}}_3} + {\text{HCOONa}} + 3{\text{NaCl}} + 3{{\text{H}}_2}{\text{O}}\)
4. Reaction of acetone with chlorine in \({\text{NaOH}}\) solution.
\({\text{C}}{{\text{H}}_3}{\text{COC}}{{\text{H}}_3} + 3{\text{C}}{{\text{l}}_2} + 4{\text{NaOH}} \to {\text{CHC}}{{\text{l}}_3} + {\text{C}}{{\text{H}}_3}{\text{COONa}} + 3{\text{NaCl}} + 3{{\text{H}}_2}{\text{O}}\)

Industrial Method

The preparation of Chloroform by the industrial method is as follows:

1. Chloroform can also be made in large quantities by heating a mixture of ethyl alcohol or acetone, water and bleaching powder. This is similar to the laboratory method of making Chloroform.
2. By partial reduction of carbon tetrachloride by iron powder and in the presence of water vapour.

\(3{\text{Fe}} + 4{{\text{H}}_2}{\text{O}} \to {\text{F}}{{\text{e}}_3}{{\text{O}}_4} + 8\left[ {\text{H}} \right]\)
\({\text{CC}}{{\text{l}}_4} + 2\left[{\text{H}} \right] \to {\text{CHC}}{{\text{l}}_3} + {\text{HCl}}\)

3. By the distillation of a mixture of chloral hydrate and concentrated solution of sodium or potassium hydroxide.

\({\text{NaOH}} + {\text{CC}}{{\text{l}}_3}{\text{CH}}{\left({{\text{OH}}} \right)_2} \to {\text{CHC}}{{\text{l}}_3} + {\text{HCOONa}} + {{\text{H}}_2}{\text{O}}\)

Physical Properties of Chloroform

The physical properties of Chloroform are as follows:

1. Chloroform is a colourless liquid.
2. Its boiling point is \(61\,^\circ {\rm{C}}.\)
3. It has a sweet and distinct smell.
4. It is almost immiscible in water but miscible in ether and alcohol.
5. It is heavier than water, so when added to water, it forms a lower surface. It is a good solvent for oils, fats, waxes, rubber, etc.
6. Chloroform inhalation leads to unconsciousness.

Chemical Properties of Chloroform

The chemical properties of Chloroform are as follows:

1. Oxidation: In the presence of sunlight and air, Chloroform is gradually oxidised to form carbonyl chloride (phosgene). Phosgene is a highly toxic gas.
\(2{\text{CHC}}{{\text{l}}_3} + {{\text{O}}_2} \to 2{\text{COC}}{{\text{l}}_2} + 2{\text{HCl}}\)

To prevent oxidation of Chloroform, it is stored in dark coloured bottles, which cuts off exposure to light.

Ethanol is also added, which prevents oxidation of Chloroform and converts phosgene to harmless ethyl carbonate.

\({\text{COC}}{{\text{l}}_2} + 2{{\text{C}}_2}{{\text{H}}_5}{\text{OH}} \to {\left( {{{\text{C}}_2}{{\text{H}}_5}} \right)_2}{\text{C}}{{\text{O}}_3} + 3{\text{HCl}}\)
2. Reduction: Chloroform is reduced to methylene chloride, methyl chloride and methane by nascent hydrogen. The nascent hydrogen utilised in this reaction is obtained by the reaction of hot iron, and water vapour or hot zinc and water vapour or zinc with dilute \({\text{HCl}}{\text{.}}\)
\({\text{CHC}}{{\text{l}}_3} \to {\text{C}}{{\text{H}}_2}{\text{C}}{{\text{l}}_2} \to {\text{C}}{{\text{H}}_3}{\text{Cl}} \to {\text{C}}{{\text{H}}_4}\left({{\text{Methane}}}\right)\)

3. Hydrolysis: On heating chloroform with an aqueous or alcohol solution of strong alkali, it forms a salt of formic acid. If an aqueous solution of alkali is used, then this reaction is called Hydrolysis.

The above reactions can also be written briefly as follows.

\({\text{CHC}}{{\text{l}}_3} + 4{\text{NaOH}} \to {\text{HCOONa}} + 2{{\text{H}}_2}{\text{O}} + 3{\text{NaCl}}\)

4. Chlorination: Chloroform reacts with chlorine in sunlight to form carbon tetrachloride.

\({\text{CHC}}{{\text{l}}_3} + {\text{C}}{{\text{l}}_2} \to {\text{CC}}{{\text{l}}_4} + {\text{HCl}}\)

5. Nitration: It reacts with concentrated nitric acid to form chloropicrin. This compound is an insecticide and is used as a poison gas in wars.

\({\text{C}}{{\text{l}}_3}{\text{C}} – {\text{H}} + {\text{HO}} – {\text{N}}{{\text{O}}_2} \to {\text{C}}{{\text{l}}_3}{\text{C}} – {\text{N}}{{\text{O}}_2} + {{\text{H}}_2}{\text{O}}\)

6. On heating with silver powder: Acetylene gas is produced by heating chloroform with silver powder.

\(2{\text{CHC}}{{\text{l}}_3} + 6{\text{Ag}} \to {{\text{C}}_2}{{\text{H}}_2} + 6{\text{AgCl}}\)

7. Reaction with Acetone: Chloroform reacts with acetone in the presence of alkali to form chloretone, used as a hypnotic in medicine.

8. Carbylamine Reaction: Primary amines (aromatic or aliphatic) on warming with Chloroform and alcoholic \({\text{KOH}}\) gives carbylamine having an offensive smell. This reaction is called the carbylamine reaction.
\({\text{C}}{{\text{H}}_3}{\text{N}}{{\text{H}}_2} + {\text{CHC}}{{\text{l}}_3} + 3{\text{KOH}} \to {\text{C}}{{\text{H}}_3}{\text{NC}} + 3{\text{KCl}} + 3{{\text{H}}_2}{\text{O}}\)
\({{\text{C}}_6}{{\text{H}}_5}{\text{N}}{{\text{H}}_2} + {\text{CHC}}{{\text{l}}_3} + 3{\text{KOH}} \to {{\text{C}}_6}{{\text{H}}_5}{\text{NC}} + 3{\text{KCl}} + 3{{\text{H}}_2}{\text{O}}\)

This reaction is used to test primary amines.

9. Reimer Tiemann reaction: When phenols, i.e. \({{\text{C}}_6}{{\text{H}}_5}{\text{OH}},\) is treated with \({\text{CHC}}{{\text{l}}_3}\)(Chloroform) in the presence of \({\text{NaOH}}\) (sodium hydroxide), an aldehyde group \(\left({ – {\text{CHO}}} \right)\) is introduced at the ortho position of the benzene ring leading to the formation of \({\text{o}}\)-hydroxybenzaldehyde. The reaction is popularly known as the Reimer Tiemann reaction.

Chloroform Tests

Below we have provided some of the chloroform tests below:

1. Chloroform forms an offensive smelling compound called carbylamine on heating with aniline (primary amine) and caustic potash.
2. With Fehling’s solution, Chloroform forms a reddish-brown precipitate of cuprous oxide \(\left({{\text{C}}{{\text{u}}_2}{\text{O}}} \right).\)

Uses of Chloroform

The uses of Chloroform are mentioned below:

1. Chloroform is used as an anaesthetic in surgery by adding \(30\% \) ether to Chloroform.
2. It is used as a solvent of oil, wax, fat, rubber etc.
3. In the laboratory as solvent and reagent.
4. In the manufacture of some useful organic compounds, such as chloretone, chloropicrin etc.
5. It is also used in the preservation of anatomical specimens.

Summary

Chloroform is an essential chemical compound for the synthesis of many organic compounds. Hence, it is necessary that we know its structure. The Chloroform formula is represented as ({\text{CHC}}{{\text{l}}_3}.) A chloroform molecule has the structure of a methane molecule. It has three hydrogen atoms which are substituted by three chlorine atoms. Chloroform is utilised as a solvent of oil, wax, fat, rubber etc. It has a sweet and distinct smell. Furthermore, it is important to note that the inhalation of Chloroform results in unconsciousness in humans.

FAQs on Chloroform Formula

Q.1. What are the uses of Chloroform?
Ans: Chloroform is used as solvent and reagent in the chemical synthesis of many important organic compounds. It is used as an anaesthetic and also as a preservative reagent in a biological specimen.

Q.2. Is it illegal to have Chloroform?
Ans: No, it is not illegal to have Chloroform. There is no permit necessary to purchase it, and the substance can be readily purchased at most chemical-supply stores.

Q.3. Can you drink Chloroform?
Ans: Chloroform, which is toxic to the central nervous system, can cause a person to become unconscious and even be fatal at high doses.

Q.4. How is \({\text{CHC}}{{\text{l}}_3}\) formed?
Ans: \({\text{CHC}}{{\text{l}}_3}\) is formed by the reaction of ethyl alcohol with chlorine in \({\text{NaOH}}\) solution.
\({\text{C}}{{\text{H}}_3}{\text{C}}{{\text{H}}_2}{\text{OH}} + 4{\text{C}}{{\text{l}}_2} + 6{\text{NaOH}} \to {\text{CHC}}{{\text{l}}_3} + {\text{HCOONa}} + 5{\text{NaCl}} + 5{{\text{H}}_2}{\text{O}}\)

Q.5. How much Chloroform is toxic to humans?
Ans: The toxic dose of Chloroform is \(7\) to \(25\,{\text{mg}}/{\text{dL}}.\) At inhaled concentrations of less than \(1500\,{\text{ppm}},\) physical effects of tiredness, dizziness, and headache are reported. However, the anaesthetic effect is observed at a range of \(1500\) to \(30000\,{\text{ppm}},\) within \(5\) to \(10\) minutes of exposure. Fatalities occur after \(5 – 10\) minutes at doses of \(25000\,{\text{ppm}},\) or greater by inhalation.

Q.6. How does Chloroform work on humans?
Ans: Exposure to Chloroform is harmful. Chloroform damages the liver, causing hepatitis, and it can also harm the kidneys, brain, heart and bone marrow. Respiratory injuries from chloroform exposure involve respiratory depression, pneumonitis and pulmonary oedema. Chloroform, which is toxic to the central nervous system, can cause a person to become unconscious and even be fatal at high doses.

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