Other preparation methods for chloroform

From acetone (from propanone):

When acetone is heated with bleaching powder, or with chlorine and alkali, the following reactions take place.

Reaction of chlorine with acetone producing trichloroacetone.

Trichloroacetone is decomposed by either calcium hydroxide or an alkali, to give chloroform.

The net reaction when bleaching powder is used is,

By partial reduction of carbon tetrachloride

Zinc and hydrochloric acid is taken and shaken at a slightly elevated temperature.

Manufacture of Chloroform:

Chloroform is generally manufactured by the following methods.

From methane: Chloroform can be manufactured by chlorinating methane. A mixture of CH₄ : Cl₂ : N₂ in the ratio 8 : 3 : 80 is passed over a partially reduced sample of cupric chloride. Chloroform is recovered by distillation.

From carbon tetrachloride: Chloroform can also be prepared on a large scale by partial reduction of carbon tetrachloride using iron filings and water.

Iodoform

Preparation of Iodoform:

Iodoform is obtained by the action of iodine on ethanol (ethyl alcohol), or on propanone (acetone) in the presence of an alkali. This reaction is called haloform reaction, and is commonly known as iodoform test.

From Ethanol:

When ethanol is warmed (60°C) with iodine in the presence of an alkali (NaOH, or Na₂CO₃), iodoform is obtained.

Step 1:

NaOH + I₂

NaI + H₂O

Step 2:

Oxidation of ethanol to ethanal (acetaldehyde).

Step 3:

Ethanol so formed undergoes iodination.

Step 4:

Hydrolysis (cleavage) of Cl₃CHO by alkali.

Cl₃CHO + NaOH

+ HCOONa

Net reaction:

C₂H₅OH + 4I₂ + 6NaOH

CHI₃ + HCOONa + 2NaI + 5H₂O

From acetone:

Iodoform can also be prepared by warming acetone with iodine in the presence of an alkali. The reactions are

Step 1:

2NaOH + I₂

NaOI + NaI + H₂O

Step 2:

Iodination of acetone.

₃

+ 3NaOH

Step 3:

Hydrolysis (cleavage) of Cl₃.CO.CH₃ by alkali.

Net reaction:

The reactions for the preparation of iodoform when Na₂CO₃ is used in place of NaOH are as follows:

when ethanol is used:
when propanone (acetone) is used:

Physical Properties of Iodoform:

Iodoform is a yellow crystalline solid (hexagonal plates) with characteristic unpleasant odor. It melts at 392 K, (119°C).
Iodoform is insoluble in water, but soluble in alcohol, chloroform and ether.
It has antiseptic properties which is due to the liberation of iodine from it.

Chemical Properties of Iodoform:

Iodoform shows chemical behavior similar to that of chloroform, but it is less stable. Some of the typical reactions given by iodoform are:

Stability
On heating, iodoform decomposes to give iodine vapor. Due to the liberation of free iodine iodoform shows antiseptic action. Moisture, air and light also cause the decomposition of iodoform.
Hydrolysis
On boiling with alcoholic sodium hydroxide, iodoform gives sodium formate.
Heating with silver powder
When heated with Ag powder, iodoform gives ethyne (acetylene).
With primary amines
Carbylamine reaction. Iodoform when heated with a primary amine and alcoholic potash, gives an offensive smelling compound known as carbylamine.
With silver nitrate
Iodoform gives yellow colored precipitate of AgI when heated with alcoholic silver nitrate.

Uses of Iodoform:

Iodoform is used as an antiseptic. Its antiseptic property is due to the liberated iodine. However, due to its unpleasant smell, it has been replaced by other formulations containing iodine. It is used in the manufacture of certain pharmaceuticals.

Carbon tetrachloride(CCl₄)

Preparation of Carbon tetrachloride:

Carbon tetrachloride can be prepared on the industrial scale by the following methods.

From methane:

By the chlorination of methane in the presence of sunlight.

From carbon disulphide:

Carbon tetrachloride can be obtained by the action of chlorine on carbon disulphide in the presence of aluminum chloride as a catalyst.

From propane:

Propane reacts with chlorine at 400°C and 70-100 atm pressure to give CCl₄,

Physical Properties of Carbon Tetrachloride:

Carbon tetrachloride is a colorless heavy liquid (b.p. 350 K, (77°C))
It is insoluble in water but soluble in organic solvents.
It is a good solvent for oils, fats and resins.
It is non-inflammable.
It is stable at red heat ( 500°C).

In past carbon tetrachloride was used as a fire extinguishing material, under the name pyrene. When a fine spray of liquid CCl₄ is directed at the fire, it vaporizes. The dense vapor of CCl₄ cut off the supply of air to the burning article. As a result, the fire gets extinguished.
However, at higher temperature in the presence of steam, carbon tetrachloride gets oxidized to phosgene. So, care should be taken while using carbon tetrachloride in fire fighting operations.

Chemical Properties of Carbon Tetrachloride:

Reduction
Carbon tetrachloride on reduction with moist iron filings gives chloroform.
Hydrolysis
On boiling with alcoholic sodium hydroxide, iodoform gives sodium formate.
Hydrolysis
In the presence of steam, CCl₄ gives phosgene.
Formation of Freon
It reacts with SbF₃ in presence of SbCl₅ to give freon.

Uses:

It is used as a fire extinguisher under the name Pyrene
It is used as a solvent for fats, oils, waxes, greases, resins etc and in dry cleaning
In medicines for the estimation of hook worms
It is used for manufacture of freon and chloroform