Laboratory Preparation of Diethyl Ether

Laboratory Preparation of Diethyl Ether

Introduction to Diethyl Ether

Diethyl ether or Ethoxy ethane is a colorless sweet liquid. Its molecular formula is CH3-CH2-O-CH2-CH3. Its IUPAC name is Ethoxyethane. For the laboratory preparation of diethyl ether, ethanol (ethyl alcohol) is dehydrated by using conc. H2SO4 at about 140 °C.

Principle

Conversion of Alcohol into Diethyl Ether

In lab, Diethyl ether is formed by heating excess of ethyl alcohol (ethanol) with conc. sulphuric acid. This process is carried out at about 140 °C.

This chemical change occurs in following two steps:

  • Sulphuric acid acts as dehydrating agent and it combines with ethyl alcohol to form ethyl hydrogen sulphate at about 110 °C.
Conversion of Ethanol into Ethyl Hydrogen Sulphate
  • Ethyl hydrogen sulphate reacts with another molecule of ethyl alcohol at about 140 °C to form diethyl ether.
Conversion of Ethyl Hydrogen Sulphate into Diethyl Ether

Procedure

Laboratory Preparation of Diethyl Ether
Laboratory Preparation of Diethyl Ether

About 100 ml of ethanol is kept in a round bottom flask. 50 ml of concentrated sulphuric acid is gradually added to ethanol with constant stirring. The flask is then fitted with a dropping funnel and a thermometer as shown in above figure. The mixture is then heated to about 140 °C for several minutes. Then the ether starts to distill over and is collected in a receiver at ice cold condition. For larger amount of yielding of diethyl ether, ethanol is added gradually from the dropping funnel.

Note: If the receiver is not kept at ice cold condition, diethyl ether may not condense to liquid form since the boiling point of nearly equal to room temperature (34.6 °C).

Purification and Dehydration

Thus formed diethyl ether contains many impurities including ethanol, S02, and water. Acidic impurities are removed by washing with NaOH and washing with water. Then it is dehydrated over anhydrous CaCl2. Finally, it is redistilled at about 34-36 °C.

General Properties of Diethyl Ether

  • Molecular mass: 74.12 g/mol
  • Appearance: Colorless
  • State: Liquid due to intermolecular H-bonding
  • Odor: Sweet smell
  • Solubility: Slightly soluble in water due to non-polar nature and presence of H-bonding
  • Melting point: 156.8 K
  • Boiling point: 307.8 K
  • Nature: Basic

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