Physical Properties of Alkenes

Alkenes contain a carbon-carbon double bond which changes the physical properties of alkenes. Alkenes are unsaturated carbon compounds which have a general formula of C_nH_2n. These compounds are also known as olefins.

Alkenes are a family of compounds containing hydrogen and carbon only (hydrocarbons) with a carbon-carbon double bond. Ethene and Propene are the first two hydrocarbons.

Table of Contents

• • Physical State
  • Solubility
  • Boiling Point
  • Melting Point
  • Polarity
  • Recommended Videos
  • Frequently Asked Questions–FAQs

1. Physical State

• • • • These double-bonded compounds are colourless and odourless in nature.
      • However, ethene is an exception because it is a colourless gas with a faintly sweet odour.
      • The first three members of the alkene group are gaseous in nature, the next fourteen members are liquids and the remaining alkenes are solids.

2. Solubility

• • • • The alkenes are insoluble in water due to their nonpolar characteristics.
      • But are completely soluble in nonpolar solvents such as benzene, ligroin, etc.

3. Boiling Point

• • • • The boiling points of the compounds increase as the number of carbon atoms in the compound increases.
      • When alkenes are compared with alkanes, it is found that the boiling points of both are almost similar, as if the compounds are made up of the same carbon skeleton.
      • The boiling point of straight-chain alkenes is more than branched-chain alkenes just as in alkanes.

4. Melting Point

• • • • The melting points of these double-bonded compounds depend upon the positioning of the molecules.
      • The melting point of alkenes is similar to that of alkanes.
      • However, cis-isomer molecules have a lower melting point than trans- isomers as the molecules are packed in a U-bending shape.

5. Polarity

• • • • Alkenes are weakly polar just like alkanes but are slightly more reactive than alkanes due to the presence of double bonds.
      • The π electrons which make up the double bonds can easily be removed or added as they are weakly held.
      • Hence, the dipole moments exhibited by alkenes are more than alkanes.
      • The polarity depends upon the functional group attached to the compounds and the chemical structures.

Recommended Videos

Check ⇒ Physical Properties of Alkanes

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