Physical Properties of Alkenes


Alkenes are determined as clear or colourless, double-bonded substances. Ethane that is denoted as alkenes is the colourless gas having a sweet odour that can intoxicate or make a person faint. The first 3 elements that are present in groups of alkenes are gases, the next 14 elements are in a liquefied state and the rest of the compounds of alkenes are in a solidified state.

What are Alkenes?

Alkenes are determined as the vital hydrocarbons having the formula $\mathrm{C_nH_{2n}}$. Alkenes are made up of the C=C functional group. Alkenes compounds are determined as unsaturated that generally undergo various additional reactions. Alkenes can also be utilised in the synthesis of alcohols, plastics, lacquers, detergents, and fuels as primary materials.

Types of alkenes

Some major types of alkenes that are widely used in manufacturing industries are discussed.

Figure 1: Types of alkenes

Propene $\mathrm{(C_3H_6)}$

Propene can also be referred to as propylene used to produce apparel, plastic squeeze bottles, outdoor furniture as it has the properties of plastic resin. Propylene oxide can also be utilized in order to manufacture furniture, automotive parts, boats and recreational vehicles, appliances, solvents and resins.

Butene $\mathrm{(C_4H_8)}$

Butene is utilized for the formation of various chemicals present in gasoline and rubber processing factories. Butenes components are widely used as alkylate and polymer gasoline. The compost of Butene often helps in the production and conversion as fuel, including fuel gas or blendstock in the case of gasoline.

Pentene $\mathrm{(C_5H_{10})}$

The major compound present in the alkene group is the n-Pentene which is a clear liquid. Pentene has a very disturbing and unpleasant smell. The compound is widely used as pesticides, additive to gasoline, and in the production of several vital chemicals.

Physical properties of Alkenes

Some common physical properties of alkenes are mentioned below −

Melting Point

Melting point of alkenes compounds that are generally denoted as double-bonded compounds highly depends on molecular positions. Alkenes have similarities to the melting points of alkanes. In this case, the cis-isomer molecules have a lower melting point whereas trans-isomers molecules remain packed within a shape that is denoted as the U-bending shape.


Solubility of alkenes in water is poor because of their non-polar characteristic features. The non-polar solvent in which the alkenes show proper solubility includes benzene and ligroin.

Boiling Point

Bolimg points of alkenes are enhanced with the increase of atoms of carbon in the compounds. Boling pints are very similar to the compounds of alkenes and alkanes. Compounds of alkenes and alkanes consist of similar carbon skeletons or structure. The straight-chain alkenes compounds have a greater boiling point than branched-chain alkenes.


Like alkanes, alkenes are also determined as weakly polar compounds. Alkenes are more reactive than alkanes as they have double bonds. The π electrons usually forms a double bond that can be removed easily or can be added as they are joined weakly. The “dipole moments that are generally exhibited through alkenes are greater than alkanes. Alkenes polarity highly depends on the functions group that remains attached to the chemical structure and the compounds present in Alkenes groups.

Chemical properties of Alkenes

Alkenes have the three major kinds of primary reactions that are generally denoted as the addition reaction as stated below.

Addition of Halides

Alkenes react with halides through a specialized rule determined as the Markovnikov rule. According to this rule, it can be stated that the portion of reactant’s negative remains attached to a carbon atom and the least number of atoms of hydrogen. This reactant’s negative part is generally denoted as the molecule that can be added to a chain.

Addition of Halogens

In the reactions of halogens and alkene, the production of vicinal dihalides is seen. Iodine does not react with alkenes like other forms of halogens. On the other side, bromide reacts with any of the alkenes and remains attached to the site that is unsaturated in nature. The proof of the unsaturation state can be seen in the reaction −

$$\mathrm{C_2H_{4(g)} +Br_{2(aq)}\:\rightarrow\:C_2H_4Br_{2(aq)}}$$

Figure 2: Dihydroxylation of alkenes with Osmium Tetraoxide

Addition of Hydrogen

Alkenes react with the molecular chain of one diatomic molecule of hydrogen that can also be determined as a dihydrogen molecular chain in presence of nickel and platinum. The molecules of nickel and platinum become alkenes because of the specialized rearrangement of atoms.

Uses of Alkenes

Several uses of compounds of alkenes are stated below −

  • Alkenes compounds are utilized in the manufacturing processes of plastics and polythene materials including buckets, bowls, bags, and many more.

  • The compounds of alkenes are used in the production of anti-knock for automobile engines like cars’ engines.

  • In manufacturing industries, alkenes compounds like “plastic and polypropene” are often used in order to make ropes and packaging material.

  • Major compounds of alkenes like ethane-1,2-diol are utilized in anti-freezing for motor car radiators.


Alkenes can also be used in “ethanol and synthetic fibre terylene” production. The “acrylic fibres and propanol” are included in the group of alkenes that helps in the production of acetone. In the reactions of hydrogen halide and alkene, the hydrogen remains attached to other hydrogen atoms. The bond that is formed here is the double bond. On the others side, there is a halide ion that will be attached to a carbon atom that has a few atoms of hydrogen attached to it.


Q1. What are the properties of propylene?

Ans. Propylene is generally referred to s propene which is the clear gas having a melting point of −185.2°C (−301.4 °F; 88.0 K) and a boiling point of −47.6°C (−53.7 °F; 225.6 K). The density of propylene is 1.81 kg/m3, gas (1.013 bar, 15 °C).

Q2. What are the major types of alkenes widely used in manufacturing industries?

Ans. Ethane-1,2-diol, plastic and polypropene are generally used in the manufacturing industry. The components are widely used in the production of automotive parts, boats and recreational vehicles, and furniture.

Q3. What are the major types of alkenes used in manufacturing industries?

Ans. The compounds of alkenes that are highly used in various manufacturing purposes include Hexene $\mathrm{(C_6H_{12)}}$, Heptene $\mathrm{(C_7H_{14)}}$, and Pentene $\mathrm{(C_5H_{10)}}$. Synthetic fibre terylene are highly used in the manufacturing of bags, buckets, and bowls.

Updated on: 25-Apr-2023


Kickstart Your Career

Get certified by completing the course

Get Started