Saturated Hydrocarbon, Difference between Saturated and Unsaturated Hydrocarbon (For CBSE, ICSE, IAS, NET, NRA 2022)

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What Are Saturated Hydrocarbons?

  • A Saturated hydrocarbon is a hydrocarbon in which all the carbon-carbon bonds are single bonds. A hydrocarbon is an organic compound whose only constituents are carbon and hydrogen.
  • Saturated hydrocarbons are hydrocarbons in which all the carbon atoms are bonded to four other atoms and are ‘saturated’ , meaning that no carbon-carbon multiple bonds exist in these organic compounds.
  • Saturated hydrocarbons are hydrocarbons that contain only single bonds between carbon atoms. They are the simplest class of hydrocarbons. They are called saturated because each carbon atom is bonded to as many hydrogen atoms as possible.
  • Carbon atoms are saturated with hydrogen. In this compound, named ethane, each carbon atom is bonded to three hydrogen atoms. In the structural formula, each dash (-) represents a single covalent bond, in which two atoms share one pair of valence electrons.
Saturated Hydrocarbons

Generally, the term ‘saturated hydrocarbon’ is used to refer to alkanes – acyclic hydrocarbons containing only hybridized carbon atoms. The general formula of an alkane is . An illustration describing the structure of a propane molecule () is provided below.

Saturated Hydrocarbons
  • It can be observed that a propane molecule is ‘saturated’ with hydrogen atoms and cannot accommodate any more in the parent chain. A few other examples of saturated hydrocarbons are listed below.
    • Butane
    • Octane
    • Cyclohexane
    • Cyclopropane
  • Cycloalkanes are the alkanes that have a monocyclic ring structure. Since all the carbon-carbon bonds in cycloalkanes are single bonds, they are considered to be saturated hydrocarbons. Therefore, the general formula of a saturated hydrocarbon can be written as , where ‘r’ is the total number of rings in the molecule.

Difference between Saturated and Unsaturated Hydrocarbon

Unsaturated hydrocarbons feature at least one double or triple bond between two adjacent carbon atoms. The key differences between saturated and unsaturated hydrocarbons are tabulated below.

Difference between Saturated and Unsaturated Hydrocarbon
Saturated HydrocarbonUnsaturated Hydrocarbon
All carbon atoms are hybridized in these compounds.They contain or sp hybridized carbons.
Contain more hydrogen atoms than the corresponding unsaturated hydrocarbons.Contain fewer hydrogens than the corresponding saturated hydrocarbon.
Examples include alkanes and cycloalkanes.Examples include alkenes, alkynes, and aromatic hydrocarbons.
They have a relatively low chemical reactivityThey are more reactive than their saturated counterparts.
They generally burn with a blue flameThey generally burn with a sooty flame.

Types of Saturated Hydrocarbons

  • A saturated hydrocarbon can have a linear, branched, or a ring-shaped structure and can, therefore, be classified into one of the following types:
    • Alkanes
    • Cycloalkanes
  • It is important to note that even polycyclic alkanes (alkanes with several rings in their structures) are also categorized as cycloalkanes and are, therefore, a type of saturated hydrocarbons.

Alkanes

  • Alkanes can feature a linear or a branched carbon chain in their structures. All the carbon atoms in these saturated hydrocarbons are hybridized. The melting point and the boiling point of an alkane is related to the length of its carbon chain. The longer the chain, the higher the melting or boiling point. This is because molecules having long carbon chains have high molecular weights.
  • At standard temperatures, alkanes containing up to four carbon atoms are gases and those containing 5 to 17 carbon atoms are liquid. Alkanes that have more than 18 carbon atoms are solids at room temperature.
  • All alkanes containing more than 3 carbon atoms can exhibit chain isomerism. An illustration describing the possible chain isomers of butane is provided below.
  • The number of possible chain isomers for an alkane depends on the total number of carbon atoms in it. For example, butane has only 2 chain isomers but octane has a total of 18 possible chain isomers.
Alkanes Can Feature a Linear

Cycloalkanes

  • Cycloalkanes feature a ring-shaped arrangement of hybridized carbon atoms. However, the ring in these saturated hydrocarbons can branch into side chains.
  • The physical properties of cycloalkanes are somewhat similar to those of alkanes.
  • The melting and boiling points of cycloalkanes are generally higher than the alkanes containing the same number of carbon atoms.
  • Owing to their structures, cycloalkanes are subject to ring strain. Since cyclopropane has a carbon-carbon bond angle of it has the highest ring strain among all cycloalkanes.

What Are the Uses of Saturated Hydrocarbons?

Alkanes are widely used as fuels, heating oils, and as solvents. A few other uses of saturated hydrocarbons are listed below.

  • Methane, the simplest alkane, is used as a fuel in several automobiles, water heaters, and ovens. In its highly refined form, liquid methane can also serve as rocket fuel.
  • Several cryogenic refrigeration systems use ethane as a refrigerant. It is also used in the production of ethylene.
  • The propellant used in several aerosol sprays is a saturated hydrocarbon known as propane. This compound is also used as a fuel for hot air balloons.
  • Octane is a very important component of gasoline since it helps prevent engine damage.
  • Cycloalkanes also find use in motor fuels, diesel, petroleum gas, and other heavy oils.
  • The manufacture of rubber and nylon also involve the use of cycloalkanes.

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