Alkanes: Definition, Structure, and Properties

Definition and Structure

• Alkanes are a type of saturated hydrocarbon, meaning they contain only single bonds between carbon atoms.
• General formula: CnH2n+2, where n is the number of carbon atoms.
• Also known as paraffins or saturated hydrocarbons.

Physical Properties

• Alkanes are colorless, odorless, and non-polar.
• They are insoluble in water, but soluble in non-polar solvents like hexane.
• Boiling points increase with molecular weight, as larger molecules have stronger intermolecular forces.
• Melting points also increase with molecular weight, but not as steadily as boiling points.

Chemical Properties

• Alkanes are relatively unreactive, but can undergo combustion reactions with oxygen.
• They can also undergo substitution reactions, where a hydrogen atom is replaced by a functional group.
• Cracking: breaking down larger alkanes into smaller ones, often used in petroleum refining.
• Isomerization: rearranging the molecular structure of an alkane to form a different isomer.

Nomenclature

• IUPAC rules are used to name alkanes.
• The longest continuous chain of carbon atoms is identified, and the suffix "-ane" is added.
• Branching chains are named as substituents, using the prefix "alk-" and the number of carbon atoms in the branch.
• Compounds with functional groups are named using the parent alkane chain and a prefix or suffix indicating the functional group.

Examples and Uses

• Methane (CH4): primary component of natural gas, used as a fuel.
• Ethane (C2H6): used as a fuel and in the production of plastics.
• Propane (C3H8): used as a fuel for grills and vehicles.
• Butane (C4H10): used as a fuel, in lighters, and in the production of plastics.
• Alkanes are also used as lubricants, in cosmetics, and as solvents.

Definition and Structure

• Alkanes are saturated hydrocarbons with single bonds between carbon atoms.
• General formula: CnH2n+2, where n is the number of carbon atoms.
• Also known as paraffins or saturated hydrocarbons.

Physical Properties

• Alkanes are colorless, odorless, and non-polar.
• Insoluble in water, but soluble in non-polar solvents like hexane.
• Boiling points increase with molecular weight due to stronger intermolecular forces.
• Melting points increase with molecular weight, but not as steadily as boiling points.

Chemical Properties

• Alkanes are relatively unreactive, but undergo combustion reactions with oxygen.
• Can undergo substitution reactions, replacing a hydrogen atom with a functional group.
• Cracking: breaking down larger alkanes into smaller ones, used in petroleum refining.
• Isomerization: rearranging the molecular structure to form a different isomer.

Nomenclature

• IUPAC rules are used to name alkanes.
• Identify the longest continuous carbon chain, and add the suffix "-ane".
• Branching chains are named as substituents using the prefix "alk-" and the number of carbon atoms.
• Functional groups are indicated by a prefix or suffix on the parent alkane chain.

Examples and Uses

• Methane (CH4): primary component of natural gas, used as a fuel.
• Ethane (C2H6): used as a fuel and in plastic production.
• Propane (C3H8): used as a fuel for grills and vehicles.
• Butane (C4H10): used as a fuel, in lighters, and in plastic production.
• Alkanes are also used as lubricants, in cosmetics, and as solvents.