• Structural isomerism can occur in several ways:
  • Chain isomerism.
  • Position isomerism.

\(C_4H_{10}\)

Butane

2-methylpropane

\(C_4H_{8}\)

But-1-ene

But-2-ene

• The isomers show:
  • The same chemical properties because each isomer has the same functional group.
  • The physical properties, such as melting point and boiling point, are different. The more branches there are, the lower the melting point and boiling point are.

• Generally, the number of isomers of a molecule increases with the increase of the number of carbon atoms in the molecule.
• The isomers of alkanes are formed by chain isomers only.
• Isomers of alkenes, alkynes and alcohol are formed from chain isomers and position isomers.

1. Start by connecting the carbon atoms in a straight chain followed by a branched chain.

1. Start with a straight chain formula and change the position of the double bond or triple bond to a different carbon position.
2. Next, draw a structural formula with a branched chain from each straight chain that has different positions of double or triple bonds.

• IUPAC: International Union of Pure and Applied Chemistry.
• There are three parts in the naming of isomers:
  1. Prefix indicated by the branch group, which is alkyl group, attached to the longest carbon chain.
  2. The root name showing the number of carbon atoms in the longest carbon chain.
  3. The suffix showing the homologous series.

1. Identify the longest carbon chain containing the functional group
2. Number the carbon atoms in the longest chain  from one end so that:

• The branch gets the lowest number for alkane.

• Longest carbon chain: 3 carbons
• Root name: Prop

• Branch: methyl
• Functional group: Only single bond in the longest carbon chain (alkane)

• Branch: attached to Carbon 2

• Prefix

• 2-methyl

• Suffix

• ane

• Name of isomer

• 2-methylpropane

1. Identify the longest carbon chain containing the functional group.
2. Number the carbon atoms in the longest chain  from one end so that:

• the functional group gets the lowest  number for alkene.

• Longest carbon chain: 3 carbons
• Root name: Prop

• Branch: methyl
• Functional group: Double bond in the longest carbon chain (alkene)

• Branch: attached to Carbon 2
• Functional group: In between Carbon 1 and Carbon 2

• Prefix

• 2-methyl

• Suffix

• -1-ene

• Name of isomer

• 2-methylprop-1-ene

1. Identify the longest carbon chain containing the functional group.
2. Number the carbon atoms in the longest chain  from one end so that:

• The functional group gets the lowest  number.

• Longest carbon chain: 3 carbons
• Root name: Prop

• Branch: methyl
• Functional group: Hydroxyl group (alcohol)

• Branch: attached to Carbon 2
• Functional group: attached to Carbon 2

• Preffix

• 2-methyl

• Suffix

• propan-2-ol

• Name of isomer

• 2-metilpropan-2-ol

• Alkanes have high heat of combustion.
• Thus, the main usages of alkanes are for fuel and raw materials in the petrochemical industry.
• Alkenes are also used as raw materials in the petrochemical industry.
• The uses of alkane and alkene is as stated below:

• Ethanol, \(C_2H_5OH\) is widely used in alcoholic beverages.
• Long term consumption of alcoholic beverages has adverse effects on the function of the central nervous system.

• The most important carboxylic acid is ethanoic acid, \(CH_3COOH\) that is widely used as:
  • food preservatives in chilli sauce, ketchup and other food flavourings.
  • raw materials with other chemicals to produce dyes, paints, pesticides and plastics.
• Methanoic acid, \(HCOOH\) is used in the rubber industry for coagulation of latex.
• Fatty acids are long-chain carboxylic acids used to make soap.
• Carboxylic acid is also used to manufacture polymers, namely polyester such as terylene and polyamide such as nylon.

• Esters with small molecules easily evaporate and are fragrant, making them suitable for use in the manufacturing of cosmetics and perfumes.
• Esters are also used as food flavourings.
• Ethyl ethanoate, \(CH_3COOC_2H_5\)​ is an ester, used as a solvent for organic compounds in lotions, nail varnishes, lacquers and glue.
• Oils and fats are esters, formed between fatty acids and glycerol that are used in the production of soap.
• Polyester is a polymer for the production of synthetic fabrics.

• Structural isomerism can occur in several ways:
  • Chain isomerism.
  • Position isomerism.

\(C_4H_{10}\)

Butane

2-methylpropane

\(C_4H_{8}\)

But-1-ene

But-2-ene

• The isomers show:
  • The same chemical properties because each isomer has the same functional group.
  • The physical properties, such as melting point and boiling point, are different. The more branches there are, the lower the melting point and boiling point are.

• Generally, the number of isomers of a molecule increases with the increase of the number of carbon atoms in the molecule.
• The isomers of alkanes are formed by chain isomers only.
• Isomers of alkenes, alkynes and alcohol are formed from chain isomers and position isomers.

1. Start by connecting the carbon atoms in a straight chain followed by a branched chain.

1. Start with a straight chain formula and change the position of the double bond or triple bond to a different carbon position.
2. Next, draw a structural formula with a branched chain from each straight chain that has different positions of double or triple bonds.

• IUPAC: International Union of Pure and Applied Chemistry.
• There are three parts in the naming of isomers:
  1. Prefix indicated by the branch group, which is alkyl group, attached to the longest carbon chain.
  2. The root name showing the number of carbon atoms in the longest carbon chain.
  3. The suffix showing the homologous series.

1. Identify the longest carbon chain containing the functional group
2. Number the carbon atoms in the longest chain  from one end so that:

• The branch gets the lowest number for alkane.

• Longest carbon chain: 3 carbons
• Root name: Prop

• Branch: methyl
• Functional group: Only single bond in the longest carbon chain (alkane)

• Branch: attached to Carbon 2

• Prefix

• 2-methyl

• Suffix

• ane

• Name of isomer

• 2-methylpropane

1. Identify the longest carbon chain containing the functional group.
2. Number the carbon atoms in the longest chain  from one end so that:

• the functional group gets the lowest  number for alkene.

• Longest carbon chain: 3 carbons
• Root name: Prop

• Branch: methyl
• Functional group: Double bond in the longest carbon chain (alkene)

• Branch: attached to Carbon 2
• Functional group: In between Carbon 1 and Carbon 2

• Prefix

• 2-methyl

• Suffix

• -1-ene

• Name of isomer

• 2-methylprop-1-ene

1. Identify the longest carbon chain containing the functional group.
2. Number the carbon atoms in the longest chain  from one end so that:

• The functional group gets the lowest  number.

• Longest carbon chain: 3 carbons
• Root name: Prop

• Branch: methyl
• Functional group: Hydroxyl group (alcohol)

• Branch: attached to Carbon 2
• Functional group: attached to Carbon 2

• Preffix

• 2-methyl

• Suffix

• propan-2-ol

• Name of isomer

• 2-metilpropan-2-ol

• Alkanes have high heat of combustion.
• Thus, the main usages of alkanes are for fuel and raw materials in the petrochemical industry.
• Alkenes are also used as raw materials in the petrochemical industry.
• The uses of alkane and alkene is as stated below:

• Ethanol, \(C_2H_5OH\) is widely used in alcoholic beverages.
• Long term consumption of alcoholic beverages has adverse effects on the function of the central nervous system.

• The most important carboxylic acid is ethanoic acid, \(CH_3COOH\) that is widely used as:
  • food preservatives in chilli sauce, ketchup and other food flavourings.
  • raw materials with other chemicals to produce dyes, paints, pesticides and plastics.
• Methanoic acid, \(HCOOH\) is used in the rubber industry for coagulation of latex.
• Fatty acids are long-chain carboxylic acids used to make soap.
• Carboxylic acid is also used to manufacture polymers, namely polyester such as terylene and polyamide such as nylon.

• Esters with small molecules easily evaporate and are fragrant, making them suitable for use in the manufacturing of cosmetics and perfumes.
• Esters are also used as food flavourings.
• Ethyl ethanoate, \(CH_3COOC_2H_5\)​ is an ester, used as a solvent for organic compounds in lotions, nail varnishes, lacquers and glue.
• Oils and fats are esters, formed between fatty acids and glycerol that are used in the production of soap.
• Polyester is a polymer for the production of synthetic fabrics.