Alkanes: Nomenclature and Isomerism - A Definition & Examples for UK Students

📚 Quick Study Guide

• ⚛️ Alkanes are saturated hydrocarbons with the general formula $C_nH_{2n+2}$, where $n$ is the number of carbon atoms.
• 🧪 Nomenclature follows IUPAC rules: Identify the longest continuous carbon chain, name the parent alkane, and number the chain to give substituents the lowest possible numbers.
• 🌳 Substituents are alkyl groups (e.g., methyl, ethyl) attached to the main chain.
• ➗ Isomers are molecules with the same molecular formula but different structural arrangements.
• ✍️ Constitutional isomers (structural isomers) differ in the connectivity of atoms. For example, butane ($C_4H_{10}$) has two isomers: n-butane and isobutane.
• 🌡️ Physical properties like boiling point increase with increasing molecular weight and decrease with branching.
• 🔥 Alkanes undergo combustion, a chemical process with oxygen to produce carbon dioxide and water: $C_nH_{2n+2} + O_2 \rightarrow CO_2 + H_2O$.

Practice Quiz

1. What is the general formula for alkanes?

   1. $C_nH_{2n}$
   2. $C_nH_{2n-2}$
   3. $C_nH_{2n+2}$
   4. $C_nH_{n+2}$

2. Which of the following is NOT an alkane?

   1. Methane
   2. Ethane
   3. Ethene
   4. Propane

3. What is the IUPAC name for $CH_3CH_2CH(CH_3)CH_3$?

   1. 2-Methylbutane
   2. 3-Methylbutane
   3. Isopentane
   4. Neopentane

4. Which of the following alkanes has the highest boiling point?

   1. Methane
   2. Ethane
   3. Propane
   4. Butane

5. Which term describes molecules with the same molecular formula but different structural arrangements?

   1. Isotopes
   2. Allotropes
   3. Isomers
   4. Polymers

6. How many constitutional isomers does pentane ($C_5H_{12}$) have?

   1. 1
   2. 2
   3. 3
   4. 4

7. What are the products of complete combustion of an alkane?

   1. Carbon monoxide and water
   2. Carbon dioxide and hydrogen
   3. Carbon and water
   4. Carbon dioxide and water