B Tech Applied Science: Naming Alkanes Using IUPAC Rules (Unit 5 Chemistry)

Overview

• Focus on naming alkanes using IUPAC rules.
• Part of a series of three videos:
  • This video: Naming alkanes
  • Next two videos: Naming alkenes and haloalkanes

Objectives

• By the end of this video, be able to name four specific alkanes.
• Introduce task assignments and provide answers.

Basic Rules of Organic Molecules

• Carbon Bonds: Carbon forms four bonds (single or combinations of double and single bonds).
• Hydrogen Bonds: Hydrogen forms only one bond.

Naming Organic Molecules

• Three Sections to a Name:
  1. Prefix: Identifies side chains or functional groups.
  2. Stem: Longest chain of carbon atoms.
  3. Suffix: Identifies the functional group (e.g., -ane for alkanes).

Alkanes Naming

• Suffix:
  • Alkanes use the suffix '-ane'.
• Stem Lengths:
  • Meth (1), Eth (2), Prop (3), But (4), Pent (5), etc., up to Dec (10).
• Common Prefixes: Methyl, Ethyl, Propyl.

Steps to Name Alkanes

1. Identify Functional Group: Alkanes (suffix '-ane').
2. Identify Longest Carbon Chain: Don't assume it's straight; side chains can extend it.
3. Circle & Name Side Chains: Indicate their position.

Examples

• Example 1:
  • Functional group: Alkane
  • Longest chain: 4 carbons (Butane)
  • Side chain: Methyl (CH3)
  • Name: 2-methylbutane (two numbering possibilities, choose the lowest).
• Example 2:
  • Longest chain: 5 carbons (Pentane)
  • Side chain: Methyl
  • Name: 3-methylpentane.
• Example 3:
  • Longest chain: 6 carbons (Hexane)
  • Side chain: Methyl
  • Name: 3-methylhexane.
• Example 4:
  • Cyclic structure: Cyclobutane.

Practice Exercise

• Name provided structures and draw them.
• Solutions:
  • Structure 1 (Top Left): Two side chains, dimethylbutane, position 2 and 3.
  • Structure 2 (Mid): Methylbutane, methyl on position 2.
  • Structure 3 (Bottom): Methylhexane, methyl on position 3.

Drawing from Names

• Example 1: 2-methylpentane.
  • Steps: Draw 5 carbons, add methyl group, complete with hydrogens.
• Example 2: 2,2-dimethyl-3-ethylpentane.
  • Steps: Draw 5 carbons, add two methyl groups on second carbon, ethyl on third, complete with hydrogens.

Next Steps

• Check out next video on naming alkenes.
• Introduction to additional functional groups and suffixes.