Nomenclature of Alkane Compounds
Introduction to Alkanes
- Alkanes: hydrocarbons with carbon-carbon single bonds.
- No carbon-carbon double or triple bonds in alkanes.
IUPAC Naming System
- Every chemical compound name has three parts:
- Prefix: Indicates position, number, type of branches, and functional groups.
- Parent: Length of the longest carbon chain or ring.
- Suffix: Type of hydrocarbons (e.g., alkane, alkyne) or functional groups (e.g., alcohol, ketone).
Prefixes for Number of Carbon Atoms
- 1 Carbon: Meth-
- 2 Carbons: Eth-
- 3 Carbons: Prop-
- 4 Carbons: But-
- 5 Carbons: Pent-
- 6 Carbons: Hex-
- 7 Carbons: Hept-
- 8 Carbons: Oct-
- 9 Carbons: Non-
- 10 Carbons: Dec-
- Memorize these prefixes for naming organic compounds.
Rules for Naming Alkanes
- Find the longest continuous carbon chain to determine the base name. Add suffix "-ane" for alkanes.
- Number the chain from the end closest to any branch or substituent.
- Name branches as alkyl groups and locate each by the carbon number.
- List branches alphabetically, ignoring "normal", "secondary", or "tertiary" prefixes; count "iso".
- Use prefixes like di-, tri-, tetra- for multiple identical substituents.
Example: Naming a Compound
- Find the longest chain: 7 carbons → Heptane.
- Identify branches: Methyl on carbon 4.
- Name: 4-Methylheptane.
Substituent Naming
- When a substituent is present, follow the numbering that gives it the lowest possible number.
- Use alkyl names: Methyl (CH₃), Ethyl (C₂H₅), Propyl (C₃H₇), etc.
Multiple Substituents
- Indicate each substituent's location and use prefixes if identical.
- Example: 2,3-Dimethylhexane for hexane with methyls on carbons 2 and 3.
Different Type of Substituents
- Non-alkyl groups (e.g., halogens) are named: Fluoro, Chloro, Bromo, Iodo.
- Other groups: Nitro (NO₂), Amino (NH₂).
Practice Problems
- Mix of compound naming from structures and vice versa.
- Example problems and solutions provided:
- Structure: 2,2,4-Trimethylhexane.
- Name from Structure: Heptane with specified substituents.
Additional Tips
- Always draw base carbon chain and add substituents.
- Ensure hydrogen atoms are added to satisfy carbon's four-bond rule.
- Memorize functional group names and substitution rules for efficient naming.
This summary captures the core concepts of alkane nomenclature, including the steps for naming, identifying substituents, and handling multiple or complex groups.