How many straight-chain isomers can you write that fit the following descriptions? See Worked Example 12.12 for guidance.
b. Amines (―NH₂) with a longest chain of 7 carbons

Verified step by step guidance

1. Understand the problem: We are tasked with determining the number of straight-chain isomers of amines (compounds containing an ―NH₂ group) where the longest carbon chain has 7 carbons. Straight-chain means the carbon atoms are connected in a continuous, unbranched chain.
2. Step 1: Start by drawing the straight-chain structure of 7 carbons (heptane). This will serve as the backbone for all possible isomers.
3. Step 2: Place the ―NH₂ group (amino group) on each carbon atom of the 7-carbon chain, one at a time. Remember that the position of the ―NH₂ group on the chain determines a unique isomer.
4. Step 3: Consider symmetry in the molecule. For example, placing the ―NH₂ group on carbon 1 is equivalent to placing it on carbon 7 due to the symmetry of the straight chain. Eliminate duplicate structures caused by symmetry.
5. Step 4: Count the unique positions of the ―NH₂ group on the 7-carbon chain after accounting for symmetry. Each unique position corresponds to a distinct isomer.

Key Concepts

Straight-Chain Isomers

Straight-chain isomers are compounds that have the same molecular formula but differ in the arrangement of their carbon atoms in a linear fashion. In the context of amines, these isomers will have variations in the positioning of the amine group (―NH₂) along the carbon chain, leading to different structural forms while maintaining the same number of carbon atoms.

Amines

Amines are organic compounds derived from ammonia (NH₃) by replacing one or more hydrogen atoms with alkyl or aryl groups. In this case, the presence of the amine functional group (―NH₂) is crucial for identifying the isomers, as it influences the chemical properties and reactivity of the compounds formed from the carbon chain.

Longest Carbon Chain

The longest carbon chain in a molecule refers to the maximum continuous sequence of carbon atoms connected by single bonds. For the purpose of identifying isomers, determining the longest chain is essential, as it establishes the backbone of the molecule and dictates the possible variations in the structure of the amine isomers based on the placement of the amine group.