Step 1: Understanding the Question:
The question requires identifying a secondary amine from a given list of compounds. Amines are classified based on the number of alkyl or aryl groups attached to the nitrogen atom.
- Primary (1° amine): One alkyl/aryl group attached to nitrogen (R-NH\(_2\)).
- Secondary (2° amine): Two alkyl/aryl groups attached to nitrogen (R\(_2\)NH).
- Tertiary (3° amine): Three alkyl/aryl groups attached to nitrogen (R\(_3\)N).
Step 2: Detailed Explanation:
Let's analyze the structure of each option:
(A) Phenylmethanamine: The structure is C\(_6\)H\(_5\)CH\(_2\)-NH\(_2\). The nitrogen atom is bonded to one carbon group (the benzyl group) and two hydrogen atoms. This is a primary amine.
(B) N-Methylethanamine: The name indicates an ethane chain with an amine group, and a methyl group on the nitrogen atom. The structure is CH\(_3\)CH\(_2\)-NH-CH\(_3\). The nitrogen atom is bonded to two carbon groups (an ethyl group and a methyl group) and one hydrogen atom. This is a secondary amine.
(C) N,N-Dimethylethanamine: The name indicates an ethanamine with two methyl groups on the nitrogen. The structure is CH\(_3\)CH\(_2\)-N(CH\(_3\))\(_2\). The nitrogen atom is bonded to three carbon groups (one ethyl and two methyl groups) and no hydrogen atoms. This is a tertiary amine.
(D) Prop-2-en-1-amine (Allylamine): The structure is CH\(_2\)=CH-CH\(_2\)-NH\(_2\). The nitrogen atom is bonded to one carbon group (the allyl group) and two hydrogen atoms. This is a primary amine.
Step 3: Final Answer:
Based on the analysis, N-Methylethanamine is the only secondary amine in the list.