Question

A secondary amine is 

• A. a compound with an NH₂ group on the carbon atom in number 2 position
• B. an organic compound with two NH₂ group
• C. a compound in which two of the hydrogen of NH₃ have been replaced by organic groups
• D. a compound with two carbon atom with an NH₂ group

Answer 1

The Correct Option is C

A secondary amine is a compound in which two of the hydrogens of NH3 have been replaced by organic groups. In a secondary amine, two of the three hydrogen atoms of ammonia (NH3) are substituted by organic groups, resulting in a structure where two carbon atoms are directly bonded to the nitrogen atom, along with one remaining hydrogen. The general formula for a secondary amine is R2NH, where R represents an organic group or hydrogen. Secondary amines are characterized by the presence of an amino group (NH2) attached to a carbon atom, which is further attached to two other carbon atoms or organic groups.

Answer 2

Amines are derivatives of ammonia ($\text{NH}_3$) where one or more hydrogen atoms are replaced by organic groups (alkyl or aryl). 

Classification of amines:
 

• Primary (1°) amine: One hydrogen replaced → $R\text{-}NH_2$
• Secondary (2°) amine: Two hydrogens replaced → $R_2\text{NH}$
• Tertiary (3°) amine: All three hydrogens replaced → $R_3\text{N}$

Correct answer: 
(C): "a compound in which two of the hydrogen of $\text{NH}_3$ have been replaced by organic groups" 

Explanation:
This is the definition of a secondary amine. Two hydrogens in $\text{NH}_3$ are replaced by alkyl or aryl groups, forming $R_2\text{NH}$. 

Why other options are incorrect:

• (A): A compound with an $\text{NH}_2$ group on the carbon atom in number 2 position – this describes a primary amine, and it’s specific to structure, not general definition.
• (B): An organic compound with two $\text{NH}_2$ groups – this refers to a diamine, not necessarily a secondary amine.
• (D): A compound with two carbon atoms with an $\text{NH}_2$ group – again, this refers to a molecule with two primary amines.