Arrange the following compounds in increasing order of `CNH_(2)` bond length: Methanamine, Aniline, p-ethoxy aniline

Options

A. 'Methanamine lt p-ethoxy aniline lt Aniline '
B. ' Aniline lt p-ethoxy aniline lt methanamine '
C. Aniline lt methanamine lt p-ethoxy aniline
D. Methanamine lt Aniline lt p-ethoxy aniline

Explanation

To determine the increasing order of CNH2 bond length for the compounds Methanamine, Aniline, and p-Ethoxy Aniline, we will analyze the bond characteristics and resonance effects in each compound.

### Step 1: Analyze Methanamine (CH3NH2)
Methanamine is a simple amine where the nitrogen is bonded to a carbon atom (C) and two hydrogen atoms (H). The bond between carbon and nitrogen in methanamine is a single bond (C-N), which typically has a longer bond length compared to bonds with partial double bond character.

**Hint:** Look for the bond type (single vs. double) to assess bond length.

### Step 2: Analyze Aniline (C6H5NH2)
Aniline contains an amino group (NH2) attached to a benzene ring. The lone pair of electrons on the nitrogen can participate in resonance with the aromatic ring. This resonance leads to a partial double bond character between the carbon of the benzene ring and the nitrogen. As a result, the C-N bond in aniline is shorter than that in methanamine due to this partial double bond character.

**Hint:** Consider resonance effects and how they influence bond length.

### Step 3: Analyze p-Ethoxy Aniline (C6H4(OCH2CH3)NH2)
p-Ethoxy Aniline is similar to aniline but has an ethoxy group (-OCH2CH3) at the para position of the benzene ring. The ethoxy group can also participate in resonance, further delocalizing the electrons. However, the resonance effect is slightly less than that in aniline because the ethoxy group is an electron-donating group but not as strong as the amino group itself. Thus, the C-N bond in p-ethoxy aniline will have some partial double bond character, but it will still be longer than that in aniline.

**Hint:** Compare the resonance stabilization of the amino group in both aniline and p-ethoxy aniline.

### Step 4: Compare and Arrange the Compounds
Now, we can summarize the bond lengths based on our analysis:
- Methanamine (C-N bond is a single bond) will have the longest bond length.
- p-Ethoxy Aniline (C-N bond has some partial double bond character) will have a shorter bond length than methanamine but longer than aniline.
- Aniline (C-N bond has significant partial double bond character due to resonance) will have the shortest bond length.

### Final Order
Thus, the increasing order of CNH2 bond length is:
**Methanamine > p-Ethoxy Aniline > Aniline**

### Final Answer
**Increasing order of CNH2 bond length: Methanamine > p-Ethoxy Aniline > Aniline**