COMEDK · Chemistry · 29. Amines

The correct increasing order of basic strength of following amines,
\(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}, \mathrm{NH}_{3},\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}_{6} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\) in gaseous state is

A \(\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH} < \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2} < \mathrm{NH}_{3} < \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\)
B \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2} < \left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH} < \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2} < \mathrm{NH}_{3}\)
C \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2} < \mathrm{NH}_{3} < \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2} < \left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}\)
D \(\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH} < \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2} < \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2} < \mathrm{NH}_{3}\)

Verified Solution

Answer & Solution

Correct Answer

(C) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2} < \mathrm{NH}_{3} < \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2} < \left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}\)

Step-by-step Solution

Detailed explanation

Aniline is less basic than ammonia and aliphatic amines due to delocalisation of lone pair of electrons on the benzene ring. Aliphatic amines are stronger bases, than ammonia due to \(+I\)-effect of alkyl group. More the number of alkyl groups stronger is the base. Hence, basic…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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The correct increasing order of basic strength of following amines,\(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}, \mathrm{NH}_{3},\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}_{6} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\) in gaseous state is

Step-by-step Solution

The correct increasing order of basic strength of following amines,
\(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}, \mathrm{NH}_{3},\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{NH}_{6} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NH}_{2}\) in gaseous state is