Read the passage carefully and answer the questions.

Amines are considered to be derivatives of ammonia obtained by replacement of hydrogen atoms with alkyl or aryl groups. They are usually prepared from nitro compounds, halides, amides, imides etc. The presence of hydrogen bonding influences its physical properties. In alkylamines, a combination of electron releasing steric and hydrogen bonding factors influences the stability of substituted ammonium cations in protic polar solvents and thus affects the basic nature of amines. Alkyl amines are found to be stronger bases than ammonia which is more basic than water. Primary and secondary amines are engaged in intermolecular association due to hydrogen bonding. This intermolecular association is more in primary amines than in secondary amines. Tertiary amines do not have intermoleulcar association due to the absence of hydrogen atom available for hydrogen bonding. Thus, the boiling point of amines depends on hydrogen bonding. In aromatic amines, electron releasing and withdrawing groups increase and decrease their basic character. Aryl diazonium salts usually obtained from arylamine undergo replacement of the diazonium group with a variety of nucleophile. Their coupling reaction of aryl diazonium salts with phenol or arylamine results in formation of dyes.

The most basic species in the following is

${NH_2}^-$

The correct answer is Option (1) → ${NH_2}^-$

Basic strength increases with:

• Presence of negative charge
• Lower electronegativity of the atom holding the charge

Thus:

$\text{NH}_2^- > \text{OH}^- > \text{NH}_3 > \text{H}_2\text{O}$

Explanation (Option-wise)

Option 1: $\text{NH}_2^-$ (Amide ion)

This ion carries a full negative charge on nitrogen, which is less electronegative than oxygen. Because nitrogen holds the negative charge less tightly, it is more willing to donate an electron pair, making $\text{NH}_2^-$ a very strong base. It readily abstracts a proton to form $\text{NH}_3$.

Option 2: $\text{H}_2\text{O}$ (Water)

Water is a neutral molecule and a very weak base. Although oxygen has lone pairs, its high electronegativity holds them tightly, so its tendency to accept protons is low compared to charged species like $\text{OH}^-$ or $\text{NH}_2^-$.

Option 3: $\text{OH}^-$ (Hydroxide ion)

Hydroxide is a strong base, but oxygen is more electronegative than nitrogen. This stabilizes the negative charge, making $\text{OH}^-$ less basic than $\text{NH}_2^-$. Thus, it is strong, but not the strongest here.

Option 4: $\text{NH}_3$ (Ammonia)

Ammonia is a neutral molecule with a lone pair on nitrogen, so it acts as a base. However, without a negative charge, its proton-accepting ability is much weaker than $\text{NH}_2^-$ or $\text{OH}^-$.