Which of the following is most basic?

Concept:

​Basicity of a compound-

• It is the ability of a compound to donate its pair of electrons.

Basicity of a compound depends on-

• The less electronegative element has greater basicity due to the low attraction of electrons.
• The compound having a negative charge will have a greater ability to donate electrons and higher will be the basicity.
• Compounds with positive charges will not be willing to give up electrons and will be least basic.
• Molecules, where the electron pair is delocalized by resonance, will be less basic.
• Compounds, where more than one donor centres are present, will be highly basic.

​Explanation:

NH3 :

• The lone pair resides on a nitrogen atom which is highly electronegative.
• Furthermore, the bond pair of electrons are attracted towards the most electronegative elements nitrogen.
• The lone pair of electrons are localized on the head of nitrogen because it does not have a vacant d orbital for its delocalization.
• Thus, the lone pair of electrons are easily available for donation.
• Hence, ammonia acts as a strong base.

​ 

Aniline:

• Aniline is an aromatic compound and has the ability to act as a Lewis base because it has lone pair of electrons on a nitrogen atom.
• However, these lone pairs of electrons are not available fully for donation because of their involvement in resonance with the aromatic ring.

• This makes the electron pair less available and aniline a weaker base than ammonia.

Ethylamine:

• All aliphatic amines are stronger than ammonia in strength.
• Ethylamine has lone pair of electrons in its Nitrogen atom which is otherwise not involved in any kind of resonance.

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• Hence, it is available for donation to act as a base. Also, the presence of electron releasing group Ethyl attached directly to nitrogen atom increases its electron density and makes it a stronger base.​
• Phenol is acidic in nature.

Hence, the strongest base is ethylamine.

Important Points

• Aromatic amines are weaker bases than ammonia.
• Aliphatic bases are stronger bases than Ammonia.