Question

Amongst the following the most basic compound is (a) benzylamine (b) aniline (c) acetanilide (d) p-nitroaniline

Short answer

The most basic compound is benzylamine.

Step-by-step solution

Define a Basic Compound

A basic compound is one that has the ability to donate a pair of electrons or accept a proton. In organic chemistry, compounds containing nitrogen with a lone pair of electrons are usually basic.

Analyze Each Compound

(a) Benzylamine is a primary amine (\(-NH_2\)) attached to a benzyl group, providing a lone pair of electrons on nitrogen, making it basic. (b) Aniline is a primary amine (\(-NH_2\)) directly attached to a benzene ring, where the lone pair on nitrogen is delocalized into the benzene ring, reducing its basicity.(c) Acetanilide has an amide group (\(NHC=O\)), where the lone pair on nitrogen is involved in resonance and not available for bonding, reducing its basicity.(d) p-Nitroaniline has an amino group (\(-NH_2\)) with an electron-withdrawing nitro group (\(-NO_2\)) at the para position, decreasing its basicity further.

Compare Basicity of Benzylamine and Aniline

Between benzylamine and aniline, benzylamine is more basic because the lone pair of electrons on the nitrogen in benzylamine is not involved in resonance with a benzene ring, as in aniline, making benzylamine's lone pair more available for donation.

Conclusion on the Most Basic Compound

From the analysis, out of the provided options, benzylamine has the highest availability of its lone pair for donation, making it the most basic compound.

Key concepts

Basic Compounds

Understanding what makes a compound basic is fundamental in organic chemistry. A basic compound is able either to donate a pair of electrons or to accept a proton. This ability is often linked to the presence of nitrogen atoms with lone pairs.
These lone pairs can participate directly in proton acceptance, creating the defining characteristic of basic compounds. For instance, primary amines, such as benzylamine, feature a nitrogen with a freely available lone pair, allowing effective electron pair donation.

Resonance Effect

Resonance plays a crucial role in determining the properties of certain compounds, including their basicity. Resonance occurs when electrons can be delocalized across adjacent atoms, usually involving pi bonds. This delocalization can reduce the availability of electrons to participate in further reactions.
For example, in aniline, the nitrogen's lone pair enters into resonance with the benzene ring, decreasing the lone pair's ability to engage in basic reactions. This results in aniline being less basic compared to compounds where resonance does not involve the lone pair, such as benzylamine.

Electron Donating and Withdrawing Groups

Electron donating groups (EDGs) and withdrawing groups (EWGs) significantly influence the reactivity and stability of organic compounds. EDGs increase electron density in a molecule, enhancing basicity, while EWGs do the opposite.

• EDGs include groups like alkyl chains, which stabilize positive charges and increase electron availability.
• EWGs, such as nitro groups, pull electron density away, reducing basicity.

In the case of p-nitroaniline, the nitro group at the para position acts as an EWG, reducing the basic nature of the nitrogen's lone pair in the amino group.

Nitrogen Compounds

Nitrogen compounds are central to understanding organic chemistry due to their versatile electronic properties. Nitrogen typically forms three covalent bonds and holds a lone pair of electrons, making it a potent base and nucleophile. This lone pair's availability dictates the compound's basic strength.
Common nitrogen-containing groups include amines and amides. Amines like benzylamine possess a nitrogen atom with a free lone pair, facilitating proton acceptance. Meanwhile, in amides like acetanilide, the lone pair partakes in resonance within the carbonyl group, limiting its basicity.
This variance underscores the importance of molecular structure on nitrogen's electron donation ability, and how substituents or connectivity can alter overall compound basicity.