Question

Basic strength of different alkyl amines depends upon:
A. + I effect
B. steric effect
C. solvation effect
D. all of these

Answer 1

Hint: Basicity of the amines is majorly affected by the stability of the conjugate acid present in the solvent. Hence basic strength of different amines with different structures do not depend upon a single or similar pattern.

Complete step-by-step answer:
The alkyl amines are stronger bases than ammonia and they can be expressed in terms of electron releasing inductive effect of alkyl groups. The basic strength of alkyl amines in aqueous solution depends upon electron releasing as well as it depends on the hydration effect and steric effect.
Basicity of amines can be expressed as the difference in the basicity order in the gas phase and aqueous solution and are the result of solvation effects. These solvation effects play a role in increasing the electron density on the amine nitrogen to a higher degree than the inductive effect of the alkyl group.
Steric effect can be defined as the crowding of alkyl groups around N atoms which hinder the attack of proton on the amine molecule and this decreases its basic strength. Also, crowding of alkyl groups around the N atom increases from ${1^0}$ to ${3^0}$ amines. Hence, the basic strength of amine ultimately decreases in the order ${1^0}\, > \,{2^0}\, > \,{3^0}$.
+ I Effect (Positive Inductive Effect): When a chemical species, with the tendency to release or donate electrons, such as alkyl group, is introduced to a carbon chain, the charge is transferred through the chain and this effect is referred to as the Positive Inductive Effect.
Steric effect: These are nonbonding interactions that guide the shape (conformation) and reactivity of ions and molecules. Steric effect complements the electronic effect, which usually edict the shape and reactivity.
Steric effect results from repulsive forces between overlapping electron clouds.
Solvation effect: Solvation is an interaction of a solute with the solvent, which leads to stabilization of the solute species in the solution.
Basic strength of different alkyl amines depends upon + I effect, steric effect, solvation effect.
Hence, the answer is option (D).

Note – The basicity of amines having different classes do not form a simple pattern as the number of bonded groups to the N atom affects the electron density at it.