NEETChemistryGeneral Organic Chemistry
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): In aqueous solution, dimethylamine is a stronger base than trimethylamine. Reason (R): Steric hindrance and lesser hydration of the conjugate acid of trimethylamine decrease its basic strength compared to dimethylamine. In the light of the above statements, choose the most appropriate answer from t
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A).
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A).
- C(A) is correct but (R) is not correct.
- D(A) is not correct but (R) is correct.
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
Step-by-step solution
Assertion (A) is correct. In aqueous solution, the order of basic strength for methyl-substituted amines is secondary > primary > tertiary. Thus, dimethylamine is a stronger base than trimethylamine. Reason (R) is also correct and explains the assertion. While the + I effect of three methyl groups in trimethylamine increases electron density on nitrogen, the bulky methyl groups cause steric hindrance to protonation. Furthermore, the conjugate acid of trimethylamine has only one hydrogen atom available for hydrogen