Fundamentals of Organic ChemistryChemistryAmines
Identify the correct order of increasing basicity for the following compounds: (I) CH ₃ CH ₂ NH ₂ (II) (III)
Options
- A(I) (III) < (II)
- B(I) < (II) < (III)
- C(II) < (III) < (I)
- D(III) < (I) < (II)
Correct answer
D. (III) < (I) < (II)
Step-by-step solution
Compound (I) is ethylamine ( CH ₃ CH ₂ NH ₂ ), an aliphatic amine. The lone pair on the nitrogen atom is localized, and the +I effect of the ethyl group increases the electron density on nitrogen, making it a moderately strong base. Compound (II) is acetamidine ( CH ₃ C (= NH ) NH ₂ ). Protonation occurs at the imine nitrogen ( = NH ). The resulting conjugate acid is highly stabilized by resonance between two equivalent structures, distributing the positive charge equally over two nitrogen atoms. This makes acetami