Consider the four amines (T, U, V and W). Structures and the p times K_a values
ID: 1057997 • Letter: C
Question
Consider the four amines (T, U, V and W). Structures and the p times K_a values for the corresponding conjugate acid of each are given below. Explain the relative basicity of T vs V. What is the hybridization of nitrogen in T? Circle the best answer. sp sp^2 sp^3 cannot tell What is the hybridization of nitrogen in v? Circle the best answer. sp sp^2 sp^3 cannot tell Which is more basic? Circle the best answer: T V cannot tell Is the dominant factor hybridization or some other effect (resonance, inductive, hybridization or polarization)? Explain how the major factor leads to the difference in basicity between T and V.Explanation / Answer
Acidity and basicity
2) For the given amines, T, U, V and W
2a) relative basicity of T vs V
V is more basic than T as the nitrogen lone pair is not delocalised in the ring as in case of T making the lone pair less avalilable for donation as required by the base to the proton. pKa2 of V is greater than T, that means the pKb of V is lower than pKb of T, a lower pKb means higher Kb value, so V is stronger base than T.
1) Hybridization of nitrogen in T : sp3
2) hybridization of nitrogen in V : sp3
3) more basic : V
4) dominant factor is resonance. Nitrogen lone pair is delocalised in Pg ring in case of T and is not available for donation as a base, so it is weaker base than V,