This video lecture focuses on the basic strength of aliphatic and aromatic bases, crucial for JEE Advanced preparation. Vishal Sir explains the factors influencing basicity, including inductive effects and solvation, using various examples and data. He emphasizes the importance of memorizing certain data points because predicting basicity solely through theory can be difficult.
Basicity of Aliphatic Amines: The order of basicity in gaseous phase is generally predicted by inductive effects (3° > 2° > 1° > NH₃). However, in solution, solvation effects play a significant role, leading to a different order (1° > 2° > 3° > NH₃). The actual order depends on the balance of inductive and solvation effects, and it's important to memorize the experimental data rather than solely relying on theoretical predictions. Specific data for methyl and ethyl amines are provided in the lecture.
Guanidine as a Superbase: Guanidine is a strong base due to high electron density on its nitrogen atom, leading to resonance stabilization of the conjugate acid. Its pKb is around 0.4, indicating its high basicity.
Aromatic Amines and Substituent Effects: The basicity of anilines is affected by substituents. Nitro groups significantly decrease basicity due to their electron-withdrawing effect and steric hindrance. The order of basicity for nitro-substituted anilines (ortho, meta, para) is discussed and data is provided. Solvation effects are less important in this case due to the presence of the benzene ring.
Special Cases: The video discusses the unusual basicity difference between two isomeric nitro-substituted anilines, highlighting the effect of steric hindrance and hydrogen bonding on the rotation barrier and resulting basicity.
Recommended Reading: Vishal Sir recommends Peter Sykes' book for a deeper understanding of acid-base strength.
