# How can a weak base act as a strong nucleophile (and vice versa)?

1. Carboxylate ion ($\ce{RCOO-}$) is a weak base as the negative charge on oxygen is delocalised due to resonance. So, it has less tendency to donate lone pair of electrons to H+ ion. Similarly, it has less tendency to donate lone pair of electrons to a carbocations. But in my textbook, it is given that, it acts as a weak base but strong nucleophile. Why does it act as strong nucleophile?

2. LDA (lithiumdiisopropylamide) is a strong bulky base. Why it is considered as a weak nucleophile?

• Nucleophilicity and basicity aren't the same concept. – Zhe May 2 '18 at 13:52
• Nucleophilicity is tendency of a nucleophile to donate electron pair to carbocation,isn't it ? – sai saandeep May 2 '18 at 14:06
• Nucleophilicity is a kinetic concept. Basicity could be kinetic or thermodynamic. – Zhe May 2 '18 at 15:23
• Sorry sir. I didn't understand you. – sai saandeep May 2 '18 at 15:50
• Right. And I think that's your problem. You're confusing two separate concepts that have some overlap. One does not imply the other or vice versa. – Zhe May 2 '18 at 17:08