A nucleophillic centre is a part of a  molecule that is nucleus-loving in nature. This basically means that it has a surplus of electrons and is negatively charged. It might be a full formal negative charge or just a partial negative charge, but they are all nucleophillic centres.  While trying to identify nucleophillic centers we must always take into account the difference in electronegativity between the bonded atoms. Now let us solve the questions- 1. In between 1,2  there is no nucleophillic centres since they are all bonded to the same atoms (carbon) having same electronegativity. But in 2 this acts as a nucleophillic center because of the electronegativity difference between carbon and Mg. Actually, carbon pulls the bond towards itself and gives rise to a carbanion. Hence, the answer is 3. 2. At 1, boron is sl ... See the full answer