chemistry

Any species that has an unshared pair of electrons (any Lewis base) can act as a nucleophile whether it is neutral or has a negative charge. A nucleophile (Nu: - ) is a species that attacks an electrophile (E + ) (electron pair acceptor) by making a pair of electrons available to it; it is an electron pair donor: Nu: -    +     E +         →       Nu-E    +     by-products S N 2 reactions and nucleophiles The rates of S N 2 reactions are dependent of the identity of the nucleophile since it does appear in the rate determining step: R =  [Nu: - ] * [E + ] This may be illustrated by the effect of changing the nucleophile from H 2 O to OH - for CH 3 Br which reacts by an S N 2 mechanism (Fig. 1). The rate of reaction is multiplied by 5000: Fig. 1: Effect of changing the nucleophile from H 2 O to OH - in the S N 2 reaction of CH 3 Br. The reaction rate is multiplied by approximately 5000 (R 2   ≈ 5000 * R 1 ). The OH -   is a more powerful nucleophile than H 2 O. Which nuc