Question 27.2: Identifying Electrophiles, Nucleophiles, Leaving Groups, Aci...
Identifying Electrophiles, Nucleophiles, Leaving Groups, Acids, and Bases
It is important to be able to distinguish when an electron pair donor in a reaction is acting as a base or as a nucleophile. The following reactions are elementary reactions. In each case, determine whether the electron pair donor is acting as a Brønsted-Lowry base or as a nucleophile. Then, identify the acid, electrophile, and leaving group, as appropriate. Finally, use arrows to indicate the movement of electrons.
(c) \begin{matrix} CH_3CH_2-Cl + \end{matrix} \begin{matrix} \underset{||}{O} \\ C \\ H\ ^{^\diagup } \ \ \ ^{^\diagdown }O^- \end{matrix} \longrightarrow \begin{matrix} \underset{||}{O} \\ C \\ \ \ CH_3CH_2-O\ ^{^\diagup } \ \ \ ^{^\diagdown }H \quad\quad\quad\quad\quad \ \ \ \end{matrix} + Cl^-
Analyze
First, we put lone pairs on the atoms, and then compare reactants and products to determine which bonds are formed and which are broken. We identify the electron pair donor and the electron pair acceptor. If the electron pair donor (the attacking species) forms a new bond with a proton, it is acting as Brønsted-Lowry base. If the attacking species forms a new bond with a carbon atom, then it is acting a nucleophile.
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