Using curved-arrow notation,show the formation of reactive intermediates when the following covalent bonds undergo heterolytic cleavage:
$(a)$ $CH_{3}-SCH_{3}$
$(b)$ $CH_{3}-CN$
$(c)$ $CH_{3}-Cu$

(N/A) Heterolytic cleavage involves the breaking of a covalent bond such that both electrons of the shared pair remain with one of the fragments.
$(a)$ $CH_{3}-SCH_{3} \rightarrow CH_{3}^{+} + ^{-}SCH_{3}$
(The sulfur atom is more electronegative than the carbon atom,so the electron pair moves towards sulfur.)
$(b)$ $CH_{3}-CN \rightarrow CH_{3}^{+} + ^{-}CN$
(The nitrogen-containing group is more electronegative than the carbon atom,so the electron pair moves towards the cyanide group.)
$(c)$ $CH_{3}-Cu \rightarrow ^{-}CH_{3} + Cu^{+}$
(Carbon is more electronegative than copper,so the electron pair moves towards the carbon atom.)