Chemistry - GOC Question with Solution | TestHub
For each transformation below, complete the mechanism by drawing the proper arrows. Which transformations proceed in a single concerted step, with no intermediate?
(a) 
(b) 
(c) 
(d) 
Options:
Answer:
Solution:
(a) SN2: In an SN2 reaction, chloride attacks the carbon from the side opposite the C-Br bond while the C-Br bond breaks. Bond making and bond breaking occur in a concerted step.
(b) SN1: In an SN1 reaction, the C-Br bond breaks first, forming a planar tertiary carbocation and a Br- ion. Chloride then attacks the carbocation.
(c) E2: In an E2 reaction, the alkoxide base removes a β-hydrogen. Simultaneously, the C-H electrons form a π bond, and the C-Cl bond breaks. All these steps occur in one concerted process.
(d) E1: In an E1 reaction, the C-Cl bond breaks first, yielding a tertiary carbocation. Subsequent loss of a β-hydrogen then forms the alkene.
Answer: (D).
