Question

What is the increasing order of reactivity of the following in an E2 reaction with ethanolic KOH solution?

• A. I < II < III < IV
• B. I < II < IV < III
• C. III < I < II < IV
• D. IV < III < II < I

Answer 1

The correct option is B I < II < IV < III

Reactivity of E2 reaction depends on the stability of formed alkene compound.
Here compound (III) is most reactive as it hs most acidic beta hydrogen as well as it gives resonance stabilised conjugated alkene.
Next to (III) is (IV) as it forms the substituted alkene
Comparing (II) and (I), II is more stable because it more substituted than (I). Thus (I) gives least substituted alkene and shows least reactivity.