Question

The correct statement regarding a unimolecular elimination reaction is

• A. Rearrangement of carbon skeleton won't occur during elimination reaction
• B. More substituted alkenes are major product
• C. Step II is the rate determining step
• D. Alkyl fluorides favours E1 reaction

Answer 1

The correct option is B More substituted alkenes are major product

E1 reaction proceeds via carbocation intermediate, rearrangement of carbon skeleton is very common in this reaction because they will try to form stable carbocation.

The E1 mechanism is a two-step process which involves a rate determining step

1. Alkyl halide ionizes to give carbocation.
2. Carbocation lost a proton from $\beta -C$ atom by the base to form an alkene.

The slowest step in a reaction which determines the rate of the reaction is step 1.

Since, rate of the reaction depends on the rate of formation of carbocation, good leaving group will favour the reaction by ease of formation of carbocation. C-F is a very strong bond and fluoride ion is a strong base. Thus, it is a poor leaving group and it doesn't undergo E1 reaction.

The major product of E1 reaction will be the alkene which has more substitution. Since, it gives the stable alkene.
Thus by saytzeff rule, E1 reaction form more substituted alkenes as their major product.