The reagent has to be identified that is used to achieve the given transformation. Concept Introduction: Elimination Reaction: To eliminate a hydroxyl group, acidic condition is needed for E1 reaction. The hydroxyl group is protonated and converted into a better leaving group. The formed intermediate carbocation loses a proton and an alkene is formed as product. E1 reaction mechanism works well with tertiary alcohol because the tertiary carbocation is more stable. Secondary alcohols also undergo E1 elimination reaction. For primary alcohol, the E1 elimination is not possible as it cannot form the carbocation. Hence, E2 mechanism is used. In this case also the hydroxyl group is a bad leaving group. This has to be converted to a good leaving group by reacting it with tosyl chloride to give tosylate which is a good leaving group. Final step is the treatment with tert-butoxide as this is used to favor elimination rather than substitution. In this case the less substituted alkene is obtained as tert-butoxide is sterically hindered. Sodium ethoxide can also be used in the final step. If sodium ethoxide is used, then the elimination will give the more substituted alkene because ethoxide is not bulky.

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Chapter 13.8, Problem 13.61P

Interpretation Introduction

Interpretation:

The reagent has to be identified that is used to achieve the given transformation.

Concept Introduction:

Elimination Reaction:

To eliminate a hydroxyl group, acidic condition is needed for E1 reaction. The hydroxyl group is protonated and converted into a better leaving group. The formed intermediate carbocation loses a proton and an alkene is formed as product. E1 reaction mechanism works well with tertiary alcohol because the tertiary carbocation is more stable. Secondary alcohols also undergo E1 elimination reaction.

For primary alcohol, the E1 elimination is not possible as it cannot form the carbocation. Hence, E2 mechanism is used. In this case also the hydroxyl group is a bad leaving group. This has to be converted to a good leaving group by reacting it with tosyl chloride to give tosylate which is a good leaving group. Final step is the treatment with tert-butoxide as this is used to favor elimination rather than substitution. In this case the less substituted alkene is obtained as tert-butoxide is sterically hindered.

Sodium ethoxide can also be used in the final step. If sodium ethoxide is used, then the elimination will give the more substituted alkene because ethoxide is not bulky.

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