Chapter 7, Problem 50P

(a)

Interpretation Introduction

Interpretation:

The mechanism for the formation of cis-2-octene starting from ethyne should be given.

Concept Introduction:

Deprotonation: The reaction in which proton is removed from the compound using reagents is known as deprotonation.

Different reagents are used for the deprotonation and one of the common reagent is sodium amide.

${\text{NaNH}}_{\text{2}}$ will deprotonate alkynes, alcohols and as a strong base it will deprotonate alkynes and produces acetylide ion.

Lindlar catalyst: The catalyst is used for the hydrogenation of alkynes in a syn manner.  This means both hydrogen are added on the same side across the triple bond and the product obtained will be a cis product.

Sodium in liquid ammonia: The catalyst is used for the formation of trans alkenes from alkynes.  Because of its more reactivity towards triple bonds, the reaction will stop at the formation of alkenes.

(b)

Interpretation Introduction

Interpretation:

The mechanism for the formation of trans-3-heptene starting from ethyne should be given.

Concept Introduction:

Deprotonation: The reaction in which proton is removed from the compound using reagents is known as deprotonation.

Different reagents are used for the deprotonation and one of the common reagent is sodium amide.

${\text{NaNH}}_{\text{2}}$ will deprotonate alkynes, alcohols and as a strong base it will deprotonate alkynes and produces acetylide ion.

Lindlar catalyst: The catalyst is used for the hydrogenation of alkynes in a syn manner.  This means both hydrogen are added on the same side across the triple bond and the product obtained will be a cis product.

Sodium in liquid ammonia: The catalyst is used for the formation of trans alkenes from alkynes.  Because of its more reactivity towards triple bonds, the reaction will stop at the formation of alkenes.