91Ó°ÊÓ

The formation of compound (a) is done by reacting 2-bromo-3-methylbutane (alkyl halide) with triphenylphosphine (C₆H₅)₃ P by S_N2 mechanism. Itresults in the formation of alkyl phosphonium salt, which on deprotonation with strong base n-butyllithium,forms ylide(Wittig reagent).

Wittig reagent is formed upon reacting with cyclohexanone (carbonyl compound) formed the desired product (3-methylbutan-2-ylidene)cyclohexane.

The formation of (3-methylbutan-2-ylidene) cyclohexane is shown below.

(3-methylbutan-2-ylidene)cyclohexane formation

The formation of compound (b) is done by reacting 1-hexyne (terminal alkyne) with the strong base (NH₂). It results in the formation of alkynide, which on reaction with ethyl bromide (alkyl halide) through nucleophilic substitution reaction,forms the desired product octa-3-yne.

The formation of octa-3-yneis shown below.

Octa-3-yne formation

The formation of the compound (d) is done by reacting two moles of butanal (aldehyde having alpha-hydrogen)with nucleophile hydroxide ion (OH^-), which forms beta-hydroxy aldehyde2-ethyl-3-hydroxyhexanal (aldol)through aldol condensation.

Beta-hydroxy aldehyde upon dehydration,removes the water molecule from the β-hydroxy aldehyde to form an α,β-unsaturated aldehyde, thusforming the desired product, (E)-2-ethylhex-2-enal.

The formation of (E)-2-ethylhex-2-enal is shown below.

Formation of (E)-2-ethylhex-2-enal

Formation of compound (d) is done by hydrogenation of octa-3-yne with the help of lindlar catalyst. Itresults in the formation of cis alkene (Z)-non-4-ene, which reacts with reagent meta-chloroperbenzoic acid(MCPBA), and as a result, the stereochemistry of the product is retained. This leads to formation of (2R,3S)-2butyl-3-propyloxirane (cyclic ether).

The formation of (2R,3S)-2butyl-3-propyloxirane is shown below.

Formation of (2R,3S)-2butyl-3-propyloxirane