In Wittig reaction, the methyl, primary and secondary alkyl halide can be used to
prepare Wittig reagent (ylide) but not tertiary alkyl halide.
In the Wittig reaction, the formation of the Wittig reagent (ylide) is a crucial step that involves the conversion of an alkyl halide into an ylide, which is a carbanion with a positive charge on the carbon atom and a negative charge on the oxygen atom. This ylide is a key intermediate that reacts with a carbonyl compound (typically an aldehyde or ketone) to form an alkene, making the Wittig reaction a powerful tool for carbon-carbon double bond formation.
The reason why tertiary alkyl halides are generally not suitable for preparing Wittig reagents lies in the reaction mechanism.
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How free radicals are generated using redox reaction? Give at least two examples.
What are the major advantages of such reactions?
In the following pairs which of the carbocation is more stable and why?
i) NC – CH – CH2 +CH2 CH3 or NC - CH2 - +CH2 H2
sec. carbocation p – carbocation
ii) CH3 CH2 +CH - CH2 CH2 CH3 or CH3 (CH2)4 +CH2
sec. carbocation p – carbocation
Taking suitable examples, discuss the migrating aptitude of the migrating group in
Pinacol-pinacolone rearrangement reactions.
How would you prepare cis and trans alkene from alkyne? Give its mechanism.
Write the main product of the following reactions giving reasons for your answer.
Complete following reactions:
Write the full reaction and mark the nucleophile and electrophile in each case.
i) Reaction between potassium cyanide and 1-chloropropane
ii) Reaction between hydrogen bromide and cis 2-butene
iii) Reaction between sodium methoxide and benzyl bromide
iv) Acid catalysed reaction of water with cyclopentene
v) Reaction between ethanal and hydrogen cyanide