Question

لا لو لوك لوك 28. Predict the major product of the following reaction? . aglagold 29. Which of the following can act as a Lewis base? a. I and IV b. ll and III c. I and III d. Il and IV 30. What is the most stable structure of trans-1,4-dimethylcyclohexane c) H (b پر هر

Answer 1

1)

• This is a Diel's-alder reaction.
• When there is unsymmetrical diene reacting with unsymmetrical dienophile two products are formed.
• These are regioisomers of each other. That is they only differ in position of functional groups.
• Reaction goes via six membered cylic transition state.
• The more nucelophilic C in the diene is highlighted in blue.
• The more electrophilic C in the dienophile is highlighted in blue.
• Therefore out of two products the 1,4-substituted product is the major one.
• This flow of electrons is more feasible.

• 
  Diene Dienophile Major Para product Minor Meta product More nucleophilic More electrophilic
  

Mechanism-

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Answer- option C

2)

• Lewis base - Defination- A substance that can donate a pair of nonbonding electrons.
• (I) and (IV) have nonbonding electrons present.
• While (II) and (III) do no have lone pair to donate.
• Therefore pyridine(I) and (IV) butan-2-ol can act as lewis base.

Answer- option A

3)

• Option C and D are 1,3 dimethylcyclohexane.
• Option A and B are Trans-1,4-dimethylcycholhexane.
• In option B two Me groups are at equatorial position and trans to each other
• In option A  two Me groups are at axial  position and trans to each other.
• Equatorial positon are more stable than axial position.
• Therfore B is correct answer.

CH3 a eCH3 CH3 a

Answer- option B