Stereochemistry And Reaction Mechanisms Mock Tests

The pinacol-pinacolone rearrangement of 2,3-dimethylbutane-2,3-diol (pinacol) in the presence of H₂SO₄ gives:

In the Newman projection of n-butane looking down the C2−C3 bond, which conformation is the most stable, and what is the primary reason for its stability?

The Claisen rearrangement of allyl phenyl ether upon heating (typically above 200°C in a solvent such as diglyme) yields which major product? (The reaction is a [3,3]-sigmatropic rearrangement that proceeds through a cyclic six-membered transition state. Consider the regiochemistry and the driving force involving aromaticity restoration.)

How many stereoisomers are possible for 2-bromo-3-chlorobutane? (Consider the molecule CH₃−CH(Br)−CH(Cl)−CH₃ and account for all chiral centres and any meso forms.)

In the conformational analysis of n-butane (CH₃−CH₂−CH₂−CH₃), considering rotation about the C2−C3 bond, which of the following correctly ranks the conformers in order of increasing potential energy? (Consider steric interactions, torsional strain, and van der Waals repulsions between the methyl groups and hydrogen atoms.)

The Sn₁ reaction of (R)-2-bromobutane with water predominantly gives:

How many stereoisomers are possible for 2-bromo-3-chlorobutane?