Isomerism

Dihedral angle of least stable conformer of ethane is :

1. 0
2. 120
3. 180
4. 60

With respect to the conformers of ethane, which of the following statements is true?

1. Bond angle changes but bond length remains same.
2. Both bond angle and bond length change.
3. Both bond angle and bond length remain same.
4. Bond angle remains same but bond length changes.

Which of the following biphenyls is optically active ?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

The correct statement regarding the comparison of staggered and eclipsed conformations of ethane, is

1. the eclipsed conformation of ethane is more stable than staggered conformation even though the eclipsed conformation has torsional strain
2. the staggered conformation of ethane is more stable than eclipsed conformation, because staggered conformation has no torsional strain
3. the staggered conformation of ethane is less stable than eclipsed conformation, because staggered conformation has torsional strain
4. the eclipsed conformation of ethane is more stable than staggered conformation, because eclipsed conformation has no torsional strain.

The correct statement regarding a carbonyl compound with a hydrogen atom on its alpha-carbon, is

1. a carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as carbonylation
2. a carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as keto-enol tautomerism
3. a carbonyl compound with a hydrogen atom on its alpha-carbon never equilibrates with its corresponding enol
4. a carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as aldehyde-ketone equilibration.

Which among the given molecules can exhibit tautomerism? [figure]

1. III only
2. Both I and III
3. Both I and II
4. Both II and III

The possible stereo-structures of CH3CHOHCOOH, which are optically active, are called

1. atropisomers
2. enantiomers
3. mesomers
4. diastereomers

In an SN1 reaction on chiral centers, there is

1. inversion more than retention leading to partial racemisation
2. 100% retention
3. 100% inversion
4. 100% racemisation

The number of structural isomers possible from the molecular formula C3H9N is

1. 5
2. 2
3. 3
4. 4

Given : [figure] Which of the given compounds can exhibit tautomerism?

1. II and III
2. I, II and III
3. I and II
4. I and III