Assertion (A): The boat conformation of cyclohexane is less stable than the chair. Reason (R): In the boat conformation the C-C-C bond angles are about $9 0^{\circ}$ , giving large angle strain.

ABoth A and R are true, and R is the correct explanation of A
BBoth A and R are true, but R is not the correct explanation of A
CA is false but R is true
DA is true but R is false

Answer: D

The boat is less stable (about 30 kJ/mol) because of torsional strain from eclipsed C-H bonds along two bonds and flagpole H/H repulsion. Its C-C-C angles are close to tetrahedral (about

109

11 5^{\circ}

), so angle strain is small. The reason given is false.

Practice Stereoisomerism More on Conformational analysis of ethane, butane and cyclohexane

Previous questionNext question

More questions on Conformational analysis of ethane, butane and cyclohexane

Select the correct statements about trans-1,4-dimethylcyclohexane. JEE Main level
The energies of some cyclohexane conformations relative to the chair (0) are: twist-boat 23, boat 30, half-chair 45 kJ/mol. The energy barri... JEE Main level
Match the butane conformations (dihedral angle between the two methyl groups, viewed along C2-C3) in List I with their descriptions in List ... JEE Main level
In cis-1-tert-butyl-4-methylcyclohexane the A-values are tert-butyl 20.0 and methyl 7.3 kJ/mol (strain of the axial position relative to equ... JEE Main level
In trans-1,2-dimethylcyclohexane the diequatorial chair has one gauche CH3/CH3 interaction, while the diaxial chair has four CH3/H 1,3-diaxi... JEE Main level
In cis-1,3-dimethylcyclohexane, the diaxial chair has one CH3/CH3 1,3-diaxial interaction (15.4 kJ/mol) and two CH3/H 1,3-diaxial interactio... JEE Main level

Assertion (A): The boat conformation of cyclohexane is less stable than the chair. Reason (R): In the boat conformation the C-C-C bond angles are about 90∘, giving large angle strain.

Answer: D

More questions on Conformational analysis of ethane, butane and cyclohexane

Assertion (A): The boat conformation of cyclohexane is less stable than the chair. Reason (R): In the boat conformation the C-C-C bond angles are about $9 0^{\circ}$ , giving large angle strain.