Conformational Stability of Ethane & Butane: Which is More Stable?

The video tutorial explains the stability of ethane and butane conformations. Staggered conformations are more stable than eclipsed ones due to less repulsion between bonds. The energy difference between these conformations is termed torsional energy, which is 12 kJ/mol for ethane. In butane, anti conformation is more stable than gauche due to steric strain. Fully eclipsed conformation is the least stable due to maximum steric strain. The video also discusses energy levels of different butane conformations and their graphical representation.

Why is the staggered conformation of ethane more stable than the eclipsed conformation?

• Due to decreased bond pair repulsions in staggered conformation

• Because of increased bond pair repulsions in staggered conformation

• Due to the presence of torsional energy in staggered conformation

• Because staggered conformation has higher energy

What is torsional energy in the context of ethane conformations?

• Energy required to break a carbon-carbon bond

• Energy difference between anti and gauche conformations

• Energy released when eclipsed conformation converts to staggered conformation

• Energy required to convert staggered conformation to eclipsed conformation

What happens to the energy of ethane conformations during a 60° rotation around the carbon-carbon bond?

• Eclipsed conformation converts to staggered conformation

• Staggered conformation converts to eclipsed conformation

• Eclipsed conformation converts to anti conformation

• Gauche conformation converts to anti conformation

Which butane conformation is the most stable?

• Fully eclipsed conformation

• Partially eclipsed conformation

• Gauche conformation

• Anti conformation

What causes the higher energy in gauche conformation compared to anti conformation?

• Higher bond pair repulsions

• Steric strain due to close proximity of methyl groups

• Lower bond pair repulsions

• Presence of torsional energy

How much energy does each HH eclipsing interaction add to the fully eclipsed conformation of butane?

• 19 kilojoules per mole

• 11 kilojoules per mole

• 8 kilojoules per mole

• 4 kilojoules per mole

What is the energy difference between partially eclipsed and anti conformations of butane?

• 19 kilojoules per mole

• 15 kilojoules per mole

• 8 kilojoules per mole

• 4 kilojoules per mole