Covalent Molecules 5: Conformers

Question 1

What are conformers?

Answer 1

Structures that can be interconverted without breaking bonds

Question 2

What are the two conformations of cyclohexane?

Answer 2

1) Chair - free or torsional and steric strain, has lowest energy, most prominent
2) Boat - has torsional strain caused by eclipsing of bonds and steric strain due to ‘flagpole’ hydrogens, causing a transannular interaction

Question 3

What is torsional strain?

Answer 3

The resistance to rotation around a bond due to the repulsion between electron clouds leading to an increase in energy when bonds are eclipsed

Question 4

What is steric strain?

Answer 4

Occurs when atoms are forced into close proximity causing electron cloud repulsion leading to an increase in energy

Question 5

What are the two interconvertible chair forms of a six-membered ring?

Answer 5

Axial bonds can flip to become equatorial, and vice versa
But all the “up” substituents stay above the plane and all the “down” substituents stay below