Conformations (Chapter 3)

conformations

different rotational arrangements of molecules

conformer

a conformation with local energy minimum

When do molecules experience strain?

When they are forced to adopt a non-ideal condition (not be in the lowest possible energy state)

angle strain

bond angles deviating from their ideal values

torsional strain

electron clouds from two atoms that are seperated by exactly three bonds come close together

steric strain

two electron clouds overlap (a specific number of bonds is NOT required)

eclipsed conformation

the substituents on two atoms are directly in front of each other in a Newman Projection

staggered conformation

the substituents on two atoms are the maximum distance from each other in a Newman Projection (lowest energy conformation)

What is the most common reason for angle strain in a molecule?

geometric constraints

What type of conformers can be made by 4-membered rings?

butterfly conformers

ring inversion (ring flip)

changing between the lowest energy conformations of a ring

What type of conformers can be made by 5-membered rings?

envelope conformers

What is the most stable conformation for 6-membered rings?

chair conformations

axial groups

the 6 substituents that align with the z-axis (up and down)

equatorial groups

the 6 substituents that point towards the mid plane of the ring