Study Set Content:
- The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing.
- The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing.
Induced in a molecule when bond angles are forced to deviate from the ideal
109° tetrahedral value
Stability of Cycloalkanes: Ring Strain
Angle strain:
can assume nonplanar conformations to minimize angle strain and torsional strain by ring-puckering
Cyclic molecules
Caused due to eclipsing of bonds between neighboring atoms
Torsional strain
Caused due to repulsive interactions when atoms approach each other too closely
Steric stain
Most strained of all rings due to angle strain caused by its C-C-C bond angles of 60°
Cyclopropane
- bonds are weaker and more reactive than typical alkane bonds
Cyclopropane
- Has less angle strain than cyclopropane
Cyclobutane
- Has considerable torsional strain
- Has bent bonds
Cyclopropane
- More torsional strain because of larger number of ring hydrogens, and their proximity to each other
cyclobutane
- Slightly bent out of plane, one carbon atom is about 25 above the plane
Cyclobutane
- Increases angle strain but decreases torsional strain
Cyclobutane
- C-H bonds are eclipsed
Cyclopropane
- No angle strain, Large torsional strain
- Non planar conformations strike balance between increased angle strain and decreased torsional strain
- Four carbon atoms are approximately in the same plane. Fifth carbon atom is bent out of the plane
Cyclopentane
Conformations of Cyclohexane
- Occur widely in nature
- Adopts chair conformation
- Chair conformation: Strain-free, three-dimensional shape
- Has neither angle strain nor torsional strain
Conformation of cyclohexane that bears a slight resemblance to a boat
Boat cyclohexane:
- No angle strain
- Large number of eclipsing interactions
Boat cyclohexane:
: Conformation of cyclohexane that is somewhat more stable than a pure boat conformation
- Nearly free of angle strain
Twist-boat conformation:
Chair conformation positions for substituents on the ring
- Axial positions
- Equatorial positions
Chair cyclohexane has six:
- Axial hydrogens perpendicular to the ring
- Equatorial hydrogens near the plane of the ring
