Organic Chemistry: Carbocycles
Terms
1,3-diaxial interactions
-
Steric hindrance between an axial substituent on a chair conformation and the hydrogens on ring positions three carbons away.
Angle strain
-
The formation of bent
σ
bonds in rings (3-, 4-membered) to accommodate
unnatural
ring angles.
A-value
-
Energetic cost of putting a substituent group in the axial position of a
cyclohexane Chair as opposed to the equatorial position.
Axial
-
Bond positions on the cyclohexane chair parallel to the central rotation axis.
These are typically drawn as vertical lines branching from the chair structure.
Bicyclic
-
A compound that contains two rings which share atoms with each other.
Bredt's Rule
-
No bridgehead alkenes. Bridgehead carbons are too constrained in the ring
structures to incorporate double bonds.
Bridged
-
Joining of rings with more than two atoms. These shared atoms constitute a
bridge.
Bridgehead carbons
-
Points at which rings meet in bridged polycyclic hydrocarbons.
Boat
-
Less stable conformation of cyclohexane; resembles a boat.
Chair
-
The most stable conformation of cyclohexane; resembles a lawn chair.
Chair flip
-
Interconversion between two chair conformations.
Equatorial
-
Bond positions on the cyclohexane chair that lie sideways toward the
equatorial plane of the chair.
Flagpole hydrogen
-
Hydrogens at two ends of the cyclohexane boat conformation that repel each
other due to steric hindrance.
Fused
-
The joining of rings that share two atoms and the bond between them.
Heat of Formation
-
The energy change that occurs when a molecule is assembled from its component
atoms.
Polycyclic
-
Compound that contains several rings joined with common atoms.
Ring strain
-
Unfavorable energetics that arise from ring formation. These include both
angle strain and torsional
strain.
Spiro
-
Ring joining that shares a single atom, creating rings that lie in perpendicular
planes.
Steric hindrance
-
Repulsion between the electron clouds on bulky groups of a molecule or
between molecules.
Torsional strain
-
Resistance to rotation about a single bond caused by steric hindrance
of
eclipsing interactions.
