Organic Chemistry: Carbocycles

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Terms

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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.

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