Chapter 1- Cycloalkanes Flashcards
Boat cyclohexane
A conformation of cyclohexane that bears a slight resemblance to a boat. Boat cyclohexane has no angle strain, but has a large number of eclipsing interactions that make it less stable than chair cyclohexane.
Axial bond
A bond to chair cyclohexane that lies along the ring axis perpendicular to the rough
plane of the ring.
Chair cyclohexane
A three-dimensional conformation of cyclohexane that resembles the rough shape of a chair. The chair form of cyclohexane is the lowest energy conformation of the molecule.
Cis-trans isomers
Stereoisomers that differ in their stereochemistry about a double bond or ring
Conformational analysis
A means of assessing the energy of a substituted cycloalkane by
totaling the steric interactions present in the molecule.
Conformational analysis
A means of assessing the energy of a substituted cycloalkane by
totaling the steric interactions present in the molecule.
Cycloalkane
An alkane that contains a ring of carbons.
1,3-Diaxial interaction:
The strain energy caused by a steric interaction between axial groups three carbon atoms apart in chair cyclohexane.
Equatorial bond
A bond to cyclohexane that lies along the rough equator of the ring.
Geo-metric isomers
An old term for cis-trans isomers.
Plane of symmetry
A plane that bisects a molecule such that one half of the molecule is the mirror image of the other half. Molecules containing a plane of symmetry are achiral
Ring-flip
A molecular motion that converts one chair conformation of cyclohexane into another chair conformation. The effect of a ring-flip is to convert an axial substituent into an equatorial substituent.
Steric strain
The strain imposed on a molecule when two groups are too close together and try to occupy the same space. Steric strain is responsible both for the greater stability of trans versus cis alkenes and for the greater stability, of equatorially substituted versus axially substituted cyclohexanes.
Twist-boat confirmation
A conformation of cyclohexane that is somewhat more stable than a pure boat conformation.
