| Anti |
Description given
to two substitutents attached to adjacent atoms when their bonds are at
180o with respect to each other |
 |
| Eclipsed |
A high energy conformation
where the bonds on adjacent atoms are aligned with each other |
 |
| Staggered |
A low energy conformation
where the bonds on adjacent atoms bisect each other, maximizing the separation |
 |
| Gauche |
Description given
to two substitutents attached to adjacent atoms when their bonds are at
60o with respect to each other |
 |
| Syn |
Description given
to two substitutents attached to adjacent atoms when their bonds are at
0o with respect to each other |
 |
| Conformations |
Different spatial
arrangments that a molecule can adopt due to rotation about sigma bonds |
|
| Conformers |
Contracted version
of Rotamers |
|
| Rotamers |
Alternative expression
for conformational isomers |
|
| Conformational
isomers |
Structures that can
be interconverted by rotation about sigma bonds |
|
| Heteroatom |
A non-carbon atom
such as O,N,S etc. |
|
| Heterocycle |
A cyclic molecule
that includes a heteratom such as O,N,S etc. as part of the ring |
|
| Puckered |
A non-planar geometry
of a cyclic structure |
|
| Ring flipping |
|
 |
| Axial |
A position on a chair
cyclohexane in which the bond to the ring is perpendicular to the average
plane of the ring |
 |
| Equatorial |
|
 |
| Chair |
The most stable conformation
for cyclohexane |
 |
| Boat |
|
 |
| Strain |
Energy associated
with a system due to it's geometry |
|
| Angle strain |
Destabilization due
to distortion of a bond angle from it's optimum value caused by the electrostatic
repulsion of the electrons in the bonds |
 |
| Steric strain |
Destabilization due
to the repulsion between the electron clouds of atoms or groups. Also
known as Van der Waals strain or repulsion. This occurs when atoms or
groups are too close to each other due to the electrostatic repulsion
of the electrons. |
 |
| Torsional strain |
Destabilization due
to the repulsion between pairs of bonds caused by the electrostatic repulsion
of the electrons in the bonds |
 |
| Torsional angle |
Angle between C-X
and C-Y bonds in a X-C-C-Y system. Also known as a dihedral angle. |
 |
| Ring strain |
The destabilization
of a cyclic structure compared to a related non-cyclic structure, mainly
due to angle and torsional strain. This extra energy is released when
the ring is broken. |
|