Return to Contents Chapter 3:Conformations of Alkanes and Cycloalkanes  Ch 3 contents

Conformational Language

An alphabetical list of key terms in the language of conformational analysis is provided below, linked to the more detailed descriptions within the chapter pages
 




Anti Description given to two substitutents attached to adjacent atoms when their bonds are at 180o with respect to each other. anti conformation
Eclipsed A high energy conformation where the bonds on adjacent atoms are aligned with each other. eclipsed conformation
Staggered A low energy conformation where the bonds on adjacent atoms bisect each other, maximising the separation. staggered conformation
Gauche Description given to two substitutents attached to adjacent atoms when their bonds are at 60o with respect to each other. gauche conformation
Syn Description given to two substitutents attached to adjacent atoms when their bonds are at 0o with respect to each other. syn conformation
Conformations Different spatial arrangments that a molecule can adopt due to rotation about sigma bonds.
Conformers Contracted version of conformational isomers.
Rotamers Alternative expression for conformational isomers.
Conformational isomers Structures that can be interconverted by rotation about σ bonds.
Cycloalkane An ring containing only C-C 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 In general terms, puckered means "wrinkled, folded or creased". In conformational analysis this is used to refer to the non-planar geometry of a cyclic structure.
Ring flipping The process by which a ring changes it's conformation. chair to chair ring flip
Axial A position on a cycloalkane in which the bond to the ring is perpendicular to the average plane of the ring (i.e. pointing towards the poles). Most commonly encountered in the chair conformation of cyclohexane. axial positions of cyclohexane
Equatorial A position on a cycloalkane in which the bond to the ring is approximately in the average plane of the ring (i.e. around the equator). Most commonly encountered in the chair conformation of cyclohexane. equatorial positions of cyclohexane
Chair The most stable conformation for cyclohexane. chair conformation of cyclohexane
Boat A high energy conformation of cyclohexane that occurs during ring flipping. boat conformation of cyclohexane
Strain Energy associated with a system due to its geometry.
Angle strain Destabilisation due to distortion of a bond angle from its optimum value caused by the electrostatic repulsion of the electrons in the bonds. angle strain
Van der Waals  strain Destabilisation due to the repulsion between the electron clouds of atoms or groups. Also known as Van der Waals repulsion. This occurs when atoms or groups are too close to each other due to the electrostatic repulsion of the electrons. steric strain
Steric strain A composite of the other strains (angle, torsional, Van der Waals) within a molecule.
Torsional strain Destabilisation due to the repulsion between pairs of bonds caused by the electrostatic repulsion of the electrons in the bonds. torsional strain
Torsional angle Angle between C-X and C-Y bonds in a X-C-C-Y system when viewed along the C-C bond. Rotation about the C-C bond will change this torsional angle.  This is also known as a dihedral angle. torsional or dihedral angle
Ring strain The destabilisation 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.


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organic chemistry © Dr. Ian Hunt, Department of Chemistry University of Calgary