Chapter 4 Vocabulary Flashcards
1,3-diaxial interaction
Steric interactions that occur between axial substituents in a chair conformation.
alkane
A hydrocarbon that lacks π bonds.
alkyl group
A substituent lack- ing π bonds and comprised of only carbon and hydrogen atoms.
Angle strain
The increase in energy associated with a bond angle that has deviated from the preferred angle of 109.5°
anti conformation
A conformation in which the dihedral angle between two groups is 180°.
axial position
For chair conforma- tions of substituted cyclohexanes, a position that is parallel to a vertical axis passing through the center of the ring.
bicyclic
A structure containing two rings that are fused together.
boat conformation
A conforma- tion of cyclohexane in which all bond angles are fairly close to 109.5° and many hydrogen atoms are eclipsing each other.
bridgeheads
In a bicyclic system, the carbon atoms where the rings are fused together.
chair conformation
The lowest energy conformation for cyclohexane, in which all bond angles are fairly close to 109.5° and all hydrogen atoms are staggered.
Conformations
A three-dimensional shape that can be adopted by a compound as a result of rotation about single bonds.
Cycloalkane
An alkane whose structure contains a ring.
Cyclohexane
C6H12. A colourless flammable liquid cycloalkane obtained from petroleum or by hydrogenating benzene, and used as a solvent and paint remover.
degenerate
Having the same energy.
dihedral angle
The angle by which two groups are separated in a Newman projection.
eclipsed conformations
A conformation in which groups are eclipsing each other in a Newman projection.
equatorial position
For chair conformations of substituted cyclohexanes, a position that is approximately along the equator of the ring.
flagpole interactions
For cyclohexane, the steric interactions that occur between the flagpole hydrogen atoms in a boat conformation.
gauche conformation
A conformation that exhibits a gauche interaction.
gauche interactions
The steric inter- action that results when two groups in a Newman projection are separated by a dihedral angle of 60°.
heat of combustion
The heat given off during a reaction in which an alkane reacts with oxygen to produce CO2 and water.
IUPAC
The International Union of Pure and Applied Chemistry. An organization that sets the rules for nomenclature (naming compounds).
locant
In nomenclature, a number used to identify the location of a substituent.
newman projections
A drawing style that is designed to show the conformation of a molecule.
nomenclature
A system for naming organic compounds.
norbornane
The common name for bicyclo[2.2.1]heptane.
ring flip
A conformational change in which one chair conformation is converted into the other.
Staggered conformations
A conformation in which nearby groups in a Newman projection have a dihedral angle of 60°.
substituent
In nomenclature, the groups connected to the parent chain.
torsional angle
The angle between two groups in a Newman projection, also called the dihedral angle.
torsional strain
The difference in energy between staggered and eclipsed conforma- tions (for example, in ethane).
twist boat
A conformation of cyclohexane that is lower in energy than a boat conformation but higher in energy than a chair conformation.
Cracking
a process by which C−C bonds of larger alkanes are broken, producing smaller alkanes suitable for gasoline
Reforming
a process in which straight-chain alkanes are converted into branched hydrocarbons and aromatic com- pounds, which exhibit less knocking during combustion.
