Unit 1 Definitions Flashcards
anti-bonding molecular orbital
Opposes bonding. Molecular orbital has a
node which prevents bonding. Given a *
notation. One forms for each bonding orbital.
bonding molecular orbital
Causes bonding. Molecular orbital caused by
overlap of atomic orbitals.
chiral
Non-superimposable stereoisomers. Has a
chiral centre: carbon with 4 different groups
attached.
chromophore
Part of a molecule responsible for colour
cis
Geometric isomers with groups on the same
side of the double bond/ring
conjugated system
System of alternating carbon to carbon single
and double bonds. Often the chromophore of
a system
enantiomers
Non-superimposable mirror image
stereoisomers. Have the same connectivity
but opposite 3D shape
geometric isomer
Stereoisomers with the same connectivity
containing a group the prevents rotation, e.g.
a ring or carbon to carbon double bond
HOMO
Highest occupied molecular orbital. Final
molecular orbital containing electrons.
LUMO
Lowest unoccupied molecular orbital. The first
molecular orbital with no electrons in, often an
antibonding molecular orbital.
hybridisation
Mixing of atomic orbitals to produce hybrid
orbitals. For every atomic orbital used a hybrid
orbital is used.
molecular orbital
Formed during the overlap of atomic orbitals.
For every atomic orbital used a molecular
orbital is formed. Location of the molecular
orbital indicates type of bonding
optical isomer
Molecule with a chiral centre. Will rotate plane
polarised light.
pi orbital
Formed by side on overlap of un-hybridised
p-orbitals. Forms when double/triple bonds
form.
sigma orbital
Formed by end on overlap of
orbitals/hybrid orbitals. All single bonds are
sigma bonds, each double/triple contains a
sigma bond.
