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22 Cards in this Set

  • Front
  • Back
Aliphatic Compound
An organic compound that is NOT aromatic.

Cyclic hydrocarbons with alternating single and double bonds.

Aromatic Compound
A cyclic compound containing some number of conjugated dboule bonds, characterized by an unsually large resonance energy.
1. All its ring atoms must have unhybridized p orbitals that overlap to form a continous ring.
2. must be planar and have (4N+2) pi electrons.
3. Delocalization of the pi electrons over the ring results in a lowering of the electronic energy.
Antiaromatic Compound
Has a continuous ring of p orbitals, but delocalization of the pi electrons over the ring increases the electronic energy.
Must be planar and have 4N pi electrons.
Aromatic hydrocarbons, usually based on the benzene ring as a structural unit.

Aryl Group
The aromatic group tha tremains after taking a hydrogen atom off an aromatic ring; the aromatic equivalent of the generic alkyl group (R).

Benzyl Group
The seven-carbon unit consisting of a benzene ring and a methylene group.

Degenerate orbitals
orbitals having the same energy.
Fused Rings
Rings that share a common carbon-carbon bond and its two carbon atoms.
Heterocyclic Compound
A cyclic compound in which one or more of the ring atoms is not carbon.
Aromatic heterocycle
A heterocyclic compound that fulfills the criteria for aromaticity and has a substantail resonance energy.
Huckle's Rule
A cyclic molecule or ion that has a continous ring of overlapping p orbitals will be
1. aromatic if the number of pi electrons is (4N+2)
2. antiaromatic if 4N
Kekule Structure
a classical structural formula for an aromatic compound, showing localized double bonds.
Nonaromatic Compound
Lacking the continouos ring of overlapping p orbitals
Having a 1,2 relationship on a benzene ring.
Having a 1,3 relationship on a benzene ring.
Having a 1,4 relationship on a benzene ring.
Phenyl Group (Ph)
The benzene ring, minus one hydrogen atom, when named as a substituent on another molecule.

Polygon Rule
The energy diagram of the MOs of a regular, completely conjugated cyclic system has the same polygonal shape as the compound, with one vertex (the all-bonding MO) at the bottom. The nonbonding line cuts horizontally through the center of the polygon.
Polynuclear aromatic compounds
Aromatic compounds with 2 or more fused aromatic rings. Naphthalene is an example of a polynuclear aromatic hydrocarbon. And indole is an example of a polynuclear aromatic heterocycle.
Resonance Energy
The extra stabilization provided by delocalization, compared with a localized structure. For aromatic compounds, the resonance energy is the extra stabilization provided by teh delocalization of the electrons in the aromatic ring.
Tropylium ion
the cycloheptatrienyl cation