Aromatic Compounds Naming Quiz and Flashcards

9 Questions

What differentiates aromatic compounds from aliphatic compounds?

Aromatic compounds have less hydrogen compared to aliphatic compounds.

Who was the first to recognize Benzene as the first aromatic compound?

Kekulé

How did Kekulé describe the two different ways to draw the structure of '1,2-dibromobenzene'?

As two sides of the same coin, always changing.

How do we differentiate the naming of aromatic compounds from chain compounds?

Naming aromatic compounds is more complex and often has multiple acceptable names.

What structural feature is common to all aromatic compounds?

They are derived from benzene and have a ring with six carbon atoms.

Why is the numbering of substituents on a benzene ring important?

To give the substituents the smallest numbers in the name

Which compound would be named 'xylene'?

Benzene with two methyl groups attached

In alkyl group naming, when is phenyl considered as the parent compound?

When phenyl is attached to an unsaturated chain

How does benzene react differently compared to unsaturated compounds when reacting with bromine?

Benzene substitutes with bromine instead of adding it

Study Notes

Aromatic Compounds

Aromatic compounds have common names that are used as formal names in the IUPAC system, e.g., Toluene, phenol, aniline.
Aromatic compounds with multiple groups attached to the benzene ring use "ortho" (o-), "meta" (m-), and "para" (p-) to show the location of the groups, or numbering.

Numbering Aromatic Compounds

The first group attached to the ring is at position 1.
Other positions are numbered 2 to 6, and can be counted in either direction.
The numbering system is chosen to give the smallest numbers in the name.

Nomenclature of Aromatic Compounds

Aromatic compounds with only one group attached to the benzene ring consider benzene as the parent and start naming with the substituent as a prefix.
If there are more than two groups on the benzene ring, numbers are used to show their location.
If there are more than two different groups, they are listed in alphabetical order.

Phenyl Group

The phenyl group (C6H5-) is formed by removing one hydrogen from benzene.
When phenyl is attached to a saturated chain, it must have more carbons than the aromatic compound to be used as the parent.
When phenyl is attached to an unsaturated chain, the chain length doesn't matter, and the unsaturated compound is used as the parent, with the aromatic compound as a substituent.

General Reactions of Aromatic Compounds

Aromatic compounds do not react like unsaturated compounds, e.g., alkenes.
Benzene reacts with bromine, but not by addition, rather by substitution, forming only one mono-bromobenzene.

Aromaticity

Benzene is said to be aromatic, and any molecule with the same characteristics is also aromatic.
Aromatic compounds have four main characteristics:
- Cyclic compounds that are planar.
- They must have a conjugated system.
- They must have high stabilization energy.
- Prefer substitution reactions over addition.

Theories of Aromaticity

There are two theories to explain why benzene has higher energy and less stability than expected:
- Resonance theory.
- Molecular Orbital (MO) theory.

Classification of Organic Compounds

Organic compounds are classified into two categories:
- Aliphatic: means "fat-like", reacts like alkane, alkene, and alkyne.
- Aromatic: means the compound has less hydrogen than aliphatic compounds, and refers to "scent or smell or fragrant".

Kekulé's Contribution

Kekulé was the first to recognize benzene as an aromatic compound.
He found two different ways to draw the structure of "1,2-dibromobenzene", but only one was found in experiments.
He proposed the concept of resonance hybrid structure, like a blend of two structures.

Aromatic Compounds Classification