Aromatic and Organic Chemistry: Study Notes

Aromatic Hydrocarbons

Compounds originally named for fragrant odors, now defined by benzene-like properties, with benzene as the parent hydrocarbon.

Benzene

A parent hydrocarbon of aromatic compounds with molecular formula C6H6, characterized by its planar ring structure, identical C-C bond lengths (1.39\~\text{Å}), 120^{\circ} bond angles, and delocalized pi electrons (resonance hybrid).

Kekulé Structure

A classical representation of benzene with six carbon atoms in a hexagonal ring, alternating single and double bonds, and one hydrogen attached to each carbon; superseded by the modern view of delocalized electrons.

Aromaticity

A property of cyclic, planar compounds with a conjugated pi-electron system where electrons are delocalized over the ring, and the number of pi electrons satisfies Huckel's rule (4n+2).

Huckel's Rule

States that aromatic systems must have (4n+2) pi electrons, where n is a non-negative integer (n=0,1,2,3,\ldots).

Monosubstituted Benzenes

Benzene derivatives with one substituent, often named as derivatives of benzene unless they have accepted common IUPAC names.

Disubstituted Benzenes

Benzene derivatives with two substituents, existing as three isomeric structures: ortho- (o-), meta- (m-), and para- (p-).

ortho- (o-)

Designation for two substituents on a benzene ring located on adjacent carbons (positions 1 and 2, or 1 and 6).

meta- (m-)

Designation for two substituents on a benzene ring located on carbons with one carbon in between (positions 1 and 3, or 1 and 5).

para- (p-)

Designation for two substituents on a benzene ring located on opposite carbons (positions 1 and 4).

Phenyl Group

The C6H5– substituent group derived from benzene.

Benzyl Group

The C6H5CH2– substituent group.

Alcohols

Organic compounds containing an -OH (hydroxyl) group connected to a saturated carbon (sp³ hybridized).

Phenols

Organic compounds containing an -OH (hydroxyl) group connected directly to a carbon atom in a benzene ring.

Aldehydes

Characterized by a carbonyl group (C=O) where the carbonyl carbon is bonded to a hydrogen atom and an alkyl or aryl group. Named by replacing the terminal -e of the alkane with -al.

Ketones

Characterized by a carbonyl group (C=O) where the carbonyl carbon is bonded to two alkyl or aryl groups. Named by replacing the terminal -e of the alkane with -one.

Carbonyl Group

A functional group consisting of a carbon atom double-bonded to an oxygen atom (\text{C}=\text{O}).

Carboxylic Acids

Organic compounds containing a carboxyl functional group (\text{–C(=O)OH}), which is a carbonyl group bonded to a hydroxyl group. They form hydrogen-bonded dimers due to strong hydrogen bonding.

Carboxyl Group

The functional group \text{–C(=O)OH} present in carboxylic acids.

Nitriles

Organic compounds with a cyano functional group (\text{RC}\equiv\text{N}), named by adding -nitrile as a suffix to the alkane name.

Acyl Derivatives

Compounds derived from carboxylic acids that contain an acyl group (\text{R–C=O}) bonded to an electronegative atom or leaving group (e.g., acid halides, anhydrides, esters, amides).

Acid Halides (RCOX)

Carboxylic acid derivatives where the -OH of the carboxyl group is replaced by a halogen (X), named by replacing -ic acid with -yl or -carbonyl and specifying the halide.

Acid Anhydrides (RCO2COR')

Carboxylic acid derivatives formed by the condensation of two carboxylic acids, symmetrical or unsymmetrical.

Esters (RCO2R')

Carboxylic acid derivatives where the -OH of the carboxyl group is replaced by an -OR' group. Named by naming the R' group first, then the carboxyl part with the suffix -ate.

Amides (RCONH2)

Carboxylic acid derivatives where the -OH of the carboxyl group is replaced by an -NR2 group. Named by replacing -ic acid or -oic acid with -amide.

Amines

Organic derivatives of ammonia (\text{NH}_3), containing a nitrogen atom with a lone pair, making them basic and nucleophilic. Classified as 1°, 2°, or 3° based on the number of alkyl/aryl groups attached to nitrogen.