Benzene Derivatives Naming

Overview

This lecture covers the naming conventions for mono-, di-, and tri-substituted benzene derivatives, focusing on key parent names, positional isomerism (ortho, meta, para), and the application of alphabetical order in naming.

Mono-substituted Benzene Derivatives

• Benzene with an NO₂ group is called nitrobenzene.
• Benzene with an OH group is called phenol.
• Benzene with an OCH₃ group is called anisole.
• Benzene with an NH₂ group is called aniline.
• Benzene with a COOH group is called benzoic acid.
• Benzene with a CHO group is called benzaldehyde.
• Benzene with a vinyl group (C=C) is called styrene (or vinylbenzene).
• Benzene with an acetyl group (ketone) is called acetophenone.
• Benzene with a halogen is called halobenzene (e.g., chlorobenzene, bromobenzene).
• Benzene with an ethyl group is called ethylbenzene.
• Benzene with a methyl group is commonly known as toluene.
• Benzene with an amide group is called benzamide.
• Benzene with a nitrile group is called benzonitrile.
• Benzene with a benzyl chloride group (CH₂Cl) is called benzyl chloride.
• Benzene with an isopropyl group is called cumene (or isopropylbenzene).
• Benzene with a tert-butyl group is called tert-butylbenzene.
• Benzene with a sulfonic acid group is called benzene sulfonic acid.

Di-Substituted Benzene Derivatives and Isomerism

• Two methyl groups on benzene form xylene.
• Ortho-xylene: 1,2-dimethylbenzene (adjacent positions, ortho/1,2).
• Meta-xylene: 1,3-dimethylbenzene (meta/1,3).
• Para-xylene: 1,4-dimethylbenzene (para/1,4).
• For different substituents, identify the parent group (e.g., toluene for methyl).
• Number to give substituents the lowest possible numbers.
• Use ortho (1,2), meta (1,3), and para (1,4) or numerical positions in names.
• Alphabetical order is used if different groups are present (e.g., 2-bromotoluene).

Tri-Substituted Benzene Derivatives

• Use the parent with highest priority as position 1.
• Number substituents to get the lowest possible set.
• List substituents alphabetically in the name.
• Example: 2,4-dinitrophenol (OH at 1, NO₂ at 2 and 4).
• Example: 5-bromo-2-nitrobenzoic acid (COOH at 1).

Key Terms & Definitions

• Phenyl group — A benzene ring minus one hydrogen (C₆H₅–).
• Benzyl group — Phenyl group attached to a CH₂ group (C₆H₅CH₂–).
• Ortho (o-) — Substituents at 1,2 positions.
• Meta (m-) — Substituents at 1,3 positions.
• Para (p-) — Substituents at 1,4 positions.
• Parent Name — The main functional group or substituent that determines numbering and base name.

Action Items / Next Steps

• Memorize common parent names and their corresponding structures.
• Practice drawing and naming substituted benzene derivatives using IUPAC and common names.