Naphthalene (C₁₀H₈)
Bicyclic Aromatic (Fused Benzene Rings)

Important Derivatives: Naphthalene sulfonates, α-Naphthol, β-Naphthol, Naphthoquinones

  1. Historically used as an antiseptic and topical antiparasitic (now obsolete due to toxicity).
  2. Naphthoquinone derivatives (e.g., Menadione – Vit K3) used as vitamin K analogs.
  3.  Anti-inflammatory (NSAIDs- Naproxen), Analgesics.
  4. Topical Antifungals (Tolnaftate, Naftifine)
  5. beta-Blockers (Propranolol)  
  6. α –naphthol (insecticide) and β-naphthol (tanning agent)

Anthracene (C₁₄H₁₀) Linearly Fused Tricyclic Aromatic

Important Derivatives: Anthraquinone, Hydroxyanthraquinones (e.g., Emodin, Chrysophanol), Danthron, Senna glycosides

  1. Emodin and related compounds show anti-inflammatory, antimicrobial, and anticancer activity (via Anthraquinones derivatives).
  2. Laxatives / stimulant purgatives e.g.  Senna and Cascara via anthraquinone glycosides.
  3. Some derivatives used in dermatological preparations: Anti-psoriatic.
  4. Danthron  and Mitoxantrone (Anthraquinone-based anticancer drug).  

Phenanthrene (C₁₄H₁₀) Angularly Fused Tricyclic Aromatic 

Important Derivatives: Morphine, Codeine, Thebaine, Hydromorphone, Oxycodone (all phenanthrene alkaloids)

  1. Core skeleton of opioid analgesics → strong pain relief ( Opiate Alkaloids).
  2. Used in cough suppression i.e. Antitussives (codeine).
  3. Some derivatives function as antidiarrheal agents (e.g., loperamide).
  4. The backbone is essential to the synthesis of many natural steroids /Hormone Precursors.

Diphenylmethane ( C₁₃H₁₂ )
Non-Fused Aromatic
(Two Benzene rings linked by a CH2 bridge)

Important Derivatives: Diphenhydramine, Orphenadrine, Methadone precursors

  1. It forms basis of many drugs e.g.
  2. Diphenhydramine (first-generation antihistamine, antiemetic).
  3. Hydroxyzine (Antihistamine/Anxiolytic).
  4. Loperamide (Anti-diarrheal).
  5. Perphenazine (Antipsychotic).
  6. Orphenadrine (muscle relaxant).

Triphenylmethane ( C₁₉H₁₆)   
 Non-Fused Aromatic
(Three Benzene rings linked to a central CH carbon)

Important Derivatives: Malachite green, Brilliant green, Crystal violet

  1. Antiseptics/Antifungals (often cationic dyes).
  2. Diagnostic Agents/Dyes.
  3. Gentian Violet (Crystal Violet – Topical antiseptic/antifungal dye used in Gram staining).
  4. Malachite Green (Antifungal for fish/dye).
  5. Phenolphthalein (pH indicator).