A liquid hydrocarbon obtained from fractional distillation of coal tar that is used in the pharmaceutical industry is

Step 1: Analyze the question We need a liquid hydrocarbon that (a) comes from fractional distillation of coal tar and (b) is used in the pharmaceutical industry.

Step 2: Key concept Coal tar is a source of aromatic hydrocarbons. Fractional distillation separates it into fractions:

• Light oil (up to about 170°C): benzene, toluene, xylene
• Middle oil (carbolic oil): phenol, naphthalene
• Heavy oil (creosote oil)
• Anthracene oil
• Pitch (residue)

Hexane is an alkane obtained from crude petroleum, not coal tar, so it is out.

Step 3: Compare the aromatic options

• Benzene: a starting material for making many pharmaceuticals, including phenol-based drugs, aspirin precursors, and sulfonamides. It is also used for dyes, plastics, and detergents. It is the classic textbook answer for "coal tar hydrocarbon used in pharmaceuticals".
• Toluene: mainly a solvent and used in making TNT, paints, and thinners.
• Xylene: mainly a solvent and used in making polyester fibres (terephthalic acid).
• Hexane: a petroleum fraction used as a solvent, not from coal tar.

Step 4: Conclusion Toluene also has some pharmaceutical uses as a solvent.

Correct answer: B. benzene

Exam tip: Remember "BTX" (benzene, toluene, xylene) as the light-oil fraction of coal tar. If the question mentions pharmaceuticals, drugs, or dyes as the starting material, pick benzene. If it mentions solvents or explosives (TNT), think toluene. If it mentions polyester, think xylene.