The electrophilic aromatic substitution reaction rate for thiophene is greater than that of benzene. It often reacts under mild reaction conditions. Substitution in thiophene occurs preferably at position 2.
Explain why thiophene is more reactive than benzene and why substitution preferably takes place at position 2 than position 3.

• A. Thiophene is more reactive because the S atom increases the ring electron density.
  The electrophile attack at position 3 is favored because the sigma complex has more resonance forms than it has when the ring is attacked at position 2.
• B. Thiophene is more reactive because the S atom decreases the ring electron density.
  The electrophile attack at position 3 is favored because the sigma complex has more resonance forms than it has when the ring is attacked at position 2.
• C. Thiophene is more reactive because the S atom increases the ring electron density.
  The electrophile attack at position 2 is favored because the sigma complex has more resonance forms than it has when the ring is attacked at position 3.
• D. Thiophene is more reactive because the S atom decreases the ring electron density.
  The electrophile attack at position 2 is favored because the sigma complex has more resonance forms than it has when the ring is attacked at position 3.

Answer: (C)