The electrophilic aromatic substitution reaction rate for indole is 10¹³ times greater than that of benzene. It often reacts under mild reaction conditions. Substitution in indole occurs preferably at position 3.

Propose a mechanism for the bromination of indole. You do not have to show steps for generating the Br⁺ ion. You may begin with indole and Br⁺ ion. Draw resonance forms for each sigma complex.

The electrophilic aromatic substitution reaction rate for indole is 10¹³ times greater than that of benzene. It often reacts under mild reaction conditions. Substitution in indole occurs preferably at position 3.

Explain why indole is more reactive than benzene and why substitution preferably takes place at position 3 than position 2.

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.