Identifying reaction type from mechanism features

Steps:

• Examine bond breaking: heterolytic fission involves unequal electron sharing, common in polar mechanisms.
• Classify reaction: substitution replaces one group with another on a central atom.
• Assess species roles: OH typically acts as nucleophile (electron donor), not electrophile.
• Evaluate overall: mechanism shows atom replacement without multiple correct traits beyond substitution.

Why B is correct:

• Substitution reactions involve one group displacing another, as defined in organic chemistry for SN1/SN2 pathways.

Why the others are wrong:

• A: Mechanism likely shows homolytic fission (equal electron split) or insufficient detail for heterolytic confirmation; not enough information.
• C: OH is a nucleophile, attracting electron-poor centers, per Lewis acid-base theory.

Final answer: B