💯 Elimination vs Substitution Revision Q&A (Class 12 Chemistry) Q: What is a substitution reaction ? A: A reaction where an atom/group in a molecule is replaced by another atom/group. Q: What is an elimination reaction ? A: A reaction where atoms/groups are removed from a molecule to form a multiple bond. Q: Which reagents favor substitution over elimination? A: Weak bases and strong nucleophiles favor substitution. Q: Which reagents favor elimination over substitution? A: Strong bulky bases favor elimination. Q: What is the leaving group in substitution/elimination reactions? A: Usually a halide ion (-X). Q: What is the difference between SN1 and SN2 mechanisms? A: SN1 is unimolecular with carbocation intermediate; SN2 is bimolecular and concerted . Q: What is the difference between E1 and E2 mechanisms? A: E1 has carbocation intermediate; E2 is concerted with base abstracting proton and leaving group leaving simultaneously. ...