Beta-agostic interactions can promote one type of these reactions in catalytic hydrogenation reactions. Xanthate pyrolysis is practically irreversible thanks to the formation of stable carbonyl sulfide and thiol byproducts in a reaction of this type. Amines can be removed through exhaustive methylation followed by treatment with silver oxide in a reaction of this type named for (*) Hofmann. For bimolecular (10[1])reactions (10[1])of this type, an anti-periplanar arrangement of atoms is required. The unimolecular form of this reaction has the same intermediates as an SN1 reaction, so its products compete with substitution products. For 10 points, name these reactions that can form pi bonds through E2 or E1 mechanisms. ■END■ (0[2])