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. (10[2]-5[1])For bimolecular (10[1])reactions (10[2])of this (10[1])type, an anti-periplanar arrangement of atoms is required. The unimolecular form of this reaction has the same intermediates (10[1]-5[1])as an SN1 reaction, so its products compete with substitution products. For 10 points, name these reactions that can form pi bonds through E2 (-5[1])or E1 (-5[1])mechanisms. ■END■ (10[1]0[4])