Question

CH3OH H-SO methyl salicylate acetylsalicylic acid NaOH aq. EtoH benzaldehyde acetone dibenzylideneacetone (dba) 2. For reactions where there is chemical equilibrium between reactants and products, a common way to increase yields is to apply Le Châtelier's Principle, and increase the amount of one reactant. This is particularly useful when one reactant is a cheap liquid that can be used as a solvent or co-solvent. Each of the two reactions shown (unbalanced) above employs a cheap organic liquid (methanol or acetone) as a reactant. However, the "trick" of using this liquid reactant in excess only works for one of the two reactions. a) (6 points) Balance the two reactions shown above. b) (6 points) For one of these two reactions, it is important that the reactants are combined according to the stoichiometry provided by the balanced reaction equation. Identify which reaction fails if an excess of the cheap organic reactant (methanol or acetone) is used, and explain why

Answer 1

First reaction can work according to Le Chatelier principle, if we add excess of ethanol it would shift equilibrium to product side because here methanol acts as a nucleophile to the acetylsalicylic acid and has no electphilic centre on its own so that no side reaction occurs and maximum product is obtained.

Whereas in second reaction if we add acetone in excess, then the enolate formed from acetone would have chance to add as a nucleophile on another acetone molecule (instead of benzaldehyde) so there would less yield of desired product.

1 shoulo attack benpaldlehpb 0 0