5094

Orthoesters are compounds that have three alkoxy groups bonded to the same carbon. When ethyl orthoacetate is treated with dilute aqueous acid under mild conditions, one mole of ethyl acetate and two moles of ethanol are obtained. Propose a reasonable mechanism for this reaction.

5146

When methyl salicylate is mixed with 10% aqueous sodium hydroxide at room temperature, a dense precipitate forms immediately. Upon heating the mixture at reflux, the precipitate dissolves slowly. After one half hour of reflux, the cooled solution is treated with cold 10% sulfuric acid and a white precipitate forms again.

(a) What is the chemistry which is taking place when a dense precipitate forms upon the addition of methyl salicylate to the sodium hydroxide solution? (Write equation and explain solubilities.)

(b) What is happening as the dense precipitate dissolves slowly upon refluxing the mixture? (Write equation and explain solubilities.)

(c) Write the equation for the reaction which occurs when dilute acid is mixed with the cooled reaction mixture to produce a precipitate.

5358

The catalytic effect of pyridine on the formation of esters from phenol plus anhydrides apparently involves an initial reaction of the anhydride with pyridine, then substitution by the alcohol (phenol). Suggest a mechanism for the preparation of phenyl acetate by this method.