Phosgene is the acid chloride of carbonic acid. Although phosgene was used as a war gas in World War I, it is now used as a reagent for the synthesis of many useful products. Phosgene reacts like other acid chlorides, but it can react twice.

(a) Predict the products formed when phosgene reacts with excess propan-2-ol.

Show how you would use anhydrides to synthesize the following compounds. In each case, explain why an anhydride might be preferable to an acid chloride.

(c) phthalic acid monoamide 

(d) succinic acid monomethyl ester

Predict the major products formed when benzoyl chloride (PhCOCl) reacts with the following reagents.

(d) anisole and aluminum chloride

(e) excess phenylmagnesium bromide, then dilute acid

(f) LiAlH(O-t-Bu)₃

Predict the products of the following reactions.

(e)

(f)

One mole of acetyl chloride is added to a liter of triethylamine, resulting in a vigorous exothermic reaction. Once the reaction mixture has cooled, 1 mole of ethanol is added. Another vigorous exothermic reaction results. The mixture is analyzed and found to contain triethylamine, ethyl acetate, and triethylammonium chloride. Propose mechanisms for the two exothermic reactions.

In each part, rank the compounds in order of increasing rate of nucleophilic attack at C=O by a strong nucleophile like methoxide.

(b)

Suggest the most appropriate reagent for each synthesis, and explain your choice.

(a)

There are many methods for activating a carboxylic acid in preparation for coupling with an amine. The following method converts the acid to an N-hydroxysuccinimide (NHS) ester.

(a) Explain why an NHS ester is much more reactive than a simple alkyl ester.