Fats and oils (triglycerides): each molecule is formed from one glycerol and three fatty-acid molecules (same or different, saturated or unsaturated):
glycerol + 3 RCOOH → triglyceride + 3H₂O.
Hydrolysis of fat or oil with a strong alkali (NaOH, KOH) is saponification, the basic reaction in makingsoapandglycerol:
Fat + 3NaOH → glycerol + 3 RCOONa (soap).
Polyesters(condensation polymers): from a dibasic acid and a dihydric alcohol. Dacron (polyethylene terephthalate) is made from terephthalic acid HOOC–C₆H₄–COOH and ethylene glycol HOCH₂CH₂OH. The acid end of one molecule reacts with the alcohol end of another repeatedly to give a very long chain. Dacron is chemically inert, so it is used for artificial blood vessels (arteries), heart valves, and for textile fibres.
Medicinal esters: aspirin(acetylsalicylic acid) andmethyl salicylate (oil of wintergreen, used as a rub on rheumatic pains) are esters of salicylic acid. Salicylic acid has both –COOH and –OH, so it can behave as an acid (with an alcohol, giving methyl salicylate) or as an alcohol (with ethanoic anhydride/acid, giving aspirin).
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