CH CH C-N N一H HaPo 4 H2PO O N CH 3 CH3 Caffeine free-base Phosphoric acid caffeine-phosphoric acid salt form(water-soluble (water-soluble Fig12.18 all alkaloids are bases that react with acids to form salts. An example is the alkaloid caffeine, shown here reacting with phosphoric acidN N N N O O H3C CH3 CH3 + H3PO4 N N N N O O H3C CH3 CH3 H H2 PO4 caffeine-phosphoric acid salt (water-soluble) Caffeine free-base form (water-soluble) Phosphoric acid Fig12.18 all alkaloids are bases that react with acids to form salts. An example is the alkaloid caffeine, shown here reacting with phosphoric acid