DDT ($$p,p'$$-Dichlorodiphenyltrichloroethane)

Made by condensing chloral with chlorobenzene in the presence of concentrated $$\text{H}_2\text{SO}_4$$:

$$\text{CCl}_3\text{CHO} + 2\text{C}_6\text{H}_5\text{Cl} \xrightarrow{\text{Conc. }\text{H}_2\text{SO}_4} (p\text{-Cl--C}_6\text{H}_4)_2\text{CH--CCl}_3 + \text{H}_2\text{O}$$

Environmental Impact: Highly fat-soluble, non-biodegradable insecticide that undergoes biomagnification across trophic levels in ecosystems, disrupting calcium metabolism in birds and causing eggshell thinning.