Q.Explain the preparation of the following compounds: i) DDT ii) Chloroform iii) Biphenyl iv) Chloropicrin v) Freon-12

Step 1 (i) DDT. Chlorobenzene is heated with chloral (trichloroacetaldehyde, CCl3CHO) in the presence of concentrated H2SO4; two chlorobenzene rings condense onto the chloral carbon, giving DDT + H2O.

Step 2 (ii) Chloroform. Ethanol + bleaching powder (a combined source of Cl2 and Ca(OH)2) undergoes the haloform reaction in three steps: oxidation of ethanol to acetaldehyde, chlorination of acetaldehyde to chloral, and hydrolysis of chloral by Ca(OH)2 to chloroform + calcium formate.

Step 3 (iii) Biphenyl. Two molecules of chlorobenzene, heated with sodium metal in dry ether (no alkyl halide partner present), couple aryl-to-aryl -- the Fittig reaction -- giving biphenyl + 2 NaCl.

Step 4 (iv) Chloropicrin. Chloroform + nitric acid undergoes nitration at its one C-H bond, giving chloropicrin (trichloronitromethane, CCl3NO2) + H2O. …

Recall each named preparation from its own dedicated section of the chapter: DDT (chlorobenzene+chloral/H2SO4), chloroform (haloform reaction), biphenyl ( …

• Writing chloroform's preparation as a single-step reaction -- the haloform reaction from ethanol is genuinely THREE steps (oxidation, chlorination, hydrolysis) via two dist …