organic chemsitry shorts notes

This chapter on Haloalkanes and Haloarenes provides a concise overview of their preparation, reactions, and properties. Haloalkanes are synthesized from alcohols using reagents like PCl₅, PCl₃, SOCl₂, HI, HBr, KI/H₃PO₄, and ZnCl₂/HCl (Lucas reagent). Other methods include Finkelstein reaction (halogen exchange), Swarts reaction (fluorination), Hunsdiecker reaction (from silver salts of carboxylic acids), and free radical halogenation with Cl₂/Br₂ under light. Haloarenes are prepared mainly through electrophilic substitution reactions such as halogenation, nitration, sulphonation, and Friedel–Crafts alkylation/acylation.

In terms of reactivity, SN1 reactions proceed via carbocation intermediates (order: 3° > 2° > 1°), while SN2 reactions involve backside attack with inversion (order: 1° > 2° > 3°). Special reactions include Wurtz, Wurtz–Fittig, Corey–House synthesis, and nucleophilic substitution with reagents like KCN, AgCN, NH₃, and NaSH.

Physical properties show trends: dipole moment (CH₃Cl > CH₃F > CH₃Br > CH₃I), bond enthalpy (CH₃F > CH₃Cl > CH₃Br > CH₃I), and boiling point (R–I > R–Br > R–Cl > R–F). Haloalkanes are slightly soluble in water, with density increasing as halogen size increases.

Special compounds include chloroform (CHCl₃), carbon tetrachloride (CCl₄), chloropicrin (tear gas), and DDT (pesticide). The haloform test is used to identify methyl ketones and alcohols with –CH₃CO groups. Overall, this chapter highlights the synthetic methods, reactivity trends, and industrial importance of haloalkanes and haloarenes.