Students can go through AP Inter 2nd Year Chemistry Notes 11th Lesson Haloalkanes and Haloarenes will help students in revising the entire concepts quickly.
AP Inter 2nd Year Chemistry Notes 11th Lesson Haloalkanes and Haloarenes
→ Haloalkanes (or) Haloarenes are formed by-the replacement of hydrogen atom (s) in a hydrocarbon by halogen atom (s).
→ Haloalkanes contain halogen (s) attached to sp3 – hybridised carbon where as in haloarenes halogen (s) attached to sp2 – hybridised carbon.
→ On the basis of number of halogen atoms halo alkanes (or) halo arenes classified as mono halo alkane/arene, Dihaloalkane/arene, Trihaloalkane/arene.
→ Comppunds containing sp3 C – X bond are (a) Alkyl halides (b) Allylic halides (c) Benzylic halides.
→ Compounds containing sp2 C – X bond are (a) Vinylic halides (b) Aryl halides.
→ The carbon-halogen bond of alkyl halide is polarised due to high electronegativity of halogen atoms than carbon.
→ Alcohols undergo treatment with HX/ZnCl2 (or) PX3 (or) PX5 (or) SOCl2 to form alkyl halides.
→ Alkyl halides arylhalides are prepared by
- free radical halogenation
- Electrophillic substitution
- Sandmeyer’s reaction
- The addition of hydrogen halide or halogens toalkenes.
→ The boiling points of alkyl halides decrease in the order RI > RBr > RCl > RF.
→ Due to polar nature of C-X bond haloalkanes under go Nucleo phillic substitution reactions 1) SN2-Reactions ii) SN1-reactions.
→ The order of reactivity of alkyl halides in SN2-reactions as follows 1°-alkyl halide > 2°-alkyl halide > 3°-alkyl halide.
→ The order of reactivity of alkyl halides in SN1-reactions as follows 3°-alkyl halides > 2°-alkyl halides > 1°-alkyl halides.
→ SN2-mechanism results in the formation of inversion configurated product where as SN1– mechanism results in the formation of racemised product.
→ Alkyl halides undergo elimination reaction with alc.KOH to form preferred product alkene. This is called dehydro halogenation reaction.
→ Alkyl halides react with certain metals to form C-metal bonds containing compounds which are known as organometallic compounds.
Eg.: Grignard reagent (RMgX).
→ Halo arenes undergo nucleophillic substitution, electrophilic substitution reactions.
→ Alkyl halides and aryl halides mixed in presence of Na and dry ether forms alkyl arene. This is called Wurtz-Fitting reaction. If only aryl halides are mixed then the reaction is called Fitting reaction.
→ Poly halogen compounds mostly useful in industry and agriculture. Some examples of poly halogen compounds are CH2Cl2, CHCl3, CHI3, DDT, Freons, CCl4.