Organic Chemistry,7th Edition L.G.Wade,Jr. Chapter 6 Alkyl Halides:Nucleophilic Substitution and Elimination Copyright 2010 Pearson Education,Inc
Chapter 6 Organic Chemistry, 7th Edition L. G. Wade, Jr. Alkyl Halides: Nucleophilic Substitution and Elimination Copyright © 2010 Pearson Education, Inc
Classes of Halides HH Alkyl halides:Halogen, H-C一C-Br X,is directly bonded to HH sp3 carbon. alkyl halide ·Vinyl halides:Xis H H bonded to sp2 carbon of C=C H CI alkene. vinyl halide ·Aryl halides:Xis bonded to sp2 carbon on benzene ring. aryl halide Chapter 6 2
Chapter 6 2 Classes of Halides • Alkyl halides: Halogen, X, is directly bonded to sp3 carbon. • Vinyl halides: X is bonded to sp2 carbon of alkene. • Aryl halides: X is bonded to sp2 carbon on benzene ring. C C H H H Cl vinyl halide C H H H C H H Br alkyl halide I aryl halide
Polarity and Reactivity H 6+ -CI chloromethane chloromethane Halogens are more electronegative than C. Carbon-halogen bond is polar,so carbon has partial positive charge. Carbon can be attacked by a nucleophile. Halogen can leave with the electron pair. Chapter6 3
Chapter 6 3 Polarity and Reactivity • Halogens are more electronegative than C. • Carbon—halogen bond is polar, so carbon has partial positive charge. • Carbon can be attacked by a nucleophile. • Halogen can leave with the electron pair
IUPAC Nomenclature 。Name as haloalkane. Choose the longest carbon chain,even if the halogen is not bonded to any of those C's. Use lowest possible numbers for position. 12 CI CH2CH2F HgHgHH CH3CH2CH2CHCH2CH2CH3 1234567 2-chlorobutane 4-(2-fluoroethyl)heptane Chapter6 4
Chapter 6 4 IUPAC Nomenclature • Name as haloalkane. • Choose the longest carbon chain, even if the halogen is not bonded to any of those C’s. • Use lowest possible numbers for position. CH3CH2CH2CHCH2CH2CH3 CH2CH2 F 1 2 3 4 2-chlorobutane 4-(2-fluoroethyl)heptane 1 2 3 4 5 6 7 1 2 CH3CHCH2CH3 Cl
Examples CH3 Br CH3CHCH2CH2CH2CHCH2CH2CH3 123456789 Br 6-bromo-2-methylnonane H 3 F H cis-1-bromo-3-fluorocyclohexane Chapter6 5
Chapter 6 5 Examples CH3CHCH2CH2CH2CHCH2CH2CH3 CH3 Br Br F H H 1 2 3 4 5 6 7 8 9 6-bromo-2-methylnonane 1 3 cis-1-bromo-3-fluorocyclohexane
Systematic Common Names The alkyl groups is a substituent on halide. Useful only for small alkyl groups. CH3 CH3 CH3 CH3CHCH2-Br CH3CH2CH-Br CH3C-Br CH3 iso-butyl bromide sec-butyl bromide tert-butyl bromide Chapter 6 6
Chapter 6 6 Systematic Common Names • The alkyl groups is a substituent on halide. • Useful only for small alkyl groups. CH3CHCH2 CH3 Br CH3CH2CH CH3 Br CH3C CH3 Br CH3 iso-butyl bromide sec-butyl bromide tert-butyl bromide
Common Names of Halides 。 CH2X2 called methylene halide. CHX3 is a haloform. 。 CX is carbon tetrahalide. Common halogenated solvents: CH2Cl2 is methylene chloride CHCla is chloroform CCl,is carbon tetrachloride. Chapter6 7
Chapter 6 7 Common Names of Halides • CH2X2 called methylene halide. • CHX3 is a haloform. • CX4 is carbon tetrahalide. • Common halogenated solvents: CH2Cl2 is methylene chloride CHCl3 is chloroform CCl4 is carbon tetrachloride
Alkyl Halides Classification Methyl halides:halide is attached to a methyl group. Primary alkyl halide:carbon to which halogen is bonded is attached to only one other carbon. Secondary alkyl halide carbon to which halogen is bonded is attached to two other carbons. 。 Tertiary alkyl halide carbon to which halogen is bonded is attached to three other carbon. Chapter 6 8
Chapter 6 8 Alkyl Halides Classification • Methyl halides: halide is attached to a methyl group. • Primary alkyl halide: carbon to which halogen is bonded is attached to only one other carbon. • Secondary alkyl halide : carbon to which halogen is bonded is attached to two other carbons. • Tertiary alkyl halide : carbon to which halogen is bonded is attached to three other carbon
Primary,Secondary,Tertiary Alkyl Halides CH3 CH3 CH3CHCH2-Br CH3CH2CH-Br primary alkyl halide secondary alkyl halide CH3 CH3C*-Br CH3 tertiary alkyl halide Chapter 6 9
Chapter 6 9 primary alkyl halide secondary alkyl halide tertiary alkyl halide Primary, Secondary, Tertiary Alkyl Halides CH3 CHCH2 CH3 Br CH3 CH2 CH CH3 Br CH3 C CH3 Br CH3 * * *
Types of Dihalides 。Geminal dihalide: Br two halogen atoms CH3-CH-Br are bonded to the same carbon. geminal dihalide ·Vicinal dihalide: two halogen atoms Br-CH2CH2-Br are bonded to adjacent carbons. vicinal dihalide Chapter 6 10
Chapter 6 10 Types of Dihalides • Geminal dihalide: two halogen atoms are bonded to the same carbon. • Vicinal dihalide: two halogen atoms are bonded to adjacent carbons. CH3 CH Br Br Br CH2 CH2 Br geminal dihalide vicinal dihalide