Organic Chemistry, 5th Edition L.G. Wade. jr Chapter 6 Alkyl Halides: Nucleophilic Substitution and elimination Jo blackburn Richland college, dallas TX Dallas County Community College District c 2003. Prentice hall
Chapter 6 Alkyl Halides: Nucleophilic Substitution and Elimination Organic Chemistry, 5th Edition L. G. Wade, Jr. Jo Blackburn Richland College, Dallas, TX Dallas County Community College District © 2003, Prentice Hall
Classes of halides Alkyl: Halogen, X, is directly bonded to sp3 carbon Vinyl: X is bonded to sp carbon of alkene Aryl: X is bonded to sp2 carbon on benzene ring. EXamples HH H-C-C-Br HH alkyl halide vinyl halide arvi halide Chapter 6
Chapter 6 2 Classes of Halides • Alkyl: Halogen, X, is directly bonded to sp3 carbon. • Vinyl: X is bonded to sp2 carbon of alkene. • Aryl: X is bonded to sp2 carbon on benzene ring. Examples: C H H H C H H Br alkyl halide C C H H H Cl vinyl halide I aryl halide =>
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 > 6+ h-C-Br Chapter 6
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. => C H H H Br + -
Classes of Alkyl Halides Methyl halides: only one C, CH3X Primary: C to which X is bonded has only one C-c bond Secondary: C to which X is bonded has two c-c bonds Tertiary: C to which X is bonded has three c-c bonds Chapter 6
Chapter 6 4 Classes of Alkyl Halides • Methyl halides: only one C, CH3X • Primary: C to which X is bonded has only one C-C bond. • Secondary: C to which X is bonded has two C-C bonds. • Tertiary: C to which X is bonded has three C-C bonds. =>
Classify These CH3--CH-CH3 CH3 CHF (CH3)3 CBr CH3I Chapter 6
Chapter 6 5 Classify These: CH3 CH CH3 Cl CH3 CH2 F (CH3) 3 CBr CH3 I =>
Dihalides Geminal dihalide: two halogen atoms are bonded to the same carbon Vicinal dihalide: two halogen atoms are bonded to adjacent carbons <Br H-C--C-Br Br h geminal dihalide vicinal dihalide Chapter 6
Chapter 6 6 Dihalides • Geminal dihalide: two halogen atoms are bonded to the same carbon • Vicinal dihalide: two halogen atoms are bonded to adjacent carbons. C H H H C H Br Br geminal dihalide C H H Br C H H Br vicinal dihalide =>
IUPAC Nomenclature Name as haloalkane Choose the longest carbon chain even if the halogen is not bonded to any of those cs Use lowest possible numbers for position CH3--CH-CH2CH3 CH, CH,Br CH3(CH2hcH(Ch2)2 CH3 2-chloro butane 4(2-bromoethyDheptane Chapter 6
Chapter 6 7 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. CH3 CH CH2 CH3 Cl CH3 (CH2 ) 2 CH(CH2 ) 2 CH3 CH2 CH2 Br 2-chlorobutane 4-(2-bromoethyl)heptane=>
Systematic Common Names Name as alkyl halide Useful only for small alkyl groups Name these (CH3)3 CBr CH3-CH-CH2 CH3 CH CH3-CH-CHF =7 Chapter 6
Chapter 6 8 Systematic Common Names • Name as alkyl halide. • Useful only for small alkyl groups. • Name these: CH3 CH CH2 CH3 Cl (CH3) 3 CBr CH3 CH CH3 CH2 F =>
Trivia” Names CH2X2 called methylene halide CHX is a haloform CX4 is carbon tetrahalide EXamples CH2 Cl2 is methylene chloride CHCl is chloroform >CCL is carbon tetrachloride Chapter 6
Chapter 6 9 “Trivial” Names • CH2X2 called methylene halide. • CHX3 is a haloform. • CX4 is carbon tetrahalide. • Examples: ➢CH2Cl2 is methylene chloride ➢CHCl3 is chloroform ➢CCl4 is carbon tetrachloride. =>
Uses of alkyl Halides Solvents-degreasers and dry cleaning fluid Reagents for synthesis of other compounds Anesthetic: Halothane is CFrCHciBr CHCI3 used originally(toxic and carcinogenic) Freons. chlorofluorocarbons or cfcs > Freon 12, CF2 Cl2, now replaced with Freon 22 CF,CHCI, not as harmful to ozone layer Pesticides -ddt banned in U.S Chapter 6 10
Chapter 6 10 Uses of Alkyl Halides • Solvents - degreasers and dry cleaning fluid • Reagents for synthesis of other compounds • Anesthetic: Halothane is CF3CHClBr ➢CHCl3 used originally (toxic and carcinogenic) • Freons, chlorofluorocarbons or CFC’s ➢Freon 12, CF2Cl2 , now replaced with Freon 22, CF2CHCl, not as harmful to ozone layer. • Pesticides - DDT banned in U.S. =>