Ch 6 - alkyl halides

Ch 6 - Alkyl Halides
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Unformatted text preview: 6 Al kyl Halides: N ucleoph i l Ic Su bstitutIon and E l i m i aTIo 6-1 I ntrod uction 212 Our study of organic chemIstry Is organized Into famlies of compounds classiFed by theIr functional groups. n this chapter, we consIder the propertIes and reactions of alkyL halIdes We use theIr reactions to Introduce substItution and elImInatIon two of the most important types of reactions In organIc chemistry Stereochemistry (Chapter 5) wiL pay a major roe In our study of these reactIons. Many other reactions show sImI- larItIes to substItution and elImination, and the techniques Introduced in thIs chapter wIll be used throughout our study of organic reactions There are three major classes of organohaogen compounds: the akyL haides the vInyl halIdes and the aryl halIdes An alkyl halide sImply has a haogen ato bonded to one of the sp 3 hybrid carbon atoms of an alkyl group A vinyl halide has a haLogen atom bonded to one of the sp 2 hybrId carbon atoms of an alkene An aryl halide has a halogen atom bonded to one of the sp 2 hybrId carbon atoms of an aromatIc Ring The chemistry of vInyl haLides and Ryl halIdes Is dierent from that of alkyl haides because their bondIng and hybrIdIzation are dierent We consIder the reactions of vinyl haides and aryL halIdes in ater chapters. The sructures of some representatIve aky halides, vInyl halIdes, and aryl halIdes are shown here with theIr most common names and uses. Alkyl haLideS CHCl3 CHC2 CC3 CH3 C3 CHClBr chlorofoRm Freon-22 1 , 1 Ltrichoroethane Haothane solvent refrIgeraNt cleaNIg fl uId noNflammable anesthetIc VinYl halides C \ / H " / C=C C=C ' H H ' vINyl chlorIde monomer for poly( v nyl chorIde) tetrafluoroethylene TFE) moNome or Teflon Arl halideS ( C C PAAdIchoroBenzene mothBalls h NH H- _ y ' CH HCOOH thyroxIne thyrod hormone 6-2 N o m e n c lat ur e of ALkyL H ali des 213 H ,8+ 8- H " IC-Cl , H chlOrOmethane EPM OF chlOrOmethane The carbonhaLogen bond n an aLKyl hade s polar because halogen atoms are more eLectronegatve than carbon atoms. Most reactons of alKyl haLdes resuLt from breaKng ths poarzed bond The eLectrostatc potentaL map of chloromethane (Fgure 6-1) shows hgher electron densty red) around the chLorne atom and reLa tvely low electron densty (blue) around the carbon and hydrogen atoms. The carbon atom has a partaL postve charge, maKng t somewhat eLectrophLc A nucleophle can attacK ths electrophLc carbon, or the haLogen atom can eave as a halde on taK ng the bondng par of electrons wth t By servng as a Leavng group the haLogen can be elmnated fro the alKyl halde, or t can be repLaced (substtuted for) by a wde varety of functonal groups. Ths versatLty allows alKyl haLdes to serve as nteredates n the synthess of many other functona groups ...
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