alkyl_halides - Alkyl halides Nucleophilic substitution and...

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© E.V. Blackburn, 2010 Alkyl halides Nucleophilic substitution and elimination reactions
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© E.V. Blackburn, 2010 Alkyl halides - industrial sources H C C H HCl HgCl 2 H 2 C=CHCl vinyl chloride H H H vinyl
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© E.V. Blackburn, 2010 Alkyl halides - industrial sources H C C H HCl HgCl 2 H 2 C=CHCl vinyl chloride H 2 C=CH 2 Cl 2 500 o H 2 C=CHCl CH 3 Cl + Hg 2 F 2 CH 3 F + Hg 2 Cl 2 CCl 4 + SbF 3 CCl 2 F 2 Freon-12
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© E.V. Blackburn, 2010 Preparation from alcohols R-OH HX or PX 3 R-X or SOCl 2 SOCl 2 - thionyl chloride RCH 2 OH + SOCl 2 RCH 2 Cl + HCl +SO 2
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© E.V. Blackburn, 2010 Halogenation of hydrocarbons R-H RX X 2 /h ν CH 3 CH 2 Br Br 2 h ν lachrymatory
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© E.V. Blackburn, 2010 Addition of HX to alkenes C C HX C C H X
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© E.V. Blackburn, 2010 C C X 2 C C X X C C 2X 2 C C X X X X Addition of halogens to alkenes and alkynes
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© E.V. Blackburn, 2010 R-X + NaI R-I + NaX acetone soluble insoluble Finkelstein reaction
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© E.V. Blackburn, 2010 Nucleophilic substitution reactions When bonded to a carbon, the halogen is easily displaced as a halide ion by stronger nucleophiles - it is a good leaving group . The typical reaction of alkyl halides is a nucleophilic substitution: R-X + Nu R-Nu + the leaving group X - The halide ion is the conjugate base of a strong acid. It is therefore a very weak base and little disposed to share its electrons.
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© E.V. Blackburn, 2010 Nucleophiles reagents that seek electron deficient centres negative ions or neutral molecules having at least one unshared pair of electrons C C H 3 C - + CH 3 -Br C C H 3 C CH 3 + Br - H 3 C H O + CH 3 -I H 3 C H O CH 3 + + I - nucleophile leaving group
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© E.V. Blackburn, 2010 Leaving groups a substituent that can leave as a weakly basic molecule or ion L L Nu Nu Nu + L: + Br Br NC NC CN - + Br - δ- δ- OH 2 Cl - OH 2 Cl Cl + H 2 O δ- δ+ + Br Br PH 3 P Ph 3 P + Br - δ+ δ- Ph 3 P: +
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© E.V. Blackburn, 2010 Nucleophilic substitution CH 3 Br + CH 3 OH + Br - OH - A knowledge of how reaction rates depend on reactant concentrations provides invaluable information about reaction mechanisms. What is known about this reaction?
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© E.V. Blackburn, 2010 Nucleophilic substitution rate = k[CH 3 Br][OH - ] CH 3 Br + CH 3 OH + Br - OH - rate α [CH 3 Br][OH - ] 0.002 M 1.0 M 6 x 10 -7 mol L -1 s -1 [CH 3 Br] I [OH - ] I initial rate 0.001 M 1.0 M 3 x 10 -7 mol L -1 s -1 0.002 M 2.0 M 1.2 x 10 -6 mol L -1 s - 1
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© E.V. Blackburn, 2010
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This note was uploaded on 04/27/2011 for the course CHEM 261 taught by Professor Drclive during the Spring '09 term at University of Alberta.

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alkyl_halides - Alkyl halides Nucleophilic substitution and...

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