Chem 2412 Lecture 01
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Transcript of Chem 2412 Lecture 01
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John E. McMurry
www.cengage.com/chemistry/mcmurry
Paul D. Adams University of Arkansas
Chapter 10
Organohalides
http://www.cengage.com/chemistry/mcmurryhttp://www.cengage.com/chemistry/mcmurryhttp://www.cengage.com/chemistry/mcmurry -
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An organic compound containing at least onecarbon-halogen bond (C-X)
X (! Cl! "r! #) replaces $
Can contain many C-X bonds
%roperties and some uses
ire-resistant sol&ents
'erigerants
%harmaceuticals and precursors
hat #s an Organohalide*
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'eactions in&ol&ing organohalides are lessre+uently encountered than other organic
compounds! but reactions such as
nucleophilic substitutions/eliminations thatthey undergo will be encountered
Al,yl halide chemistry is model or
mechanistically similar but more comple
reactions
hy this Chapter*
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ind longest chain! name it as parent chain
(Contains double or triple bond i present)
umber rom end nearest any substituent (al,yl
or halogen)
10.1 aming Al,yl $alides
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"egin at the end nearer the substituent ha&ing itsname irst in the alphabet
aming i wo $alides or Al,yl Are
+ually istant rom nds o Chain
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C-X bond is longer as you go down periodic table C-X bond is wea,er as you go down periodic table C-X bond is polari2ed with slight positi&e charge on
carbon and slight negati&e charge on halogen
10.1 3tructure o Al,yl $alides
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Al,yl halide romaddition o $Cl!$"r! $# toal,anes
10.4 %reparing Al,yl $alides rom
Al,anes5 'adical $alogenation
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Al,ane 6 Cl4or "r4! heat or light replaces C-$ with C-X butgi&es mitures $ard to control 7ia ree radical mechanism
#t is usually not a good idea to plan a synthesis that usesthis method
%reparing Al,yl $alides rom
Al,anes5 'adical $alogenation
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# there is more than one type o hydrogen in an al,ane!reactions a&or replacing the hydrogen at the most highlysubstituted carbons (not absolute)
'adical $alogenation o Al,anes
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"ased on +uantitati&e analysis o reaction products! relati&ereacti&ity is estimated
Order parallels stability o radicals 'eaction distinction is more selecti&e with bromine than
chlorine
'elati&e 'eacti&ity
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Chlorination &s. "romination
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-bromosuccinimide ("3) selecti&ely brominates allylicpositions (due to lower resulting rom resonance)
'e+uires light or acti&ation
A source o dilute bromine atoms
10.8 %reparing Al,yl $alides rom
Al,enes5 Allylic "romination
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Allyl radical is delocali2ed 9ore stable than typical al,yl radical by :0 ,;/mol (