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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 (