11.15 Preparation of Alkenylbenzenes

11.1511.15

Preparation of AlkenylbenzenesPreparation of Alkenylbenzenes

dehydrogenationdehydrogenation

dehydrationdehydration

dehydrohalogenationdehydrohalogenation

industrial preparation of styreneindustrial preparation of styrene

11,800,000,000 lbs. produced in U.S. in 1999.11,800,000,000 lbs. produced in U.S. in 1999.

DehydrogenationDehydrogenation

CHCH22CHCH33630°C630°C

ZnOZnO

CHCH22CHCH

+ H+ H22

Acid-Catalyzed Dehydration of Acid-Catalyzed Dehydration of Benzylic AlcoholsBenzylic Alcohols

KHSOKHSO44

heatheat

(80-82%)(80-82%)

CHCH22CHCHCHCHCHCH33

OHOH

ClCl ClCl

++ HH22OO

Acid-Catalyzed Dehydration of Acid-Catalyzed Dehydration of Benzylic AlcoholsBenzylic Alcohols

KHSOKHSO44

heatheat(80-82%)(80-82%)

CHCH22CHCHCHCHCHCH33

OHOH

ClCl ClCl

CHCHCHCH33

ClCl

++

DehydrohalogenationDehydrohalogenation

NaOCHNaOCH22CHCH33 ethanol, 50°Cethanol, 50°C

(99%)(99%)

HH33CC CHCH22CHCHCHCH33

BrBr

CHCHHH33CC

CHCHCHCH33

hydrogenationhydrogenation

halogenationhalogenation

addition of hydrogen halidesaddition of hydrogen halides

11.1611.16Addition Reactions of AlkenylbenzenesAddition Reactions of Alkenylbenzenes

HydrogenationHydrogenation

HH22

PtPt

(92%)(92%)

BrBr

CC

CHCH33

CHCHCHCH33

BrBr

CHCHCHCH22CHCH33

CHCH33

HalogenationHalogenation

CHCH22CHCH

BrBr22

CHCH22CHCH

BrBrBrBr

(82%)(82%)

Addition of Hydrogen HalidesAddition of Hydrogen Halides

HClHCl

(75-84%)(75-84%)

ClCl

Addition of Hydrogen HalidesAddition of Hydrogen Halides

HClHCl

via benzylic carbocationvia benzylic carbocation

ClCl

++

Free-Radical Addition of HBrFree-Radical Addition of HBr

CHCH22CHCH

CHCH22CHCH22BrBrHBrHBr

peroxidesperoxides

Free-Radical Addition of HBrFree-Radical Addition of HBr

CHCH22CHCH

CHCH22CHCH22BrBrHBrHBr

peroxidesperoxides

via benzylic radicalvia benzylic radical

CHCH22BrBrCHCH••

11.1711.17Polymerization of StyrenePolymerization of Styrene

Polymerization of StyrenePolymerization of Styrene

HH22CC CHCHCC66HH55

CHCH22 CHCH

CC66HH55

CHCH22 CHCH

CC66HH55

CHCH22 CHCH

CC66HH55

polystyrenepolystyrene

MechanismMechanism

RORO•••• ••••

HH22CC CHCHCC66HH55

••

MechanismMechanism

HH22CC CHCHCC66HH55

RORO•••• ••••

••

MechanismMechanism

HH22CC CHCHCC66HH55

RORO•••• ••••

HH22CC CHCHCC66HH55

••

MechanismMechanism

HH22CC CHCHCC66HH55

RORO•••• ••••

HH22CC CHCHCC66HH55

••

MechanismMechanism

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

RORO•••• ••••

••

MechanismMechanism

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

RORO•••• ••••

HH22CC CHCHCC66HH55

••

MechanismMechanism

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

RORO•••• ••••

HH22CC CHCHCC66HH55

••

MechanismMechanism

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

RORO•••• ••••

••

MechanismMechanism

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

RORO•••• ••••

••

MechanismMechanism

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

HH22CC CHCHCC66HH55

RORO•••• ••••

••