Transcript 11.15 Preparation of Alkenylbenzenes dehydrogenation dehydration

11.15
Preparation of Alkenylbenzenes
dehydrogenation
dehydration
dehydrohalogenation
Dehydrogenation
industrial preparation of styrene
11,800,000,000 lbs. produced in U.S. in 1999.
CH2CH3
630°C
ZnO
CH
+ H2
CH2
Acid-Catalyzed Dehydration of
Benzylic Alcohols
Cl
Cl
KHSO4
CHCH3
OH
CH
heat
CH2
+ H2O
(80-82%)
Acid-Catalyzed Dehydration of
Benzylic Alcohols
Cl
Cl
KHSO4
CH
CHCH3
heat
CH2
(80-82%)
OH
Cl
CHCH3
+
Dehydrohalogenation
CH2CHCH3
H3C
Br
NaOCH2CH3
ethanol, 50°C
CH
H3C
(99%)
CHCH3
11.16
Addition Reactions of Alkenylbenzenes
hydrogenation
halogenation
addition of hydrogen halides
Hydrogenation
CH3
C
CH3
CHCH2CH3
CHCH3
H2
Pt
Br
Br
(92%)
Halogenation
Br2
CH
CH2
CH
CH2
Br
Br
(82%)
Addition of Hydrogen Halides
Cl
HCl
(75-84%)
Addition of Hydrogen Halides
Cl
HCl
+
via benzylic carbocation
Free-Radical Addition of HBr
HBr
CH
CH2CH2Br
CH2
peroxides
Free-Radical Addition of HBr
HBr
CH
CH2CH2Br
CH2
peroxides
CH
•
CH2Br
via benzylic radical
11.17
Polymerization of Styrene
Polymerization of Styrene
H2C
CH2
CH
C6H5
CH2
CHC6H5
CH
C6H5
polystyrene
CH2
CH
C6H5
Mechanism
•• •
RO •
•
H2C
CHC6H5
Mechanism
•• •
RO •
H2C
CHC6H5
•
Mechanism
•• •
RO •
H2C
CHC6H5
•
H2C
CHC6H5
Mechanism
•• •
RO •
H2C
CHC6H5
•
H2C
CHC6H5
Mechanism
•• •
RO •
H2C
CHC6H5
H2C
CHC6H5
•
Mechanism
•• •
RO •
H2C
CHC6H5
H2C
CHC6H5
•
H2 C
CHC6H5
Mechanism
•• •
RO •
H2C
CHC6H5
H2C
CHC6H5
•
H2 C
CHC6H5
Mechanism
•• •
RO •
H2C
CHC6H5
H2C
CHC6H5
H2C
CHC6H5
•
Mechanism
•• •
RO •
H2C
CHC6H5
H2C
CHC6H5
H2C
CHC6H5
•
H2C
CHC6H5
Mechanism
•• •
RO •
H2C
CHC6H5
H2C
CHC6H5
H2C
CHC6H5
•
H2C
CHC6H5