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Chemistry 2100
Lecture 2
Alkynes and Alkenes
alkene (olefins): CnH2n
alkyne (acetylenes): CnH2n-2
H
H
C C
H
H
H C C H
Ethene
Ethyne
Ethylene
Acetylene
Naming Alkenes and Alkynes
• Parent name is that of the longest chain that contains
the C=C or C≡C.
• Number the chain from the end that gives the lower
numbers to the carbons of the C=C or C≡C.
• Locate the C=C or C≡C by the number of its first
carbon.
• Use -ene to show C=C, -yne for C≡C.
• For cycloalkenes:
– Number ring carbons to give carbon 1 and 2 to the C=C
bond.
– Because of this convention, no need to specify the number of
CH3
theBrC=C.
CH 3
CH
C CH 2
CH 2
CH 3
CH3
C
C C CH3
CH3
Alkene Isomerism
H
H
H
C=C
CH3
C=C
H3 C
H3 C
H
cis-2-Buten e
mp -139°C, bp 4°C
H
t rans-2-Bu ten e
mp -106°C, b p 1°C
CH 3CHH
2
CH 3
H
C
C C
CH 3
CH 3CH
H2
CH 3
CH3
C
CH 3
3-methyl-cis-2-pentene
3-methyl-trans-2-pentene
H
C C
CH3
H
CH2 CH3
2-methyl-2-pentene
Conjugation
-carotene
-carotene
[ O]
-carotene
[ O]
CH2OH
2
Vitamin A
CH2OH
Vitamin A
CH2OH
Vitamin A
[ O]
CHO
trans-retinal
CH2OH
Vitamin A
[ O]
CHO
trans-retinal
CH2OH
Vitamin A
[ O]
CHO
trans-retinal
CH2OH
Vitamin A
[ O]
CHO
trans-retinal
iso me ri z at ion
11-cis-retinal
CHO
C O
H
C O
H
H2N
opsin
C O
H
H2N
opsin
C O
H
H2N
opsin
(- H2O)
C O
H
H2N
opsin
(- H2O)
C N
H
rhodopsin
C N
H
rhodopsin
metarhodopsin
C N
H
rhodopsin
h
C N
H
metarhodopsin
C N
H
rhodopsin
h
C N
H
metarhodopsin
C N
H
rhodopsin
h
C N
H
neural
impulse
metarhodopsin
C N
H
neural
impulse
metarhodopsin
H2O
+
11-cis-retinal
trans-retinal
C O
H
C N
H
neural
impulse
metarhodopsin
H2O
+
11-cis-retinal
trans-retinal
C O
H
C N
H
neural
impulse
metarhodopsin
H2O
+
11-cis-retinal
trans-retinal
C O
H
C N
H
neural
impulse
metarhodopsin
H2N
H2O
+
11-cis-retinal
trans-retinal
C O
H
opsin
C N
H
neural
impulse
metarhodopsin
H2N
H2O
+
11-cis-retinal
trans-retinal
C O
H
opsin
Terpenes – natural polyenes
CH3
CH2
C CH
CH2
isoprene
(2-methyl-1,3-butadiene)
O
OH
OH
myrcene
(bay)
zingiberene
(ginger)
geraniol
(rose)
limonene
(orange, dill)
-selinene
(celery)
menthol
(mint)
carvone
(spearmint, dill)
caryophyllene
(cloves)
CH2
OPP
+
PPO
squalene
CH2
O2
squalene
~25 steps
HO
lanosterol
HO
cholesterol
Making Alkenes
R'
C
C
A
B
R'
R ''
C
C
tetra
C
>
R '''
R
C C
R ''
C
R
tri
R'
>
H
+
C
"A
H
H
C
R
H
C
>
H
di
B"
C
R
H
mono
H2
Reactions of Alkenes
C C
+
A
B
C
C
A
B
Hydrogenation
CH3
C
CH2 CH3
CH3
or
CH3
C
CHCH 3
CH3CH CHCH2CH3
(cis or trans)
H2
Pt
H2
Pt
CH 3
CH 3
CH
CH3 CH2
CH2 CH 3
CH2 CH2 CH3
Partially Hydrogenated Vegetable Oil
H2 catalyst
• +•
"partially hydrogenated vegetable oil"
COOH
COOH
COOH
Halogenation
C C
+
Br2
CH2Cl2
RT
C
C
Br Br
C
C
+
Br2
∆ / h
H
C
C
Br
CH3
CH3
Cl2
Cl
CH2Cl2
Cl
+
H Br
Acid Addition
H
CH3CH
CHCH3
+
H Cl
CH2Cl2
Cl
CH3CH CHCH3
H
CH3CH2CH
CH2
+
H Br
Cl
CH3CH2CH
CH3CH CHCH3
Br
CH2
Br
+
CH3CH2CH
minor
CH2
CH2
CH2
+
+
H OH
H OH
H2SO4
H2SO4
H
major
CH3
CH2
CH3
OH
OH
H
CH2
Polymerization
n CH2
CH
CH2CH
Z
Z
Z
Z
Z
Z
=
=
=
=
CH3
Cl
CN
OH
CH2CH
CH2 CH
Z
polypropylene
polypropylene
PVC
PVC
polyacrylonitrile
polyacrylonitrile
polyvinyl
polyvinylalcohol
alcohol
Z
CH2 CH
Z
Polymers & Health
Bisphenol A = hard shell plastic
Pthalate, plasticizer