Chemistry 2100

Lecture 2

Alkynes and Alkenesalkene (olefins): CnH2n

alkyne (acetylenes): CnH2n-2 CC

H

HH

H HCCH

Ethene EthyneEthylene 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 -eneene 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 the C=C.

CH2CCH3 CH

CH2

CH3

Br CH3 C C C CH3

CH3

CH3

Constitutional

IsomersStereoisomers ConformationalIsomers

GeometricIsomersEnantiomers Diastereomers

single bond rotation

chiral achiral

sameconnections

differentconnections

notmirrorimages

mirrorimages

Isomers

Alkene Isomerism

C=CH3C

H H

HC=C

H3C

H CH3

Htrans-2-Butene

mp -106°C, bp 1°Ccis-2-Butene

mp -139°C, bp 4°C C C

H H

CH3 CH3

C C

CH3 H

H CH3

CH3CH2

CH3CH2

3-methyl-cis-2-pentene3-methyl-trans-2-pentene

2-methyl-2-pentene

C C

CH3 H

CH3 CH2CH3

Conjugation

-carotene

-carotene

[O]

-carotene

2

[O]

Vitamin A

CH2OH

Vitamin A

CH2OH

trans-retinal

[O]

CHO

Vitamin A

CH2OH

trans-retinal

[O]

CHO

Vitamin A

CH2OH

trans-retinal

[O]

CHO

Vitamin A

CH2OH

trans-retinal

11-cis-retinal

isomerization

CHO

[O]

CHO

Vitamin A

CH2OH

C O

H

H2N

opsin

C O

H

H2N

opsin

C O

H

H2N

opsin

C O

H (- H2O)

H2N

rhodopsin

opsin

C O

H C N

H

(- H2O)

metarhodopsin

rhodopsin

C N

H

C

H

N

h

metarhodopsin

rhodopsin

C N

H

C

H

N

h

metarhodopsin

rhodopsin

C N

H

C

H

N

h

neuralimpulse

metarhodopsin

rhodopsin

C N

H

trans-retinal

11-cis-retinal

neural

impulse

metarhodopsin

C

H

N H2O

C

H

O

+

trans-retinal

11-cis-retinal

neural

impulse

metarhodopsin

C

H

N C

H

O

+

H2O

trans-retinal

11-cis-retinal

neural

impulse

metarhodopsin

C

H

N C

H

O

+

H2O

H2N

opsintrans-retinal

11-cis-retinal

neural

impulse

metarhodopsin

C

H

N C

H

O

+

H2O

H2N

opsintrans-retinal

11-cis-retinal

neural

impulse

metarhodopsin

C

H

N C

H

O

+

H2O

Terpenes – natural polyenes isoprene

(2-methyl-1,3-butadiene)

CH3

CHCCH2 CH2

limonene(orange, dill)

myrcene(bay)

geraniol(rose)

menthol(mint)

carvone(spearmint, dill)

OH

OH

O

zingiberene

(ginger)

-selinene(celery)

caryophyllene(cloves)

CH2PPOCH2 OPP +

squalene

squalene

O2

cholesterol

~25 steps

HO

lanosterol

HO

Making Alkenes B""A

B

CC

A

+CC

tetra tri di mono

CC

R

RR

R>

'''

'''

CC

R

HR

R>

'''

CCH

HR

R>

'

CCH

HR

H

Reactions of Alkenes C C

BA

+ BACC

Hydrogenation

(cis or trans)

CH3

CH3 CH CH2CH3 CH3CH CHCH2CH3 Pt

H2 CH3CH2 CH2CH2CH3

CH3

CCH2 CH2CH3

CH3

CHCH3CCH3orPt

H2

Partially Hydrogenated Vegetable Oil

"partially hydrogenated vegetable oil"

+

COOH

COOH

COOH

H2 catalyst

• •

Halogenation C C

H

+ Br2 C C

Br

BrH+

CH2Cl2

RT

∆ / h

C C

BrBr

Br2CC +

CH2Cl2

Cl2

Cl

Cl

CH3CH3

Acid Addition

CH2Cl2

H ClCHCH3CH3CH + CHCH3

Cl

CH3CH

H

CH3CH

Cl

CHCH3

H

minor major

H BrCH2CH3CH2CH + +CH2CH3CH2CH

BrH

CH2CH3CH2CH

HBr

H2SO4

H2SO4

H OH CH3 CH2 OHCH2 CH2 +

CH2 + H OHCH3

OH

Polymerization

Z = CH3 polypropyleneZ = Cl PVCZ = CN polyacrylonitrileZ = OH polyvinyl alcohol

polypropylenePVCpolyacrylonitrilepolyvinyl alcohol

CH2 CH

Z

n CH2CHCH2CHCH2CH CH2CH

Z Z Z Z

Polymers & Health

Pthalate, plasticizerBisphenol A = hard shell plastic