r. susanti benzene

7/31/2019 r. Susanti Benzene

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Aromaticity

hydrocarbons

aliphatic aromatic

alkanes alkenes alkynes


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Aliphatic compounds: open-chain compounds andring compounds that are chemically similar to open-chain compounds. Alkanes, alkenes, alkynes, dienes,alicyclics, etc.

Aromatic compounds: unsaturated ring compoundsthat are far more stable than they should be and resistthe addition reactions typical of unsaturated aliphaticcompounds. Benzene and related compounds.


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The structure of benzene


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All the chemistry they knew suggested that anysubstance with a double or triple bond would bevery reactive and react readily with HBr in the

dark.

Benzene did not, it was surprisinglyunreactive

This new hydrocarbon isolated by Michael Faradayin 1825

The molecular formula is C6H6 suggesting thatthe molecule contained a large number of doublebonds.


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Benzene. This aromatic hydrocarbon was firstdiscovered in 1825 but its structure was not

generally agreed upon until 1946

In 1865 after a dream about a snake biting itsown tale, Kekul suggested the following

structure for benzene


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Facts about benzene:

a) Formula = C6H6b) Isomer number:

one monosubstituted isomer C6H5Y

three disubstituted isomers C6H4Y2

c) Benzene resists addition reaction,undergoes substitution reactions.

d) From X-ray, all of the CC bonds inbenzene are the same length andintermediate in length between single and

double bonds.


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Benzene is a flatmolecule, with all atomsin the same plane, (bond

angle 120)

When the benzene ring isattached to an aliphatic

skeleton, it is called thephenyl group. The formulaof a phenyl group id C6H5.

Any compoundwhere the ratio ofC:H is about 1:1 islikely to contain a

benzene ring.


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ISOMER


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Reactions of benzene:

1. Nitration

C6H6 + HNO3 C6H5NO2 + H2O

2. Sulfonation

C6H6 + H2SO4 C6H5SO3H + H2O

3. Halogenation

C6H6 + X2 C6H5X + HX

4. Freidel-Crafts alkylation

C6H6 + RX C6H5R + HX

substitutions


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Hckels Rule

If the compound has a continuous ring of

overlappingp orbitals and has 4N+ 2

electrons, it is aromatic.

If the compound has a continuous ring of

overlappingp orbitals and has 4Nelectrons,

it is antiaromatic.

=>


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4n + 2 = 4

n = 0.5

not aromaticantiaromatic


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4n + 2 = 8

n = 1.5

nonplanar

nonaromatic


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4n + 2 = 10

n = 2


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Naming benzene molecules

1.2-dimethyl

benzene

1,3-dimethyl

benzene

1,4-dimethyl

benzene


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naftalen antracen fenantren tetracen

trifenilen piren krisen

Fused ring systems


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H

H H

H

H

HH

H

Naftalen

H

H H

HH

H

H

H

H

H

Antracen


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Fenantren

H

H H

H

H

H

H

HH

H

H

H

H

H

H

H

H

H

H

H

H H

Koronen


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Naftalen: nomenklature

monosubstitusi: - 1-- 2-

NO2

2-nitronaphthalene-nitronaphthalene

OH NH2 SO3H

-naphthol -naphthylamine -naphthalenesulfonic acid

also

2-nitronaftalen-nitronaftalen


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1-nitronaftalen

-nitronaftalen

1-bromnaftalen


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Common Names of

Benzene DerivativesOH OCH3NH2

CH3

phenol toluene aniline anisole

C

H

CH2 C

O

CH3C

O

H

C

O

OH

styrene acetophenone benzaldehyde benzoic acid

=>


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Mercedes Benzene


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Disubstituted Benzenes

The prefixes ortho-, meta-, and para- arecommonly used for the 1,2-, 1,3-, and 1,4-

positions, respectively.Br

Bro-dibromobenzene o

1,2-dibromobenzene

HO

NO2

p-nitrophenol or4-nitrophenol

=>


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Br

Br

NO2

Cl

CH3

Br

o-dibromobenzene m-chloronitrobenzene p-bromotoluene

1,2-dibromobenzene 3-chloro-1-nitrobenzene 4-bromotoluene

Br

Br

If more than two groups on the ring, use numbers!

BrNH

2Br

Br

Br

1,2,4-tribromobenzene 2,4,6-tribromoaniline


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3 or More Substituents

Use the smallest possible numbers, butthe carbon with a functional group is #1.

NO2

NO2

O2N

1,3,5-trinitrobenzen

NO2

NO2

O2N

OH

2,4,6-trinitrophenol

=>


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Common Names for

Disubstituted Benzenes

CH3

CH3

CH3

CH3H3C

CH3

CO OH

OH

H3Cm-xylene mesitylene o-toluic acid p-cresol

=>


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Chloro Methyl benzene

2,4,6-trichlorophenol

benzene-1,4-dicarboxylic aci

2-hydroxybenzoic acid

phenolphenylethanone

phenyl ethanoate

phenylamine

chlorobenzene

phenylethene

nitrobenzene

Benzoic acid

Methyl 3-nitrobenzoate


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Phenyl and Benzyl

Br

phenyl bromide

CH2Br

benzyl bromide

Phenyl indicates the benzene ringattachment. The benzyl group hasan additional carbon.


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r. susanti benzene

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