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AROMATIC SUBSTITUTION REACTIONS

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AROMATIC SUBSTITUTION REACTIONS . NOMENCLATURE. Learn Nomeclature Either on Your Own or Use the Organic Nomeclature Software. 1-bromo-3-nitrobenzene. methylbenzene. (toluene). 1-chloro-3-methylbenzene. 1,4-dimethylbenzene. SOME SPECIAL NAMES. toluene. aniline. anisole.

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Presentation Transcript
slide3

Learn Nomeclature Either on Your Own

or Use the Organic Nomeclature Software

1-bromo-3-nitrobenzene

methylbenzene

(toluene)

1-chloro-3-methylbenzene

1,4-dimethylbenzene

slide4

SOME SPECIAL NAMES

toluene

aniline

anisole

phenol

o-xylene

m-xylene

benzoic

acid

p-xylene

slide5

ortho, meta and para Positions

m-nitrotoluene

3-nitrotoluene

ipso

1

o-

ortho

6

2

1-methyl-3-nitrobenzene

meta

m-

5

3

4

para

p-dichlorobenzene

p-

1,4-dichlorobenzene

slide7
Compounds containing aromatic rings are often used in dyes, such as these for sale in a market in Nepal

Source: Getty Images

slide10

BENZENE RESONANCE

Review Sections 6.8 - 6.14

KEKULE

STRUCTURES

Resonance Energy = 36 Kcal / mole

All bonds are equivalent

The ring is symmetric.

Bond lengths are between a single and a double bond.

Very Stable

Less reactive than other groupings of atoms.

slide11

.

.

H

H

.

.

.

.

H

H

H

H

All 2p orbitals overlap equally.

slide12

BENZENE

Isodensity surfaces - electron potential mapped in color.

(van der Waal’s)

Highest

electron density

is red.

Color adjusted

to enhance the

pi system.

Note the symmetry.

slide13

BENZENE - DETERMINATION OF RESONANCE ENERGY

cyclohexatriene

(hypothetical)

benzene

RESONANCE

ENERGY

36 kcal/mol

cyclohexene

-49.8 kcal/mol

-85.8 kcal/mol

(calculated)

-28.6 kcal/mol

cyclohexane

slide15

The “Double Bonds” in a Benzene Ring Do Not React Like Others

Alkene

Benzene

no

reaction

+

+

no

reaction

+

+

no

reaction

+

+

no

reaction

+

+

slide16

Benzene is a Weak Base and Poor Nucleophile

Stronger

base

+

Readily donates electrons

to an electrophile.

alkene

+

Donation of electrons would

interrupt ring resonance

(36 kcal / mole).

Weaker

base

A strong electrophile is

required - and often a

catalyst.

benzene

slide17

Benzene Reactivity

Benzene requires a strong electrophile and a catalyst

…..and then it undergoes substitution reactions, not addition.

+

+

catalyst

substitution

compare:

+

no catalyst

addition

slide18

Some Substitution Reactions of Benzene

Halogenation

+

Friedel-Crafts

Alkylation

+

Friedel-Crafts

Acylation

+

-

+

+

Nitration

+

-

Sulfonation

+

alcohols and water
Alcohols and Water
  • alcohols are “monosubstituted” water, ROH, hydrocarbon radical, R, substituted for one of the hydrogen atoms in water, HOH
  • alcohols form hydrogen bonds to other alcohol molecules, increasing boiling point, and to water, making them very soluble in water
oxidation of alcohols
Oxidation of Alcohols

primary alcohol  aldehyde  carboxylic acids

RCH2OH  RCHO  RCOOH

secondary alcohols  ketones

RCHOHR’  RC=OR’

tertiary alcohols  No Reaction

ethanol is being tested in selected areas as a fuel for automobiles
Ethanol is being tested in selected areas as a fuel for automobiles

Source: AP/Wide World Photos

slide29

STRUCTURE

Aldehyde

Ketone

slide32

IUPAC Nomenclature of Ketones

  • Choose the longest continuous carbon chain that contains the carbonyl carbon
  • Number from the end of the chain closest to the carbonyl carbon
  • Ketone ending is -one

Do the ketonessection of Organic Nomenclature

program!

slide33

EXAMPLES

2-Pentanone

4-Ethyl-3-hexanone

slide34

3-Isopropylcyclopentanone

or 3-(1-Methylethyl)cyclopentanone

common or trivial names

KETONES

Common, or Trivial, Names
  • Name each group attached to the carbonyl group as an alkyl group
  • Combine into a name, according to the pattern:

alkyl alkyl’ ketone

NOTE: This is not all one word!

slide36

Example of Common Names

Methyl propyl ketone

Diethyl ketone

slide37

SPECIAL CASES

diphenyl ketone

dimethyl ketone

benzophenone

acetone

A common laboratory

solvent and cleaning

agent

methyl phenyl ketone

KNOW

THESE

acetophenone

slide38

IUPAC Nomenclature of Aldehydes

  • Choose the longest continuous carbon chain that contains the carbonyl carbon
  • Number from the end of the chain closest to the carbonyl carbon (carbon #1!)
  • Aldehyde ending is -al

Do the aldehydessection of Organic Nomenclature

program.

slide39

EXAMPLES

aldehyde group is

always carbon 1

pentanal

3

1

4

2

2-chloro-3-methylbutanal

slide40

RECOGNIZE

THESE

Common Names of the Aldehydes

slide41

SPECIAL CASES

formaldehyde

benzaldehyde

KNOW

THESE

acetaldehyde

computer generated space filling model of acetylsalicylic acid aspirin
Computer-generated space-filling model of acetylsalicylic acid (aspirin)

Source: Photo Researchers, Inc.

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