AROMATIC SUBSTITUTIONAROMATIC SUBSTITUTION REACTIONS REACTIONS

NOMENCLATURENOMENCLATURE

Learn Nomeclature Either on Your Own Learn Nomeclature Either on Your Own or Use the Organic Nomeclature Softwareor Use the Organic Nomeclature Software

CH3

methylbenzene

CH3

Cl

1-chloro-3-methylbenzene

(toluene)

Br

NO2

1-bromo-3-nitrobenzene

CH3

CH3

1,4-dimethylbenzene

SOME SPECIAL NAMESSOME SPECIAL NAMES

CH3 NH2

toluene aniline anisole

O CH3

CH3

CH3

o-xylene m-xylene

p-xylene

phenol

CH3

CH3

CH3

CH3

OH

COOH

benzoicacid

Ripso

ortho

meta

para

orthoortho, , metameta and and parapara Positions Positions

CH3

NO2

m-nitrotoluene3-nitrotoluene

1-methyl-3-nitrobenzeneo-

m-

p-

12

3

4

5

6

Cl

Cl

p-dichlorobenzene

1,4-dichlorobenzene

Compounds containing aromatic rings

are often used in dyes, such as these for

sale in a market in Nepal

Source: Getty Images

REVIEW OF BENZENE PROPERTIES

Figure 22.11: The structure of benzene

BENZENE RESONANCEBENZENE RESONANCEReview Sections 6.8 - 6.14

KEKULESTRUCTURES

Resonance Energy = 36 Kcal / mole

All bonds are equivalent

The ring is symmetric.Bond lengths are between a single and a double bond.

Very StableLess reactive than other groupings of atoms.

HH

HH

HH.

. ..

..

All 2p orbitals overlap equally.

BENZENEBENZENEIsodensity surfaces - electron potential mapped in color.(van der Waal’s)

Color adjustedto enhance thepi system.

Highest electron density is red.

Note the symmetry.

+ H2

+ 3 H2

+ 3 H2

cyclohexatriene(hypothetical)

benzene

cyclohexene

cyclohexane

RESONANCEENERGY36 kcal/mol

-85.8 kcal/mol(calculated)-28.6 kcal/mol

-49.8 kcal/mol

BENZENE - DETERMINATION OF RESONANCE ENERGYBENZENE - DETERMINATION OF RESONANCE ENERGY

REACTIVITYREACTIVITY

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

Alkene Benzene

RClH

R

H

Cl

ClH+ +noreaction

RCl2

R

Cl

Cl

Cl2+ +noreaction

RBr2

R

Br

Br

Br2+ +noreaction

R R ORCO3H RCO3H+ +

noreaction

H

H

+

+

Strongerbase

Weaker base

Readily donates electronsto an electrophile.

Donation of electrons wouldinterrupt ring resonance(36 kcal / mole).

A strong electrophile isrequired - and often acatalyst.

Benzene is a Weak Base and Poor NucleophileBenzene is a Weak Base and Poor Nucleophile

alkene

benzene

Benzene requires a strong electrophile and a catalyst…..and then it undergoes substitution reactions, not addition.

Cl2FeCl3

Cl

ClH+ +

Benzene ReactivityBenzene Reactivity

substitutioncatalyst

Cl2Cl

Cl+

compare:

additionno catalyst

Some Substitution Reactions of BenzeneSome Substitution Reactions of Benzene

Cl2AlCl3

Cl

CH3ClAlCl3

CH3

CH3

CCl

O AlCl3 C CH3

O

OH NO

O

H2SO4

N O

O

S

O

OH

OOH S

O

O

OHSO3

+

+

+

+

+

Halogenation

Friedel-CraftsAlkylation

Friedel-CraftsAcylation

Nitration

Sulfonation

+ +

-

-

Blood Alcohol Level

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

Classes of Alcohols

Oxidation of Alcoholsprimary alcohol aldehyde carboxylic acids

RCH2OH RCHO RCOOH

secondary alcohols ketones

RCHOHR’ RC=OR’

tertiary alcohols No Reaction

Large Molecules Containing Alcohol Groups

More Large Molecules Containing

Alcohol Groups

HO

OHH3C

estradiol(female hormone,

an estrogen)

O

OH

estrone(female hormone,

an estrogen)

HO

OH3C

testostrone(male hormone)

H3C

H3C

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

Source: AP/Wide World Photos

ALDEHYDES AND KETONES I

Aldehyde

Ketone

O

CR H

R = H, alkyl, aryl

O

CR R'

R and R' = alkyl or arylR and R' cannot be hydrogen!

STRUCTURE

Cinnamaldehyde produces the characteristic odor of cinnamon

Source: Visuals Unlimited

NOMENCLATURENOMENCLATURE

• 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

IUPAC Nomenclature of KetonesIUPAC Nomenclature of Ketones

Do the ketones section of Organic Nomenclature program!

CH3

CCH2

CH2CH3

O

2-Pentanone

EXAMPLES

O

CCH2 CH

CH3 CH2

CH2

CH3

CH3

4-Ethyl-3-hexanone

O

CH

CH3

CH3

3-Isopropylcyclopentanone

or 3-(1-Methylethyl)cyclopentanone

Common, or Trivial, NamesCommon, 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!

KETONESKETONES

CH3

CCH2

CH2CH3

O

Methyl propyl ketone

Example of Common NamesExample of Common Names

O

CCH2 CH2

CH3 CH3

Diethyl ketone

O

CCH3 CH3

acetone

dimethyl ketone

A common laboratorysolvent and cleaningagent

SPECIAL CASESSPECIAL CASES

C

O

benzophenone

diphenyl ketone

C

O

CH3

acetophenone

methyl phenyl ketoneKNOWTHESE

• 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

IUPAC Nomenclature of AldehydesIUPAC Nomenclature of Aldehydes

Do the aldehydes section of Organic Nomenclatureprogram.

EXAMPLES

CH3

CH2CH2

CH2C

O

Hpentanal

CH3CH

CHC

O

HCH3

Cl

2-chloro-3-methylbutanal

12

34

always carbon 1aldehyde group is

O

CH H

O

CCH3 H

O

CCH2 HCH3

O

CC HCH2CH3

O

CC HCH2CH2CH3

O

CCH2 HCH2CH2CH2CH3

Formaldehyde Acetaldehyde Propionaldehyde

Butyraldehyde Valeraldehyde

Caproaldehyde

1 2 3

4 5

6

Common Names of the AldehydesCommon Names of the Aldehydes

RECOGNIZE THESE

O

CH H

O

CH CH3

C

O

H

SPECIAL CASESSPECIAL CASES

formaldehyde

acetaldehyde

benzaldehyde

KNOWTHESE

Figure 22.13: Some common ketones and akdehydes

Figure 22.14: Some carboxylic acids

Computer-generated space-filling

model of acetylsalicylic acid (aspirin)

Source: Photo Researchers, Inc.