ochem 2 reactions

Preparation of conjugated dienes

potassium tert-butoxide

Electrophilic addition of dienes

1,2 vs 1,4 addition

1,2 adduct is the

Kinetic product

1,4 adduct is the

Thermodynamic product

Diels-Alder reaction is

Pericyclic, concerted and stereospecific

Diene must adopt

s-cis conformation

The dienophile works best with

one or more electron withdrawing groups

when the bicyclic product is formed

The endo product is preferred

The longer the wavelength

the ==***lower***== the energy of the HOMO-LUMO gap and the ==***greater***== the degree of conjugation

Toluene

Phenol

Anisole

Aniline

Benzoic Acid

Benzaldehyde

Acetophenone

Styrene

Xylene

Naphthalene

Pyridine

Furan

Thiophene

Benzene only undergoes

Electrophilic Aromatic Substitution

A ring is acidic

when it can be deprotonated to form an aromatic compound

Requirements for Aromaticity

A planar ring

Fully conjugated

Obeys Huckel’s rule (4n + 2pi e)

Antiaromatic

Planar

Fully conjuated

4n pi e

Oxidation of Alkylbenzene side chains

Also Na2Cr2O7→ H2SO4, H2O

Bromination of Alkyl Benzene Side chains

AIBN should be h nu

pg 63

Birch reduction

Birch Reduction Mechanism

pg 64

Benzene IR spectrum

sp2 C-H stretch (3000-3100)

bands and overtones (1700-2000)

C=C stretching and ring vibrations (1450, 1500, 1600)

13C NMR splitting patterns

The three steps of Electrophilic Aromatic Substitution

Formation of the electrophile

formation of the sigma complex

deprotonation to restore aromaticity

Halogenation of benzene

Br2→AlBr3

Sulfonation of Benzene

Desulfonation of Benzene

dilute H2SO4

Nitration of Benzene

HNO3

\------→

H2SO4

Reduction of a Nitro group

Friedel Crafts Alkylation

LImitations of Friedel Crafts Alkylation

only alkyl halides

only works with benzene, halobenzene, or activated benzene

does not work if there is a deactivating group

often difficult to avoid polysubstitution

Electrophile is a carbocation so rearrangement may occur

Friedel Crafts Acylation

No rearrangement occurs

Clemmesen Reduction

can use this to avoid rearrangement

Requirements for Nucleophilic Aromatic Substitution

The ring must contain one or more electron withdrawing groups, a good leaving group and it must be either ortho or para to the withdrawing group

5

Methanal

Formaldehyde

Ethanal

Acetaldehyde

Propanal

Propionaldehyde

butanal

butyraldehyde

Pentanal

Valeraldehyde

Benzaldehyde

Acetone

Acetophenone

Benzophenone

Aldehyde IR stretch

2 absorptions around 2720 and 2820

Important H NMR shifts

vinyl proton 4.5-6.5

aromatic proton 6.5-8.0

aldehyde proton 10

carboxylic acid proton \`12

C NMR shift

Benzene ring 100-150

carbonyl group-200

Oxalic Acid

Malonic Acid

Succinic acid

Glutaric Acid

Naming Acid Halides

replace -ic acid with -yl chloride

Naming acid anhydrides

replace acid with anhydride

Naming esters

replace -ic with -atet

R group next to o is substituent

naming amides

replace -ic or -oic acid with amide

Naming nitriles

replace -ic/ -oic acid with -onitrate

Relative reactivity of carboxylic acid derivatives

Acid chloride > acid anhydride > ester > amide