Organic Chemistry
Download
1 / 69

pp Chap 16 - PowerPoint PPT Presentation


  • 287 Views
  • Uploaded on

Organic Chemistry 4 th Edition Paula Yurkanis Bruice. Chapter 16 Reactions of Substituted Benzenes. Irene Lee Case Western Reserve University Cleveland, OH ©2004, Prentice Hall. Examples of Substituted Benzenes. The relative positions of the two substituents are

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'pp Chap 16' - MartaAdara


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Slide1 l.jpg

Organic Chemistry

4th Edition

Paula Yurkanis Bruice

Chapter 16

Reactions

of

Substituted Benzenes

Irene Lee

Case Western Reserve University

Cleveland, OH

©2004, Prentice Hall



Slide3 l.jpg

The relative positions of the two substituents are

indicated by numbers or by prefixes



Slide5 l.jpg

If one of the substituents can be incorporated into a

name, that name is used and the incorporated substituent is given the 1-position

2-chlorotoluene

ortho-chlorotoluene

4-nitroaniline

para-nitroaniline

2-ethylphenol

ortho-ethylphenol


Slide6 l.jpg

Some disubstituted benzenes have names that

incorporate both substituents



Slide8 l.jpg

The incorporated substituent is given the 1-position; the

ring is numbered in the direction that yields the lowest

possible number







Slide14 l.jpg

The same reagent that oxidizes the alkyl substituent will

oxidize the alcohol

Therefore, a milder oxidizing reagent is used:


Slide15 l.jpg

Reduction of a Nitro Substituent

It is possible to selectively reduce just one nitro group


Slide17 l.jpg

Donation of electrons through a s bond is called inductive

electron donation

An alkyl group is more electron donating than hydrogen

because of hyperconjugation

Withdrawal of electrons through a s bond is called

inductive electron withdrawal

The NH3 group is more electronegative than a hydrogen


Slide18 l.jpg

A substituent can also donate electrons into the ring by

delocalizing its lone-pair electrons


Slide19 l.jpg

Electron withdrawing by resonance occurs when the p

electrons from the ring are delocalized onto the

substituent

Substituents such as CO, CN, and NO2 withdraw

electrons by resonance


Slide21 l.jpg

The strongly activating substituents make the benzene

ring more reactive toward electrophilic substitution

All the strongly activating substituents donate electrons

by resonance and withdraw electrons inductively


Slide22 l.jpg

The moderately activating substituents can donate

electrons into the ring and away from the ring

Overall, they donate electrons by resonance more

strongly than they withdraw electrons inductively


Slide24 l.jpg

These substituents are slightly more electron donating

than they are electron withdrawing


Slide25 l.jpg

These substituents donate into the ring by resonance and

withdraw electrons from the ring inductively

They withdraw electrons inductively more strongly than

they donate electrons by resonance



Slide27 l.jpg

These substituents are powerful electron-withdrawing

groups

These substituents withdraw electrons both inductively

and by resonance


Slide28 l.jpg

The substituent already attached to the benzene ring

determines the location of the new substituent

All activating substituents and the weakly deactivating

halogens are ortho–para directors

All substituents that are more deactivating than halogens

are meta directors


Slide29 l.jpg

  • Any substituent that donates electrons inductively is an

  • ortho–para director

  • All substituents that donate electrons by resonance are

  • ortho–para directors


Slide33 l.jpg

Electron withdrawal decreases reactivity toward

electrophilic substitution and increases acidity

Electron donation increases reactivity toward electrophilic

substitution and decreases acidity



Slide35 l.jpg

Methoxy and hydroxy substituents are so strongly

activating that halogenation is carried out without Lewis




Slide38 l.jpg

In designing a disubstituted benzene, the order in which

the substituents are to be placed on the ring must be

considered




Slide45 l.jpg

A strongly activating substituent will win out over a

weakly activating substituent or a deactivating substituent





Slide50 l.jpg

Consider the synthesis of para-chloroethylbenzene



Slide52 l.jpg

The Arenediazonium Ion as an Electrophile

Only highly activated benzene rings can undergo this

reaction

Substitution takes place preferentially at the para position





Slide61 l.jpg

The electron-withdrawing substituents must be ortho or

para to the site of nucleophile attack

The electrons of the attacking nucleophile can be

delocalized






Slide68 l.jpg

1-substituted naphthalenes are easier to form

2-substituted naphthalenes are more stable


Slide69 l.jpg

In substituted naphthalenes, the nature of the substituent determines which ring will undergo electrophilic substitution


ad