Arenes and Phenols Powerpoint

7/23/2019 Arenes and Phenols Powerpoint

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A2 Chemistry

Chapter 2

Chapter 2 Objectives

Delocalisation of Benzene

Nitration of Benzene

Halogenation of Benzene

Properties of Phenol

Phenol + NaOH

Phenol + Na(s)

Phenol + Br 2

S! 2"# S! 2"$ S! 2"%



A2: Arenes

Chapter 2 Objectives (1-8)

1.1. Show unerstanin! o" the concept o" e#oca#isation o"Show unerstanin! o" the concept o" e#oca#isation o"e#ectrons as use in a moe# o" ben$enee#ectrons as use in a moe# o" ben$ene

2.2. %escribe e#ectrophi#ic substitution o" arenes with concentrate%escribe e#ectrophi#ic substitution o" arenes with concentratenitric aci in the presence o" concentrate su#phuric aci& anitric aci in the presence o" concentrate su#phuric aci& aha#o!en in the presence o" a ha#o!en carrier& an aha#o!en in the presence o" a ha#o!en carrier& an a

ha#o!enoa#'ane such as ch#oromethane in the presence o" aha#o!enoa#'ane such as ch#oromethane in the presence o" aha#o!en carrier (riee#-Cra"ts reaction).ha#o!en carrier (riee#-Cra"ts reaction).

.. %escribe the mechanism o" e#ectrophi#ic substitution in%escribe the mechanism o" e#ectrophi#ic substitution inarenes& usin! the mononitration o" ben$ene as an e*amp#earenes& usin! the mononitration o" ben$ene as an e*amp#e

+.+. ,nerstan that reactions o" arenes& such as those in point 2,nerstan that reactions o" arenes& such as those in point 2above& are use by inustry urin! the synthesis o"above& are use by inustry urin! the synthesis o"commercia##y important materia#s& "or e*amp#e e*p#osives&commercia##y important materia#s& "or e*amp#e e*p#osives&pharmaceutica#s an yes ("rom nitration)& an po#ymers suchpharmaceutica#s an yes ("rom nitration)& an po#ymers suchas po#ystyrene ("rom a#'y#ation)&as po#ystyrene ("rom a#'y#ation)&



Chapter 2 Objectives

(continue)

.. *p#ain the re#ative resistance to bromination o" ben$ene&*p#ain the re#ative resistance to bromination o" ben$ene&compare with cyc#ohe*ene& in terms o" e#oca#isation o" thecompare with cyc#ohe*ene& in terms o" e#oca#isation o" theben$ene rin!.ben$ene rin!.

/./. %escribe the reactions o" pheno# with bases an soium to "orm%escribe the reactions o" pheno# with bases an soium to "ormsa#ts an with bromine to "orm 2&+&/-tribromopheno#sa#ts an with bromine to "orm 2&+&/-tribromopheno#

0.0. *p#ain the re#ative ease o" bromination o" pheno#& compare with*p#ain the re#ative ease o" bromination o" pheno#& compare withben$ene& in terms o" activation o" the ben$ene rin!ben$ene& in terms o" activation o" the ben$ene rin!

8.8. State the uses o" pheno#s in antiseptics an isin"ectantsState the uses o" pheno#s in antiseptics an isin"ectants



C

C C

C

CC

&he str'ct're of benzene

can be represente in a

variet of *as

Consier onl

the carbon ring

that lies in a

plain"

the bons noticing the

are aing perpenic'lar to the

plain of the ring then ta,ing a*a the lo*er lobes for clarit

-f o' i.aginet

he lobes

being large

eno'gh to

overlap the

i.age

changes to/

HC

HC CH

CH

CHHC



e0

C

C C

C

CC

e0

e0

e0e0

e

0

gain for clarit the electron clo's

above an belo* the plain of the ring

have been re'ce in size the

green being above the plain of

the ring an pin,below

"

&hree electrons are ae to each clo' area"Beca'se of the overlapping orbitals the are able to

.ove over the entire peri.eter of the ring"

&his is ,no*n as elocalisation"

Beca'se of the

elocalisation a

benzene ringoes not attract

electrophiles *ith

the sa.e force as

aliphatic o'ble

bon .olec'les"

1epla

slies



#ectrophi#ic Substitution o" Arenes

*amp#e 1: A mi*ture o" concentrate nitric aci

(3O) an concentrate su#phuric aci (2SO+)&he s'lph'ric aci catalst provies protons

H2SO (l) + HSO0H+

HNO$

3oss of H2O occ'rs

NO2+

Nitroni'. ion

&his is the

electrophile

*hich *ill a

.olec'les *ith

o'ble bons"

&he proton fro. H2SO

as to HNO$ creating a

ne* arrange.entNitric aci has this

spatial

arrange.ent"

1earrange.ent

then occ'rs

To replay the sequence, right click on the screen and select previo's.



NO2+

4oss o" 5

occurs "ina##y!ivin! nitro

ben$ene

Substitution on the ben$ene rin! continues as i##ustrate

6he nitronium ion

moves towar the

ben$ene rin! A pair o" e#ectrons

moves "rom therin! towar the

nitronium ion7

!ivin! the

intermeiate

ben$enenitronium ion

To replay the sequence, right click on the screen and select previo's.



#ectrophi#ic Substitution o" Arenes

*amp#e 2: A ha#o!en (2) in the presence o" a

ha#o!en carrier. (9r 2 with eC#)

4eCl$4e

Cl

Cl

Cl+

Br 2Br Br

Br Br

9en$ene7

7is !oin! to

react with

bromine

9romine;s

e#ectron ensity

is imma!ine

as7

<nitia##y& bromine

oes not become

po#ari$e enou!h to

react with ben$ene.

<ron (<<<) ch#orie arrives

as the cata#yst to he#p

the reaction.

<t spatia#

arran!ement

creates the

"o##owin!ipo#es7

<n the presence o"

the cata#yst&

bromine;s po#arity

chan!es "rom7

<nto7

+

#ecton

ensity

shi"ts7

4e

Cl

Cl

ClBr 6o

create75 9r 5



9r

9r 5

9r 5 ion is a stron! enou!h

e#ectrophi#e to a to the ben$ene

rin!

+ HBr

4e

Cl

Cl

ClBr 4eCl$

+

0

6he hyro!en

atom is

substitute by

the bromine

atom

6he cata#yst is re!enerate

To replay the sequence, click

ns*er S! 2"# 2"2 5 2"$



Phenol

6anillin

7straiol

Phenols an their properties

=heno# occurs wie#y in

nature but the e""ects i""er

remar'ab#y.

oun in see pos o" vani##a

orchi,se as "#avourin! aitive in ice

cream an choco#ate

An important "ema#e se*

hormone>aintains "ema#e se*ua#

characteristicsStimu#ates ?3A synthesis an

there"ore promotes !rowth.

O

O

OC

C

O2C

O

2C

C2

2C

C

C

C

O

O

Cholesterol



NaOHNa+OH

6he rin!

raws

e#ectron

ensity

towar it

+ OH00

H2O

O+

6his wea'ens

the O- bon

a##owin! it

issociate more

easi#y than

other a#coho#s.

<t is there"ore

s#i!ht#y aciic.

An a#'a#i wi##

react withpheno# in the

e*pecte way

proucin! a sa#t

an water.

0 Na+

Soi'. pheno8ie

+

pH 9 %

=heno# reactin! with A#'a#i (3aO)



=heno# reactin! with soium meta# (3a(s))

O + 2Na O Na + H2 (g)

3a(s) reacts simi#ar#y with a## a#coho#s7

7but pheno# is somewhat more reactive.

9ecause ensity is rawn into the rin!7

7the hyro!en comes o"" more reai#y (5)

Na(s) + 2H+(a:) Na+

(a:) + H2(g)

1e'ction/ gain of electrons

O8iation/ loss of electrons

Soium meta# anhyro!en ions uner!o

o*iation an reuction.

2



O2

Br 29r 9r

O2

9r

H

Br

HBr

O2

9r

9r 9r

O

9r

9r

HBr

O

9r

9r

9r 9r

HBr

HBr

O

9r

9r

9r

H

Br #

$

#

2

$

2



O

+ 3Br 2 +

O

9r

9r

9r

3HBr

pheno# bromine

2&+&/-tribromopheno#yro!en

bromie

ns*er S!s 2" 2"; 5 2"%

CH



SA@ 2.1CH$

NO2

2-nitro methyl benzene

CH$

NO2

2,4,6-trinitro methyl benzene

NO2O2N

CH$

NO2

3-nitro methyl benzene" Dra* an na.e three

iso.ers *hich .ight be

pro'ce follo*ing

electrophilic s'bstit'tion of

NO2+ for one hrogen

ato. in .ethlbenzene"

B" &N& has the sste.atic

na.e #0.ethl02%0trinitrobenzene" Dra* the

str'ct'ral for.'la of &N&

CH$

NO2

4-nitro methyl benzene



SA@ 2.

" S'ggest a s'itable halogencarrier to 'se in the

reaction of benzene *ith

chloro.ethane"

B" S'ggest s'itable reactants

*hich .ight lea to the

for.ation of the follo*ing

co.po'n in the presence

of a halogen carrier"

nhro's 4eCl$ or lCl$

Benzene + 20chloro020.ethl propane

+ H$C C CH$

Cl

CH$

B" <rite a balance e:'ation'sing o'r s'ggeste

reactants

+ Cl C

CH$

CH$

CH$CH$

CH$

CH$



4e Br

Br

Br

SA@ 2./

" Ho* oes bro.ine ina:'eo's sol'tion beco.e

s'fficientl polar to achieve

electrophilic s'bstit'tion

Br Br

9romine has a

symmetrica# e#ectron

ensity arran!ement

<n the presence o"

e9r & the e#ectron

ensity shape

chan!es

4eCl$

+

Date post:	19-Feb-2018
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Arenes and Phenols Powerpoint

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