neet 1yr chemistry (batch-3)

NEET 1Yr Chemistry

(Batch-3)

Alcohols, Phenols & Ethers

ABOUT ME

Maurine Dias• 4 years of teaching experience for

NEET & JEE• B.Tech from ICT

Today’s TopicChemical Reactions of Phenols

Last Class

05

Chemical Properties of Alcohols01

02 Chemical Reactions of Alcohols and Phenols

Today

05

Chemical Reactions of Phenols01

02 Some Commercially Important Alcohols

RECALL

Which is the only alcohol that can be prepared by the indirect hydration of

alkene?

A. Ethyl alcohol

C. Isobutyl alcohol D. Methyl alcohol

B. Propyl alcohol

Among the alkenes which one produces tertiary butyl alcohol on acid

hydration?

D. CH3CH=CH2

A. (CH3)2C=CH2 B. CH3-CH=CH-CH3

C. CH3CH2CH=CH2

In the reaction given below, the molecular formula of X is;

A. C4H6O

C. C2H4O D. C2H6O

B. C4H10O

In the reaction given below, the molecular formula of X is;

A. C4H6O

C. C2H4O D. C2H6O

B. C4H10O

Solution:

Chemical Reactions

Halogenation

Nitration

Sulphonation

Kolbe's reaction

Friedel crafts

reaction

Phenols

Reimer-Tiemann

reaction

Claisen

rearrangement

Mercuration

Hydrogenation

Gattermann's

reaction

Electrophilic Substitution Miscellaneous Reactions

Reaction with Zn

dust Coupling reaction

Condensation with

formaldehyde

Chemical Reactions of Phenols

Electrophilic Substitution Reactions

• The –OH group attached to the benzene ring activates phenols towards

electrophilic substitution.

i) Nitration



ii) Halogenation

• Bromine water on reaction with phenol gets decolorized and a white ppt of

2,4,6-Tribromophenol is formed.



iii) Sulphonation



iv) Friedel–Craft Alkylation Reaction



iv) Friedel–Craft Acylation Reaction

Phenol on treatment with conc.HNO3 gives:

A. Picric acid

C. Ortho and para-

nitrophenolD. None of the above

B. Ortho and meta-

phenol

Phenol on treatment with conc.HNO3 gives:

A. Picric acid

C. Ortho and para-

nitrophenolD. None of the above

B. Ortho and meta-

phenol

Solution:


1. Kolbe-Schmidt reaction/ Kolbe's reaction

• Reaction of sodium phenoxide with carbon dioxide at 130-140°C under

pressure of (4-7) atmospheres followed by acid hydrolysis forms salicylic acid

(o-Hydroxy benzoic acid).

Miscellaneous Reactions


1. Kolbe-Schmidt reaction/ Kolbe's reaction

Mechanism

• Nucleophilic addition of phenoxide to carbon dioxide yields salicylate.

• The salicylate formed further reacts with the acid to form salicylic acid


2. Reimer-Tiemann reaction

• When phenol is treated with chloroform in the presence of NaOH, a –CHO group

is introduced at ortho position of benzene ring and salicylaldehyde is formed.



• When carbon tetrachloride is used, salicylic acid (predominating product) is

formed.



Mechanism



Mechanism

iii. Hydrolysis


3. Gattermann’s reaction

• Phenol on reaction with liquid hydrogen cyanide and hydrochloric acid gas in

presence of anhydrous aluminium chloride yields p-hydroxy benzaldehyde

(Formylation).


4. Mercuration

• Phenol when heated with mercuric acetate undergoes Mercuration to form o- and p-

isomers.


5. Hydrogenation

• Phenol, when hydrogenated in presence of a nickel catalyst at about 150-200°C,

forms cyclohexanol.

A new C-C bond formation is possible in:

A. Cannizaro reaction

C. Clemmensen reduction D. Reimer-Tiemann

reaction

B. Rosenmund’s reduction


5. Claisen rearrangement

• Rearrangement of allyl aryl ethers to allyl phenols.

• The reaction takes place when the substrate is heated alone to about 200°C or in

some inert solvent like diphenyl ether.

• Allyl group migrates to ortho-position and if ortho-position is already occupied,

para-isomer is obtained.


6. Claisen rearrangement


7. Reaction with zinc dust

• When phenol is distilled with zinc dust, benzene is obtained.


8. Coupling Reaction

• Phenol couples with benzene diazonium chloride in presence of slightly

alkaline medium at low temperature to form a red dye (p-hydroxy

azobenzene).


8. Coupling Reaction

• Phenol couples with phthalic anhydride in presence of concentrated H2SO4 to

form a dye, (phenolphthalein)used as an indicator.


9. Condensation Reaction with Formaldehyde

• Phenol condenses with formaldehyde (excess) in presence of sodium

hydroxide or acid to form a cross-linked polymer known as Bakelite.

• Bakelite is used to manufacture electrical goods.

Identification Tests for Phenols

1.Reaction with ferric chloride.

• Aqueous solution of phenol gives a violet coloration with a drop of ferric

chloride.


2. Reaction with bromine water

• Aqueous solution of phenol gives a white precipitate of 2,4,6-tribromophenol

with bromine water.


3. Liebermann's nitroso reaction

• When phenol is reacted with NaNO2 and concentrated H2SO4, it gives a deep

green or blue colour which changes to red on dilution with water.

• When made alkaline with NaOH original green or blue colour is restored.


4. Reaction with phthalic anhydride

• Phenol combines with phthalic anhydride in presence of conc. H2SO4 to form

phenolphthalein which gives pink colour with alkali and is used as an indicator.

Phenol can be distinguish from ethyl alcohol using:

A. Na

C. NaOH D. FeCl3

B. AlCl3

Phenol can be distinguish from ethyl alcohol using:

A. Na

C. NaOH D. FeCl3

B. AlCl3

Solution:

Phenol with FeCl3 gives violet colour. This test is not given by ethyl alcohol.

SOME COMMERCIALLY IMPORTANT ALCOHOLS

• The simplest monohydric alcohol.

• Also referred as wood alcohol or wood spirit or wood naphtha.

• It occurs in combined state in some essential oils, e.g., oil of winter green

(methyl salicylate), oil of cloves (methyl benzoate), oil of orange flowers

(methyl anthranilate), etc.


Preparation

• Produced by catalytic hydrogenation


2. Ethyl Alcohol

• Glucose and fructose undergo fermentation in the presence of enzyme zymase

to form ethyl alcohol


2. Ethyl Alcohol

Uses of Phenols

Phenol

Antiseptic

Dyes

Picric Acid

Cyclohexanol

Phenol-formaldehyde plastic

Drugs

Disinfectant

Phenol on distillation with zinc dust gives:

AIIMS 2018

D. zinc powder

A. benzene B. diphenyl ether

C. biphenyl

Phenol on distillation with zinc dust gives:

AIIMS 2018

D. zinc powder

A. benzene B. diphenyl ether

C. biphenyl

Solution

:Identify X and Y in the above reaction

NEET 2021

D. X is phenols, Y is Zinc

powder

B. X is Phenol, Y is

Na2Cr2O7/ H2SO,

C. X is cyclohex-2-ene-1-

ol,Y is Na2Cr2O2/H2SO4

A. X is cyclohexanol, Y is

Zn

:Identify X and Y in the above reaction NEET 2021

B. X is Phenol, Y is

Na2Cr2O7/ H2SO,

C. X is cyclohex-2-ene-1-

ol,Y is Na2Cr2O2/H2SO4

A. X is cyclohexanol, Y is

Zn

D. X is phenols, Y is Zinc

powder

Solution

Chloroform gives salicylaldehyde on treatment with phenol in the presence of

a base. This reaction is called as:

[ NEET 2018]

D. Cannizaro’s reaction

A. Wurtz reaction B. Reimer-Tiemann

reaction

C. Friedel-Crafts

reaction

Chloroform gives salicylaldehyde on treatment with phenol in the presence of

a base. This reaction is called as:

[ NEET 2018]

D. Cannizaro’s reaction

A. Wurtz reaction B. Reimer-Tiemann

reaction

C. Friedel-Crafts

reaction

Solution

Summary

Summary

Reactions of Phenols


i. Nitration ii. Halogenation

Summary



iii. Sulphonation iv. Friedel–Craft

reaction

Summary



1. Kolbe-Schmidt reaction 2. Reimer-Tiemann reaction

Summary



3. Gattermann’s reaction 4. Mercuration

Summary



5. Hydrogenation 6. Claisen rearrangement

Summary



7. Reaction with zinc dust 8. Coupling Reaction

Summary



9. Condensation Reaction with Formaldehyde

SummaryTest for Phenols

Importance of:

• Methanol

• Ethyl Alcohol

• Phenols

1. Reaction with Ferric chloride

2. Reaction with bromine water

3. Liebermann's nitroso reaction

4. Reaction with phthalic anhydride

HOMEWORK

UPCOMING CLASS

Let’s Talk

Thank you!

neet 1yr chemistry (batch-3)

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