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CONTENTS

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LEARNING OBJECTIVES

AT THE END OF THIS LECTURE ,THE STUDENT WILL BE ABLE TO

EXPLAIN THE ACIDITY OF PHENOLS AND FACTORS THAT AFFECTS ITS ACIDITY
DISCUSS THE QUALITATIVE TESTS AND STRUCTURE AND USES OF PHENOL, CRESOLS, RESORCINOL, NAPHTHOLS

PHENOL

ACIDITY OF PHENOL

EFFECT OF SUBSTITUENTS ON ACIDITY OF PHENOL

QUALITATIVE TESTS

QUALITATIVE TESTS

Experiment	Observation	Inference
To one drop of dilute solution of phenol , a few drops of neutral ferric chloride solition are added	Violet colour	Presence of phenolic group
Chemical equation
Liebermann’s reaction : To two drops of melted phenol, added little solid sodium nitrite. Cooled and added 4 drops of concentrated sulphuric acid . Diluted causiously with water	A deep red solution is obtained which turned green or blue with excess of alkali	Characteristic reactions of phenol
Chemical equation

QUALITATIVE TESTS CONTD...

Experiment	Observation	Inference
Phthalein test: About 2 drops of melted phenol is mixed with a small quantity of phthalic anhydride in a dry test tube. 2 drops of concentrated sulphuric acid are added. The mixture is heated at about 150^οC for two minutes. Cooled and excess of 10 % sodium hydroxide solution is added	Pink solution	Due to formation of phenolphthalein
Chemical equation
Azo-dye formation: Dissolved two drops of aniline in 1 ml of dilute hydrochloric acid and well cooled in ice. A few drops of saturated sodium nitrite solution are added . The diazonium solution thus obtained is added to a well cooled solution of phenol in aqueous sodium hydroxide solution	A red colour	Formation of azo dye
Chemical equation

QUALITATIVE TESTS CONTD...

Experiment	Observation	Inference
Scotten-Baumann reaction : Dissolved about 0.25g of phenol in about 5 ml of 10 % sodium hydroxide solution contained in a boiling tube. About 1 ml of benzoyl chloride is added . The boiling tube is corked and shaken vigorously for about 15 minutes	A white precipitate is formed	Formation of phenyl benzoate
Chemical equation

STRUCTURE AND USES OF PHENOL

PHENOLS ARE WIDELY USED IN HOUSEHOLD PRODUCTS AND AS INTERMEDIATES FOR INDUSTRIAL SYNTHESIS
USED (IN LOW CONCENTRATIONS) AS A DISINFECTANT IN HOUSEHOLD CLEANERS AND IN MOUTHWASH

STRUCTURE AND USES CRESOLS

STRUCTURE AND USES OF RESORCINOL

TO TREAT ACNE, SEBORRHEIC DERMATITIS, ECZEMA, PSORIASIS, AND OTHER SKIN DISORDERS
TO TREAT CORNS AND WARTS
RESORCINOL WORKS BY HELPING TO REMOVE HARD, SCALY, OR ROUGHENED SKIN

STRUCTURE AND USES OF NAPHTHOLS

2-NAPHTHOL IS A WIDELY USED AS INTERMEDIATE FOR THE PRODUCTION OF DYES AND OTHER COMPOUNDS

SUMMARY

ACIDITY OF PHENOL IS EXPLAINED BY DIFFERENCE IN THE RESONANCE STABILIZATION OF PHENOL AND PHENOXIDE ION
ELECTRON WITHDRAWING GROUPS INCREASES THE ACIDITY OF PHENOL
ELECTRON DONATING GROUPS DECREASES' THE ACIDITY OF PHENOL
LIEBERMANN’S REACTION AND PHTHALEIN TEST ARE CHARACTERISTIC REACTIONS OF PHENOL
PHENOL IS USED (IN LOW CONCENTRATIONS) AS A DISINFECTANT IN HOUSEHOLD CLEANERS AND IN MOUTHWASH

SUMMARY CONTD...

CRESOL HAS ANTIBACTERIAL AND INSECTICIDAL PROPERTIES
RESORCINOL IS USED TO TREAT ACNE, SEBORRHEIC DERMATITIS, ECZEMA, PSORIASIS, AND OTHER SKIN DISORDERS
2-NAPHTHOL IS A WIDELY USED AS INTERMEDIATE FOR THE PRODUCTION OF DYES AND OTHER COMPOUNDS