HMCS Vancouver Pre-Deployment Brief - May 2024 (Web Version).pptx
Phenols
1. Made By : Group no 11
Roll no: 81-88
Sir. Dr. M. S. Gosavi College of Pharmaceutical
Education and Research
Pharmaceutical Organic Chemistry-2
CONTINOUS ASSESSMENT 1
PHENOLS
3. INTRODUCTION
Phenols are aromatic organic compounds containing
hydroxyl group (-OH group).
Phenols are generally named as the derivatives of the
simplest member of the family, phenol. (C6H5OH)
Methylphenols are named as cresols.
Sometimes phenols are named as hydroxy- compounds
3-hydroxybenzoic acid phenol p-cresol
5. MECHANISM
• STEP 1: Hydroxide ion removes the proton from carbon
adjacent to the carbon bonded to chlorine. This leads to the
elimination of a water molecule followed by the formation of
the short lived benzyne intermediate.
• STEP 2: The hydroxide ion attacks the benzyne intermediate
to give the sodium phenoxide which on acidification gives
phenol.
• NOTE: The mechanism is also called as benzyne mechanism as
it involves formation of benzyne intermediate.
9. Qualitative tests
To identify phenolic group in a compound following tests
are done:
1. Litmus paper
2. Phthalein Dye test
3. Solubility test
4. Feric chloride test
5. Bromine water test
6. Coupling test
10. 1. LITMUS PAPER TEST
Phenol turns blue litmus paper red showing its acidic
nature.
2. PHTHALEIN DYE TEST
Phenol gets condensed on heating with phenolphthalic
anhydride in the presence of conc. Sulfuric acid and
forms phenolphthalein. Phenolphthalein gives pink
colored compounds on reaction with a limited amount of
sodium hydroxide while in excess of sodium hydroxide it
gives a colorless compound.
11. .
3. SOLUBILITY TEST
phenols being weakly acidic I nature are soluble
in sodium hydroxide but insoluble in sodium
carbonate and bicarbonate.
4. FERRIC CHLORIDE TEST:
Compounds with a phenol group will form a blue,
violet, purple, green, or red-brown color upon
addition of aqueous ferric chloride. This reaction
can be used as a test for phenol groups
Phenol, resorcinol, Ortho
cresol, Para cresol.
Violet or blue colouration
Catechol Green colouration
Hydroquinone Violet or transient blue color
Pyrogallol Blue rapidly changing to red
12. 5. BROMINE WATER TEST;
If bromine water is added to a solution of phenol in water, the
bromine water is decolorized and a white precipitate is formed
which smells of antiseptic. The precipitate is 2,4,6-
tribromophenol.
6.COUPLING TEST:
When treated with ice-cold alkaline solution of diazonium salt,
phenols get coupled up mainly at p-position and form p-
hydroxyazo compounds which are bright coloured azo dyes.
13. Acidity of phenols
• Phenol is a weak acid They are more acidic than
aliphatic alcohols but less than water and carboxylic
acids.
• Acidity of Phenol:
In water phenol ionises as:
14. • The various resonance stabilized contributing
structures of phenols and phenoxide ion are as follows
Phenol resonance structure:
• It is evident from the contributing structure II, III
and IV that oxygen atom acquires partial +ve charge
due to resonance. As a result, bond between O - H
becomes weak which helps the release of proton and
makes phenol acidic.
15. • Phenoxide ion resonance structure:
• Phenoxide ion is more stabilized by resonance than phenol,
because in phenol contributing structure II, III , IV
involve charge separation and therefore less stable than
structure I.
• On the other hand, in phenoxide ions none of the
contributing structures V to VIII involves charge
separation and all the contributing structure in phenoxide
ion are almost equally stable.
• Hence phenol shows acidic properties.
16. Effect of substituents :
A. Presence of electron releasing groups:
Electron releasing groups decrease acidity of phenols
REASON: The groups ( -CH3, -OCH3, -NH2 - OR, -OR)
release electrons towards ring system , thus
neutralizing positive charge on oxygen. Hence this
causes destabilizes the phenoxide ion making the
removal of proton difficult.
17. B. Presence of electron withdrawing groups:
Electron withdrawing groups increase acidity of phenols.
• REASON : Electrons from phenolic ring are taken by the
electron withdrawing groups ,decreasing electron density
on phenoxide ion and hence stabilizing it.
• 2. Position of substituent relative to hydroxyl group:
The effect of electron withdrawing or electron releasing
substituent is felt more at ortho or para positions than
meta position. Moreover , the effect at para position is
less than at ortho position due to greater distance from
phenolic group in para isomer.
18. REACTIONS OF PHENOL
A) RING/ ELECTROPHILIC SUBSTITUTION:
i. Nitration:
ii. Sulphonation:
p-phenolsulfonic acid o-phenolsulfonic acid
19. iii. Halogenation:
Due to a highly activating effect of the hydroxyl group in phenols, they
undergo halogenation even in the absence of Lewis acids. This reaction
takes place in presence of solvents of low polarity (CS,CHCl3).
When phenol is treated with bromine water, a white precipitate of 2, 4,
6-tribromophenol is formed.
21. vi. Reimer –Tiemann Reaction (Aldehyde formation) :
Mec
vii. Williamson Synthesis:
22. • REARRANGEMENT REACTIONS:
FRIES REARRANGEMENT
The reaction of an aryl ester with a Lewis acid catalyst
followed by an aqueous acid to give phenols is known as
Fries rearrangement.
26. STRUCTURE & USES:
1. PHENOL
•Phenol is proven to be effective anti-bacterial,
anti-fungi and anti-viral agent
• Phenol, is also used in the manufacturing of
mouthwashes for effective cleansing of the mouth
and removal of mouth bacteria.
• Phenol is also sometimes used as an oral analgesic
and mild anesthetic. This is due to the numbing
sensation it provides due to its astringent
properties since it is an alcohol.
27. CRESOLS
• Cresols are precursors or
synthetic intermediates to other
compounds and materials
including plastics, pesticides,
pharmaceuticals and dyes.
• Cresols are used to dissolve other chemicals, as disinfectants
and deodorizers, and to make specific chemicals that kill
insect pests.
• Cresol solutions are used as household cleaners and
disinfectants, perhaps most famously under the trade name
Lysol.
• Cresols are found in many foods and crude oil, coal tar, and in
wood preservatives.
• Xylenols are dimethylphenols, or they can be thought of as
methylcresols.
28. • RESORCINOL
• It is present in over-the-counter topical acne
treatments at 2% or less concentration.
• Resorcinol is also used as a chemical intermediate for
the synthesis of pharmaceuticals and other organic
compounds.
• It is used in the production of diazo dyes .
• Resorcinol is an analytical reagent for the qualitative
determination of ketoses (Seliwanoff's test).
29. • NAPHTHOL
• 1-Naphthol is a precursor to a variety of insecticides
including carbaryl and pharmaceuticals .
• 1-Naphthol is used in each of the following chemical
tests:
• Molisch's test gives a red- or purple-colored
compound to indicate the presence of carbohydrate.
• The rapid furfural test turns purple quickly (<30s)
if fructose is present, distinguishing it from glucose.
• The Sakaguchi test turns red to indicate the
presence of arginine in proteins.
• It undergoes azo coupling to give various azo dyes.
