Phenol is an aromatic organic compound with the chemical formula C6H5OH. It has an -OH group attached directly to the benzene ring. Phenol is a colorless, crystalline solid that is mildly acidic and corrosive. It has a distinct, sweet and tarry odor. Phenol is prepared industrially via the Dow process involving chlorobenzene. It undergoes reactions involving both the aromatic ring and -OH group, such as hydrogenation, sulphonation, halogenation, and salt formation. Phenol has many applications as a disinfectant, antiseptic, resin, and precursor to other compounds.
2. INTRODUCTION:
Defination:
Compounds containing –OH Group attached directly to an aromatic ring.
• Aromatic compound, any of a large class of unsaturated (double or triple
bond)chemical compounds.
Phenol is an aromatic compound. The chemical formula of this organic compound
is C6H6O. Phenol is also known as Carbolic acid.
3. • It is mildly acidic and is corrosive to the respiratory tract, eyes, and skin.
Structure:
OH group attached to one side of benzene. Molecular Formula C6H5OH or
C6H6O. Derivative of benzene Three double bonds sp2 Hibridization.
4. Nomenclature
The simplest hydroxyl derivative of benzene is called Phenol.
IUPAC NAMING RULES
Rule1 Give the numbering to carbon atom cyclic compounds of Phenol,
considering the – OH is at C – 1
Rule 2 Substituent's are indicated why using the number of carbon atom to
which these are attached.
Rule 3 In IUPAC naming use the phenol word after the substituent's.
5. Benzene ring can be substituted by three ways:
Ortho 1 , 2 substituted
Meta 1 , 3 substituted
Para 1 , 4 substituted
o-cresol m-nitrophenyl
7. Physical properties:
1 Phenol is a colourless,deliquescent solid.
2 It is crystalline in nature.
3 Its melting point is 41⁰C.
4 Its boiling point is181.7⁰C.
5 It has a distinct odour that is sickeningly sweet and tarry.
8. 6 It is sparingly soluble in water forming pink solution at room temperature (Due to the
formation of HBond).
7 Phenols are less soluble in alcohols than water.
8 Phenol is acidic in nature with a ph of 5-6.
9 Phenol is a COMBUSTIBLE SOLId.
10 Its is highly poisonous.
9. Preparation of Phenol:
DOW’S PROCESS:
The reactant chlorobenzene is heated with aqueous sodium hydroxide at temperatures 623K and
300atm to get sodium phenoxide ion. Then in the next step sodium phenoxide ion is treated with
Dilute HCl which gives the final product as phenol.
10. From Diazonium Salts:
When an aromatic amine is treated with nitrous (NaNO2 + HCl) acid at 160°C,
diazonium salts are obtained.Upon warming with water, these diazonium salts
finally hydrolyze to phenols.
11. FROM BENZENE SULPHONIC ACID:
• Benzenesulphonic acid can be obtained from benzene by reacting it with oleum.
This benzene sulphonic acid which is treated with sodium hydroxide at high
temperatures for the formation of sodium phenoxide. Finally, sodium phenoxide
on acidification gives phenol.
12. FROM GRIGNARD REAGENT:
• In the presence of dry ether, chlorobenzene or bromobenzene is first
transformed into phenyl magnesium halide. The Grignard reagent produces
phenol when it reacts with oxygen and is then hydrolysed by a mineral acid.
13. CHEMICAL PROPERTIES:
Phenol give two types of reactions:
1. Reactions involving ring:
Examples:
a. Hydrogenation b. Sulphonation c. Halogenation
2. Reactions involving −OH group:
a. Salt formation b. Reduction with Zn
14. Reactions involving ring:
Hydrogenation:
When hydrogen reacts with phenol at 150℃ in the presence of Ni catalyst it gives
cyclohexanol.
15. Sulphonation :
Phenol reacts with H2SO4 at 25℃ and 100℃ to give ortho and para phenolsulphonic
acid respectively.
o-phenolsulphonic
acid
p-phenolsulphonic
acid
17. Reactions involving –OH group:
Salt formation :
Phenol reacts with alkalies to form salts.
18. Reduction with zinc :
Phenol reacts with zinc to give benzene and zinc oxide.
19. Application or Uses of Phenol:
It is used as disinfectant in hospitals and washrooms.
Phenol is included in the production of ear and nose drops.
It is widely used as antiseptic and disinfectant in several mouth wash, lotion,
deodorant and soap.
It is used in the manufacturing of drugs like aspirin etc.
It is used for the manufacturing of resins.
It is used for the manufacturing of polymers like Bakelite which is used for the
manufacturing of electrical goods like plugs and switches etc.
20. It is used for the production of ply-wood.
It is used for the laboratory preparation of benzene.
Several commercial compounds are synthesized from precursors containing
phenols.
It is used for the manufacturing of phenolphthalein.
It is used for the production of nitro derivative of phenol like 2, 4, 6 trinitrophenol
(picric acid) used to make explosives and dyeing wool and silk.