Alcohol, Phenol,Ether class 12

Alcohol, Phenol & Ether


Alcohols
Alcohols are hydroxy derivatives of alkanes or Concept Ladder
alkyl derivatives of water with a general formula
R–OH.
All alcohols mainly can
Types of Alcohols be divided into two broad
Alcohols are of following types: categories, (i) aliphatic
Monohydric alcohols: alcohols; (ii) aromatic
These are alcohols with only one –OH group. alcohols.
Their general formula is CnH2n + 1 OH.
They are further divided in following types:
Primary alcohol (1°) RCH2OH, for example, CH3OH
methyl alcohol (Methanol).
Secondary alcohol (2°) R2CHOH, for example,
(CH3)2CHOH isopropyl alcohol (Propan-2-ol).
Tertiary alcohol (3°) R3COH, for example,
(CH3)3COH–tertiary butyl alcohol (2-Methyl-
propan-2-ol). Rack your Brain
Dihydric alcohols:
Alcohols that have two –OH groups. What are alcohols and how are
For example, glycol, Propan 1, 2 diol they classifie?



Trihydric alcohols:
Alcohols that having three –OH groups.
For example, glycerol




Previous Year’s Questions
Nomenclature of Alcohols
Alcohols are named as alkanol as below. Which of the following compounds
CH3–CH2–CH2OH Propanol can be used as antifreeze in
Propan-2-ol automobile radiators?
Alcohol, Phenol & Ether




[AIPMT-2012]
(CH3)3COH 2-Methyl-propan-2-ol (1) Methyl alcohol
Ethan-1, 2-diol (2) Glycol
(3) Nitrophenol
(4) Ethyl alcohol



1.

, Isomerism Shown by Alcohols
Alcohol may show chain, position and
functional isomerism.
For example,
1. Butan-1-ol and 2-Methylpropan-1-ol are chain Rack your Brain
isomers.
2. Propan-1-ol and Popan-2-ol are position Draw the isomeric structure of
isomers. all isomeric alcohol of molecular
3. Benzyl alcohol and Anisole are functional formula C5H12O.
isomers.
General Methods of Preparation
Alcohols are mainly prepared by following
methods:
From alkanes (R–H): (Only by tertiary alkanes)
KMnO /OH−
R3C − H 
4
→ R3C − OH


KMnO /OH−
(CH3 )3 C − H 
4
→ (CH3 )3 C − OH
2−methyl Tertiary butyl alcohol Previous Year’s Questions
propane (2−methylpropan−2−ol)

y Here pink colour of KMnO4 disappears as the How many isomers of C5H11OH will
reaction proceeds forward. be primary alcohols?
From haloalkanes (R–X): [AIPMT]
Alkyl halides on hydrolysis by aqueous alkali (1) 5 (2) 4
like NaOH, KOH or moist Ag2O, give alcohols by (3) 2 (4) 3
substitution reaction as follows:


R − X + AgOH(aq) or KOH(aq) 
→ R − OH + AgX or KX

CH3Br + AgOH(aq) or KOH(aq) 
→ CH3OH + AgBr or KBr

y This method is suitable only for the production
of primary alcohols as secondary alkyl halides
give a mixture of alcohol and alkene. Tertiary
alkyl halides give only alkenes.
Alcohol, Phenol & Ether




For example,

(CH3 )2 CHBr 
KOH (aq)
→ CH3 ( )2 CHOH + CH3 − CH
= CH2 + KBr + H2O
Iso −proylbromide Isopropylalcohol Propene
(2°−halide)




2.

,From ether (R–O–R):
Ethers, on hydrolysis by dilute acids, produce Concept Ladder
alcohols.
dil.H2SO4 , ∆
R − O − R + H.OH  → 2R − OH
Addition of grignard reagent
For example, followed by hydrolysis with
dil. HCl gives, following
dil.H SO , ∆
CH3 − O − CH3 + H.OH 
2 4
→ 2CH3 − OH compounds;
Dimethyl ether Methanol (i) HCHO → 1° alcohols
y If alkyl groups are different, two types of (ii) Aldehydes (except
alcohols will be formed. For example, HCHO) → 2° alcohols
(iii) Ketone & Esters → 3°
alcohols
dil.H SO , ∆
C2H5 − O − C3H7 + H2O 
2 4
→ C2H5 − OH + C3H7OH
Ethylproyl ether Ethanol Pr opyl alcohol



From grignard reagent:
Preparation of primary, secondary and tertiary
alcohols using Grignard reagent is the ideal
method Grignard reagent reacts with carbonyl
compounds to form an intermediate compound,
which on hydrolysis, gives alcohol.




y Formaldehyde when reacted with Grignard
reagent gives primary alcohol while the other
aldehydes give secondary alcohols. Ketones Previous Year’s Questions
give tertiary alcohols.
Ethylene oxide when treated with
Grignard reagent yields
[AIPMT]
(1) primary alcohols
(2) secondary alcohols
Alcohol, Phenol & Ether




(3) tertiary alcohols
(4) cyclopropyl alcohol




3.

, Grignard reagent also reacts with oxirane
(Epoxy ethane) to give alcohol as follows:




Grignard reagent on reaction with Ethyl
formate gives 2°-alcohols and with other esters
give 3°-alcohols as follows.




By the reduction of carbonyl compound (R–CHO
and R–CO–R):
Carbonyl compounds on reduction by
reducing agents like LiAlH4, NaBH4, Zn/HCl or H2/
Ni, produce alcohols.
y Aldehydes on reduction, give primary alcohols
as shown: Concept Ladder
Ni
R − CHO + H2 
orLiAlH
→ R − CH2OH
4
Pr imary alcohol The reduction of carbonyl
For example, compound by addition of
H2 in presence of catalyst
Ni
CH3CHO + H2 →
orNa/C H OH
CH3CH2OH such as finely divided
2 5
Ethanal Ethanol
platinum, palladium, nickel
y Ketones on reduction, give secondary alcohols. or ruthenium.
Ni
R − CO − R '+ H2 
orLiAlH
→ R2CHOH
Alcohol, Phenol & Ether




4


For example,
Ni
CH3 − CO − CH3 + H2 
orLiAlH
→ (CH3 )2 CHOH
4
Pr opan−2−one Pr opan−2−ol




4.