Chapter 14 Hydroxy Compounds (Alcohals, Phenols) and ethers Part 3- Chemistry free study material by TEACHING CARE online tuition and coaching classes
Ethers are anhydride of alcohols, they may be obtained by elimination of a water molecule from two alcohol molecules.
R – OH + HO – R ® R – O – R+ H 2O
General formula is Cn H 2n+ 2 O
- Classification : It may be divided in two
- Aliphatic ethers : Both R of ether are alkyl
Example : CH3 – O – CH3 , CH3 – C – O– CH 2 – CH 2 – CH3 .
Isopropyl propyl ether
- Aromatic ethers : In which either one or both R of ether are aryl
Example : C6 H5 – O – CH3
Methyl phenyl ether
or C6 H5 – O – C6 H5
Aromatic ethers are divided in two category.
- Phenolic ethers : Ethers in which one of the group is aryl and other one is
Example : C6 H5 – O – CH3 .
methyl phenyl ether
- Diaryl ether : In which both the groups are aryl group.
Example : C6 H5 – O – C6 H5
- Symmetrical and unsymmetrical ethers,
- An ether in which both the R are same known as symmetrical
Example : CH3 – O – CH3 , C6 H5 – O – C6 H5 .
Dimethyl ether Diphenyl ether
- An ether in which the both R are different called unsymmetrical ethers or mixed
Example: CH3 – O – C2 H5 and CH3 – O – C6 H5 .
Ethyl methyl ether Methyl phenyl ether
- Structure : The oxygen atom in ether is
hybridised. Two of the hybrid orbitals overlap with hybrid
orbital (one each) of two carbon atoms to form sigma bonds.
C O C
. The bond angle is 110o .
Besides the open chain saturated homologous series, there are numerous organic compounds in which – O – functional group is present. These compounds are also termed ethers.
CH3 – OCH = CH 2 ; CH2 – CH2 ; H 2C– CH 2 ; H C CH ; C6 H5 OCH3
Methyl vinyl ether
| (Methyl phenyl ether)
Tetra hydro furan
(3) Nomenclature :
There are two systems for naming ethers.
- Common names : When both the alkyl group are same, the prefix di– is In case of unsymmetrical ethers two alkyl groups are named in alphabetical order.
Example : CH3 OCH3 , C2 H5 OC3 H7 .
Di methyl ether Ethyl propyl ether
- IUPAC system : Ethers are named as alkoxy alkanes.
- The ethernal oxygen is taken with smaller alkyl
Example : CH3 O ;
C2 H5 O .
- The R group having the longest carbon chain is chosen as the parent
Example : CH3 – O – C2 H5 , OCH
Note : ® In case of simple ethers common names are also accepted in IUPAC system.
- Isomerism : Ether show the following types of isomerism :
- Chain isomerism
Example : CH3 – O – CH 2 CH 2 CH 2 CH3 , CH3 – O – CH2 – CH – CH3 .
- Functional isomerism
Example : CH3 – O – CH3 « CH3 – CH2 – OH ,
Example : CH3 CH2 – O – CH2CH3 « CH3 – O – CH2 – CH2 – CH3
Ethoxy ethane Methoxy propane
(1) From alkyl halides
- Williamson’s synthesis : It is the laboratory method for the preparation of
It is a nucleophilic substitution reaction and proceed through
RONa + R¢X ® ROR¢ + NaX
C2 H5 ONa + CH3 – I ® CH3 OC2 H5 + NaI
SN 2 mechanism.
Sodium ethoxide Ethyl methyl ether
C2 H5 ONa + C2 H5 Br ® C2 H5 OC2 H5 + NaBr
- Order of reactivity of primary halide is CH3 X > CH3 CH 2 X > CH3 CH 2 CH 2 X .
- Tendency of alkyl halide to undergo elimination is 3o > 2o > 1o .
- For better yield alkyl halide should be primary and alkoxide should be secondary or
C2 H5 Br + NaO – C– CH3 ® C2 H5 – O – C– CH3
Sodium salt of tert. butyl alcohol
Ethyl tert. butyl ether
- Secondary and tertiary alkyl halides readily undergo E2
elimination in the presence of a strong base to
CH3 – C– Cl ¾¾C2 H¾5O¾Na ® CH3 – CÅ + Cl – , CH3 – CÅ + C2 H5 O– ® CH3 – C+ C2 H5 OH
SN 2 mechanism : C2 H5 ONa ⇌ C2 H5 O– + Na + ,
C2 H5 O– + C2 H5 I ¾¾slo¾w ® C2 H5 O – – – –C2 H5 – – – –I ¾¾Fa¾st ® C2 H5 OC2 H5 + I ,
Na + + I –
Note : ® Aryl halide and sodium alkoxide cannot be used for preparing phenolic ethers because aryl halide are less reactive toward nucleophilic substitution reaction than alkyl halides.
- By heating alkyl halide with dry silver oxide
2RX + Ag 2 O ¾¾he¾at ® R – O – R + 2AgX , 2C2 H5 Br+ Ag 2O ¾¾he¾at ® C2 H5OC2 H5 + 2AgBr
(2) From alcohols
- By dehydration of alcohols
- With H2SO4 at 140° C :
ROH + HOR ¾¾H2S¾O4¾(con¾c.) ® ROR+ H 2 O .
2 molecules of alcohol
Note : ® In this reaction alcohol must be present in excess.
- This reaction is mainly applicable for the dehydration of primary Secondary and tertiary alcohols form alkenes mainly.
- When this reaction is carried out between different alcohols then there is a mixture of different ethers is obtained.
Example : CH3 OH+ C2 H5 OH ¾¾H2S¾O4¾(con¾c.) ® CH3 – O – C2 H5 + CH3 – O – CH3 + C2 H5 – O – C2 H5
- With Al2O3 at 250° C :
2ROH ¾¾Al2¾O¾3 ® R – O – R + H2O
- By the action of diazomethane on alcohols : This reaction is in presence of catalyst, boron trifluoride or HBF4 .
ROH + CH 2 N 2 ¾¾B¾F3 ® R – O – CH3 + N 2
- Addition of alcohols to alkenes :
CH 2 = CH 2 + HOR ¾¾H2S¾O¾4 ® CH3 – CH 2 – OR .
The intermediate is carbonium ion.
= CH 2
+ H +
⇌ CH3 C H 2 ,
CH3 C H2
+ HOR ® CH3CH2
- O– R
CH3 CH 2
– O– R ¾¾¾® CH
- O – R .
- This method is very useful for preparing mixed
- In higher cases, there can be 1, 2-hydride or 1, 2-methyl shift to form more stable carbonium
(3) Alkoxy mercuration-demercuration
- C = C < +R – OH + Hg[OOCCF ]
® – –
¾¾¾¾4 ® – –
3 2 C C C C
Mercuric trifluoro acetate | | | |
Note : ® This is the best method for the preparation of t-ethers.
(4) Reaction of lower halogenated ether with grignard reagent
ROCH2 X+ XMgR¢ ® ROCH2 R¢+ MgX 2
- Higher members can be prepared by the action of grignard reagent on lower halogenated
- Ether form soluble coordinated complexes with grignard
- Physical state : Methoxy methane and methoxy ethane are gases while other members are volatile liquid with pleasant
- Dipole moment (D.M.) : Bond angle of ether is due to
hybridisation of oxygen atom. Since C – O
bond is a polar bond, hence ether possess a net dipole moment, even if they are symmetrical.
D.M. of dimethyl ether is 1.3 D
D.M. of di ethyl ether is 1.18 D
Note : ® The larger bond angle may be because of greater repulsive interaction between bulkier alkyl groups as compared to smaller H-atoms in water.
- Boiling points : Boiling points of ethers are much lower than those of isomeric alcohols, but closer to alkanes having comparable This is due to the absence of hydrogen bonding in ethers.
- Solubility : Solubilities of ethers in water are comparable with those of alcohols.
Example : Di ethyl ether and n-butyl alcohol have approximately the same solubility in water. This is because, ether form hydrogen bond with water much in the same way as alcohol do with water.
R O………. H O
Note :® Solubility of ether in water decreases with the size of alkyl groups.
- Hydrogen bonding : There is no hydrogen directly attach (bonded) to oxygen in ethers, so ethers do not show any intermolecular hydrogen
R R R
| | |
H – O– – – H – O– – – H – O– – –
hydrogenbonding in alcohols
R – O – R
No hydrogen bond in ether
- Density : Ethers are lighter than
Chemical properties : Ethers are quite stable compounds. These are not easily attacked by alkalies, dilute mineral acids, active metals, reducing agents or oxidising agents under ordinary conditions.
(1) Reaction due to alkyl group
- Halogenation :
CH3 CH 2 OCH 2 CH3 ¾¾C¾l2 ® CH3 CHClOCH2 CH3
(a -Monochlorodiethyl ether )
CH3CH2OCH2CH3 ¾¾C¾l2 ® CH3CHClOCHClCH3
(a ,a ¢-Dichlorodiethyl ether )
C2 H5OC2 H5 + 10Cl2 ¾¾C¾l2 ®
- 10 HCl
- Burning : Ethers are highly They burn like alkanes.
C2 H5 – O – C2 H5 + 6O2 ® 4CO2 + 5H 2 O
(2) Reaction due to ethernal oxygen
.. .. ..
- Peroxide formation :
C2 H5 OC2 H5 + O :® C2 H5 O C2 H5
or (C2H5 )2 O ® O .
- The boiling point of peroxide is higher than that of It is left as residue in the distillation of ether and may cause explosion. Therefore ether may never be evaporated to dryness.
- Absolute ether can be prepared by distillation of ordinary ether from H 2SO4
over metallic sodium.
and subsequent storing
Note :® Formation of peroxide can be prevented by adding small amount of Cu2 O
- With strong oxidising agent like acid, dichromate ethers are oxidised to CH3CH2OCH2CH3 ¾¾2[¾O] ® 2CH3CHO+ H2O
- The presence of peroxide can be indicated by the formation of blood red colour complex in the following
Peroxide + Fe +2 ® Fe +3 ¾¾SCN¾- ®[Fe(SCN) ]3–n
Blood red colour (n=1 to 6)
- Oxidation with K Cr O
/ HÅ : R –
a ¢ R¢
- O –
2 2 7
- Oxidation of ether can only be possible if any one of the alkyl groups of ether has hydrogen on a-carbon.
- a-carbon having two hydrogens converts in carboxylic group and a-carbon having only one hydrogen converts into keto
a a ¢
CH3 – CH2 – O – CH2 – CH 2 – CH3 ¾¾K2C¾r2O¾7 ® CH3 – COOH + CH3 – CH 2 – COOH
H Å / D
- O – CH
CH3 ¾¾K2 C¾r2 O¾7 ® CH
- COOH + CH3
- C– CH3
CH3 H Å / D
- Salt formation : Due to lone pair of electrons on oxygen Ether behaves as Lewis base and form stable oxonium salt with strong inorganic acids at low temperature.
C2 H5OC2 H5 + HCl ® (C2 H5 )2 O+ Cl – or [(C H ) O × H]+ Cl –
2 5 2
Diethyl oxonium chloride
C H OC H + H SO ®
- + HSO–
or [(C H ) O × H]+ HSO–
2 5 2 5 2 4
(C2 H5 )2 O 4
2 5 2 4
Diethyl oxonium hydrogen sulphate
The oxonium salts are soluble in acid solution and ethers can be recovered from the oxonium salts by treatment with water. (C2 H5 )2 O Cl ¾¾H2¾O ®(C2 H5 )2 O+ HCl
Note : ® The formation of oxonium salt is similar to the formation of ammonium salts from ammonia and acids.
- Ether is removed from alkyl halides by shaking with H 2 SO4 .
- Ethers can be distinguished from alkanes with the help of this
- Reaction with Lewis acids : Being Lewis bases, ethers form complexes with Lewis acids such as
FeCl , etc. These complexes are called etherates. CH3CH2
- 3 CH3CH2
3 CH3CH2 3
Boron trifluoride etherate (complex)
Similarly, diethyl ether reacts with Grignard reagent forming Grignard reagent etherate.
2)2 O + RMgX ®
(CH3CH2 )2 O
Mg O(CH2CH3 )2
Grignard reagent etherate
Due to the formation of the etherate, Grignard reagents dissolve in ether. That is why Grignard reagents are usually prepared in ethers. However, they cannot be prepared in benzene, because benzene has no lone pair of electrons and therefore, cannot form complexes with them.
(3) Reaction involving cleavage of carbon-oxygen bond
- With dil. H 2 SO4 : ROR + H 2 O ¾¾H2S¾O¾4 ® 2ROH
C2 H5 OC2 H5 + H 2 O ¾¾H2S¾O¾4 ® 2C2 H5 OH
- With H 2SO4 :
C2 H5OC2 H5 + H2SO4 ® C2 H5OH + C2 H5 HSO4 C2H5OH+H2SO4 ®C2H5 HSO4 +H2O
C2 H5OC2 H5 +2H2SO4 ® 2C2 H5 HSO4 +H2O
- Action of hydroiodic acid
Ethyl hydrogen sulphate
- With cold HI :
C2 H5OC2 H5 + HI ¾¾Co¾ld ® C2 H5 I + C2 H5OH
Note : ® Same reaction are observed with HBr and HCl. The order of reactivity of halogen acid HI>HBr>HCl.
+ HBr ® + C2H5Br
Phenyl ethyl ether
Mechanism of the reaction
.+. + R
R – O – R+ H – X ® R – O– R + X – , X– + R – O
® R – X + R – OH
- This can be explained on the basis of steric hinderence.
- The above reaction is a SN ¢
- The ether molecule gets protonated by the hydrogen of the acid to form protonated ether and the
protonated ether undergoes nucleophilic attack by halide ion halide.
[X – ]
and form alkyl alcohol and alkyl
- With hot HI :
R – O – R¢ + 2HI ¾¾he¾at ® RI + R¢I + H 2 O
- Zeisel method : RI + AgNO3 (alc.) ® AgI ¯ +RNO3
Note : ® The silver iodide thus form can be detected and estimated. This formed the basis of Zeisel method for the detection and estimation of alkoxy group in a compound.
- Action of PCl5 :
R – O – R + PCl5 ¾¾he¾at ® 2RCl + POCl3 . There is no reaction in cold.
- Reaction with acetyl chloride :
CH3 COCl+ C2 H5 × O × C2 H5 ¾¾ZnC¾l2 ® CH3 COOC2 H5
- Reaction with acid anhydride :
CH3 CO × O × OCCH3 + C2 H5 × O × C2 H5 ¾¾ZnC¾l2 ® 2CH3 COOC2 H5
- Dehydration :
C2 H5 OC2 H5 ¾¾Al2O¾3 ® 2CH2 = CH2 + H2O
- Reaction with carbon mono oxide : C2 H5 OC2 H5
+ CO ¾¾BF3¾/15¾0o¾C ® C
H5 COOC2 H5
- Action of bases :
Li CH3 + H – CH2 – CH2 – O – CH2 – CH3 ® CH4 + CH2 = CH2 + Li OC2 H5
- Ring substitution in aromatic ethers : Alkoxy group is ortho and para directing and it directs the incoming groups to ortho and para It activates the aromatic ring towards electrophilic substitution reaction.
:O – R
I II III IV V
III, Iv and V show high electron density at ortho and para position.
- Halogenation : Phenyl alkyl ethers undergo usual halogenation in benzene
For example, Bromination of anisole gives ortho and para bromo derivative even in the absence of iron (III)
Para isomer is obtained in 90% yield.
- Friedel craft reaction
+ CH3 Cl
3COCl ¾¾AlC¾l3 ®
p Methoxy acetophenone
- Nitration :
¾¾HN¾O3 /¾H2S¾O¾4 ® +
Methyl phenyl ether (Anisole)
Methyl-2 nitrophenyl ether (o-Nitroanisole)
nitrophenyl ether (p-Nitroanisole)
Note : ® Ethers are relatively less reactive than phenol towards electrophilic substitution reaction.
- Di methyl ether : It is the simplest
(a) It can be prepared by using any of the general method of preparation.
2CH3 OH ¾¾D,¾Alu¾min¾a¾® CH3 – O – CH3 + H2O 350o -400o C,15 atm
(c) It can be manufactured by dehydration of methyl alcohol with conc. H 2SO4
at 140o C .
- It is colourless highly inflammable gas having P. of – 24.8o C .
- It is soluble in water, alcohols and other organic solvents and gives all the characteristic reactions of
- It is used in the form of compressed liquid as a refrigerant, low temperature solvent and propellant for
- It is used for storing food stuffs by freezing on direct contact because it doe not leave any undesirable taste or
- Diethyl ether (Sulphuric ether) : It is the most important member of the ether series and is known as It may also be regarded as an anhydride of C2 H5OH (ethanol).
- Preparation : Laboratory method : C2 H5 OH + H2 SO4 ¾¾he¾at ® C2 H5 HSO4 + H2O
C2 H5 HSO4 + C2 H5 OH ® C2 H5 OC2 H5 + H 2 SO4
It is also known as Williamson’s etheral continuous process.
- It is a colourless, highly volatile and inflammable liquid having boiling point
- It has a pleasant smell and burning
- It is only slightly soluble in water but readily soluble in organic
- Di ethyl ether is itself a very good solvent even for fats and
- It produces unconsciousness when
34.5o C .
- It is used as a
- It is used as a reaction medium in
reduction and grignard synthesis.
- It is used as an extracting solvent in
- Mixture of alcohol and ether is used as petrol substitute under the trade name
- It is used in perfumary and in the manufacture of smokeless
(3) Di-isopropyl ether
- Preparation :
3CH = CH2
O ¾¾H¾+ ®(CH )
- Properties : It is a colourless liquid with a pear like odour having P. 68.5o C .
- Uses : It is used for reducing knocking of petrol.
(4) Divinyl ether
- Preparation :
+ 2KOH ¾¾D ® CH2
= CHO– CH = CH2
- 2KCl + H2O
- It is highly inflammable
- It is colourless and boils at 3o C .
- Uses : It is better anaesthetic than di ethyl ether because of its rapid action and rapidrecovery from
(5) Epoxides [oxirane] or cyclic ether – C– C–
- By oxidation of ethylene with oxygen :
2CH2 = CH2 + O2 ¾¾A¾g ® 2CH2 – CH2
- By oxidation of ethylene with peroxy acids :
RCH = CHR ¾¾C6 H¾5CO¾3¾H ® R – CH – CH – R .
- By treatment of ethylene chlorohydrin with NaOH
CH2 = CH2 ¾¾HO¾Cl ® ClCH2 – CH2OH ¾¾NaO¾H ® CH2 – CH2 Ethylene chlorohydrin
- It is a poisonous, flammable
- Its P. is 14 o C .
- It is very reactive compound because of its strained
- An epoxide is converted into protonated epoxide by acid which can undergo attack by any nucleophilic
– | | H+
| | | |
C– C – C– C– ¾¾¾® – C – C – + H
Some of the chemical reactions
- Case I : Base catalysed ring opening : In this case nucleophile attack on less hindered carbon of the oxirane ring and reaction is SN 2
C – CH– R ¾¾CH¾3 O¾Na ¾/ C¾H3¾O¾H ®
R O R
C – CH– R .
- Case II : Acid catalysed ring opening : Nucleophile attacks on carbon of oxirane ring which is highly
substituted. SN 2 reaction is there.
R C – CH– R ¾¾CH¾3 OH¾/ H¾Å ® R C– CH – R
R R |
Some reactions of oxirane are given below
CH OH – CH X
CH OH – CH NH
CH2 – CH2 O
2 2 2
CH2 – CH2OH
R – CH2 R – CH2
- It is used in the manufacture of ethylene
- It is used in the manufacture of
- It is used in the manufacture of solvent ethoxy ethanol used in varnishes and enamels for quick
- Crown ethers : The crown ethers are heterocyclic poly-ethers usually with at least four oxygen These are called crown ethers because they have crown like shape.
18-crown-6 means compound is eighteen member ring compound out of which [18 – 6 = 12] 12 atoms are carbon [i.e. six ethylene group – CH 2 – CH 2 – ] and six atoms of oxygen.
Crown ethers have remarkable affinity for metal ions.
Example : 12-crown-4 has affinity with Li Å and 18-crown-6 has affinity with K Å .
Example : Å
K C N + R – CH 2 – X ¾¾¾¾¾® R – CH 2 – CN + KX
C6 H5 – CH2 – Cl + K Å F ¾¾18-c¾row¾n¾-6 ® C6 H5 – CH 2 – F + K ÅCl
A crown ether binds certain metal ions depending on the size of the cavity.
+ Na+ ®
In this reaction, the crown ether is the ‘host’ and the species it binds is the ‘guest’. The crown-guest complex is called an inclusion compound.
(7) Anisole (Methyl phenyl ether) C6H5OCH3 or (methoxy benzene)
- By the action of methyl iodide on sodium
C6 H5 ONa + ICH3 ® C6 H5 OCH3 + NaI
- By passing vapours of phenol and methyl alcohol over heated
C6 H5 OH + CH3 OH ¾¾ThO¾2 ® C6 H5 OCH3 + H2O
- By methylation of phenol with
C6 H5 OH + CH2 N 2 ® C6 H5 OCH3 + N 2
- Properties : It is a pleasant smelling It is used as a solvent in some organic reactions. Anisole
undergoes electrophilic substitution reactions. – OCH3
group is o– and p– directing.
Anisole is decomposed by conc. hydroiodic acid again into phenol.