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

Ether

General formula is Cn H 2n+ 2 O

• Classification : It may be divided in two
  • Aliphatic ethers : Both R of ether are alkyl

H

|

Example : CH3  – O – CH3 , CH3  – C – O– CH 2  – CH 2  – CH3 .

 

Dimethyl ether

|

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

Diphenyl ether

 

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

Diphenyl ether

• 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

sp ³

hybridised. Two of the hybrid orbitals overlap with hybrid

 

 

orbital (one each) of two carbon atoms to form sigma bonds.

s         s

–

–

C O  C

. The bond angle is 110^o .

 

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.

O

CH3 – OCH = CH 2 ; CH₂ – CH₂ ; H ₂C– CH ₂ ; H C                CH  ;  C6 H5 OCH3

 

Methyl vinyl ether

{unsaturated}

|

O                   H2C

|               2

CH2           |

• Anisole

|            (Methyl phenyl ether)

 

Ethylene oxide

{cyclic}

O

Tetra hydro furan

H₂C

O

CH₂

 

(3)  Nomenclature :

Dioxan

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 ;

Methoxy

C2 H5 O  .

Ethoxy group

 

• The R group having the longest carbon chain is chosen as the parent

Example : CH3  – O – C2 H5 ,           OCH

 

Methoxy ethane

3

 

Methoxy benzene

 

Note : ® In case of simple ethers common names are also accepted in IUPAC system.

• Isomerism : Ether show the following types of isomerism :
  • Chain isomerism

CH3

|

Example : CH3 – O – CH 2 CH 2 CH 2 CH3 , CH3  – O – CH2  – CH – CH3 .

 

1-methoxy butane

 

• Functional isomerism

1-methoxy-2-methyl propane

 

 

 

OCH₃

 

CH₂OH

 

Example : CH3 – O – CH3  « CH3  – CH2  – OH ,

 

Dimethyl ether

 

• Metamerism

Ethanol

Anisole

Benzyl alcohol

 

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

 

Sodium ethoxide

Ethyl bromide

Ethoxyethane

 

• 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 3^o > 2^o > 1^o .
• For better yield alkyl halide should be primary and alkoxide should be secondary or

 

CH3

|

CH3

|

 

C2 H5 Br + NaO – C– CH3 ® C2 H5  – O – C– CH3

 

Ethyl bromide

|

CH3

Sodium salt of tert. butyl alcohol

|

CH3

Ethyl tert. butyl ether

 

 

 

• Secondary and tertiary alkyl halides readily undergo E₂

form alkenes.

elimination in the presence of a strong base to

 

CH3

|

CH3

|

CH3

|

CH3

|

 

CH3  – C– Cl ¾¾^C2 H¾5O¾^Na ® CH3  – C^Å + Cl ^– , CH3  – C^Å + C2 H5 O^–  ® CH3  – C+ C2 H5 OH

 

|

CH3

|

CH3

|

CH2 –H

||

CH2

 

SN ² mechanism : C2 H5 ONa ⇌ C2 H5 O^– + Na ⁺ ,

 

C2 H5 O^– + C2 H5 I ¾¾^slo¾^w ® C2 H5 O – – – –C2 H5  – – – –I ¾¾^Fa¾^st ® C2 H5 OC2 H5  + I ,

Trnsition state

Na ⁺ + I ^–

⇌ NaI

 

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 ¾¾^he¾^at ® R – O – R + 2AgX , 2C₂ H₅ Br+ Ag ₂O ¾¾^he¾^at ® C₂ H₅OC₂ H₅ + 2AgBr

 

 

(2)  From alcohols

• By dehydration of alcohols

Ethyl bromide

Diethyl ether

 

• With H₂SO₄ at 140° C :

ROH + HOR  ¾¾^H2S¾^O4¾^(con¾^c.) ® ROR+ H 2 O .

 

2 molecules of alcohol

140^o C

Ether

 

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 ¾¾^H2S¾^O4¾^(con¾^c.) ® CH3  – O – C2 H5  + CH3  – O – CH3  + C2 H5  – O – C2 H5

 

Methanol

Ethanol

140^o C

 

• With Al₂O₃ at 250° C :

2ROH  ¾¾^Al2¾^O¾3  ® R – O – R + H2O

250^o C

 

• By the action of diazomethane on alcohols : This reaction is in presence of catalyst, boron trifluoride or HBF₄ .

ROH + CH 2 N 2  ¾¾^B¾^F3  ® R – O – CH3  + N 2

 

• Addition of alcohols to alkenes :

CH 2  = CH 2  + HOR ¾¾^H2S¾^O¾4  ® CH3  – CH 2  – OR .

 

 

The intermediate is carbonium ion.

Alcohol

Ether

 

CH 2

= CH 2

+ H ⁺

+

⇌ CH3 C H 2 ,

+

CH3 C H2

+ HOR ® CH₃CH₂

+

,

• O– R

|

H

 

CH3 CH 2

+

–H +

– O– R ¾¾¾® CH

₃CH 2

• O – R .

 

|                                           Ether

H

• 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 ]

|          |

® –       –

|       |

NaBH

¾¾¾¾4  ® –      –

 

_{3 2}        C         C                                                 C     C

 

alkene

Mercuric trifluoro acetate                    |          |                                                   |       |

 

OR  HgOOCCF₃

OR H

Ether

 

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

 

Halogenated ether

Grignard reagant

Higher ether

 

• Higher members can be prepared by the action of grignard reagent on lower halogenated

• Ether form soluble coordinated complexes with grignard

Physical properties

• 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

sp ³

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

R                                                                                 R

 

Ether

Water

H………..O    R

 

Ether

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  ¾¾^C¾^l2  ® CH3 CHClOCH2 CH3

 

Diethyl ether

dark

(a -Monochlorodiethyl ether )

 

CH3CH2OCH2CH3 ¾¾^C¾^l2  ® CH3CHClOCHClCH3

 

Diethyl ether

dark

(a ,a ¢-Dichlorodiethyl ether )

 

C2 H5OC2 H5  + 10Cl2  ¾¾^C¾^l2  ®

light

C2Cl5OC2Cl5

(Perchlorodiethyl ether)

• 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 .

 

..          ..

¯..

: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

to ether.

 

• With strong oxidising agent like acid, dichromate ethers are oxidised to CH3CH2OCH2CH3 ¾¾^2[¾^O] ® 2CH3CHO+ H2O

Acetaldehyde

• The presence of peroxide can be indicated by the formation of blood red colour complex in the following

n

Peroxide + Fe ⁺² ® Fe ⁺³ ¾¾^SCN¾-  ®[Fe(SCN) ]^3–n

Blood red colour (n=1 to 6)

 

 

• Oxidation with K Cr O

a

/ H^Å : R –

a ¢               R¢

• O –

 

2      2    7

CH2

CH       R¢

 

• 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  ¾¾^K2C¾^r2O¾7  ® CH3  – COOH + CH3  – CH 2  – COOH

H ^Å / D

 

 

CH3

• CH2

• O – CH

CH3 ¾¾^K2 C¾^r2 O¾7  ® CH

• COOH + CH₃

O

||

• C– CH3

 

3

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.

H

|

..

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

|

H

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 ¾¾^H2¾^O ®(C2 H5 )2 O+ HCl

 

|

H

Oxonium salt

Diethyl ether

 

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

BF3 ,

 

AlCl  ,

FeCl , etc. These complexes are called etherates. CH3CH2

..

O :

+BF

®  CH3CH2

..

® BF

 

• ³ CH3CH2

O

³     CH3CH2                          3

 

Boron trifluoride etherate (complex)

Similarly, diethyl ether reacts with Grignard reagent forming Grignard reagent etherate.

 

2(CH₃CH

₂)₂ O + RMgX ®

R

(CH3CH2 )2 O

Mg        O(CH2CH3  )2

X

 

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

• Hydrolysis

• With dil. H 2 SO4 :  ROR + H 2 O ¾¾^H2S¾^O¾4  ® 2ROH

C2 H5 OC2 H5 + H 2 O ¾¾^H2S¾^O¾4  ® 2C2 H5 OH

 

Diethyl ether

 

• With H ₂SO₄ :

Ethanol

 

C2 H5OC2 H5 + H2SO4 ® C2 H5OH + C2 H5 HSO4 C2H5OH+H2SO4 ®C2H5 HSO4 +H2O

 

C2 H5OC2 H5 +2H2SO4 ®  2C2 H5 HSO4   +H2O

 

Diethyl ether

• Action of hydroiodic acid

Ethyl hydrogen sulphate

 

• With cold HI :

C2 H5OC2 H5 + HI ¾¾^Co¾^ld ® C2 H5 I  + C2 H5OH

 

Diethyl ether

Ethyl iodide

Ethyl alcohol

 

Note : ® Same reaction are observed with HBr and HCl. The order of reactivity of halogen acid HI>HBr>HCl.

OC₂H₅                    OH

 

+ HBr  ®                    + C₂H₅Br

 

 

Phenyl ethyl ether

Phenol

Ethyl bromide

 

 

 

Mechanism of the reaction

.⁺.                               ₊      R

 

R – O – R+ H – X ®  R – O– R +       X ^–     , X^– + R – O

®  R – X  + R – OH

 

Ether

|

H

Protonated ether

Nucleophile

..    H

Alkyl halide

Alcohol

 

• 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 ¾¾^he¾^at ® 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  ¾¾^he¾^at ® 2RCl + POCl3 . There is no reaction in cold.

 

• Reaction with acetyl chloride :

CH3 COCl+ C2 H5  × O × C2 H5  ¾¾^ZnC¾^l2  ® CH3 COOC2 H5

 

Acetyl chloride

Diethyl ether

heat

Ethyl acetate

 

• Reaction with acid anhydride :

CH3 CO × O × OCCH3 + C2 H5 × O × C2 H5  ¾¾^ZnC¾^l2  ® 2CH3 COOC2 H5

 

 

• Dehydration :

Acetic anhydride

 

C2 H5 OC2 H5  ¾¾^Al2O¾3  ® 2CH2  = CH2  + H2O

2

300^o C

Diethyl ether

heat

Ethyl acetate

 

• Reaction with carbon mono oxide : C2 H5 OC2 H5

+ CO ¾¾^BF3¾^/15¾⁰o¾^C ® C

500 atm.

H5 COOC2 H5

 

Diethyl ether

+    –

Ethyl propionate

+     –

 

• 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.

 

..

:OR

..

:O – R

..

⁺OR

..

⁺OR

..

⁺OR

:

 

 

 

 

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)

 

bromide catalyst.

OCH₃

 

¾¾^B¾^r2  ®

CS2

OCH₃

Br

+

OCH₃

 

Anisole

 

Para isomer is obtained in 90% yield.

o-Bromoanisole

Br

p-Bromoanisole

 

 

 

 

• Friedel craft reaction

OCH₃

 

AlCl

 

OCH₃

 

 

CH₃

 

OCH₃

;

 

OCH₃

 

OCH₃

 

 

COCH₃

 

OCH₃

 

 

 

 

Anisole

+  CH3 Cl

Methyl chloride

¾¾¾3  ®

 

 

OCH₃

 

 

Ortho

+

 

CH₃

Para

 

 

 

OCH₃

 

 

Anisole

 

 

 

NO₃

+ CH

₃COCl ¾¾^AlC¾^l3  ®

 

 

OCH₃

+

o-Methoxy acetophenone

 

COCH₃

p Methoxy acetophenone

 

• Nitration :

¾¾^HN¾^O3 /¾^H2S¾^O¾4  ®                          +

 

 

 

Methyl phenyl ether (Anisole)

Methyl-2 nitrophenyl ether (o-Nitroanisole)

NO₃

Methyl-4

nitrophenyl ether (p-Nitroanisole)

 

Note : ® Ethers are relatively less reactive than phenol towards electrophilic substitution reaction.

• Di methyl ether : It is the simplest
  • Preparation

(a) It can be prepared by using any of the general method of preparation.

 

(b)

2CH3 OH ¾¾^D,¾^Alu¾^min¾^a¾® CH3  – O – CH3  + H2O 350^o -400^o C,15 atm

 

(c) It can be manufactured by dehydration of methyl alcohol with conc. H ₂SO₄

• Properties

at 140^o C .

 

• It is colourless highly inflammable gas having P. of – 24.8^o C .
• It is soluble in water, alcohols and other organic solvents and gives all the characteristic reactions of
  • Uses
• 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  ¾¾^he¾^at ® C2 H5 HSO4  + H2O

C2 H5 HSO4  + C2 H5 OH ® C2 H5 OC2 H5 + H 2 SO4

 

[Excess]

It is also known as Williamson’s etheral continuous process.

• Properties

Diethyl ether

 

• 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

34.5^o C .

 

 

 

 

• Uses
• It is used as a
• It is used as a reaction medium in

 

LiAlH4

 

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 :

2CH

₃CH = CH2

• H2

O ¾¾^H¾+  ®(CH  )

3

2

3-7 atm

75-125^o C

CHOCH(CH₃ )₂

 

• Properties : It is a colourless liquid with a pear like odour having P. 68.5^o C .
• Uses : It is used for reducing knocking of petrol.

(4)  Divinyl ether

 

• Preparation :
• Properties

CH2

ClCH

₂OCH

₂ClCH2

+ 2KOH ¾¾^D ® CH₂



= CHO– CH = CH₂

• 2KCl + H₂O

 

• It is highly inflammable
• It is colourless and boils at 3^o 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–

O

 

• Preparation

• By oxidation of ethylene with oxygen :

2CH2  = CH2  + O2  ¾¾^A¾^g ® 2CH2  – CH2

250^o C

 

 

• By oxidation of ethylene with peroxy acids :

O

RCH = CHR ¾¾^C6 H¾5CO¾3¾^H ® R – CH – CH – R .

or CF3CO3H

 

O

• By treatment of ethylene chlorohydrin with NaOH

CH2  = CH2 ¾¾^HO¾^Cl ® ClCH2 – CH2OH ¾¾^NaO¾^H ® CH2 – CH2 Ethylene chlorohydrin

O

• Properties

• 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+

|      |                              |       |

HOH                                                         +

 

C– C                    – C– C– ¾¾¾® – C – C – + H

|       |

 

O                              O+

|

H

(Protonated epoxide)

OH OH

Glycol

 

 

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

 

 

R                                                    Å

OCH3

R                |

 

C – CH– R ¾¾^CH¾3 O¾^Na ¾^{/ C}¾^H3¾^O¾^H ®

R          O                                                            R

C – CH– R .

|

OH

 

• Case II : Acid catalysed ring opening : Nucleophile attacks on carbon of oxirane ring which is highly

 

substituted. SN ² reaction is there.

OCH3

 

R      C – CH– R ¾¾^CH¾3 OH¾^{/ H}¾Å  ® R       C– CH – R

|

O

R                                                             R              |

OH

Some reactions of oxirane are given below

 

 

 



CH₃OH/H

CH₂

– CH₂OH

 

|

OCH₃

2-Methoxy ethanol

CH OH – CH X

2                    2

Ethylene halohydrin

 

CH OH – CH NH

 

CH₂ – CH₂ O

(Ethylene oxide)

2                    2       2

2-Amino ethanol

OCH₃

|

CH₂ – CH₂OH

2-Methoxy ethanol

 

 

 

R – CH₂ R – CH₂

• CH₂

Alcohol

 

• CH₂

• OH

 

• OH

 

 

Uses

Å

(ii) HOH/H

CH₃

– CH₂

Ethanol

– OH

 

• 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

 

18-crown-6

 

K    C N + R – CH 2  – X ¾¾¾¾¾® R – CH 2  – CN + KX

 

benzene

100% yield

 

 

C6 H5  – CH2  – Cl + K ^Å F ^ ¾¾^18-c¾^row¾ⁿ¾^-6 ® C6 H5  – CH 2  – F + K ^ÅCl ^

 

acetonitrile

100% yield

 

 

 

 

18-crown-6                                             12-crown-6

A crown ether binds certain metal ions depending on the size of the cavity.

 

 

 

+ Na⁺ ®

 

 

 

 

Host

Inclusion compound

 

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)

• Preparation

• 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 ¾¾^ThO¾2  ® 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.

 

OCH₃

 

+ E⁺

OCH₃

 

E        +

OCH₃

 

 

E

 

+ H⁺

 

Anisole is decomposed by conc. hydroiodic acid again into phenol.

OCH₃                    OH

 

 

+ HI

 

heat

 

+ CH₃I