Chemistry

Organic Compounds with Functional Groups Containing Oxygen - I

Session

Session Objectives

1. Preparation of alcohols

2. Intermolecular dehydration

3. Esterfication

4. Iodoform reaction

5. Identification of different alcohols

Preparation of alcohols

Reduction of carbonyl compounds

Hydration of Alkenes

Grignard reactions

Reduction of Carbonyl Compounds

Strong reducing reagent are

required.

Reduction of compounds to alcoholsC O

R – CHO

CR

RO

R – COOHR – COOR`

R – COCl

2R – CH OH

CHOHR

R

2R – CH OH

2RCH OH+R`OH

2R – CH OH

Reduction of aldehydes and ketones

Reduction of carbohylic acids and their derivatives

Reagents used in reduction

4LiAlH

4NaBH

2H /Ni

2 6B H /THF

Reduce all the compounds except unsaturation

Can not reduce Acids, estersacid anhydride and unsaturation

Can reduce any groups and also unsaturation

Can reduce other groups except acid chloride

Hydration of Alkenes

Acid catalyzed Hydration

Oxymercuration-Demercuration

Hydroboration-Oxidation

Acid-Catalyzed Hydration of Alkenes R C C H

H HH+

H2OR C C

H

H

H

H

OH

R C C

HR'

R''H+

H2OR C C

H

HOH

R'

R''

Markovnikov addition

Formation of most stable carbocation

Shifts/rearrangements possible

Hydration of Alkenes via Oxymercuration/Demercuration

R C C H

H H

H2OR C C

H

H

H

H

OH

R C C

HR'

R'' R C C

H

HOH

R'

R''

Hg(OAc)2 NaBH4

H2O

Hg(OAc)2 NaBH4

Markovnikov addition

Typically no shifts/rearrangements

Mercurinium ion involvement

Hydroboration - Oxidation of Alkenes R C C H

H H

R C C

H

H

H

H OH

R C C

HR'

R'' R C C

HR'

R''

H OH

(BH3)2 OH-

H2O2

(BH3)2 OH-

H2O2

Anti-Markovnikov addition

No shifts/rearrangements

Syn addition

Grignard Addition Reactions

• Addition to Aldehydes/Ketones

• Addition to Esters

• Addition to Epoxides

Grignard Additions to Aldehydes/Ketones H C H

O

RMgXRCH2OH Primary ROH

RMgX

RMgX

R' C

OH

H

RR'

O

HC

R' R"

O

C R' C

OH

R

R"

Secondary ROH

Tertiary ROH

Formation of primary, secondary, and tertiary alcohols

Grignard Additions to Esters H C

O

OR R'MgX+ 2 R'2CHOH +ROHSecondary ROH

R'MgX+ 2R" C

O

OR R" C

R'

R'

OH +ROH

Teriary ROH

Formation of secondary and tertiary alcohols

Grignard Addition to Epoxides O +RMgX RCH2CH2OH

O

R' R'

+RMgX R' C

R

H

C R'

OH

H

Primary ROH

Secondary ROH

OR'

R'

R'

R'

+RMgX R' C

R

C R'

OH

R' R'Tertiary ROH

Typical Alcohol Reactions

Salt formation

Dehydration to alkene

Oxidation to aldehyde, ketone

Substitution to form alkyl halide

Reduction to alkane

Esterification

Williamson synthesis of ether

Reaction with Active Metals ROH

NaRO- Na++H2

Dehydration of Alcohols E-1 E-2

R C C

H

H

OHH+

R C C

H

H

OH2+

R C C

H

H

OH2+

H2Ords R C C

H

H+

R C C

H

H+ H+

R C

H

C

1,2-shifts/rearrangements possible

R C C

H

H

OHPOCl3

R C C

H

H

OPOCl2

N

R C C

H

H

OPOCl2 R C

H

C

a dichlorophosphate intermediate

Anti periplanar (coplanar) eliminationNo 1,2-shifts/rearrangements possible

Oxidation of Alcohols

Primary RCH2OH

RCHO

RCOOH

PCC

KMnO 4 or

K2Cr2O7²

Secondary R2CHOHPCC or

KMnO 4or

K2Cr2O7²

R C

O

R

Tertiary R3COHPCC or

KMnO 4²

no reaction

Alcohol Conversion to Alkyl Halides

Reaction with Hydrogen halides

Reaction with Thionyl chloride

Reaction with Phosphorus trihalides or pentahalides

Hydrogen halide conversion of alcohols to alkyl halides RCH2OH HX RCH2X

SN1

SN2 predominantly

predominantly

SN1 SN2orHX

HX

R2CHOH R2CHX

R3COH R3CX

where HX = HI, HBr, or HCl

Alcohols to Alkyl Chlorides via Thionyl Chloride

primary or secondaryalcohol

C OHSOCl2

C O S

O

Cl

alkyl chlorosulfite

Cl-

SN2C Cl +SO2 +HCl

Alcohols to Alkyl Halides via Phosphorus Halides primary or secondaryalcohol

C OH C O

H

PX2 SN

2C X HOPX2+

+

X-PX3

protonatedalkyl dihalophosphite

Ester Formation from Alcohols R C

O

ClR'OH

R C

O

OR'+

R C

O

OHR'OH

R C

O

OR'+H+

R C

O

O C

O

RR'OH

R C

O

OR'+R C OH

O

HCl

H2O

Haloform Reaction CH3 C

OH

H

HX2

OH-H+

H C

O

OHHCX3 +

CH3 C

OH

H

RX2

OH-H+

HCX3 + C

O

OHR

Methyl carbinol cleavage to give Carboxylic acids and Haloform

Physical properties

Alcohols consist of two parts, an alkyl group and a hydroxyl group. Due to which they have following properties:

They are capable to form hydrogen bonds.

High boiling points

Distinction between 1°, 2° and 3° alcohols

Victor–Meyer test

3° alcohols does not react.

1° alcohols

2° alcohols

blood red colouration

blue colouration

Lucas test

conc.hydrochloric acid and anhydrous zinc chloride.

2R O H ZnCl..

2R O ZnCl

|

H

Cl + R O ZnCl2 Cl R + [Zn(OH)Cl2]

H- +

2 2 2[Zn(OH)Cl ] + H ZnCl + H O

Lucas reagent

Lucas test

3R C– OH2

Conc. HCl

anhyd. ZnCl 3

Immediateturbidity

R C– Cl

2R CH– OH 2turbidityafter 5 min.

R CH– Cl2

Conc. HCl

anhyd. ZnCl

2RCH – OH No. reaction at

room temp.2

Conc. HCl

anhyd. ZnCl

2 2CH CH – CH OH2

Conc. HCl

anhyd. ZnCl 2 2CH CH – CH Cl

Immediate reaction

Illustrative example

Cyclobutyl bromide on reaction with Mg / dry ether forms an organometallic (A) The organometallic reacts with ethanol to give an alcohol (B) With an equivalent amount of HBr gives 1–bromo–1–methyl cyclopentane (C) Write the structures of (A),(B) and (C) and explain how (C) is obtained from (B).

Br Mg / Br

CH3CHO+Mg/dry ether

H+CH–CH3

OH

HBr CH–CH3

OH2+

2H O

CH–CH3

+

Solution

Solution

H

H

CH3

+–H shift

H

CH3

H

+–Br

CH3

Br

Ring transformation

20 cation 30 cation

Thank you