LECTURE NOTE SK025 (ORGANIC) KMKt

(D) DEHYDRATION

❑ Reactant : alcohol

❑ Condition : • conc. H2SO4
• heat

❑ Product : alkene and H2O

CC acid CC + H2O
H OH heat

H and OH eliminated!

❑ Follow Saytzeff’s rule

EXAMPLE:

ethanol ethene

H conc. H2SO4 + H2O
H OH heat
cyclohexene
cyclohexanol

EXERCISE:

Give the product formed for the following reaction:

a) O—H + Na

b) O

C—OH + CH3OH H+

∆

c) CH3 conc. H2SO4
CH3C–CH2CH3
OH ∆

(E) SUBSTITUTION REACTION USING HX, PX3 ,
PCl5 OR SOCl2

❑ ROH reacts with HX, PX3 , PCl5 or SOCl2
to produce haloalkane.

General reaction: RX + H2O (X = Cl, Br)
(i) ROH + HX
RX + H3PO3 (X = Cl, Br)
(ii) ROH + PX3
(iii) ROH + PCl5 RCl + POCl3 + HCl
(iv) ROH + SOCl2
RCl + SO2 + HCl

EXAMPLE:

CH3 CH3
CH3 C Cl + H2O
CH3 C OH + HCl
(conc.) CH3

CH3 Hydrogen chloride

(CH3)2CHCH2OH + PBr3 (CH3)2CHCH2Br + H3PO3

Phosphorus tribromide

CH3CH2OH + PCl5 CH3CH2Cl + POCl3 + HCl

Phosphorus pentachloride

CH2OH CH2Cl
+ SO2 + HCl
+ SOCl2

thionyl chloride

EXERCISE:

Give the structures of the products you
would expect when 2–methyl–2–butanol
reacts with:

a) HCl
b) PBr3
c) SOCl2

ANSWER :

a)

b)

ANSWER :

c)

EXERCISE:

Show how each of the following transformations
could be accomplished:

O

a) CH2OH ? CH

b) CH2OH ? O
C OH

OH ?O
c)

1) LUCAS TEST

❑ Lucas reagent : HCl(conc.) + ZnCl2

R-OH conc. HCl, R-Cl + H2O
ZnCl2

TYPE OF ALCOHOL OBSERVATION

1o No cloudy solution form at room
temperature even after 15 minutes.

2o Cloudy solution formed within 5 - 10
minutes.

3o Cloudy solution formed immediately.
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Example :

CH3CH2CH2CH2CH2OH conc. HCl no observable changes
1–pentanol
ZnCl2 even after 15 minutes at
room temperature

(1o alcohol)

OBSERVATION: No cloudy solution form at room
temperature even after 15 minutes.

OH conc. HCl Cl
ZnCl2
CH3CH2CHCH2CH3 CH3CH2CHCH2CH3 + H2O

3–pentanol 3–chloropentane
(2o alcohol)

OBSERVATION: Cloudy solution formed within 5 - 10
minutes.

OH Cl

CH3CHCH2CH3 conc. HCl CH3CHCH2CH3 + H2O
CH3 ZnCl2 CH3

2–methyl-2-butanol 2–chloro-2-methylbutane
(3o alcohol)

OBSERVATION: Cloudy solution formed immediately.

2) OXIDATION TEST

Class of alcohol Reaction with Observation

1o acidified K2Cr2O7 or Na2Cr2O7 Orange colour of K2Cr2O7
turned to green.

acidified KMnO4 Purple colour of KMnO4
is decolourised.

2o acidified K2Cr2O7 or Na2Cr2O7 Orange colour of K2Cr2O7
turned to green.

acidified KMnO4 Purple colour of KMnO4
is decolourised.

acidified K2Cr2O7 or Na2Cr2O7 Orange colour of K2Cr2O7
remain unchanged.
3o
Purple colour of KMnO4
acidified KMnO4 remain unchanged.

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❑ Oxidation using acidified solution of
K2Cr2O7 or Na2Cr2O7 or CrO3 :

Ethanol Orange (Cr6+) Ethanoic acid
(1o alcohol)
Green (Cr3+)

OBSERVATION: Orange colour of K2Cr2O7 turns to green.

Example: Na2Cr2O7/H+ O
CH3C–OH
CH3CH2–OH ∆
ethanoic acid
ethanol
(1o alcohol)

OBSERVATION: Orange colour of Na2Cr2O7 turns to

green.

OH Na2Cr2O/,H+ O

CH3CHCH3 ∆ CH3C–CH3

2–propanol propanone
(2o alcohol)

OBSERVATION: Orange colour of Na2Cr2O7 turns to green.

OH

CH3C–CH3 Na2Cr2O7/H+ no reaction
CH3
∆

2–methyl-2–propanol
(3o alcohol)

OBSERVATION: Orange color of Na2Cr2O7 remain
unchanged.

3) IODOFORM TEST

❑ To detect methyl carbinol group.
❑ Reagent: excess I2 , NaOH (base)
❑ Methyl carbinol cleavage to give

carboxylate ion and iodoform.

OH excess I2 O + CHI3 ↓
R–C–CH3 OH– R–C–O-
iodoform
H
(yellow precipitate)

OBSERVATION: Light yellow precipitate formed.

Example:

OH excess I2 O + CHI3 ↓
CH3CH2C–CH3 OH– CH3CH2C–O–
iodoform
H

OBSERVATION: Light yellow precipitate formed.

OH excess I2 O + CHI3 ↓
CH3C— OH– –O–C—
iodoform
H

OBSERVATION: Light yellow precipitate formed.

EXERCISE:

Show how you would use a simple test to
distinguish between the following pairs of
compounds. Tell what you would observe with
each compound:

(a) 1–hexanol and cyclohexanol
(b) 2-butanol and 3-pentanol
(c) 2–butanol and 1–methylcyclohexanol

ANSWER :

(a) 1–hexanol and cyclohexanol

ANSWER :

(b) 2-butanol and 3-pentanol

ANSWER :

(c) 2–butanol and 1–methylcyclohexanol

8.5 LEARNING OUTCOMES

Phenol
a) Compare the acidity of phenol, alcohol and water
b) Explain the chemical properties of phenol with

reference to:
i. Reaction with sodium
ii. Reaction with sodium hydroxide

c) Identification tests using
i. FeCl3 solution and
ii. bromine water

8.5 PHENOL

Phenol Acidity of phenol

Compare the acidity of phenol, alcohol and water

Chemical Properties of Phenol

Reaction with sodium
Reaction with sodium hydroxide
Identification test using:

Bromine water
FeCl3

ACIDITY OF PHENOL, ALCOHOL AND WATER

❑ Alcohol, water and phenol have different
acidity (different Ka values).

❑ Acidity increases in the order of :

Alcohol < water < phenol
(aliphatic alcohol)

❑ Like water, both alcohol and phenol are
weakly acidic.

– As weak acid (donate H+):

Water H—O—H H—O– + H+
hydoxide ion
(Ka ≈ 10-14 )

Alcohol R—O—H R—O– + H+

alkoxide ion (Ka ≈ 10-16 )

Phenol

O—H O– + H+

(Ka ≈ 10-10 )

phenoxide ion

Alcohol(aliphatic alcohol) < Water < Phenol

❑ Phenol more acidic than aliphatic alcohol
and water.
⮚ due to phenoxide ion formed is more
stable than the alkoxide ion (from alcohol)
and hydroxide ions (from water).

O H release proton O-
+ H+

phenoxide ion

❑ The phenoxide ion formed is stabilised by
resonance effect.

RESONANCE–STABILIZED PHENOXIDE ION

●●●O●●●– ●●O●● ●●O●● ●●O●● ●●●O●●●–
– –

–

❑ The ability to spread the negative charge
over four atoms rather than concentrated
it on just one atom produces more stable ion.

Example:

OH CH2CH2OH CH2OH OH

,, ,

Acidity increase

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CHEMICAL PROPERTIES OF PHENOL

1) Reaction with Na

❑ Both alcohols and phenols can react with Na.

EXAMPLE: O– Na+ + ½H2↑
OH + Na O– Na+ + ½H2↑

phenol
OH + Na

cyclohexanol

2) Reaction with NaOH

❑Phenols are soluble in aqueous NaOH but
alcohols with six C atom or more do not.

❑ Phenols are much more acidic than alcohols.

EXAMPLE: O– Na+ + H2O
O—H + NaOH
sodium phenoxide
phenol
almost insoluble
CH3(CH2)4CH2OH + NaOH
1–hexanol 96

IDENTIFICATION TEST

1) Using FeCl3 solution

❑ Phenol reacts with aqueous solution of
iron (III) chloride to form a purple complex.

OH OH

+ FeCl3 (aq)

FeCl3

Purple complex

OBSERVATION: Purple complex formed.

2) Using bromine water

❑ Phenol reacts with aqueous bromine to
form white precipitate.

OH OH
+ Br2
H2O Br Br
+ HBr

Br

2,4,6-tribromophenol

White precipitate

OBSERVATION: White precipitate formed.

CHAPTER 9 :
CARBONYL

COMPOUNDS

This Photo by Unknown Author is licensed under CC BY-SA

9.1 Introduction
9.2 Nomenclature
9.3 Preparation
9.4 Chemical Properties

9.1 Introduction –
Carbonyl compounds in daily life

Vanilla beans: Cinnamon
Vanilin cinnamaldehyde

Bitter almonds Odor of roses
benzaldehyde -damascone

2

9.1 Introduction

O O FORMALIN
camphor carvone
aqueous solution of
37% formaldehyde

(by mass)

3

Learning Outcomes:
9.1 a)

State the general formula of

aldehyde and ketones:

OO
|| ||
R—C—H and R—C— R’

9.1 Introduction

General Aldehyde &
formula: Ketone are
CnH2nO
isomeric

O

C polar

compound

Functional group:
Carbonyl

5

Aldehyde Ketone

RCHO RCOR’

Oδ- Oδ-
||δ+ R—C||δ—+ R’
R—C—H

R: Carbonyl R and R’ :
alkyl, Compounds alkyl or aryl
aryl or H

6

Learning Outcomes:

9.1 b)

Give name for aldehydes and
ketones according to the
IUPAC nomenclature.

9.1 c)

Give the structures for
aldehydes and ketones in 9.1 b)
(parent chain ≤ C10)

9.1 Nomenclature Aldehyde

ALDEHYDE is BASIC NAME The CHAIN is
named by depends on NUMBERED
substituting the the longest by starting
letter –e of the chain with with –CHO
corresponding –CHO group. group as C1.
alkane with
-al.

8

SIMPLE ALDEHYDE

Structure IUPAC name Common name

O Methanal Formaldehyde
HCH

O Ethanal Acetaldehyde
H3C C H
benzenecarbaldehyde
O
C phenylmethanal (benzaldehyde)

H

9

ALDEHYDE

The chain is numbered by starting with –CHO
group as C1.

Example : O

CH2 CH CH2 C H

4 3 21

3-butenal

1

Example :

OH O

H3C4 CH CH C H
3
21

CH2CH3

2-ethyl -3-hydroxy butanal

*alphabetical order; e followed by h

11

Example :

Br

2

64 O
3
1
5

4-bromo -3-cyclopentylhex-5-enal 12

Example :

O
CH

cyclohexane carbaldehyde

13

Example :

O

CH2 C H

2 1

2-phenylethanal

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9.1 Nomenclature Ketone

KETONE is BASIC NAME Chain is Common
numbered in functional group
named by depends on the way that names for
gives the ketones
substituting the the longest carbonyl separately
letter –e of the chain with carbon atom naming the two
corresponding carbonyl the lower groups attached
alkane with group. possible to carbonyl
number, this group and
–one. number is used adding the word
to designated ketone as a
its position. separate word.

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KETONE

EXAMPLE: O

H3C CH2CH3 CH3 C CH3

propane → propanone

O

H3C CH2CH2CH3 CH3 C CH2CH3

butane → butanone @ 2-butanone

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