Chapter 3 ketone

Chapter 3: KETONE

Norfazrin Mohd Hanif

Faculty of Applied Science

UiTM Negeri Sembilan

SUBTOPICS

Nomenclature – common and IUPAC names for ketones

Physical properties of ketones : Boiling points and solubility

Preparation of ketone

Oxidation of 2 °Alcohol Friedel – Crafts Acylation

Reactions of aldehyde

Reduction To 2 ° Alcohol Nucleophilic Addition Reaction with Grignard Reagent Iodoform Reaction

• Functional group: carbonyl group

C O

C

O

R'R

ketone

R, R' = substituents

Ketone: the carbon atom in the carbonyl group is

bonded to two hydrocarbon groups.

Ketones

• The IUPAC name of a ketone is derived from the name of the alkane corresponding to the longest carbon chain that contains the ketone-carbonyl group.

• The parent name is formed by changing the –e ending of the alkane to -one.

propane propanone one

IUPAC NAME

If the carbon chain is longer than 4 carbons, it’s numbered so that the carbonyl carbon has the smallest number possible, and this number is prefixed to the name of the ketone.

This end of the chain is closest to the C=O.

Begin numbering here.

IUPAC NAME

IUPAC name: 3-hexanone

New IUPAC name: hexan-3-one

4 3 2 1 5 6

IUPAC NAME

7

Common Names of Ketones

: :

R C

O

R'

alkyl alkyl ketone

• Most common names for ketones are formed

by naming both alkyl groups on the carbonyl

carbon, arranging them alphabetically, and

adding the word “ketone”.

cyclohexanone 4-methylcyclohexanone

O

O

CH3

1 234

56

phenylethanone diphenylmethanone

C

O

CH3 C

O

Aromatic compound:

- phenyl is used as part of the name.

• The parent name is formed by changing the –e ending of the cycloalkane to -one.

• Carbonyl carbon is designated C1.

NOMENCLATURE OF CYCLIC KETONES AND AROMATIC COMPOUNDS

A ketone group can also be named as a substituent on

a molecule with another functional group as its root.

The ketone carbonyl is designated by the prefix oxo-.

Carboxylic acids frequently contain ketone group

named as substituents.

CH2 C

O

CCH3CH2

O

H CH2 C

O

CCH3

O

OH

3-oxopentanal

12345

3-oxobutanoic acid

1234

NOMENCLATURE OF KETONES CONTAINING TWO DIFFERENT FUNCTIONAL GROUPS

10

Physical Properties : Boiling point

• Oxygen is more electronegative than carbon (3.5

vs 2.5) and, therefore, a C=O group is polar

•Ketones are polar due to this C=O bond and

therefore have stronger intermolecular forces than

hydrocarbons making their boiling points higher.

C O C O –

Polarity of acarbonyl group

-+C O

+

More importantcontributing

structure

::: : :

11 11

Physical Properties : solubility

The small ketones are freely soluble in water but solubility falls

with chain length.

The reason for the solubility is that they can form hydrogen

bond with water molecules.

One of the slightly positive hydrogen atoms in a water

molecule can be sufficiently attracted to one of the lone pairs

on the oxygen atom of a ketone for a hydrogen bond to be

formed.

12 12

Physical Properties : solubility

• Ketones can form hydrogen bonds with water and therefore low

molecular weight ketones have appreciable water solubility

13

PreparationS

OXIDATION OF 2 °ALCOHOL

FRIEDEL – CRAFTS ACYLATION

14

• Examples

• Ketones can be made from 2o alcohols by oxidation

* [O] =

2.1 Oxidation of 2 °Alcohol

15

• Aromatic ketones can be made by Friedel-Crafts Acylation

• Examples

2.2 Friedel – Crafts Acylation

16

REACTIONS

REDUCTION TO 2 ° ALCOHOL

NUCLEOPHILIC addition

REACTION with grignard reagent

IODOFORM REACTION

REACTIONS OF KETONES

Reduction

Addition

Condensation

Iodoform reaction

Reaction with Grignard reagent

Ketones can be reduced to alcohols using:

a) lithium aluminium hydride (LiAlH4)

b) sodium borohydride (NaBH4)

c) catalytic hydrogenation

H+ = diluted acid such as H2SO4

R C R'

O-

H

R C R'

OH

H

H+

2o alcohol

R C R'

O

LiAlH4 or NaBH4 or H2, Niketone

CH3 C CH3

O-

H

H+

2-propanol

CH3 C CH3

O

H2/Ni

propanone

CH3 C CH3

OH

H

Example:

3.1 Reduction to Secondary Alcohols

C

O

R R' HCN

C

O

CH3 CH3 HCN

CR R'

OH

CN

CCH3 CH3

OH

CN

ketone

cyanohydrin

example

propanone

2-hydroxy-2-methylpropanenitrile

* Cyanohydrin may be formed using liquid HCN with a

catalytic amount of sodium cyanide or potassium cyanide.

3.2a Nucleophilic addition of hydrogen cyanide

C

O

R R' HCN

C

O

CH3 CH2CH3 HCN

CR CN

OH

R'

CCH3 CN

OH

CH2CH3

ketone

cyanohydrin

example

propan-2-one

H2O/H+

CR COOH

OH

R

a-hydroxyacid

NH4+

H2O/H+

CCH3 COOH

OH

CH2CH3

NH4+

'

Cyanohydrin can be hydrolysed to give α-hydroxyacids.

The nitrile (-CN) group is converted to the –COOH group by

reflux the cyanohydrin with dilute sulphuric acid (H2O/H+) or

concentrated HCl.

3.2a Nucleophilic addition of hydrogen cyanide

When shaken with an aqueous of sodium bisulphite, most

aldehydes and ketones formed carbonyl bisulphite (a

colourless crystal).

The reaction takes place more readily with aldehydes than

with ketones.

The nucleophile is the hydrogensulphite ion, HSO3-

Example:

NaHSO3 C

O

CH3 C

OH

CH3

OSO2- Na+

Bisulphite salts

3.2b Nucleophilic addition of sodium bisulphite

(NaHSO3)

Aldehydes and ketones condense with ammonia derivatives such as

hydroxylamine and substituted hydrazines to give imine derivatives.

i) Reaction with hydrazine:

Hydrazines derivatives reacts with aldehydes or ketones to form

hydrazones.

R C

O

R' H2N-NH2 R C

N

R'

NH2H+

H2Oaldehyde or ketone hydrazine

hydrazone derivative

Example:

C

O

H2N-NH2H+

hydrazineH2O

propanonepropanone hydrazone

H3C CH3 C

NNH2

H3C CH3

3.3 Condensation with hydrazines, hydroxlamine,

phenylhydrazine and 2,4-dinitrophenylhydrazine

ii) Reaction with hydroxylamine:

Hydroxylamine reacts with ketones and aldehydes to form

oximes.

R C

O

R' H2N-OH R C

N

R'

OHH+

H2Oaldehyde or ketone hydroxylamine oxime

Example:

H2N-OH H+

hydroxylamine

H2O

phenyl-2-propanone phenyl-2-propanone oxime

O N

OH



iii) Reaction with phenylhydrazine:

R C

O

R' R C

N

R'

NH-PhH+

H2Oaldehyde or ketone phenylhydrazine

phenylhydrazone

Example:

H+

H2O

penta-2-onepenta-2-one phenylhydrazone

H N NH

H

Ph

phenylhydrazine

H N NH

H

PhO N-NH-Ph



NO2

NO2NH2N

H

NO2

NO2NN

H

C

CH3

H2Oroom

temperature

butan-2-one 2,4-dinitrophenylhydrazonebutan-2-one 2,4-dinitrophenylhydrazine

C O

NO2

NO2NH2N

H

NO2

NO2NN

H

CR'

R

H2Oroom

temperature

2,4-dinitrophenylhydrazine

R

R'

2,4-dinitrophenylhydrazone(yellow-orange precipitate)

aldehyde or ketone

Example:

CH3 C CH2CH3

O

CH3CH2

iv) Reaction with 2,4-dinitrophenylhydrazine:



A Grignard reagent (a strong nucleophile resembling a

carbanion, R:- attacks the electrophilic carbonyl carbon atom to

give an alkoxide intermediate.

Subsequent protonation gives an alcohol.

MgBrCH3CH2C O

H3C

H3CC O- +MgBr

CH3

CH3

CH3CH2

C OH

CH3

CH3

CH3CH2

H3O+

2-methyl-2-butanol

alkoxideacetoneethylmagnesium bromide

3.4 Reaction with Grignard Reagent

IODOFORM TEST

- Reagent: solution of I2 in an alkaline medium such as NaOH or KOH.

- Iodoform test is useful for the methyl ketone group (CH3C=O) in ketones.

- when ketones containing methyl ketone group is warmed with iodoform reagent, a yellow precipitate of triiodomethane (iodoform) is formed.

The overall reaction is

R C

O

CH3 3I2heat

NaOH R C

O

O- Na+ CHI3 3HI

salts iodoform(yellow precipitate)

3.5 Haloform Reaction

TESTS ALDEHYDES KETONES

Tollens’ Test / silver mirror test

Reagent and condition:

- ammoniacal silver nitrate

solution ([Ag(NH3)2]+)

Observation:

Formation of silver mirror

Observation:

Silver mirror did not formed

* Ketones do not react with

Tollens’ reagent

Fehling’s test / Benedict’s test


-Solution of Cu2+ (aq) ions in an

alkaline solution of sodium

potassium tartate.

*Can be used to distinguish

between:

i) Aldehydes and ketones

ii) Aliphatic aldehydes and

benzaldehyde

Observation;

Blue colour of the Fehling’s

solution dissappears and

brick-red precipitate is

obtained

* Except benzaldehyde

Observation:

Blue colour remains.

* Ketones do not react with

Fehling’s/Benedict’s reagent

Schiff’s test


- Schiff’s reagent

Observation:

Formation of magenta-pink

colour (simple aldehydes)

* Except benzaldehyde and

a few aromatic aldehydes)

Observation:

Ketones (except propanone)

do not react with Schiff’s

reagent.

Tests to Distinguish Aldehydes and Ketones, and Aliphatic Aldehydes and

Aromatic Aldehydes

Thank you!

CHM 301 Chapter 1 : Alcohol

Question a. A compound , J (C4H10O), has three isomers K,L

and M. K is 2-methyl-1-propanol and L is 2-

methyl-2-propanol.

i) Draw the structural formulae of K and L

ii) Describe how you would prepare K using

Grignard reagent

iii) Draw structural formula of M and name it.

b. Compare and provide justification for the acidity

of phenol, ethanol and water.

Technology

Chapter 3 ketone