Transcript
Page 1: Preparation of p-nitroacetanilide- Dotsha J. Raheem

Week (1): Nitration of Acetanilide

Preparation of

p-nitroaniline Lecture by: Dotsha J. Raheem

Assistant LecturerDepartment of Chemistry

College of ScienceUniversity of Salahadin

2010

Page 2: Preparation of p-nitroacetanilide- Dotsha J. Raheem

Preparation of Acetanilide

NH2

Aniline

+ CH3

O

H3C

O

O

Acetic anhydride

H3C

O

OH

CH3HN

O

Acetanilide

H3C

O

OH+

Acetic acid

1.

Page 3: Preparation of p-nitroacetanilide- Dotsha J. Raheem

Nitration of Acetanilide2.

CH3HN

O

Acetanilide

HNO3 / H2SO4

CH3HN

OCH3HN

O

+NO2

NO2

o-nitroacetanilide p-nitroacetanilide"Major product"

Page 4: Preparation of p-nitroacetanilide- Dotsha J. Raheem

Hydrolysis of Acetanilide3.

CH3HN

O

NO2

p-nitroacetanilide

1) Hydrolysis

H+, H2O

2) OH

NH2

NO2

p-nitroaniline

Page 5: Preparation of p-nitroacetanilide- Dotsha J. Raheem

Importance of Acetanilide

NH2

Aniline

+ HNO3 / H2SO4

NH3

Anilinium ion

HNO3H2SO4 meta

substitution

Charring and oxidation of aniline

o,p-director

m-director

So, acetylation protects aniline

from protonation, charring and

oxidation

Page 6: Preparation of p-nitroacetanilide- Dotsha J. Raheem

This lab.:

CH3HN

O

Acetanilide

HNO3 / H2SO4

CH3HN

OCH3HN

O

+NO2

NO2

o-nitroacetanilide p-nitroacetanilide"Major product"

Page 7: Preparation of p-nitroacetanilide- Dotsha J. Raheem

Q/ The major product is para, but why not ortho?

This is mainly due to steric effect.

Page 8: Preparation of p-nitroacetanilide- Dotsha J. Raheem

ortho-nitroacetanilidepara-

nitroacetanilide

Page 9: Preparation of p-nitroacetanilide- Dotsha J. Raheem

ortho-nitroacetanilidepara-

nitroacetanilide

Page 10: Preparation of p-nitroacetanilide- Dotsha J. Raheem

Notes on the Experiment

Nitration of acetanilide is an exothermic reaction ; the temperature must be carefully controlled by chilling, stirring, and the slow addition of reagents.

The reaction is conducted below 10˚ C to maintain selectivity by preventing less favorable reactions from occurring [o- and 2,4-dinitro products require higher energy]

Page 11: Preparation of p-nitroacetanilide- Dotsha J. Raheem

Notes on the Experiment

Glacial acetic acid is used because it is a polar solvent capable of dissolving acetanilide, and the acetate ion is a poor nucleophile so no substitution is possible.

A mixture of concentrated nitric and sulfuric acids is used as the nitrating mixture.

Page 12: Preparation of p-nitroacetanilide- Dotsha J. Raheem

Notes on the Experiment

To prevent dinitration of the acetanilide, the nitrating mixture is added in small portions to the acetanilide solution (and not vice versa) so that the concentration of HNO3 is kept at a minimum.

After the addition is complete the beaker is allowed to stand at room temperature for 30 minutes [more than that will lead to the formation of 2,4-dinitroacetanilide].

Page 13: Preparation of p-nitroacetanilide- Dotsha J. Raheem

Notes on the Experiment

o-nitroacetanilide has higher solubility in the aqueous solution than p-nitroacetanilide.


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