Preparation Of P-nitroacetanilide- Dotsha J. Raheem 5s72r

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Preparation of Acetanilide O O

NH2

O

H3C + H3C Aniline

HN

O O

CH3

CH3

Acetic anhydride

O

OH + Acetanilide

H3C

OH

Acetic acid

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Nitration of Acetanilide O

HN

O

O CH3

HN HNO3 / H2SO4

HN

CH3 NO2

CH3

+ NO2

Acetanilide o-nitroacetanilide

p-nitroacetanilide "Major product"

ï

Hydrolysis of Acetanilide H

H

1) Hydrolysis

H

H ,H ) -nitroacetanilide

H -nitroaniline

_ m-director o,p-director à

à







à



à





So, acetylation protects aniline from protonation, charring and oxidation

















¯his lab.:

/

c ta ili - itr ac ta ili

- itr ac ta ili " a r r ct"

Æ ô

ô

¯he major product is para, but why not ortho? ¯his is mainly due to steric effect.

ortho-nitroacetanilide

para-nitroacetanilide

ortho-nitroacetanilide

para-nitroacetanilide

Notes on the Experiment ô

ô

Nitration of acetanilide is an exothermic reaction ; the temperature must be carefully controlled by chilling, stirring, and the slow addition of reagents. ¯he reaction is conducted below 0Û C to maintain selectivity by preventing less favorable reactions from occurring [o- and 2,4dinitro products require higher energy]

Notes on the Experiment ô

ô

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.

Notes on the Experiment ô

ô

¯o 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].

Notes on the Experiment ô

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