Preparation of P-Nitroacetanilide - Dotsha J. Raheem [PDF]

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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



$



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.