Lab Report Preparation of p-nitroaniline PDF

Preview

Summary

Download Lab Report Preparation of p-nitroaniline PDF

Description

Preparation of p-Nitroaniline Maria Roca February 12th, 2020 Aim: to make p-nitroaniline from aniline through a three- step synthesis Fist Step, acylation of aniline, second step Nitration of Acetanilide; and third step, deacylation of nitro acetanilide. Reaction Mechanisms:

Data: Table #1: Acylation of Aniline Reactant (Aniline) Grams Microliters(µL 100 ) Table #2: Nitration of Acetanilide Reactant (Acetanilide) Grams 0.0194 g Microliters(µL )

Reagent (Acetic anhydride)

Solvent (Acetic Acid)

200

400

Reactant (Acetic Acid)

Solvent (Sulfuric Acid)

Reagent HNO2 + H2SO4

200

300

300

Table #3: Deacylation of nitro acetanilide Reactant (p-nitro Solvent acetanilide) (Distilled Water) Grams 0.0197 Microliters(µL 700 )

Hydrochloric Acid 700

Results: Table #4: Acylation of Aniline Calculations Mass of Weighting Paper 0.4001 (g) Mass of Weighting Paper 0.4195 + Product (g) Mass of Product 0.0194 (Acetanilide) (g) 3 Moles of acetanilide 10 mmol 1 mol =0.1435 mmol × 0.0194 g × (mol) 1mol 135.17 g /mol g Moles of aniline (mol) ×0.1 mL=0.1022 g 1.022 reactant mL 1 mL =0.1 mL 100 µL × 1000 µL 103 mmol 1 mol × =1.097 mmol 0.1022 g × 93.13 g/mol 1 mol 0.1435mmol Percent Yield (%) ×100=13.08 % 1.097 mmol Table #5: Nitration of Acetanilide Calculations Mass of Weighting Paper 0.4047 (g) Mass of Weighting Paper + 0.4244 Product (g) Mass of Product (p-nitro 0.0197 acetanilide) (g) Moles of p-nitro 103 mmol 1mol =0.1093 mmol × 0.0197 g × acetanilide (mol) 1 mol 180.16 g /mol 0.1093mmol Percent Yield (%) ×100=76.16 % 0.1435mmol Table #6: Deacylation of nitro Calculations Mass of Weighting Paper 0.3883 (g) Mass of Weighting Paper + 0.3885 Product (g) Mass of Product (p0.0002 nitroaniline) (g) Moles of p-nitroaniline 1 mol 10 3 mmol 0.0002 g × =0.001448 mmol × (mol) 1mol 138.12 g /mol

Percent Yield (%)

0.001448mmol ×100=1.32 % 0.1093mmol

Discussion: Nitroanilines are used as a chemical intermediate in many manufactured dyes. In this particular experiment we synthesized p-nitroaniline which is used in the synthesis of the azo dye Para Red. The preparation of p-nitroaniline was accomplished by a three-step synthesis. In the first step, acetylation of aniline, where aniline reacted with acetic anhydride to form acetanilide as the major product by nucleophilic substitution. In this reaction, acetic anhydride acts as the electrophile and aniline acts as the nucleophile. We needed to put the removable acetyl protecting group on the nitrogen of aniline. The acetyl group is an electron withdrawing group which makes the lone pairs in the nitrogen atom less reactive during a protonation reaction or an oxydation reaction. The second step, nitration of acetanilide, a nitro group is added into an organic chemical compound. In this step we first formed a nitronium ion in situ by dehydration of nitric acid. We also used sulfuric acid as the dehydrating agent. Because the nitronium ion is a very powerful electrophile, it will cause it to react with the pi electrons of the aromatic ring of aniline. The third and last step, involves the deacylation of nitro acetanilide, the solution was refluxed and HCL was used in order to hydrolyze the n-acyl group so we could be able to regenerate the amino group. Lastly, the solution was poured in ammonia solution to produce free amine. Initially in the first step after the aniline, acetic acid and acetic anhydride were added, the flask became warm because it was an exothermic reaction. During the third step, the deacylation of nitro acetanilide, we added hydrochloric acid and heated the mixture at a gentle boil. As we heated all of the solid dissolved and the solution became orange in color. After the flask was removed from the heating source, we let it cool to room temperature and the crystals of pnitroaniline separated. We added to the solution ammonia in order to make it strongly basic, we tested the basicity by placing a drop of the solution on the test strip (blue color). After, we performed vacuum filtration and we were able to successful collect the orange precipitate of pnitroaniline. Acetanilide was successful obtained after performing acetylation of aniline with a 13.08% yield. During the second step, p-nitro acetanilide was obtained after the nitration of acetanilide with a 76.16% yield. Lastly, we were able to synthesize p-nitro aniline after the deacylation of nitro acetanilide with a 1.32% yield. Some of the yield was lost while doing the vacuum filtration some of the solid might have stayed dissolved in the liquid filtrate. Also, we might have lost product while measuring the masses or transferring the reactants or products....