对硝基甲苯合成对氨基苯甲酸实验报告Word下载.docx

1、Aromatic carboxylic acids are often prepared by oxidation of aromatic side chains. The aromatic ring of aromatic hydrocarbons is relatively stable and difficult to oxidize, and the chain of the ring regardless of length, as long as it has -H, in the strong oxidation, it will finally be oxidized to c

2、arboxyl groups. The laboratory generally oxidizes toluene by potassium permanganate to produce benzoic acidSince toluene is insoluble in potassium permanganate aqueous solution, the reaction is a two-phase reaction, so the reaction needs to be sufficiently stirred and refluxed at a higher temperatur

3、e for a relatively long period of time. After heating and refluxing, the potassium salt of the benzoic acid and the precipitation of manganese dioxide are obtained in the first place. The precipitate is separated and the potassium salt of the benzoic acid is acidified with hydrochloric acid to obtai

4、n benzoic acid, which is hardly soluble in water and crystallized easily.The reduction of nitro group can be done by Fe powder with acetate or Sn powder with condensed HCl. Fe is much cheaper but the yield is lower, so we choose to use Sn as reductant. As a matter of fact, the Sn salt of amino benzo

5、ic acid is toxic and needs special care to prevent skin exposure and inhalation.三主要试剂及产物的物理常数：名称分子量性状折光率比重熔点（oC）沸点（oC）溶解度（克/100ml溶剂）水醇醚4-nitrotoluene137.1378Yellow oblique facade crystal1.53821.2951.7238.5insolubleReadily soluble4-nitrobenzoic acid167.13Yellow or white oblique facade crystalunknown1

6、.6102392410.1gsoluble4-aminobenzoic acid137.14Colorless needle-like crystal1.374（25）187187.5Readily soluble（hot）sparingly soluble（cold）四主要试剂用量及规格：试剂名称用量规格2.5gA.R.ligroin20ml60-90 oCPotassium permanganate12.5gNaOH （aq）50%Sulfuric acid7.5mlcondensedEthyl acetateSn 4gpowderammonia water30mlHydrochloric

7、 acid15mlcyclohexaneethanol五实验装置图：六时间表TimesynthesischaracterizationWEEK1Oxidation of 4-nitrotolueneWEEK2Purificationm.p. determination, TLCIRWEEK3Reduction of 4-nitrobenzoic acidWEEK4H-NMRWEEK5七实验步骤及现象：The first week: oxidation of p-nitrotoluene1. Preparation of crude productPlace the magnet in a 10

8、0ml round bottom flask, and add 2.5 g （0.02 mol） of p-nitrotoluene and 30 mL of water, charge the reflux condenser, stir and heat to reflux. Add 6.00 g （0.04 mol） of potassium permanganate in portions from the mouth of the condenser tube within 30 minutes. In case of potassium permanganate plugging

9、the condenser, a small amount of water can be used to rinse the inner wall of the condenser tube. After that, plus a small amount of water to wash the potassium permanganate attached to the inner wall of the condenser into the bottle, the total water should not exceed 10mL. Continue reflux until the

10、 toluene largely disappears. Keep reflux for more than 60min after the addition of potassium permanganate.2. Crude product separationPump the mixture in the round bottom flask under reduced pressure with a water pump and wash the MnO2 residue with a small amount of hot water. If the filtrate is purp

11、le, add a small amount of saturated sodium bisulfite solution to make the color disappear, and re-filter. Pour the filtrate into a beaker and place in an ice-water bath, cool and acidify with concentrated hydrochloric acid until all p-nitrobenzoic acid is precipitated. Filter the precipitated p-nitr

12、obenzoic acid under reduced pressure, wash it with a small amount of ice water, and then dry it to obtain crude product. The second week: purification and characterization of p-nitrobenzoic acid3. Product refinementAfter drying, recrystallized the crude product in water. After the product is dried,

13、weigh it and calculate the yield.4. characterizationDo TLC analyses of both crude and purified product, melting point determination of both crude and purified product, IR determination of purified product.The third week: reduction of p-nitrobenzoic acid5.Preparation of crude productPlace the magnet

14、in a 50 ml three-necked flask, then add 4 g （0.025 mol） of Sn powder, 2.00 g （0.012 mol） of p-nitrobenzoic acid product and 5 ml of water to the mouth. Then add 3.5 ml （about 0.04 mol） of concentrated hydrochloric acid dropwise to the reaction system. During the addition of concentrated hydrochloric

15、 acid, keep the magnet spinning. When the addition is completed, keep heating to reflux until the reaction is completed. 6. Crude product separationCooling the system, then add 50% sodium hydroxide solution to the system is alkaline. Slowly add dilute hydrochloric acid, precipitation of solid will a

16、ppear in the ice bath. Filter the crude product under reduced pressure.The fourth week: Recrystallization of p-aminobenzoic acid7. Product refinementDissolve the crude product with a small amount of ethanol with heating, and then add petroleum ether. Cool the solution and solid precipitates.Do H-NMR

17、 determination. The fifth week: IR determination and cleaning the apparatus8.characerization and end of the experimentDo IR determination of the final product and clean and check the apparatuses.The potassium permanganate was crushed by a glass stopper, and then added into the flask in 3 times in 30

18、 minutes.（1:40-14:05）The plug in the condenser block occurred in the second addition.The solution turned purple after the addition, and some brown substance clung to the inner surface of the flask. After shaking, it gradually dissolved into the solution.Small amount of sodium bisulfite solution was

19、added, and the solution fainted.Relux（14:05-15:06）0.85g light yellow subsidence was collected.The subsidence was added into around 20ml water, then NaOH solution was added to make the solid dissolve. The solution became light yellow. By addition of dilute hydrochloric acid, subsidence appeared in ic

20、e bath.0.73g of refined grayish yellow product was obtained. Because the product did not reach expected amount, other chemicals was modified accordingly.The dosage:p-nitrobenzoic acid: 0.70gSn powder: 2.18gH2O: 4mlconcentrated hydrochloric acid: 2.5mlThe solution was yellow.There still remained some

21、 Sn powder which was separated by filtering.During the addition of sodium hydroxide, a series of phenomenon appeared: the solution became white and sticky at first（it was still acidic）, then it became white solution, after that the solution became clear（it was alkaline, pH=11）. After filtrating out

22、the subsidence, dilute hydrochloric acid was added. In the first place, some grain like subsidence showed up, then it became turbid. 0.9020g crude product was gained after filtration and drying.As soon as petroleum ether was added, white subsidence appeared.0.1103g refined product was gained after f

23、iltration and drying.八数据记录表格：The oxidation procedure:The weight of crude p-nitrobenzoic acid: 0.85gThe weight of purified p-nitrobenzoic acid: 0.73g TLC analyses:Product（crude） p-nitrotoluene Product（purfied） p-nitrotolueneRf=0.18 Rf=0.87 Rf=0.17 Rf=0.89m.p. determination （crude product）TfirstTtotTT

24、Taverage1234239523623722354m.p. determination （refined product）2403238241The reduction procedure:The weight of crude p-aminobenzoic acid: 0.9020gThe weight of recrystallized p-aminobenzoic acid: 0.1103g九产率计算：The yield of p-nitrobenzoic acid:0.73g167.13g/mol（2.5g137.1378 g/mol） 100%=23.96%The yield o

25、f p-aminobenzoic acid:0.1103g137.14g/mol（0.73g167.13 g/mol） 100%=18.41%Total yield:23.96%18.41%=4.41%十实验讨论：The yield was relatively low, and did not reach the reported yield according to the references. The following reasons may give the explanations:1.Because 250ml three-necked flask was not offere

26、d, the amount of ingredient could not match what had been required in the experimental scheme. The amount of ingredient was halved, which meant the regular loss in transfer and other experimental operations accounted for more proportion.2.In the oxidation procedure, the time for reflux was 60 min, w

27、hich seemed not long enough for p-nitrotoluene to be completely oxidized.3.There was no need to do the purification in the second week since TLC analysis showed the product did not contain the ingredient- p-nitrotoluene. And recrystallization inevitably reduced the yield of p-nitrobenzoic acid.4.Although petroleum lowered p-aminobenzoic acids solubility in ethanol, there still dissolved a relative large amount of product in the solvent. 5.The pH was not set well when crude p-aminobenzo