Thursday, February 28, 2019
Organic Chemistry Experiment 4 Ã¢â¬ Recrystallization Essay
INTRODUCTIONRecrystallization is the primary method for purifying solid organic fertiliser compounds. Compounds obtained from natural sources or from reaction mixtures almost always contain impurities. The impurities may include some combination of insoluble, soluble, and colored impurities. To obtain a tenuous compound, these impurities must be removed. Each is removed in a stop step in the recrystallization procedure. 8Acetylation of aniline by acetic anhydride was per word formed to synthesize the sodding(a) phenylacetamide. The obtained bare-assed acetanilid contained acetic acid as well as unreacted acetic anhydride. The said impurities of the crude acetanilide were removed using activated charcoal, filtration and recrystallization.EXPERIMENTALA. Compounds sieveedaniline oil aminobenzine is a clear to about yellow liquid with a characteristic odor. It does not readily vaporize at room temperature. Aniline is slightly solublein piss system and mixes readily with most organic solvents. Aniline is used to make a wide variety of products such as polyurethane foam, agricultural chemicals, synthetic substance dyes, antioxidants, stabilizers for the rubber industry, herbicides, varnishes and explosives. 2 Aniline is wide-awake commercially by the catalytic hydrogenation of nitrobenzene or by the action of ammonia on chlorobenzene. The reduction of nitrobenzene can to a fault be carried out with iron borings in aqueous acid. 6 Preparation of AnilineC6H5NO2 + 3 H2 C6H5NH2 + 2 H2O(a)(b) estimate 1. (a) Hydrogenation of nitrobenzene (b) Bechamp reductionacetic anhydrideacetic anhydride is clear, colorless liquid with a strong, pungent, sour vinegar-like odor, lachrymator. 5 Acetic anhydride is an important solvent and acetylation agent. 4 It is used in the manufacture of acetyl compound, cellulose ethanoates, acetylizer and solvent in examining sheepskin fat, glycerol, fatty and volatile oils, resins, detection of rosin, in organic synthesis, such a s dehydrating agent in nitrations, sulfonations and other reactions where removal of water is necessary. 5 Acetic anhydride is prepared by the carbonylation of methyl acetate. There is a two-stage process for the preparation of acetic anhydride, in which, in a first step, methyl bromide or, preferably, iodide is carbonylated to raise the corresponding acetyl halide, such acetyl halide in turn cosmos reacted with methyl acetate, in a second step, to provide acetic anhydride, which corresponds to the succeeding(a) reaction scheme, in the event that methyl iodide is the starting material 7 flavour 1CH3I + CO CH3COIStep 2CH3COI + CH3COOCH3 (CH3CO)2O + CH3I telephone number 2. Carbonylation of methyl acetateB. Procedure1. Choosing the Recrystallizing SolventA corn-grain amount of keen acetanilide was position into each of three test thermionic valves. Methanol, hexane, and water were added to each test tube respectively. Each was shaken and was placed in a warm lavatorytub (37 oC-40oC) for 1-5 minutes and then was cooled.Figure 3. Pure acetanilide in test tubes containing different solvents methanol, hexane, water respectively.2. Acetylation of Aniline by Acetic AnhydrideAniline solvent was made by mixing 2mL of aniline with 20mL of distilled water. 3mL of acetic anhydride was then added to the resolvent to form acetylation. The over-all closure was then placed in an ice bath to form crystals of crude acetanilide.Figure 4. 2mL of aniline mixed with 20mL of distilled waterFigure 5. 3mL of acetic anhydride added to the aniline dissolverFigure 6. Crystallization of crude acetanilide in an ice bath 3. refinement of Crude acetanilid by RecrystallizationThe crude acetanilide crystals were filtered through a wet filter paper. The respite was then arid and weighed. In a separate Erlenmeyer flask, the crude acetanilide residue was placed and 20mL of the recrystallizing solvent was added. The solution was then heated on a hot plate until the entire solid di ssolved completely. When the solution became colored, it was removed from the heat and enough amount of activated charcoal was added. The estrus process continued until the solution became colorless. While the solution was still hot, it was speedily filtered using a fluted filter paper. Its filtrate was then cooled by placing the manslayer in a beaker with cold water. The crystals that formed were collected and were washed. When thecrystals completely dried up, it was then weighed.Figure 7. Filtration of the crude acetanilide crystalsFigure 8. Crude acetanilide residue mixed with the recrystallizing solventFigure 9. Heating process of the solutionFigure 10. Addition of the activated charcoal to the solutionFigure 11. go along heating process of the solution until colorlessFigure 12. Filtration and recrystallization of the acetanilideFigure 13. Weighing of the dried acetanilide crystalsRESULTS AND DISCUSSION1. Choosing the Recrystallizing SolventAmong the three recrystallizing so lvents methanol, hexane, and water, water was chosen to be used in the recrystallization of the acetanilide. Table 1. Solubility of polished acetanilide in various solvents At room temp. During heating Upon alterWater Insoluble oil-soluble InsolubleMethanol Soluble Soluble SolubleHexane Insoluble Insoluble Insoluble2. Acetylation of Aniline by Acetic AnhydrideThe crude acetanilide was obtained by the acetylation of the aniline. The crude acetanilide obtained was 7.2 grams in its weight. 3. Purification of Crude Acetanilide by RecrystallizationPure acetanilide was obtained by the recrystallization of the crude acetanilide. From the 7.2 grams of crude acetanilide, 1.2 grams of pure acetanilide was gathered.Theoretical YieldAniline2mL x 1.0217 g/mL = 2.0434 g2.04 g x 1 seawalle x 135.17 g =93.13 g 1 mol2.96 g AcetanilideAcetic Anhydride3mL x 1.082 g/mL = 3.246 g3.246 g x 1 mol x 135.17 g =102.09 g 1 mol4.30 g Acetanilide Aniline is the limiting reagent.Percentage Yield= literal Yield x blowTheoretical Yield= 1.20 grams x 1002.96 grams= 40.54 %The experiment conducted was able to perform different chemical processes. In choosing the recrystallizing solvent, solubility test was conducted among various solvents methanol, hexane, and water. The solubility test resulted to the conclusion of choosing water as the recrystallizing solvent. The experiment also included the acetylation of aniline by acetic anhydride toform the crude acetanilide. In the experiment, 7.2 grams of crude acetanilide was obtained. Since the crude acetanilide has impurities, it was purified by several processes heating of solution, activated charcoal addition, and recrystallization. When recrystallization has already occurred in the solution, the pure acetanilide was then obtained. 40.54% of the pure acetanilide was gathered with its weight of 1.2 grams.REFERENCES1 Acetylation of Aniline using Acetic Anhydride. http//prolabscientific.com/Acetylation-of-Aniline-using-Acetic-Anhydride-p- 23917.html. 2 Agency for poisonous Substances & Disease Registry Toxic Substances Portal Aniline. http//www.atsdr.cdc.gov/toxfaqs/tf.asp?id=449&tid=79. 3 Bayquen, A. V., Cruz, C. T., de Guia, R. M., Lampa, F. F., Pea, G. T., Sarile, A. S., & Torres, P. C. (2009). Laboratory Manual in Organic Chemistry. 839 EDSA, South Triangle, Quezon metropolis C & E Publishing, Inc. 4 Chemical moderate Acetic Anhydride. http//www.chemicalbook.com/ChemicalProductProperty_EN_CB2852742.htm. 5 Chemical Book Acetic anhydride (108-24-7). http//www.chemicalbook.com/ProductMSDSDetailCB2852742_EN.htm. 6 Encyclopdia Britannica Aniline. http//global.britannica.com/EBchecked/topic/25473/aniline. 7 Gauthier-Lafaye et al. Carbonylation of methyl acetate. http//www.google.com.ph/patents?hl=en&lr=&vid=USPAT4500474&id=ymY2AAAAEBAJ&oi=fnd&dq=carbonylation+of+methyl+acetate&printsec=abstractv=onepage&q=carbonylation%20of%20methyl%20acetate&f=false. 8 Recrystallization. http//www.chem.umass.edu/samal/269/cryst1.pd f.