Postlab 9

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Texas Tech University *

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3106

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Chemistry

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Feb 20, 2024

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TEXAS TECH CHEM 3106-382 Experiment 9: Preparation of Unknown Derivatives Purpose : Experiment 9 is the third and final part of our unknown analysis. Today we aim to conduct pure organic analysis by preparing and characterize crystalline derivatives. First, we aim to determine which functional groups (from experiments 7 and 8) fit best with IR and functional group test data. Second, we aim to synthesize, isolate, and characterize at least one crystalline derivative from each unknown. Safety : Note that many of the derivatives are extremely hazardous and must be handled properly, under the fume hood. Be sure to wear gloves, goggles, lab coat, and appropriate footwear. Carboxylic Acids—Preparation of an Amide Acid Chloride Intermediate Procedure : Step 1: Preparation of Acid Chloride Intermediate 1. Add 40 mg of carboxylic acid and a boiling chip to a 3.0 mL conical vial. 2. Under the hood, add 8 drops of oxalyl chloride and 1 drop of DMF. 3. Immediately attach air condenser fitted with drying tube and allow the mixture to stand at room temperature. 4. Using a hot plate, gently heat mixture to reflux for 15 minutes. 5. Allow mixture to cool. 6. Add 0.5 mL of CH 2 Cl 2. 1. Anilide Derivative Procedure: 1. Add 10 drops of aniline and ~1 mL of CH 2 Cl 2 to 5mL conical vial. 2. Add a spin vane. 3. Cool in an ice bath. 4. Slowly add (while stirring) crude acid chloride solution. 5. Continue stirring for 10 min.

6. Extract the CH 2 Cl 2 solution with ~mL of water, followed by ~1 mL 5% HCl (aq), followed by ~1 mL 5% NaOH (aq), and finally ~mL of water. The top layer will be aqueous. 7. Transfer to centrifuge tube for easier extraction. 8. Dry organic solution with anhydrous MgSO 4 . 9. Use heat and compressed air to evaporate solvent. 10. Using a shell vial, recrystallize by heating the solid in ~1 mL of ethanol till boiling. 11. Once solid has fully dissolved, slowly add water. 12. Return vial to hot plate. 1. The solid will go in and out of solution. As more water is added, it will take longer for solid to redissolve. 13. Stop adding water when the solid barely dissolves back to solution and lengthy swirling is observed. 14. Allow to cool to room temperature. 15. Using a Hirsch funnel and a 10mm filter paper, use vacuum filtration to isolate your crystals. 16. Find the melting point of unknown crystals. 2. Toluidide Derivative Procedure: 1. This procedure is identical to the Anilide Derivative above, only substitute 50 mg of toluidine (methyl aniline) for aniline. Alcohols Phenylurathane Derivative Procedure: 1. Add ~45 mg unknown alcohol to conical vial. If liquid, preweigh the vial and add alcohol drop wise. 2. Under the hood, add 6 drops of phenyl isocyanate drop wise with swirling. 3. If there is a visible solid, collect using a Hirsch funnel and 10 mm filter. 4. If a solid is not observed, add air condenser and warm on a hot plate for five minutes. Then cool to room temperature and then transfer to an ice bath. 5. If solid is goopy, pipet any remaining liquids and leave the solid in the conical vial. 6. Add 1-2 mL of ligroin and heat vial to extract urethane product. 7. Transfer warm ligroin to shell vial to cool (ice bath may be needed). 8. Collect crystals via vacuum filtration using a Hirsch funnel and a 10mm filter. 9. Find melting point.

Aldehydes and Ketones 2,4-Dinitrophenylhydrazone Derivative Procedure: 1. Liquid: Add 5 drops of unknown liquid to shell vial and ~1 mL of 2,4-DNP reagent solution. Mix and allow solid to form. 2. Solid: Dissolve ~50 mg of unknown in ~1-2 mL of ethanol. Heat to dissolve if needed. 3. Add ~1 mL of 2,4-DNP reagent solution. 4. Collect crystals via vacuum filtration using Hirsch funnel and 10 mm filter. 5. Rinse solid on the Hirsch funnel with ~0.5 mL cold ethanol 6. Obtain melting point. Amines Benzamide Derivative Procedure: 1. Add spin vane to conical vial. 2. Add ~0.5 mL 10% NaOH (aq) and 50 mg of amine (~5-6 drops if liquid). 3. Stir rapidly (under hood) and slowly add 5-6 drops of benzoyl chloride. 4. Allow to stir for 10 min. 5. Use vacuum filtration to obtain crystals, rinsing with ~0.5 mL of dilute HCl (aq) and then ~0.5 mL of water. 6. Obtain melting point.

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Phenols Bromo Derivatives Procedure: 1. Add 30 mg of unknown, 6 drops of methanol, and 6 drops of water to a shell vial. 2. Mix until homogenized. 3. Add phenol brominating solution dropwise (swirl to mix). 4. Once bromine color persists, stop adding brominating reagent. 5. Add ~0.5 mL water. 6. Mix well and allow to sit for 10 minutes while solid forms. 7. Collect crystals via vacuum filtration. 8. Rinse the crystals in the funnel with ~0.5 mL 5% sodium bisulfite solution. 9. Recrystallize the solid from hot ethanol/water. 10. Heat solid in ~1 mL ethanol till boiling. 11. Once solution is hot and homogenized, slowly add water. When the solid barely returns to solution, stop adding water and allow to cool. 12. Collect crystals via vacuum filtration. Rinse with ~0.5 mL cold ethanol. 13. Determine melting point. Chemicals List: Carboxylic Acid Oxalyl chloride N,N-dimethylformamide (DMF) CH 2 Cl 2 Analine 5% HCl 5% NaOH MgSO 4 Toluidine (methyl analine) Phenyl isocyanate Ligroin 3,5-dinitrobenzoyl chloride 2% Sodium Carbonate Ethanol 2,4-DNP Semicarbazide hydrochloride Sodium acetate 10% NaOH Methanol 5% sodium bisulfite

Results & Discussion: This series of experiments (7,8, & 9) allowed us to identify our unknown compound. We started the unknown analysis by determining the solubility of our compound. The solubility results gave us a rough idea of the unknown’s basic physical and chemical properties such as polarity, ionic character, pH, size, and purity. For example, polar functional groups like carboxylic acids, amines, and alcohols are soluble in water (which is also polar), and nonpolar functional groups like aromatic rings and alkyl chains are soluble in hexane (which is also nonpolar) because like dissolves like. Solubility reveals the ionic character of a compound because salts and ionizable acids and bases are soluble in water. It can also reveal the relative size and purity of compound. If an unknown is only partially soluble in a solvent, this could indicate the presence of a larger compound with various functional groups, a mixture, or a compound with low purity. Once we determined the solubility of our compound in experiment 7, we moved on to gathering a general chemical overview of our unknown in experiment 8. By administering classification tests, we were able to determine the presence of specific functional groups in our unknown. These classification tests were utilized to chemically alter our compound in visible way. For example, positive classification tests would produce a color change, form a precipitate, or trigger gas formation. Once the solubility and functional groups were discovered, we moved on to a completely organic unknown analysis here in experiment 9. Experiment 9 Organic Tests Depending on Functional Groups/Molecules:  The determination of an amide involves two steps. First, we react carboxylic acid with oxylyl chloride in the presence of DMF, to produce an Acyl Chloride Intermediate. This is then combined with the unknown, and if it is an amide, the two will react to form acetanilide which is a colorless, odorless, transparent crystal.  If the unknown is an alcohol, we can test for phenylurethane derivatives. When Phenyl isocyanate is reacted with an alcohol, urethane is produced which is a white-yellow crystalline.  The presence of aldehydes and ketones can be determined by combining your unknown with 2,4- dinitrophenylhydrazine. If the unknown contains an aldehyde or ketone, the reaction will produce 2,4- dinitrophenylhydrazone derivatives which are orange-red crystals.  To analyze primary and secondary amines, you can use benzoic chlorides. The mechanism involved with tertiary amines is identical to secondary amine mechanisms. And likewise, in the end you can produce benzamide. If you use secondary amine, you can produce benzamide with R group whereas if you use primary amine, you can produce benzamide with Hydrogen. Benzamide derivatives are not crystalline, but rather a white solid powder.  Phenol analysis should resemble alcohols, but they are in fact very different because the benzene in phenol changes everything. In the presence of bromine gas, phenyl can easily undergo bromine addition by replacing the H bonded to the aromatic benzene carbons. After bromine addition, the bromine color should disappear and a white needle/prism-like shaped precipitate will form called 2,4,6-tribromophenol.  Note: Characterizing crystals based on odor, color, and shape is not enough. We have so many crystals that are odorless and colorless. Therefore, we need to verify their boiling point and melting point.