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BRANDEIS UNIVERSITY CHEMISTRY 29A PRELAB WRITEUP AND EXPERIMENTAL REPORT SHEET NAME_ T.A.’S NAME DATE_________ EXPERIMENT # __6_____ TITLE Aldehyde Identification Purpose: to characterize an unknown carbonyl compound using BP analysis, MP derivative analysis, NMR and IR spectra analysis PRELIMINARY WRITEUP* (INCLUDING EQUATIONS, TABLE OF MATERIALS, THEIR AMOUNTS AND CONSTANTS. AND PRELAB QUESTIONS. Place these questions on the reverse of this page) (* use reverse of both sheets if necessary) Substance Purpose Melting Point (Celsius) Other notes Water Solvent, cleaning agent, catalyst in multiple reactions N/A Sodium hydroxide Forms insoluble silver hydroxide with silver nitrate N/A Silver nitrate Source of silver +2 for the tollen’s test N/A 2.8% aqueous ammonia Aqueous acid acts as catalyst for DNP synthesis N/A Phosphoric acid Catalyst for DNP reaction with aldehyde N/A Unkown aldehyde (3- methylbutanal) The unknown N/A 2,4 dinitrophenylhydrazine Substance which reacts with the aldehyde or ketone via a condensation reaction forming an imine, an insoluble compound N/A Schiff’s reagent Tests for presence of aldehyde, by color formation N/A Methylene chloride Cleaning IR plates, and IR solvent N/A Trichloro dutero methane NMR solvent N/A TMS NMR reference compound N/A Nitrogen gas Purging oxygen from NMR samples N/A EXPERIMENTAL PROCEDURES* (include in preliminary writeup) Tollen’s test 1. clean test tubes with sodium hydroxide, and heat 2. combine 2mL of 0.03M silver nitrate solution and 1 mL of sodium hydroxide 3. add 0.5 mL 2.8% aqueous ammonia (or until grey precipitate is dissolved, 3mL max) while shaking 4. dilute to 10 mL with water 5. add 1mL of the diluted reagent to each test tube (1 for each compound to be tested) 6. add 1 drop of substance to be tested to the test tube 7. allow solution to sit for 1-2 min then warm gently 8. after observation, promptly destroy all reagents Schiff’s test 1. add 3 drops of unknown to 2 mL of Schiff’s reagent 2. allow 10 min for the reaction DNP synthesis 1. add 0.05g of unknown to 5mL solution of 2,4 dinitrophenylhydrazine in phosphoric acid 2. warm reaction for 1-3 min, then allow to air cool 3. help crystallization by ice cooling 4. collect crystals by suction filtration 5. wash crystals with large excess water to remove phosphoric acid, until litmus paper does not read as acidic 6. dry further with filter paper 7. determine melting point MODIFICATIONS AND OBSERVATIONS* (Obtained from the lab experience.) After addition of schiff’s reagent to the test tubes the aldhyes rapidly turned dark purple, the positive control (acetone) and sample 82 were both the same color while 233 was not dark purple. The aldehyde smelled like a strong sweet smell, similar to bananna.
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