2,4-dinitrophenylhydrazone
Derivative Preparation
Wear Gloves
In a test tube, add 10 drops of unknown to 10 mL 2,4-DNPH Reagent.
(IF your unknown is a solid, dissolve it in a minimum amount of 95% Ethanol).
Stopper the tube and shake vigorously
If crystallization is not immediate, warm the tube in a hot water bath ( ~90oC ),and set the tube aside to cool
to room temp.
Collect the precipitate via suction filtration, and wash with cold water.
If necessary, recrystallize using 95% Ethanol as your solvent.
Oxime Derivative Preparation
Disolve 0.5 gm. hydroxylamine hydrochloride in 5 mL. of water and 3 mL. of 3M NaOH.
Add 0.5 gm./mL of your unknown to the above solution.
Warm the mixture in a boiling water bath for 10 minutes.
Cool in an ice bath and collect the crystals using vacuum filtration.
Dry overnight and determine the compound’s melting range.
Semicarbazone Derivative Preparation
Disolve 0.5 gm. semicarbazide hydrochloride and 0.8 gm. of Na(OAc) in 5 mL. of water.
Add 0.5 gm. of your compound, stopper and shake the solution vigorously.
Warm the mixture in a boiling water bath for 10 minutes.
Remove the beaker from the heat source and allow the solution to cool to cool to room temperature in the beaker.
Collect the crystals using vacuum filtration.
Phenylurethane Derivative Preparation
Place 0.25 gm. of unknown into a dry test tube and add 5 drops of phenylisocyanate.
If no precipitate forms, heat the tube in a 90oC water bath for 5-10 mins.
Cool the test tube in a small beaker of ice and scratch the test tube inner wall to induce recrystallization.
Decant the liquid from the product.
Dissolve the product in 3 mL hot hexane. Perform a hot filtration on the solution, if necessary, to remove any insoluble diphenylurea that may have been produced.
Cool the filtrate to induce cryatallization. Collect the product by vacuum filtration.
3,5-Dinitrobenzoate Derivative Preparation
Dissolve 0.25 gm. 3,5-dinitrobenzoyl chloride in 0.25 mL of unknown.
Alternatively, dissolve 0.25 gm. 3,5-dinitrobenzoyl chloride in a mixture of 0.25 gm of unknown in 1.5 mL
of pyridine..
Heat/reflux the mixture for 5*-15** mins.
Allow the mixture to cool and add 1.5* – 2.5** mL 5% Na2CO3 and 1* - 2.5** mL H2O.
Vortex the mixture and collect the product by vacuum filtration.
Wash the product with cold water and recrystallize from an appropriate ethanol: H2O mixture. ( Technique 11, Section 11.10 ).
*Liquid Unknown
**Solid unknown
Bromo Derivative Preparation
In a large test tube, add 1 mL of Brominating Solution to a mixture of 0.1 gm of unknown dissolved in 1 mL Methanol and 1 mL H2O.
Vortex the mixture vigorously. Continue adding brominating solution dropwise, with mixing, until the orange bromine color persists.
Add 5 mL of H2O, stopper, and shake vigorously.
Collect the precipitate by vacuum filtration.
Wash the precipitate with cold water.
Recrystallize from an appropriate Methanol: H2O mixture. ( Technique 11, Section 11.10 ).
Benzamide Derivative Preparation
Suspend 0.15 gm. of unknown in 1 mL 10% NaOH and add 0.5 gm. Benzoyl Chloride.
Stopper and shake the tube vigorously for 10 mins.
Add sufficient 1.5 M HCl ro reduce the pH to 7-8.
Vacuum filter, wash with ice cold water and recrystallize from EtOH/water.
Benzenesulfonamide Derivative Preparation
Mix 10 mL. 2 M KOH with 0.2 mL/gm of compound and 0.7 mL benzenesulfonyl chloride.
Stopper and shake the solution vigorously, with cooling if necessary, for a period of five minutes.
Test the solution to be sure it is basic – if not, add 2 M KOH until basic.
Collect the crystals using vacuum filtration.
If an oil forms, test its solubility with 1.5 M HCl. (The sulfonamide if a secondary amine is insoluble, whereas an amine is at least partially soluble. If this solubility test indicates an amine, it may be either tertiary, or one of certain secondary amines that react with benzenesulfonyl chloride only very slowly.)
A solid sulfonamide of a secondary amine is insoluble in both water and 1.5 M HCl.
Acidify the solution from the original reaction mixture to pH 4 ( test with Congo Red paper ); the formation of a precipitate or oil indicates a primary amine.
Picrate Derivative Preparation
Dissolve 0.2 gm. Of unknown in 5 mL of ethanol.
Add 5 mL Sat. Picric Acid in ethanol and heat to boiling.
Allow to cool to room temperature slowly ( no ice ).
Collect product by vacuum filtration.
Wash the compound with ice cold ethanol.
Methyliodode Derivative Preparation
Mix equal amounts (0.25 mL ) of unknown and methyl iodide in a 25 mL RBF.
Allow to stand 10 minutes.
Heat to reflux for 5 minutes.
Allow to cool to room temperature.
If no crystals form, scratch and ice the flask contents.
Collect product by vacuum filtration.
Rinse with ice cold ethanol.
Recrystallize from ethanol .