Prelab 10

Lourdes Patricia L. Carreon Zaborah Eunice Bobadilla, Nerissa Unielle Quenga, Bernadette Toledo

January 26, 2011

Aldehydes and ketones I. Objectives 

To perform qualitative analysis in order to examine the reactivities of various aldehydes and ketones

II. Schematic Diagram of Procedure A. Reaction with 2,4-dinitrophenylhydrazine (2,4-DNPH) 5 drops 95% CH3CH2OH in three separate micro test tubes

+2 drops acetone to one test tube and +2 drops of benzaldehyde to another one

+1mL 2,4DNPH in HCl soln to each of the three test tubes

record color of ppt formed

B. Tollens’ Test

5 drops Tollens' reagent in 3 separate micro test tubes

TT1: + 1 drop formalin; TT2: +1 drop acetone; TT3: +1 drop benzaldehyde

observe formation of silver mirror

when silver mirror forms, pour out contents of TT and rinse with water

if no formation, warm in hot bath (aromatic halides: heating)

TT 1: +1 drop formalin; TT2: +1 drop acetone; TT2: +1 drop benzaldehyde

shake and record color development in 3-4 mins

C. Schiff’s Test

4 drops Schiff's reagent in 3 separate micro test tubes

D. Benedict’s Test

TT 1: + 2 drops formalin; TT 2: +2 drops benzaldehyde

place in hot water bath and note formation of brick red ppt

5 drops 10% NaOH in 2 separate TTs

TT 1: + 2 drops acetone; TT 2: 2 drops 95% CH3CH2OH

+ I2 in KI soln dropwise and shake TT's after each drop

if soln becomes colorless, + I2 in KI soln and note if soln turns yellow

warm soln in water bath

continue until soln turns pale yellow

5 drops Benedict's reagent in 2 separate micro TT's

E. Iodoform Test

F. Effect of Acid Concentration on the Rate of Addition of 2,4-dinitrophenylhydrazine weigh 0.15g 2,4dinitrophenylhydrazine in beaker and dissolve in 15 mL acetone

decant if there are undissolved solids

5 drops of 2,4dinitrophenylhydrazine soln into 4 diff TT's

note time of mixing and time when crystals appear

TT 1: +1 drop 0.1M CH3COOH; TT 2: +1 drop 0.1 M HCl; TT 3: +1 drop 1.0 M HCl

one TT is the standard

III. Table of Reagents/Products

IV. Waste Disposal 

All wastes – non-halogenated waste jars