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Experiment C Identification And Separation Of Dyes By TLC 1

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Experiment C Identification And Separation Of Dyes By TLC 1
Experiment C: Identification and Separation of Dyes by TLC

Pre-lab Properties:
Ethyl acetate, ethanol, silica, azobenzene, azulene, 4-(p-nitrophenylazo) resorcinol, methyl red, bromocresol green (solubilities in water and ethanol)

Purpose: To identify compounds from an unknown mixture using TLC

Up to 100% of missed points can be recovered from this lab
Watch the video: http://www.youtube.com/watch?v=e99nsCAsJrw (MIT)
TLC plates are near the main hood
DO NOT BREAK CAPILLARY TUBES
Keep spots small and concentrated (video)
Stop TLC before solvent runs over the top (video)
While waiting for plate development, update procedure and spot next plate
Dispose of all solvents in waste containers
Report your own TLC plate distances in procedure along with showing full-scale drawings
Make sure bottom of TLC plate wets evenly
TA will provide unknown, RECORD UNKNOWN NUMBER!
Make sure capillaries are clearly “square at end”

Post-lab Reminders:
Check Policies and Procedures
Report unknown number
Optimum eluent for TLC
Complete table (below) for optimum eluent conditions
Structures of unknowns
Considering the structures of the dyes, explain the trend in Rf values

Dye Name
Solvent (cm)
Spot (cm)
Rf
Color
Azobenzene

Azulene

4-(p-nitrophenylazo)resorcinol

Methyl red

Bromocresol green

Unknown Spot 1

Unknown Spot 2

Unknown Spot 3

Rf = (spot distance) / (solvent front)

Directions

Key terms (define): Stationary phase, mobile phase, elutropic series, adsorbent, eluent, spotting, development solvent, paper wick, solvent front, Rf value

WATCH THE VIDEO ON THE NOTES PAGE!

Introduction: You will try to identify the components of an unknown mixture of colored compounds. The mixture will have three compounds from the following: azobenzene, azulene, 4-(p-nitrophenylazo)resorcinol, methyl red, bromocresol green. You can identify the components by separating them using thin layer chromatography (TLC) and comparing their Rf values with those of the
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