Post-Lab Questions Flashcards
What is the order of polarity of the 3 TLC eluents? (hexane, toluene, and ethyl acetate)
least to most 1. hexane 2. toluene 3. ethyl acetate
What is the difference between adding NaHCO3 and NaOH to the extraction compound mixture of acetanilide, p-t-butyl phenol, p-toluic acid?
NaHCO3 only deprotonates strong acid p-toluic acid so you are able to isolate it. If you used NaOH first, it would deprotonate both t-butyl phenol and p-toluic acid so you couldn’t get crystals
What would happen if you removed the plate when the eluent traveled up only half way?
the compounds would not be separated properly and an inaccurate Rf value would result.
What happens if the TLC plate develops in an unclosed chamber?
the compound or eluent may dissolve instead of traveling
What was the purpose of the extraction of clove oil and aqueous NaOH?
remove impurities by trapping them in the extracted layer
What would happen if TBME was used as the only eluent?
TBME would be strong enough (polar enough) to move ferrocene and acetylferrocene and I wouldn’t be able to separate the compounds because they would move together
What would happen if hexane was used as the only fluent?
The acetylferrocene would take a lot of eluent and a long time to be collected.
What happens if the eluent level is higher than the level of the origin?
the mixture spots would dissolve rather than travel up
What is the result of an increase in eluent polarity?
It increases the attraction of the compounds to the eluent and therefore they move farther and lead to a larger Rf value
What is the difference between adding NaHCO3 and NaOH to the extraction compound mixture of acetanilide, p-t-butyl phenol, p-toluic acid?
NaHCO3 only deprotonates strong acid p-toluic acid so you are able to isolate it. If you used NaOH first, it would deprotonate both t-butyl phenol and p-toluic acid so you couldn’t get crystals
What was the purpose of the extraction of clove oil and aqueous NaOH?
remove impurities by trapping them in the extracted layer
