Lab Procedures and Setups Flashcards
What is the first thing that should be done before adding sample to a separatory funnel?
A LEAK TEST
–> Put water into the separatory funnel and open and close the stopcock to ensure that when closed, no liquid comes out
What should be utilized to put the sample into the separatory funnel?
A funnel!
After each inversion and shake of the separatory funnel…
VENT the funnel!
–> Pressure builds up within the funnel due to gas evolution; this pressure must be released!
Why was the acid-base reaction for the ester washing step NOT conducted in the separatory funnel?
The reaction is vigorous and produces A LOT of CO2 –> Doing this in the separatory funnel would cause immense amounts of pressure within the apparatus leading to it exploding
How do you determine what size RBF to use for distillation?
RBF MUST be between 1/3 to 1/2 FULL!
So if given a reaction, based upon THEORETICAL YIELD (the max amount of product formed), determine the size of RBF needed
What is a limitation of simple distillation?
Can only separate out components of a mixture that have a BP difference > 50C!
Full Procedure for Ester Synthesis:
1) Add carboxylic acid, alcohol, and H2SO4 into an RBF
2) Reflux this reaction mixture for 1 hour and then cool
3) Leak test the separatory funnel
4) Pour the reflux contents into separatory funnel and add equal volumes of diethyl ether and cold water
5) Mix and vent the separatory funnel and then release the aqueous phase and discard
6) Release the organic phase and keep
7) Wash the organic layer with Na2CO3: Add Na2CO3 to the organic phase (not in the sep. funnel)
8) Pour into separatory funnel and release the aqueous phase
–> Repeat until aqueous phase is BASIC
9) Dry the organic layer (remove invisible water) with magnesium sulfate (drying agent)
10) Remove the ether using rotovap
11) Distill the ester mixture + collect the constant BP fraction
12) Run IR –> To identify ester formed
13) Run GC –> To determine purity
Full Procedure for Isomerization Experiment:
1) Prepare a TLC plate with lanes for different time points in reaction
2) Add dimethyl maleate and methylene chloride together; spot this mixture onto the 0 min lane
3) Add in 10% bromine and start clock
4) At the corresponding time points, spot the reaction mixture onto the TLC plate
5) Once reaction is done, add in cold hexane to the mixture and chill
6) Spot the dimethyl fumarate standard onto the TLC plate and run the TLC in a chamber with developer of 3:1 hexane:ethyl acetate
7) Develop the TLC and analyze the spots
8) Add more hexane to the mixture to form crystals
9) Decant the solution to isolate the crystals
10) Dissolve crystals in methylene chloride
11) Run a TLC with the crystals and dimethyl fumarate standard
12) Develop and analyze TLC
Full Procedure for Beta Carotene Extraction:
1) Prepare mini column: cotton into bottom of pipette and fill with silica
2) Dry spinach and add ethyl acetate; mix together to extract the pigments (get them into solution)
3) Transfer the organic solvent w/ pigments to another flask
4) Dry the organic layer (remove invisible water) with sodium sulfate
5) Rotovap the “dried” solution to remove the ethyl acetate
6) Wet the stationary phase with 100% ligroin
7) Prepare eluent of 10:1 ligroin:ethyl acetate
8) Add the pigment solution directly to the head of the column
9) Continuously add in the eluent to allow for migration
10) Collect the fraction for beta carotene (first band, will be yellow)
11) Run a TLC for 3 substances: the collected fraction, beta-carotene standard, and the initial pigment solution
Full Procedure for Lidocaine Synthesis:
1) Add 2,6-dimethylaniline, acetic acid, and alpha-chloroacetylchloride to a flask (let react)
2) Add half-sat. sodium acetate solution (contains H2O) = the alpha-chloro-2,6,-dimethylacetanilide precipitates out
3) Collect precipitate by vacuum filtration and transfer into an RBF
4) Dissolve the solid alpha-chloro-2,6,-dimethylacetanilide in toluene
5) Add diethylamine and reflux for one hour (with stir bar)
6) Transfer the refluxed reaction mixture into a separatory funnel using a funnel with FILTER PAPER
7) Wash the reaction mixture with water 4 times (keeping the organic layer each time and discarding the aqueous layer)
8) Add HCl to the organic layer left in the separatory funnel and mix (protonates lidocaine = salt)
9) Collect the aqueous layer
10) Wash the organic layer with water and collect the aqueous layer
11) Combine both collected aqueous layers
12) On ice, add NaOH into the aqueous layers to precipitate out the lidocaine (deprotonates the lidocaine salt to reform lidocaine)
13) Separate out lidocaine by vacuum filtration
14) Wash the precipitate with cold water over vacuum filtration
15) Collect the lidocaine
Abridged Procedure for Ester Synthesis:
1) Reflux reaction mixture of alcohol, carboxylic acid, and acid catalyst (H2SO4)
2) Extraction by adding ether and water the product: Collect the organic and discard the aqueous
3) Wash the organic phase with base (Na2CO3); Collect the organic phase
4) Dry the organic layer with magnesium sulfate
5) Rotovap to remove organic solvent
6) Distill to isolate ester from unwanted byproducts
7) Analyze ester with IR and GC
Abridged Procedure for Beta Carotene Extraction:
1) Extract pigments from spinach using ethyl acetate
2) Dry the organic solution with sodium sulfate
3) Rotovap to remove ethyl acetate
4) Run column chromatography of the pigment solution and collect B-carotene fraction
5) Run a TLC with collected fraction, B-carotene standard, and pigment solution
Abridged Procedure for Isomerization Experiment:
1) Create reaction mixture of dimethyl maleate and methylene chloride
2) Add Bromine to begin isomerization reaction
3) Spot reaction mix onto TLC plate at varying time points
4) Add the dimethyl fumarate (isomer) standard to the TLC and run
5) Use cold hexane to crystallize dimethyl fumarate out of solution
6) Run TLC with the crystals dissolved in methylene chloride and a dimethyl fumarate standard
Abridged Procedure for Lidocaine Synthesis:
1) React the 2,6-dimethlyaniline and alpha-chloroacetlychloride in acetic acid
2) Precipitate out the produced alpha-chloro-2,6-dimethylacetanalide by adding aqueous sodium acetate
3) Collect the solid product by vacuum filtration
4) Dissolve the solid intermediate product in toluene and react with diethylamine
5) Reflux reaction mixture
6) Wash the mixture with water 4 times and keep organic layer
7) Add HCl to the organic layer to protonate lidocaine (=salt) and collect the aqueous phase
8) Add NaOH to deprotonate (reform) and precipitate out lidocaine
7) Collect by vacuum filtration
