Lab Final Flashcards
Desiccator
Provides storage for moister sensitive materials
ATAGO
refractometer- measures refractive index
Purpose of Steam Distillation
isolate essential oil from orange peels
Describe Process for Steam Distillation
Slurry Orange peels, set up apparatus, boil and liquid will drain into separatory funnel, aqueous layer in funnel is discarded, limonene is removed and dried using sodium sulfate, FTIR taken
What is the FTIR accessory used most in lab?
ATR
Benefits of using FTIR transmission vs ATR
Transmission- more distinct peaks because the light goes directly through sample in an enclosed space.
ATR is exposed to outside factors and light just goes through surface making it less distinct
What is FTIR used for?
To determine functional groups
Purpose of Thin Layer Chromatography
identify compounds present in mixture
How do you determine if the compounds are the same in TLC?
IF they have the same Rf values, however multiple compounds can have the same one
Purpose of 20% Ethyl acetate?
solution compounds were dissolved in.
What were the elutants in the lab and which one worked the best?
Hexane, 30% Ethyl acetate, 100% ethyl acetate
The 30% was the best because it contained both polar (ethyl acetate) and non-polar (hexane) components
What was the purpose of the foil
saturate the atmosphere to increase the possibility of reproducible results
Spotter
micropipette used to dispense samples using capillary action
UV lamp
used to track and see solvents on UV plate
Rf equation
Distance of sample/distance of solvent front
What is an indication of a sample having multiple components in TLC?
Multiple Rf values
Purpose of Gas Chromatography
Identify organic compounds in mixture
How does the GC work?
Has a stationary phase that remains in the machine and a moble phase that carries the inserted sample at different rates out of the machine, compounds are detected as they exit and produce and electrical current that is read to make a peak on the graph
How can you tell if two compounds are the same using GC?
If they have the same retention time
Why do some molecules travel through GC at a faster rate?
More volatile, they are not as strongly bonded with stationary phase
Explain how to isolate the samples of the mixture using acid base extraction. Note what compounds were used.
%5 NaOH used to extract carboxylic acid into water soluble salt into the aqueous phase, base and neutral remains in organic. 5% HCL is used to remove the amine and turn it into a salt from organic phase and into aqueous phase, leaving neutral in organic. Neutral is extracted from hot plate.
6 M HCL added to carboxylic salt to form a solid and then cooled. 6M NaOH to the amine salt to form a solid. Suction filtration to collect solid.
What was the purpose of cooling and using the litmus paper in the Separation?
Cooling the sample slowed down the particles in solution, decreasing solubility and the litmus paper was used to make sure the solutions were acidic and basic
Where does Polarization and intermolecular forces come into play with separation?
Polarization-caused the polar (aqueous) layer to form on the bottom and nonpolar (organic) layer to form on the stop to be separated using funnel
Intermolecular forces- formed to solid when the water did not want to interact with the nonpolar acid/base
How was the purification of the separated Acid/Base/Neutral done
They were recrystallized by heating the sample and the solvent in a water filled beaker on a hot plate. Solvent is slowly added until sample is dissolved. Let recrystallize. Melting point and FTIR is used to distinguish between possibilities
What are the solvents for the acid, base, and neutral in recrystallization?
Acid-Water
Base-hexanes
Neutrals-methanol
What is the purpose of recrystallization?
Purifying the sample
Purpose of Dichloromethane and NaCO3 in caffeine extraction?
DiChloro-extraction of caffeine into a layer on the bottom
NaCO3- prevent Tannis from being extracted as well, turns it into sodium salts not soluble in dichloro
Partition coefficient and formula
(k)- ratio of solubilities, equilibrium constant
k= (concentration of solute in solvent 1/concentration of solute in solvent 2) = (solubility of solute in solvent 1/solubility of solute in solvent 2)
What are the two extractions taking place. Describe them.
Extraction 1: Heated tea leaves with water, NaCO3 and boiled and cooled
Extraction 2: Dichloro added and extracted and filtered using gravity filtration, dicholor evaporates leaving caffeine
What is the purpose of Sodium sulfate in Caffeine extraction?
Drying agent
Sublimation
solid to gas with high temperatures and pure substances
Advantage and disadvantages of multiple extractions?
Advantages- more intended product, higher yield
Disadvantages- takes longer, more money, more waste
Purpose of ethanol in Reduction of Benzoin
creates a suspension
Steps of the Reduction of Benzoin
Ethanol is added with sodium borohydride on a stire plate. DI water is added, product is collected using vacuum filtration
What is the limiting reactant in Benzoin lab?
Benzoin, used less moles than NaBH4
S and R
S=counterclockwise
R=Clockwise
Using the FTIR how could you tell the Benzoin reaction was complete?
no carbonyl peak and broader alcohol curve
Steps of using separatory funnel
fill funnel in hood, place stopper, secure stopper, point into hood and tilt burping immediately, tilt and swirl horizontally burping often till there is no burps. Remove stopper and drain
Steps of vacuum filtration
Use beaker with tube connector, attach to ring stand, place tube connected to white nozzle on beaker, place funnel and filter paper, saturate with water, open green valve and yellow lever, dump in sample, turn everything off
IR Steps
Select icon, select name, do a background, clean with ethanol and wipe, place drop of sample, hit scan, clean with ethanol
Melting point Steps
Fill tube with substance, drop to get to bottom, set temps: Start- 5 below, except, Stop-5 above, except, hit start and wait, place sample and hit start, will finish and hit report
Steps for GC
Fill to 0.2 with air and 0.60 with liquid, inject into machine using thumb and 4th finger to hold and pointer to plunge other hand on bumper, go down to bumper, hit button immediately, stop after 2.5 minutes
