Orgo Lab Final
a
A reaction has yielded a phenol (pKa 10) dissolved in an aqueous solution at pH 12, but you want to isolate the phenol as a powder. Which option below might successfully isolate the phenol as a powder? (a) Adjust the solution to pH 7 with HCl, then extract into ether and evaporate the ether with a rotovap (b) Extract the phenol into ether, then evaporate the ether with a rotovap (c) Precipitate the phenol by adding brine (d) Extract the phenol into ethanol, then evaporate the ethanol with a rotovap (e) Adjust the pH to 14 with NaOH, then extract with ether and evaporate the ether with a rotovap
0.27, Compound A, more polar
A student conducted an organic reaction where 1 mole of Compound A was reacted with 1 mole of Compound B. The TLC plate below was spotted with Compound A, Compound B, and a sample from the reaction mixture (Rxn mix) and shows the results after eluting with 50/50 ethyl acetate/hexane. Given these results, use the dropdowns below to answer the following questions: a) What is the Rf value for Compound B? b) Which compound, A or B, was the limiting reagent in this reaction? c) Consider the lane that shows the reaction mixture. Are the starting materials more or less polar than the reaction product?
false
Addition polymerizations have a small molecule byproduct. True or False
5 minutes undisturbed
After vaccum filtrating, how long should you let the cake sit?
a
An advantage of synthesizing block copolymers is the ability to tune the properties of the material by varying the length of each block. Of the following block copolymers, which composition would have the highest degree of crystallinity? (a) 75% PLA, 25% poly(-decalactone) (b) 25% PLA, 75% poly(-decalactone) (c) 45% PLA, 55% poly(-decalactone) (d) 50% PLA, 50% poly(-decalactone) (e) 10% PLA, 90% poly(-decalactone)
diethyl ether, water
Assume that an extraction has been carried out using water and diethyl ether, similar to the Kd experiment in the lab, as illustrated with the separatory funnel drawn below. The solvent in the top layer will be _____ and the solvent in the bottom layer will be _____ .
101
Assume that you are conducting a chain-addition polymerization using 4.09 grams of monomer (MW= 68.7g/mol) and 112 mg of initiator (MW= 190.5 g/mol). What is the expected number of repeat units (n) per chain? Report your answer to the nearest whole number (i.e., an answer of 112.3 should be reported as 112).
73.62
Assume that you carried out a recrystallization of ibuprofen using ethanol. If you started with 5.42 grams of crude ibuprofen and isolated 3.99 grams of pure ibuprofen, what is your percent recovery? Report your answer to the nearest 0.01%.
2200-2250
C-N nitrile stretch
1700
C=O stretch peak
30.14
Consider the dehydration reaction shown below. If you started this reaction with 38.28 mL of cyclohexanol (MW 100.16 g/mol, density 0.96 g/mL), what is the theoretical yield of cyclohexene in grams (MW 82.14 g/mol, density 0.81 g/mL)? Report your answer to two decimal places.
singlet, sextet, doublet, singlet
Consider the molecule shown below, and use the dropdown menus to indicate the expected splitting patterns for the indicated protons.
b
Daniel was trying to make a polyester. He knew that he needed to utilize condensation polymerization, so he added ethyl alcohol and butanoic acid together in the presence of sulfuric acid. However, when the reaction ceased, he was left with a clear, non-viscous liquid that had a fruity odor. It appeared as if no polymerization had occurred. What did Daniel do wrong? (a) He ran the polymerization under acidic conditions. He needed to run the reaction in basic conditions in order for the polymerization to occur. (b) He needed to use difunctional molecules like ethane-1,2-diol and propane-1,3-dicarboxylic acid in order to form the polymer he desired. (c) You cannot form a polyester via condensation polymerization. He should have utilized addition polymerization. (d) He didn't do anything wrong. The fruity odor is indicative of the polymerization working.
4
Dopamine,C8H11NO2, has ____________ degrees of unsaturation.
absorb water
Even though organic solvents frequently used for extraction are immiscible with water, what usually still happens?
1/2 (2C+2+N-H-X)
Formula for IHD
final mass of solute (still dissolved) / initial mass solute = ( Vwater / Vwater + Vorg x Kd) to the power of the number of extractions
Formula used to calculate Kd
exploits differences in pKa values for various organic compounds
How does selective extraction work?
if the oxygen in water attacks the carbonyl rather than the anhydrous methanol
How does soap form in the synthesis of biodiesel
The Pechmann condensation produces coumarins via the acid-catalyzed reaction of a phenol with a β-keto ester
How does the Pechmann condensation work?
as CO2 sublimes, pressure builds up and causes CO2 to liquify and it then percolates through the orange rind and extracts. then the liquid CO2 becomes gas and escapes as the tube heats up
How does the use of CO2 dry ice as a solvent extract the orange oil?
0.1
How many decimal points do you record your temperature going to?
3
How many distinct peaks would you expect to see in the 1H NMR of the following compound?
a
How many proton NMR signals will be observed for the molecule shown below? (a) 3 (b) 4 (c) 2 (d) 5
must dissolve compound and impurities when hot, and as it cools, compound becomes insoluble but impurities remain soluble
How should you chose your re-crystallization solvent
1-2mm
How tall must the sample be in the capillary tube for melting point?
mass of recovered recrystallized product/mass of crude product used in re-crystallization
How to calculate percent recovery
actual over theoretical
How to calculate percent yield?
fragrant compound with a sweet odor
How to characterize coumarin
divide all percentages gathered by the molar mass and then divide all by the smallest number of mols found
How to find empirical formula
decanting or gravity filtration and evaporation
How to remove the drying agent and organic solvent from the extraction lab?
wash with brine, then contact it with an anhydrous inorganic salt which will absorb the water dissolved in the solvent
How to remove the water absorbed by immiscible solvents in extraction?
back extraction using a fresh portion of organic solvent
If precipitation does not occur after neutralization, what is needed to be done
fine with just one extraction
If the Kd is large (10 or more) what does this mean in terms of number of extractions?
a
If the Rf value of chlorophyll-a is smaller than b-carotene, this means: (a) Chlorophyll-a is more polar than b-carotene (b) none of these are correct statements (c) Chlorophyll-a is less polar than b-carotene (d) Rf value cannot determine the more polar sample
b
If you measure the melting point of a sample, allowed the capillary to cool, and then measure the melting point of the sample a second time, will the second melting point reading be identical to the first? a) Yes - the melting point of a compound is a fixed value and would not be impacted by heating and cooling. b) No - the crystal structure of the sample may change during the heating and cooling, and this will impact the melting point range. c) It is not possible to take a second melting point on the sample because it will remain in liquid form after the first melting point measurement.
F
Impurities disrupt the crystalline lattice of a sample so more energy is required to convert the solid phase into a liquid phase. True or False
31.9
In an EAS iodination reaction, 1.06 grams of phenol (MW: 94.11 g/mol) was reacted with 2.99 grams of sodium iodide (MW: 149.89 g/mol) . If 0.79 grams of product (MW: 220.01 g/mol) was collected, what was the percent yield (%) of the reaction? Report your answer to one decimal place (i.e., 23.1% should be entered as 23.1).
the solvents must be immiscible and the compounds must have different affinities for the two solvents.
In liquid-liquid extractions, what is the criteria for the two solvents and the compounds that need to be extracted
it is not possible because some of it will still be dissolved in the solvent that was utilized from when it was extracted
Is it ever possible to extract 100% of a compound from a solution?
diesel is heavier, oilier, higher boiling point, higher energy density (more efficient in burning fuels) hobe
Main differences between diesel and gasoline (4)
Pechmann is catalyzed then undergoes EAS. Knovenagel begins by attacking the middle then the alcohol completes the ring
Major differences between the Knoevenagel and Pechmann
both begin with an aromatic alcohol and both use ethyl acetoacetate
Major similarities between the Knoevenagel and Pechmann
Buchner funnel, filter flask, pinch clamp, hose connector to vaccum
Match the items in the filtration apparatus below with their name/function. Item A Item B Item C Item D
sharp 3100-3550
N-H stretch peak
broad, 3200-3650
O-H stretch peak
e
Poly (vinyl alcohol) is the starting material we use for "slime" synthesis. However, poly(vinyl alcohol) is not made from vinyl alcohol, but instead from vinyl acetate. What type of chemical reaction is performed to convert poly(vinyl acetate) into poly(vinyl alcohol), shown below? (a) Depolymerization (b) Reduction (c) Transesterification (d) Combustion (e) Hydrolysis
ethanol, electrophilic aromatic substitution, dehydration
The synthesis of one of the coumarin derivatives proceeds through the following mechanism. The first step is transesterification, with the small molecule of ____ being lost. This is followed by a ring-closing step via ____. The final step in this mechanism is the loss of water, also known as a ____.
False
True or False: Light with a higher frequency will have a longer wavelength. True or False
a
Two groups of students (Group A and Group B) analyzed the pigments present in a spinach extract by thin layer chromatography (TLC). For the extract preparation, both groups ground a mixture of spinach, sand, and magnesium sulfate using a mortar and pestle. The mixture was transferred to a test tube and anhydrous acetone was added. The mobile phase of the TLC was 30:70 hexane/ethyl acetate for both groups. Group A observed a good separation of the pigments, while Group B recorded larger Rf values and some spots were overlapping. Which mistake Group B could have done? (a) Not adding enough magnesium sulfate to remove the water from the spinach (b) Not adding enough acetone for the pigments extraction (c) Not using enough spinach to extract the pigments (d) Not adding the filter paper to the TLC developing chamber
gasoline burns quicker than biodiesel and yes because diesel must be under pressure to burn so it burns slower
What are the observations from the burn tests of gasoline and biodiesel and does this align with the information from the video?
ethanol and biodiesel
What are the two most common biofuels for transportation
Pechmann condensation and Knoevenagel condensation
What are the two reactions to make coumarin derivatives?
williamson ether and amide (we only did amide in class)
What are the two synthetic methods used to form acetophenetidin
functional groups
What does IR spec tell?
grams compound per mL organic solvent/grams compound per mL water
What does Kd equal
structure and bonding of the molecule
What does NMR spec tell?
The device heats up faster
What does a higher ramp rate mean
it is more efficient to do multiple extractions using smaller volumes of organic solvents
What does the Kd usually tell about the number of extractions?
not just removing water, it means that the solution contains no dissolved water
What does the term "drying" mean in organic chemistry
lowers and broadens it
What effect does the presence of a soluble impurity have on the melting point?
no effect
What effect does the presence of an insoluble impurity have on the melting point?
soap, and several portions of DI water and brine for breaking up foam
What is a common byproduct of formation of biodiesel and how can it be removed?
vegetable oils and a simple transesterification catalyzed by hydroxide ion
What is biodiesel made from and how is it made
neutralization and HCl
What is needed to be done in extraction after the desired compound has been extracted into the aqueous phase and what is used to do this process?
extraction removes the desired compound from its current solution and washing means removing impurities from a solution while leaving behind the desired compound
What is the difference between extracting and washing
polar head and nonpolar tail, a micellin
What is the generic structure of soap
e
What is the purpose of dilute HCl in the synthesis of Acetophenetidin? (a) To activate the decolorizing carbon (b) To protonate the acetic anhydride making it a better nucleophile (c) To protonate the p-phenetidin to make it a better nucleophile (d) To neutralize excess sodium acetate used in the reaction (e) To protonate p-phenetidin to increase its solubility in the solution
b
What is the purpose of sodium thiosulfate in the iodination of salicylamide? (a) Acidifies the reaction mixture (b) Removes any residual iodine from solution (c) None of these (d) Removes any residual salicylamide from solution (e) Precipitates the product
it acts as a buffer to drive the reaction forward
What is the purpose of the sodium acetate solution in the amide synthesis of acetophenitidin?
b
What is the role of potassium hydroxide in the synthesis of biodiesel? (a) Potassium hydroxide is the nucleophile that reacts with the triglyceride to form biodiesel. (b) Potassium hydroxide reacts with methanol to form potassium methoxide. (c) Potassium hydroxide deprotonates the oil. (d) Potassium hydroxide is a Lewis acid that activates the ester for faster transesterification.
d
What is the splitting pattern for the underlined protons in the molecule shown? (a) triplet (b) singlet (c) doublet (d) quartet
4-methylumbelliferone
What product is the Pechmann (green synthesis) making?
CO2 (dry ice in our case)
What solvent is usually used to perform solid-liquid extractions?
4-methyl was a green color and 3-acetyl was blue
What was the color of the fluorescence of 4-methyl vs the 3-acetyl
D-limonene
What was the orange oil that we extracted called?
No purification has occurred
What would happen if you chose a re-crystallization solvent that is insoluble to impurities too at cold temperatures
F
When choosing a recrystallization solvent, you want to use a solvent in which both the product and impurities are highly soluble at all temperatures. True or False
d
When conducting an extraction, the bottom layer in the separatory funnel is always the ____ . (a) aqueous phase (b) less dense solution that is being used (c) organic phase (d) more dense solution that is being used
d
Which molecule is most likely represented by the IR spectrum shown here (attached)? (a) hexane (b) hexanoic acid (c) 2-hexene (d) 3-hexanol
a
Which of the following wavelengths of light is the highest in energy? (a) 250 nanometers (b) 3 centimeters (c) 400 micrometers (d) 450 nanometers
b
Which of the molecules listed below is most likely to give this IR spectrum (attached)? (a) hexane (b) 1-hexene (c) 2,3-dimethyl-2-butene
b
Which of the sequences below represents a block copolymer? (Assume "A" and "B" as two different repeating units.) (a) none of these is a block copolymer (b) ·····AAAAAAABBBBBBBBB····· (c) ·····ABABABABABABABAB····· (d) ·····AABABBBABABBABAA·····
b
Which of these esters would give the proton NMR spectrum shown? (a) ethyl acetate (b) methyl propionate (c) propyl formate
amide synthesis
Which procedure, Williamson ether or amide synthesis is more green?
it removes the colored impurities from the sample caused by air oxidation of amino functional group
Why do we use the activated carbon as the first step in synthesis of acetophenetidin?
prevent methanol from evaporating
Why do you cork the flask after pouring methanol into KOH
prevent steam pockets
Why do you stir the vegetable oil periodically when heating
the stem could develop crystals on it which could affect your yield as well as create a blockage
Why do you use the stemless funnel for hot gravity filtration?
e
Why does the boiling point of a solvent drastically drop in a rotovap? (a) the density of the solvent is being reduced (b) the cold water in the condenser lowers the boiling point of the solvent (c) the reaction mixture is being heated in the water bath (d) there is a greater surface area due to rotating the flask (e) the pressure in the system is being lowered
if you boil all of the methoxide out of the solution, there will just be water remaining which will make exclusively soap and no biodiesel
Why is it important to monitor the temperature of the oil prior to adding the potassium methoxide solution and not exceed the target range?
b
Without doing a calculation, which of the bonds below would you expect to have the higher stretching frequency? (a) C-O (b) C=O
a
You are asked to recrystallize succinic acid with one of three solvents (hexane, ethanol and acetone). The solubility data for each is shown in the table below. Which one is the best solvent to obtain the highest yield for the recrystallization? (a) Acetone (b) Hexane (c) Ethanol
4.31
You are asked to synthesize 8.83 grams of coumarin via Pechmann reaction. Assuming that your reaction will proceed with 100%, what volume (mL) of resorcinol is required? Report your answer to two decimal places.
0.72
You conducted a TLC experiment and found that your compound traveled 6.75 cm and the eluting solvent traveled 9.33 cm. What is the Rf value for your compound? Report your answer to two decimal places (i.e., 0.01).
d
You need to use your separatory funnel for an extraction, but you notice that there is some residual water in it from when it was washed during the previous lab period. What should you do? (a) Use a paper towel to dry the inside of the funnel prior to using it again (b) Borrow a lab mate's funnel and wait for yours to dry (c) Take the funnel to the stockroom and ask to exchange it (d) Go ahead and use the funnel - you will be adding aqueous solutions anyway
2.04
You were asked to dissolve 9.61 g of compound A in 60 ml of water. After single extraction with 60 ml ether, you recovered 6.45 g of compound A from the ether layer. Calculate the Kd value for the compound A in ether/water system. Report your answer to 2 decimal places (i.e., 0.01). Recall that
2850-3000
alkane C-H stretch
the temperature at which the solid phase is in equilibrium with the liquid phase
what is the melting point defined as
it protonates the p-phenitidin, raising its polarity and increasing its solubility
why is HCl used instead of just plain deionized water in the acid base reaction when p-phenitidine is dissolved in HCl?
