Lab Final Flashcards
TLC can be used to
purify small amounts of impure compounds and quickly indicate the quantity and identity of pure compounds in a mixture
TLC was used in lab to test
4 solutions of dissolved analgesic tablets to identify the compounds as Bayer, Walgreens, or Goody’s
Aspirin and Caffeine
Bayer
Acetaminophen
Walgreens
Aspirin, Caffeine, and Acetaminophen
Goody’s
The plate was developed in 100% hexanes (very non-polar). Which of the two spots is the more non-polar?
The one that traveled the furthest because it is more drawn to the hexanes
Organic compounds often used in products like Vicks vapor rub
Camphor
Secondary alcohol oxidized to form Camphor (a ketone)
Borneol
The Jones reagent contains chromium (VI), which is reduced to chromium (III) as the alcohol is oxidized. What visual indicator shows that the Jones reagent is reacting?
It starts a red-yellow color and turns green when it reacts.
State one safety hazard associated with the Jones Reagent.
It is toxic. If ingested can be very harmful.
Removes acids
5% sodium bicarbonate
Reduce remaining Cr6+ to less toxic Cr3+
5% Sodium Bisulfite
Removes excess water
Saturated sodium chloride
Reagent that will reduce carbonyl compounds, but is not as reactive as lithium aluminum hydride (LAH
NaBH4: Sodium Borohydride
What is the purpose of adding water and/or HCL at the end of the Sodium Borohydride reaction
To protonate the reaction as a means of neutralizing it.
Why can’t acetone be used as a solvent for reduction reactions that involve NaBH4 or LAH?
Because it turns the product into 2-propanol
When a carbonyl is reduced to an alcohol, where should the broad IR peak be?
around 3300 cm-1
When creating a solution for an NMR sample, why must the solvent be deuterated (using D2O instead of H2O)
Because the hydrogens from the H2O would interfere with the NMR results by showing 2 extra hydrogens that were not originally in the product.
What is the purpose of adding tetramethylsilane (TMS) to NMR sample solutions?
To create the absolute zero ppm as a starting point for the data.
Acidic hydrogens (like ROH or RCO2H) tend to appear as quartets in H-NMR regardless of the number of adjacent hydrogens in the molecular structure. True or False?
False
A Diels-Alder reaction forming a diacid has a high yield due to what?
Kinetic control which favors the endo adduct over the eco adduct at low temperatures
Diels-Alder reaction could be done in one step with _______ ______ instead of two steps with maleic anhydride.
Maleic Acid
But, then the endo product would be less favored leading to less of the desired product
Stable dimer for Diels-Alder
Dicyclopentadiene
The generation of cyclopentadiene by heating and distillation (pyrolysis) of the dimer represents
A reverse Diels-Alder reaction
After adding the acetone to the hydroxide solution, what visual indicator should appear when the enolate forms in the Aldol Condensation?
It should turn yellow
Nitrate methyl benzoate with
A mixture of nitric acid and sulfuric acid
Methyl benzoate is a
Deactivated arene
Adding nitro to methyl benzoate
further deactivates the aromatic ring, guaranteeing that only a single nitration will occur
Why is a crystallization done slowly?
If the solution is allowed to cool slowly, the impurities may attach briefly to the growing crystal lattice, but they soon leave as a compound with a more suitable geometry comes in to take their place.
True or False.
Nitric acid may be added to the organic wast container?
FALSE
Many of the artificial fruit and plant odors are
Carboxylic Esters
One of the simplest processes to make esters is
Fischer Esterification
The reaction of an alcohol and carboxylic acid with heat and catalytic acid to form an ester and water.
Fischer Esterification
If a chemical system at equilibrium experiences a change in concentration, temperature, volume, or partial pressure, then the equilibrium shifts to counteract the imposed change and a new equilibrium is established.
Le Chatelier’s Principle
Two ways that Le Chatelier’s Principle could be used to favor formation of the ester product?
- Increase the temperature of an endothermic reaction, because in endothermic reaction, energy is absorbed. Therefore, and increase int temperature increases the product yield.
- In aqueous solutions, adding water lowers the concentrations of all the components. To increase the concentration, the system will go to the side with the greatest moles to favor the forward reaction.
Reaction of an aldehyde with a ketone employing sodium hydroxide as the base is an example of a
mixed Aldol condensation reaction, the Claisen-Schmidt reaction
Readily prepared by the condensation of acetone with two equivalents of benzalaldehyde.
Dibenzalacetone
Indicated formation of benzalacetone
It turns yellow
Grignard reagents
Alkyl- and Aryl-magnesium halides
Easily formed by a reaction of an alkyl or aryl halide with magnesium metal in anhydrous diethyl ether.
Grignard Reagent
The Grignard reagent is both a
Strong nucleophile and strong base
Solvent used in most Grignard reaction
Usually an ether like diethyl ether or THF to make sure all traces of water, alcohols, ketones, and other reactive compounds are removed.
What visual cue will indicate that the bromobenzene and magnesium are reacting to form the Grignard reagent?
The solution will begin to fizz and bubble on the magnesium surface
Why must the Grignard reagent be used right after it is formed?
Because Grignard reagents readily participate in transmetalation reactions that are irreversible. Therefore you want to use the reagent before it has a change to do so.
Which compounds would be the best solvent for a Grignard reaction?
Diethyl Ether
