CHM2211L UF
Cross-linked polymer
joining molecules through a covalent bond, have reactive ends that can chemically bond with specific functional groups
LC/MS
liquid chromatography/tandem mass spectrometry (liquid, sensitive to polarity of the solvent)
Dyes usually applied to fabrics
"fixes" to the fabric through intermolecular forces
What resolution would be required to distinguish the compounds mentioned in questions 3 and 4 above? What was the resolution of the HRMS instrument described in the paper (Catlin, et al., 2004)? What is the advantage of a high resolution instrument?
1,000 which measures to the 0.01 position but the one used in the case study was 10,000 which measures to 0.001. The advantage of a high resolution instrument is the ability to obtain more specific data.
Which of three diacetylferrocene (again, see text p. 83) will be the major product in the reaction (Figure 10-2)? Why?
1,1'-diacetylferrocene would be the major product due to the acetyl group being an EWG pulling the electron density away from the ring. The creation of a weak nucleophile allows the other ring to attack.
Which diacetylferrocene product (if any) forms when ferrocene is reacted with acetic anhydride?
1-1' -Diacetylferrocene
UV light will always be in the range
100-400 nm on the electromagnetic spectrum, 215nm
Why do we add glacial acetic acid in part 1b when you react with N,N-dimethylaniline, but we don't use it with the other aromatic coupling reagents
Aniline derivatives are highly activated unless they become protonated. Glacial acetic acid serves as an acid catalyst that does not completely protonate the aniline, leaving some highly activated aniline to react with the diazonium salt.
What is the wavelength for the same electronic transition in 1,3,5-hexatriene? What does this tell you about the HOMO-LUMO gap for 1,3,5-hexatriene as compared to 1,3-butadiene
Approximately 258 nm Smaller HOMO-LUMO gap
Sand prevent
solvent from disturbing silica
If PPV itself (and BuEH-PPV) emits light in the green/yellow-green region, whereas BEH-PPV emits red light, what does that tell you about their respective HOMO-LUMO gaps?
BEH-PPV emits an orange-red light which is a larger wavelength compared to yellow-green. A longer wavelength correlates to a lower frequency = less energy. Thus, BEH-PPV has the smaller HOMO-LUMO gap.
Condensation Polymerization
BYPRODUCT
Why can elimination step (3) occur on simple heating? Why is this a good procedure to form materials for commercial use?
Chloride ion is a weak base, and under heated conditions can promote b-elimination reaction (and protonated sulfide is a good leaving group so it leaves easily with little heat) Two byproducts (which are volatile) can be easily removed from the solid polymer by evaporation under reduced pressure Don't need a separate purification step
Did chromatography serve to purify the sample? Explain any conflicting results.
Chromatography served to purify the sample. On the TLC plate for the purified sample, the yellow and orange were clearly separated.
Conjugation
Connected p-orbital (π) systems
Which do you suspect will be the most difficult to dye? Explain why
Dacron would be the most difficult to dye due to its fairly nonpolar structure (high symmetry), making it difficult for it to interact with the polar sulfonate groups in the azo dye.
Polystyrene solubility
Dissolved in toluene, mostly dissolved in acetone, and did not dissolve in ethanol
Why do conjugated compounds absorb light in the ultraviolet region?
Energy required to promote electron from HOMO to LUMO corresponds to energy in UV light
How do the male sex hormones differ from the female sex hormones? Use estradiol and testosterone as examples.
Estradiol has one less CH3 group, aromatic. Testosterone has a double bond to O and estradiol has an alcohol group.
Synthesizing acetylferrocene from ferrocene
Friedel-Crafts acylation
determined the structure of THG
From a spent syringe, detected by matching retention time and spectra with those of a reference standard.
HOMO
Highest Occupied MO, nucleophilic electron donor
A "defect" is defined in this case as an interruption of the conjugation in the polymer. How might this damage or change the light emitting properties of the material?
If a conjugated system is interrupted, the band gap increases, visible light changes color and reduces so eventually no light would be emitted. The work of going to an excited state is not spread evenly if there are broken pi bonds, so band gap energy would increase.
Based on that information, what types of substituents would you add to the PPV aromatic rings to favor the emission of blue light?
In order to favor the emission of blue light, there would need to be an addition of a EWG like nitro (-NO2) which would shorten the wavelength (=high frequency, high energy) and correspondingly increase the HOMO-LUMO gap.
Nylon-10,6 solubility
It's not soluble in any of these
Iodination of aromatic compounds
Least reactive, it requires use of an oxidizing agent (bleach - deprotonate) to oxidize I2 and generate the electrophile, easily sublimes and can cause irritation if inhaled
LUMO
Lowest Unoccupied MO, electrophilic electron acceptor
Polymer
Macromolecule consisting of repeating monomer units
Why do more conjugated compounds absorb at higher wavelengths/lower energies?
More conjugated compounds have lower energy gaps between their HOMO and LUMO, so electrons can 'jump' from the homo to the lumo to make the HOMO* with lower energy
Did you notice any significant changes when the Congo red fabric was treated with acid? Describe your results.
Most of the fabrics (except wool) changed color and resembled the stains from indigo bath (more blue) - this is because acid will protonate, pH indicator, Base = red Acid = blue
You can synthesize the PPV precursor below in one step from p-xylene. How?
NBS and light (allylic bromination)
Chain Additions
NO BYPRODUCT
What is required for organic compounds to absorb in the visible light region?
Need many many conjugated double bonds (at least greater than 5 for wavelength of at least 380 nm)
Would you expect OLEDs to be more or less robust than inorganic LEDs? Why?
Organic OLEDs are less robust. The transport layers within the structure are sensitive to high temperature, humidity, oxygen, high currents, and high fields. These layers also affect the color purity of the LED light emitted. This causes it to degrade faster.
Which do you suspect will absorb dyes in a similar way? Explain why
Orlon (poly acrylic) will absorb dyes in a similar fashion due to its fairly symmetrical and nonpolar structure. Like Dacron, this will make it difficult to interact with the polar sulfonate groups in the azo dye.
What is the purpose of the sodium carbonate in part 1a?
Sodium carbonate is used to deprotonate HSO3-. When deprotonated it becomes soluble and a better nucleophile.
One of the largest global suppliers of paclitaxel today is Phyton Biotech. What type of process do they use to generate paclitaxel?
Phyton Biotech utilizes Plant Cell Fermentation (PCF) Technology to generate paclitaxel as it is an environmentally friendly process that produces natural pharmaceutical ingredients directly from plant cells.
Which of the fabrics was most resistant to dyeing? Explain why this is the case.
Polyester due to its hydrophobic nature, lacks hydrogen bonding sites, the most non-polar
Would this cause a "defect"? How likely is this reaction? Can you think of any other common solutions/chemicals in everyday life that can react with systems such as these?
Polymer to Sp3 (acid protonates double bond), removing conjugation. Use vinegar or oxygen, any weak acid, although the reaction will be slow. Rxn could be faster if EDGs are present. The reaction breaks the conjugation, therefore, it can be considered a defect. PPV structure: repeating aromatic ring, double bond, aromatic ring, double bond...
Draw the mechanism for the polymerization step (2), showing the connection of three repeating units. Why do these reaction conditions cause polymer formation?
Polymerization begins with an acid/base reaction that deprotonates the benzyl carbon and then an SN2 substitution occurs Followed by another deprotonation and another monomer unit being added
One method of characterization is 1H NMR (proton NMR). What type of information does this technique provide?
Proton NMR gives structural information about where protons lie in a compound and the environment they exist in due to connectivity to neighboring groups. Provides information about the number of signals, location of signals, intensity, spin quantum.
Salicylamide is an active ingredient in BC powder, a common OTC remedy. What its purpose?
Salicylamide enhances plasma levels of aspirin which would correspondingly decrease an individual's level of pain.
What is the important characteristic that classifies a compound as a steroid?
Steroids have four "fused" rings. They have 3 six-membered rings and 1 five-membered ring.
Why is Bristol-Myers so interested in the Pacific yew tree? What substance are they trying to harvest, and which part of the tree contains this substance? Why can't they just harvest that portion of the tree?
Taxol is extracted from the bark of the Pacific yew tree. Taxol was one of a few drugs that showed incredible promise in the treatment of rapidly growing cancers. By removing the bark, you kill the tree.
What do your results tell you about the directing effects of the substituents on salicylamide?
The IR data supported the iodine being added para to the hydroxyl substituent. This could be seen in the larger absorptions between 800 and 850 cm. However, there is still a minor product of the iodine being ortho to the hydroxyl which can be seen in the much smaller absorption between 750 and 790 cm.
How would you anticipate that this 1H NMR spectrum would change following catalytic hydrogenation of gestrinone to produce THG?
The alkynyl proton would be a singlet, and using the predicted splitting patterns from the structure, one of the vinyl protons is a singlet, whereas the other two are doublets. The vinyl protons should be easily identified as those between 5-6.5 ppm, so the singlet at roughly 3.6 must be the alkynyl proton. The singlet at roughly 6 ppm is the vinyl proton that is adjacent to the ketone. The other two vinyl protons can be assigned using electron withdrawing effects.
If you wanted to create a PPV precursor with two electron withdrawing groups in two steps from p-xylene, how would you do it? Which electron withdrawing groups would you choose, and why?
The first step would be halogenation to add electron-withdrawing halogen groups onto the benzene ring, and the second step would be NBS and light.
The first test was performed by LC/MS and by GC/HRMS. What information is obtained from these methods?
The information that can be obtained from these methods were purity of compounds, structure and bonding, and information about the different chemical environments of protons in a chemical structure.
Which do you think will be the major product?
The major product will form with iodide bonding para to the hydroxyl substituent, and meta to the amide substituent. This position is favored due to the amide directing meta and the hydroxyl directing ortho/para, creating an overlap. This would be the least sterically hindered position.
Describe the one-step synthesis that was performed. How would you classify this reaction? How would this change the results of the MS and HRMS analysis?
The one-step synthesis was hydrogenation, a reduction reaction that uses Pd/C and H2. By adding 4 hydrogen atoms, we increased the mass of the compound. MS, which measures nominal mass, would record this as an increase of 4g. HRMS, which measures exact mass, would record this as an increase of 4.0313, assuming the resolution of the instrument is 10000
Draw the mechanism for step (1)
The sulfur electrons would just go to the benzyl carbon and kick Cl out like SN2 (C is already partially positive because of the Cl)
What happened to the fabric strip when it was treated with the test identification stain? How might this dye be used?
The test strip was dyed many different colors; this is useful in identifying different fabrics since the dye will react with each fabrics' functional groups differently
Which compound would you expect to elute first from the column: unreacted ferrocene, acetyl ferrocene, or diacetylferrocene? Why?
The unreacted ferrocene would elute first as it is the most nonpolar of the three compounds, due to no acetyl groups being present.
How do substituents on aromatic rings affect electrophilic aromatic substitution?
They direct incoming groups
Why must long conjugated polymers be used as these materials rather than small molecules
Visible light is emitted from 380 to 700 nm. The larger and more conjugated the polymer is, the smaller the HOMO-LUMO gap and the larger the wavelength.
However, poly (vinyl alcohol) (PVA) is not made from vinyl alcohol, but instead from vinyl acetate that is hydrolyzed after formation of the polymer. Why can't we use vinyl alcohol in this polymerization
We cannot use vinyl alcohol as it exists in its acetaldehyde form (tautomer) which is too unstable to be used in this polymerization.
How can you tell that white indigo is the reduced form? What chemical process happens as the fabric dries?
White indigo contains two alcohol groups (reduced) whereas blue indigo has two carbonyl groups (oxidized), As the fabric dries, the white indigo (reduced form) is oxidized to blue indigo (oxidized form), resembling an enol-keto tautomerization.
When dyeing with your azo dye, which fibers seemed to interact best with the dye? Explain your results.
Wool, silk and nylon interacted the best because they were the darkest stain/took up the most color, the most polar of the fabrics, Their polar sites interact strongly with the dye via hydrogen bonding
Assuming you obtained diacetylferrocene, how can you identify which of the three diacetylferrocenes (see text p. 83) you obtained?
You could identify which of the three diacetylferrocenes you obtained by measuring its melting point: 1,2-diacetylferrocene (96-97), 1,3-diacetylferrocene (187-188), or 1, 1'-diacetylferrocene (127-127.5).
All dye molecules are chromophores
a compound that is highly conjugated and usually has a characteristic group such as azo (-N=N-), nitro (-NO2), or carbonyl (C=O)
THG
a derivative drug, one of the most effective anabolic steroids
percent yield
actual yield/theoretical yield
Chain growth
adds monomers onto the end of a chain (Ex: STYRENE
Electrophilic aromatic substitution
aromatic ring acts as nucleophile and attacks an electrophile, aromaticity of ring regenerated through loss of a proton
If all light absorbed
black
polar solvents elute
both polar and nonpolar compounds
Why is it important not to dilute the initial sample before it has been loaded onto the chromatography column?
could cause broad bands that are difficult to separate.
Slime
cross-linked polymer formed from the reaction of poly(vinyl alcohol) and borax (sodium borate decahydrate), cross-link and break apart easily
% yield > 100%
due to not recrystallizing product and moisture leftover from vacuum filtration
synthesize Nylon-10,6, using
interfacial polymerization or condensation polymerization
Least polar compounds elute
first
GC/HRMS
for gas chromatography/ high-resolution mass spectrometry (sensitive through temperature; identify samples, purification)
Condensation polymerization
formation of polymers by the loss of water, or some other small molecule like HCl, when the molecules bind to each other
Ethanol used because
it forms hydrogen bonds with -OH and -NH2 that allow for good solubility
Monomer
molecule (small units) that can react with other molecules to form a polymer
If it dries out there is risk
of channeling, which results in poor separation
Repeating unit
part of a polymer, when multiple repeating units are linked together it forms the polymer
HCl is used to
protonate it again and precipitate the iodosalicylamide
Step growth
reacts monomers in the beginning (Ex: NYLON-10,6)
Sodium thiosulfate
removes any residual iodine from the solution
Designer drugs
same or similar properties as existing drugs
Ferrocene
superaromatic and 105 times more reactive than benzene for EAS, iron atom between two cyclopentadienyl anions
If a more polar solvent was used
the Rf values would increase because all the spots would travel further up.
A desirable feature of OLEDs
the ability to closely tune the emission frequency to release light of different colors.
EWG
to position meta and deactivate the ring, ortho/para positions electron deficient (halogens-ortho and para even EWG)
EDG
to position ortho and para and activate the ring, more electron rich
If all light reflected
white
colorfast
won't fade or rub off the fabric with washing