CHE 233 FINAL

There are three kinds of co-polymers. What are they? How are they different from each other?

If two different monomers are used then they are called co-polymers. The three kinds of co-polymers are alternating co-polymers, block co-polymers and alternating block co-polymers. Alternating co-polymers alternate between "A" and "B" monomers. In block co-polymers, all of the first monomer polymerizes and then the next monomer grows off that original chain which forms large "blocks" of different composition. Lastly, the alternating block co-polymers work by having different segments of each monomer of different lengths alternating all along the chain.

Alginic acid is a block co-polymer of modified forms of the two carbohydrates:

D-Mannose, L-Gulose

What is the effect of crosslinking in polymers?

Cross linking makes the polymers more dense, structurally rigid and it significantly reduces their solubility

What we will be using to achieve crosslinking in this experiment? (polymer)

calcium chloride

Solubility of the polymer decreases as cross linking ________

increases

crosslinking that is found within the same polymer chain

intra-chain

crosslinking that is found between two different polymer chains

inter-chain

why is sodium alginate water soluble?

it is an ionic compound with a negatively charged oxygen and positive sodium atom

What is the role of the Ca+2 ions during the microcapsule formation? How are the properties changed after addition of Ca+2?

Ca+2 ions form the macrocapsule core by cross linking with sodium alginate. Ca+2 replaces the Na+ ion, forming bridging ionic bonds, when forming the capsule. the properties of the macrocapsules after the addition effects the stability and pore size of the beads, making it more dense and less soluble

In the biodiesel experiment, the
NaOCH3 serves as a ____

catalyst

Determine the limiting reagent and excess reagent in the reaction you will perform in the biodiesel experiment.

Limiting Reagent: Triglyceride
Excess Reagent: Methanol

Complete the statements below by matching the following.
1. Unsaturated fatty acids
2. Saturated fatty acids

1. have one (or more) C=C bonds
2. have no C=C bonds

The addition of water to sodium methoxide produces ____ & ____

sodium hydroxide & methanol

After completion of the biodiesel experiment, where do you dispose of FAMEs?

Organic liquid hazardous chemical waste container

How will you characterize your product in the biodiesel experiment? What specific differences will you be looking for compared to the starting material?

-Appearance of peak due to -OCH3
-1H NMR Spectroscopy
-Disappearance of -CH2 peak due to triglyceride

During the FAMEs synthesis, a mixture will be added to a vial and two layers will form. Identify the components of each layer.

Top: FAMEs with methanol
Bottom: Glycerol

What are allylic and vinylic hydrogens? Explain briefly using examples

Allylic hydrogens are hydrogens bonded to an sp3 hybridized carbon that is adjacent to a carbon-carbon double bond. Vinylic hydrogens are hydrogens bonded to an sp2 hybridized carbon (or the carbon involved in the carbon-carbon double bond).

What are common impurities that you might see in your NMR spectrum? What are the chemical shifts for those impurities in your NMR spectrum? (biodiesel)

Common impurities that might be seen in the NMR spectrum are Acetone at 2.17 ppm, Water at 1.56 ppm, dichloromethane at 5.30 ppm, methanol at 3.49 and 1.09 ppm, and chloroform at 7.26 ppm.;include triglyceride peak as impurity

The tin(II)chloride in the synthesis of pentacene derivative works as an oxidizing agent. (T or F)

False

In this experiment, you will be recording IR spectra of 6,13-pentacenequinone and 6,13-dihexynylpentacene. Match the following functional groups with the approximate wavenumbers (cm-1) that you expect to see in the spectra

C≡C: ~2100
C=O: 1650-1780

Column chromatography uses a stationary and a mobile phase to separate compounds. What is the stationary phase in the column chromatographic purification of crude pentacene derivative?

silica gel

What major differences would you be looking for in the IR spectra of 6,13-pentacenequinone and 6,13-dihexynylpentacene?

Disappearance of peak due to C=O in 6,13-pentacenequinone and appearance of peak due to C≡C from 6,13-dihexynylpentacene

For the following reaction, which is the limiting reagent? Reagents and quantities are provided.
(0.22 ml 1-hexyne) + (1 ml of 1 M LiHMDS in THF)---> Hexynyl Lithium

Limiting Reagent: LiHMDS

For the previous reaction, how many grams of hexynyl lithium should be produced?

0.0881 grams

What is the purpose of adding base in the aldol condensation reaction? Choose the best answer

Deprotonate α-carbon to generate nucleophile

The elimination step of the aldol condensation reaction is an example of

E1cB

Hexynide lithium reacts with 6,13-pentacenequinone via

Nucleophilic addition to carbonyl

Increasing the conjugation will decrease the energy of absorption. (T or F)

True

In this experiment, LiHMDS acts as an acid.

False (LiHMDS)

Briefly explain why is LiHMDS such a strong base relative to hydroxide ion

LIHMDS is a stronger base than the hydroxide ion because the nitrogen atom in LiHMDS is less electronegative than the oxygen atom in the hydroxide ion. This makes LiHMDS more basic because when deprotonated, the lone pair is much more unstable than when the lone pair on the hydroxide ion when it is deprotonated. The instability of the lone pair on the nitrogen makes it more reactive, and therefore, is more basic.

The elimination of water during the aldol condensation is named a(n) __________________ type elimination

E1cB type elimination. This stands for elimination, unimolecular, and conjugate base

What is the driving force for elimination of water during the reaction to form pentacenequinone?

The driving force for E1cB elimination is the increased conjugation when forming the product.

What might happen if the pentacenequinone was not dried completely of methanol and/or any residual water it might have absorbed, before reacting it with hexynyl lithium? What would the result be?

If the pentacenequinone was not completely dried then the residual water and methanol could react with the strong bases used (i.e. hexynyllithium). This would affect step two in this experiment (synthesis) and the reaction may or may not take place

What type of electrons are responsible for the photophysical properties of pentacene?

pi electrons

Match the following reagents with their role during the work-up of the reaction mixture.
1. Aqueous sodium bicarbonate _______
2. Aqueous hydrochloric acid ______
3. Water ______
4. Sodium sulfate ______

1. to remove unreacted acid
2. to remove unreacted amine, DMAP
3. to remove urea, any other salts (byproducts after the reaction)
4. to remove water from the organic layer

Which organic solvent is used to extract the product during the work-up of the reaction? (dipeptide)

dichloromethane

How are dipeptides formed?

Dipeptides are formed when two amino acids (peptides) condense and are linked with a peptide bond. This process happens through a condensation reaction, and water can seen as a product. A mixture of products is possible from this reaction.

What is the importance of using protected amino acids during dipeptide formation?

A protecting group prevents cross-coupled reactions. This means that only the single desired product is obtained with no other mixture of products

Name the solutions that were used to wash the reaction mixture during the work up and explain their roles.

The solutions that were used to wash the reaction mixture were HCl, Sodium Bicarbonate (NaHCO3), water, and brine. The HCl was was used to remove any amine or DMAP in the solution that may have been unreacted. The NaHCO3 wash was used to remove an unreacted acid that may have remained in the solution. The water wash was used to remove urea and any other salts that may have been present in the solution. The brine wash was used to remove any water that may have been left in the solution.

What was the purpose of using thin-layer chromatography in this experiment?

TLC is used to see if the experiment was successful and the reaction was complete. The R.M. column should be absent of the BocPhe Spot and this will tell you that the reaction was complete/successful

Why is BocPhe used for comparison in TLC?

BocPhe is used for comparison in the TLC because it is aromatic and shows the UV-visible absorption. Also, it is the limiting Reagent.