Synthesis of Heterobifunctional

Carboxylic Acid PEG and Characterization of

Unknowns by Means of Infrared, Proton, Carbon, and UV/Vis Spectroscopy

Introduction• Heterobifunctional molecules possess a structure that allows for

binding at two different sites• Applications include:• Linkage of macromolecules to surfaces• Site-specific targeting of drugs

• Used extensively due to lack of toxicity• When bound other molecules, PEG increases their solubility in

aqueous environments to improve circulation times in vivo.

Problems• Incorrect vacuum setting• Incorrect cooling temperature• Incorrect round bottom flask placement• Incorrect product filtration solvent• Incorrect uniform ring formation of product in column

ExperimentalPart 1:• Dehydrate 3 grams PEG in a 250 mL round bottom flask atop a hot plate• Set temperature to 90 °C and RPM to 360• Let PEG react in round bottom flask with magnetic bar for 24 hours with

vacuum on

Experimental

ExperimentalPart 2:• Let oil bath cool to 50 °C• Turn off vacuum • Syringe 100 mL of THF into the round bottom flask with nitrogen on• Add 181.6 mg of NaH into flask• Let mixture react for 30 minutes• Add .55 mL of tertbutylbromoacetate into flask• Let mixture react for 24 hours at room temperature, spinning continuously

ExperimentalPart 3:• Transfer contents into another 250 mL round bottom flask• Obtain a trap flask and turn Rotoevaportor on• RPM to max and temperature to 50°C• Turn on vacuum and water • Once done, fill flask with ether until precipitate is dissolved• Obtain filter sheet, and filter into a beaker

Experimental

ExperimentalPart 4:• Obtain a clean column and make mixture in 1000 mL graduated cylinder that

is 900 mL DCM and 100 mL MeOH• Weigh out 245 grams of silica and use DCM and MeOH mixture to dissolve the

silica in the column• Keep pouring mixture into column until a uniform band is created in the

column • Scape filtered precipitate into a new round bottom flask and dissolve this with

DCM/MeOH mixture• Slowly pipette this mixture along sides of column until a yellow band forms

ExperimentalPart 5:• Fill column up with DCM/MeOH mixture• Make 75-100 fractions of this solution in test tubes• Use TLC plates to locate product in fractions• Dip in dye (amber bottle)• Blowtorch• Place fractions with product into new round bottom flask and Rotoevap• Mix chloroform inside round bottom flask and place mixture inside NMR tube• Retrieve NMR spectra

Experimental

Results

Results

Results

Results

Results• % yield:

Conclusions and Future Work• Good technique is required in order to receive better % yield due to

large room for error in synthesis• Due to large room for error, maybe different approach is needed to

synthesize product• Methoxy PEG

Introduction• Identifying signature features a compound possesses by different

means of spectroscopy is important in determining if the desire compound has been isolated.

• Unknowns were characterized by means of UV/Vis, Proton NMR, Carbon NMR, and IR spectroscopy

Introduction• UV/Vis - Determines UV radiation frequencies within a molecule to

show details about compounds structure. Done so by matching UV frequencies with the conjugated double bonds inside compound.• NMR – Displays the elements located around hydrogen/carbon atoms

by means of chemical shifting, splitting, and/or means of integration.• IR – Used to identify different functional groups that reside within

compound

Experimental• NMR used to determine elements around hydrogen/carbon atoms• Solubility test was done before any spectroscopy could begin• Methanol used for unknown #1 and #3• DMSO used for unknown #2

• UV/Vis was only used in unknown #3• Quartz cuvette with methanol blank was used to get baseline reading

• IR was used to determine all unknowns• Background used• Once test was over, wiped surface with methanol

Experimental

Experimental

Experimental

Results

Results

Results

Results

Results

Results

Results

Results310

Results

Results

Discussion

Unknown #1 -

Unknown #2 -

Unknown #3 -

Discussion- Don’t leave NMR tubes unattended in NMR room- Pick a proper time to do Carbon NMR- “3” finger rule- Clean NMR tubes properly- Choose proper solvent for characterization