Sustainable Polymers Derived from Carbohydrates by Derek Saxon
Chemistry
Plastic waste is generated across the globe on an alarming scale, with only a small
fraction recovered for recycling. As a result, sustainable polymers derived from renewable
resources have recently been gaining attention. Carbohydrates offer an inexpensive, renewable
resource for the development of polymeric materials. The current study details the synthesis of
renewable aliphatic polyesters from two cyclic esters derived from glucose, gluconolactone (GL)
and acetyl-gluconolactone (AGL). Poly(gluconolactone) [PGL] and poly(acetyl-gluconolactone)
[PAGL] were prepared by ring-opening polymerization (ROP) at low temperatures and initiated
by an aluminum alkoxide with 1.0 mol% loading. Characterization was carried out via 1H NMR,
13C NMR, FT-IR, GC/EI-MS and LC/ESI-TOF MS. Analysis revealed the synthesis of highly
functional aliphatic polyesters with attractive properties. Density functional calculations were
performed with Gaussian 09 using the M06L functional and the 6-31G(d) basis set, suggesting a
metal-mediated coordination-insertion mechanism. These polymers are excellent candidates for
the manufacture of sustainable polymers derived from a fully renewable carbohydrate feedstock.
Saxon, Derek
Senior Showcase Oral presentation
Ripon College
April 23, 2015
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Major: Chemistry
Iron Mountain, Michigan
Substituent and Solvent Effects: Examining Acidity via Infrared Spectroscopy by Jordan Buhle
Chemistry
There is a large collection of substituent constant data measured in polar protic and polar aprotic solvents, but a lack of information on substituent effects in nonpolar aprotic solvents. In this study, substituent effects on the acidities of phenol derivatives were examined in CCl4 using infrared (IR) spectroscopy. The IR peak of the free phenolic -OH appears at approximately 3600 cm-1 which is red shifted in the presence of a hydrogen bond acceptor. The magnitude of the splitting between the free and the hydrogen-bonded -OH peak is related to the acidity of the protic hydrogen. Deuterated acetonitrile was used as the hydrogen-bond acceptor to probe the relative acidities of 21 phenol derivatives in CCl4. While most phenol derivatives exhibited similar acidity trends in CCl4 as in DMSO and the gas phase, several demonstrated a reduction in acidity which indicates a solvent dependence on substituent effects. This study offers a facile method to examine substituent effects on the acidity of alcohols and has identified several solvent-dependent substituent effects.
Buhle, Jordan
Senior Showcase Oral presentation
Ripon College
April 23, 2015
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Major: Chemistry
Minors: Spanish, Physics
Milton, Wisconsin
CHM 502 Chemistry Senior Seminar
Lithium-Promoted Reaction of Aldehydes with N-Acylphthalimides by Lucas Henningsen
Chemistry
Phthalimides can easily be converted into primary amines, which are useful in a wide variety of laboratory and industrial applications. A new reaction has been discovered which allows for the synthesis of N-phthalimido-O-acyl-N,O-acetals from acyl phthalimides and aldehydes. These products can undergo hydrazinolysis to become useful primary amines. In addition, it is possible to combine the reaction with the synthesis of the participating acyl phthalimides, resulting in a one-pot synthesis of N-phthalimido-O-acyl-N,O-acetals from an acid chloride, phthalimide salt, and aldehyde.
Previous research showed that a metal Lewis acid and a tertiary amine were required for the reaction to take place. The optimal conditions included at least 10 mole percent LiBF4 and acetonitrile as the solvent. The reaction proceeds to 99% completion in less than 1 hour. Early mechanistic experiments show that the acyl group and phthalimide group completely dissociate to facilitate the insertion of the aldehyde.
Henningsen, Lucas
Senior Showcase Poster presentation
Ripon College
April 23, 2015
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Major: Chemistry-Biology
Minor: Music
Rice Lake, Wisconsin
Toward the Structure of the C-terminal Domain of EcoR124I Restriction Enzyme by Nicholas Leudtke
Chemistry
Using the type I restriction-modification (R-M) system of plasmid EcoR124I, E. coli cells systematically distinguish their own DNA from foreign DNA. Self DNA is protected by
methylation within a specific recognition sequence, while foreign DNA, which lacks methylation, promotes DNA translocation through the stationary R-M enzyme and cleavage at unspecific sites. The R-M system consists of three subunits: HsdS (specificity), HsdM (modification) and HsdR (restriction).
The published structure of the HsdR subunit of EcoR124I1 contained four functionally integrated domains. The last 150 amino acids in the C-terminal domain were unresolved in the crystal structure. A single point mutation led to a new crystal structure indicating that the last 150 residues form a 5th domain perpendicular to the other four domains.
To facilitate expression and crystallization, the C-terminal part of HsdR was appended after a fluorescent protein domain and a hexahistidine tag. Three constructs that include HsdR residues 705-1038, 867-1038, or 887-1038 were developed through PCR mediated deletions. Following expression, each protein was purified by nickel-NTA affinity and DEAE-Sepharose anion exchange chromatography. Crystals of the construct containing residues 887-1038 diffract x-rays to 8 Å and a model structure has been predicted for the C-terminal domain.
Molecular dynamics simulations with GROMACS software is being used to simulate the restriction subunit. The aim is to estimate if the proposed C-terminal structure maintains its secondary and tertiary structures during molecular dynamics simulations in solvent. Simulations of the protein are being examined for features that can evaluate the acceptability of the current model of EcoR124I.
This project was completed with all of the creators listed below, as well as the support from the Czech Science Foundation (P207/12/2323) and the United States National Science Foundation REU program (award 1358737).
Luedtke, Nicholas
Grinkevich, Pavel
McIntosh, Bennett
Baikova, Tatsiana
Lapkouski, Mikalai
Ettrich, Rüdiger
Carey, Jannette
Senior Showcase Poster presentation
Ripon College
April 19, 2016
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Major: Chemistry
Appleton, WI