Thursday, April 19, 2007

Students Present at 71st Annual ISCC

Six IUP students presented their research at the 71st Annual Intercollegiate Student Chemist Convention at Salisbury University in Maryland, escorted by Drs. Ron See and Heba Abourahma.

Ms. Amanda Davis, under the direction of Dr. Carl LeBlond, presented "A Novel Synthesis of Iodohydrins Derived from Styrene and Related Compounds".
The purpose of our research is to optimize a novel pathway for the synthesis of iodohydrin compounds, derived from styrene and similar chemicals. Iodohydrins are important in a variety of industrial and pharmaceutical applications because they are often an intermediate in the synthesis of biologically active pharmaceuticals and specialty chemicals. Recently, a new procedure for the synthesis of iodohydrins was developed in our laboratory. Unlike a more common method, which employs N-chlorosuccinimide (NCS), this procedure for the iodohydroxylation of styrene utilizes sodium hypochlorite (bleach) as a more environmentally favorable and cost effective oxidizing agent. A yield of 81% iodohydrin product (isolated, characterized and determined by GC/MS and 1H NMR) has been achieved using styrene as the substrate. In our presentation, we intend to detail this result as well as our plans for future explorations.

Ms. Elizabeth Paladin, under the direction of Dr. Heba Abourahma, presented "Modifying the Physical Properties of Indomethacin by Co-Crystal Formation".
Many organic molecules which are used as active pharmaceutical ingredients (APIs) exhibit polymorphism. This property of APIs leads to problems in the production of APIs in the solid state. The goal of this research project is two-fold: the first goal is to study the phenomenon of polymorphism. The second goal is to study co-crystal formation as an alternative to polymorph formation. Specifically, the objective of this study is to form co-crystals of indomethacin (C19H16ClNO4), an anti-inflammatory API. In order to accomplish this, non-covalent interactions will be exploited, which are spontaneous and reversible under thermodynamic equilibrium. Indomethacin has been combined with several co-crystal formers, identified by known favorable interactions between functional groups. If crystal formation or precipitation occurred, the product has been analyzed by observation of melting point and nuclear magnetic resonance. After combining indomethacin with isophthalic acid, benzoic acid, acetamide, phenol, p-aminobenzoic acid in a variety of solvent conditions and at a variety of stoichiometric ratios, the precipitate or crystalline material has been shown to have the same characteristics as the starting material. It has been concluded that indomethacin crystallizes with itself more readily than with any of these compounds under the given conditions. When combined with urea, it has been shown that the product has characteristics which are unique from those of the starting material. In this case, there are favorable interactions between the molecules which cause indomethacin to co-crystallize with urea in a thermodynamically favorable manner. Indomethacin has been crystallized in toluene and ethanol, and melting point analyses suggest that the crystals formed in toluene are new material. This shows that the intermolecular interactions between toluene and indomethacin are more favorable than those between indomethacin molecules.

Ms. Catherine Gumm, under the direction of Dr. Keith Kyler, presented "The Chemical and Enzymatic Degradation of Biomass into Glucose Utilizing Ultrafiltration".
Abstract removed on advice of legal counsel (proprietary information).

Mr. Chad Myers, under the direction of Dr. Ron See, presented "Analysis of the AX2E Molecules Using the NBI Model: The Physical Basis for the Lone Pair Effect".
The effect of stereochemical, non-bonding electrons, also called the lone pair effect, on the geometry of molecules is a universally recognized phenomenon. Common conceptual models of molecular geometry, such as hybridization and VSEPR, give a qualitative estimation of the result of the lone pair effect, but neither includes a realistic physical basis for the observed molecular distortions caused by stereochemical lone pairs. An analysis of the AX2E (carbenes and their Si and Ge analogues) was performed, using computations at the MP2/6-31G** level. It was found that the stabilization energy provided by the stereochemical electrons is a linear function of the X-A-X angle, indicating that the radial space available to the stereochemical electrons about the central atom is the primary physical force resulting in the lone pair effect. This result is consistent with the Non-Bonded Interaction model, and constitutes evidence that this model provides a more physically realistic picture of molecular geometry.

Mr. Joseph Zewe, under the direction of Dr. Carl LeBlond, presented his work on the computational study of cross-coupling of organic halides.
Palladium catalyzed cross-coupling reactions have proven to be powerful synthetic methods for the preparation of pharmaceutical intermediates and fine chemicals due to their selectivity, relatively mild reaction conditions and their ability to tolerate a variety of functional groups. The Suzuki-Miyaura cross-coupling of organic halides with organoboron reagents constitutes a direct and efficient approach for the formation of carbon-carbon bonds. An extensive computational study providing key insights into the mechanism and synthetic trends of the transmetalation step of the Suzuki-Miyaura cross-coupling reaction was performed. The role of base, phosphine ligand inhibition and effect of the spectator organic and phosphine ligands, were studied using hybrid density functional methods. Herein we report our computational results concerning transmetalation (B to Pd) to saturated and unsaturated Pd intermediates. We show that transmetalation to 3-coordinate Pd intermediates is more facile than to 4-coordinate. We also demonstrate that solvent ligated Pd intermediates are more efficient in promoting transmetalation than model phosphine ligands. Our results correlate well with experimental observations concerning the base, ligand stoichiometry, substrate electronic effects and reactivity of various substrates.

Mr. Michael Deible, under the direction of Dr. Ron See, presented "The Physical Basis of the Lone Pair Effect in the AX3E and AX4E Molecule Types".
The lone pair effect is based on the observation that a nonbonding electron pair on the central atom will distort the geometry of a molecule. Using the Non-Bonded Interaction (NBI) model as a framework, the lone pair effect has been explained as the maximization of radial volume for the electron pair about the central atom. However, the work leading to this explanation used only the simplest (AX2E) molecule type displaying the lone pair effect in its analysis, and it is not clear that this conception can be extended to more complex molecules. Therefore, a computational study, at the B3LYP/6-31G** level, was undertaken to determine if this conception of the lone pair effect can be extended to the AX3E (A = N, P, As; X = H, F, Cl) and AX4E (A = S, Se; X = H, F, Cl) molecule types. The results show that the explanation of the lone pair effect found in the AX2E molecules is generally applicable to these more complex species, and the stabilization energy of the lone electron pairs is a function of the number of X atoms.

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