Chemistry Presentations

In all organic chemistry classes at Mount St. Mary’s University, students are required to complete a three-step synthesis experiment in which bromobenzene is converted to methyl m-nitrobenzoate. Many of the chemicals used in this experiment, specifically methanol, are toxic and should be handled with extreme care. If the experiment could yield the same results at a smaller scale, students would be safer, and the administration would be spending less for reagents and the removal of waste as a result. In this study, we focus on the second step: the esterification of benzoic acid using a different distillation apparatus: a Hickman Head. The Hickman allows one to use a shorter distillation path and typically increases the yield of product on small scales. The current protocol calls for15 grams of benzoic acid as the starting reagent. We will study trials at full scale (15 grams), 2/3 scale (10 grams), and 1/3 scale (5 grams). Preliminary studies were conducted using reagent grade benzoic acid. These studies will utilize student-synthesized benzoic acid. Yield, percent yield, and purity data will be collected. Purity is assessed by distillation temperature and IR spectroscopy, using a Shimadzu IR Affinity-1 with an ATR reflection adaptor. The data will be analyzed and presented.

Gold nanoparticles are useful for many purposes including electronics, photodynamic therapy, delivery for therapeutic agents, and other catalytic purposes. They are utilized because of their surface area-to-volume ratio, emphasizing the significance of the gold nanoparticles’ size. In this experiment, gold nanoparticles are synthesized from the reduction of tetrachloroaurate (III) ion by sodium citrate. Multiple trials of this experiment will be conducted. Each trial uses a different amount of sodium citrate to examine whether it increases or decreases the diameter and size of the gold nanoparticles. The amounts of sodium citrate used will be 1.8 milliliters, 1.0 milliliters, and 2.4 milliliters. The amount of sodium citrate increases or decreases the diameter of the gold nanoparticles. A lesser volume of sodium citrate increases the diameter of the gold nanoparticles while a greater amount of sodium citrate decreases its diameter. After the gold nanoparticles are synthesized, their absorbance will be measured using a Uv-Vis spectrophotometer. The absorbance displays the λ_max which can be used to find the diameter of the nanoparticles. The diameter and size of the synthesized gold nanoparticles will be tested using Dynamic Light Scattering (DLS). A laser pointer will be used to evaluate the light scattering properties by the colloids, called the Tyndall Effect.

Cetyltrimethylammonium bromide (CTAB) has been reported to stabilize and grow gold nanoparticles. Gold nanoparticles are particles on the nanoscale with a gold core. These types of nanoparticles are commonly used in targeted drug-delivery systems for cancer therapy. The purpose of this research is to determine the influence the bromide counterion and the micelle morphology have on the stability and growth of the aforementioned nanoparticles. Controlling the size and shape of the gold nanoparticles will allow for more powerful and efficient treatments to particular parts of the body. Understanding the influence of these two factors could lead scientists and researchers to develop less-harmful cures for cancer patients. CTAB is the parent surfactant used for the synthesis of cetyltrimethylammonium-4-chlorobenzoate (CTA4), cetyltrimethylammonium-3,5-dichlorobenzoate (CTA3,5), and cetyltrimethylammonium-2,6-dichlorobenzoate (CTA2,6). Each of these surfactants form micelles at a particular critical micelle concentration (CMC). The CMC, as well as the size and shape of the micelles, can be determined through dynamic light scattering (DLS) and ultraviolet-visible (UV-Vis) spectroscopy. CTAB and CTA2,6 form spherical micelles, CTA3,5 forms rod-like micelles, and CTA4 forms a combination of spherical and rod-like micelles. The first step of this research is to develop a procedure for the synthesis of all three of these surfactants and prove the synthesis produced the target molecule. This is done through characterizing the products in nuclear magnetic resonance (NMR) spectroscopy and infrared (IR) spectroscopy. Next, the CMC, size, and shape can be experimentally determined and compared to the published values using UV-Vis and DLS.

Tuberculosis is one of the top ten leading causes of death in the world. While a regime of four drugs exists to treat tuberculosis, the treatment requires daily dosing over six to nine months which many people in third world countries do not have access. Drug resistance has also led to ineffective treatment of tuberculosis infections. Polyketide Synthase 13 (Pks13) is an enzyme in Mycobacterium tuberculosis (M.Tb) responsible for the synthesis of mycolic acids. Mycolic acids build up the cell wall in M.Tb. Last summer, I interned with the Neglected Disease Initiative at AbbVie Pharmaceuticals to help develop novel inhibitors of Pks13 with the intent of developing a new drug-lead for tuberculosis. We studied the use of pyridine derivatives which proved effective inhibitors in vitro. Specifically, I studied pyrazines with different functional groups including amides, sulfonamides, aldoximes, ketoximes, and carboxylic acids. The pyrazines with sulfonamide and aldoxime functional groups proved active and potent in the initial biological activity assay. The sulfonamide proved to be a better target through clearance assays and work was continued modifying the structure. While a final drug-lead was not obtained at the end of the summer, much work was accomplished, and the research could produce a novel drug in the future.

Human perception is greatly influenced by color. In response, textile industries have developed a vast array of various colors to appeal to their many consumers. However, many industries employ techniques that result in toxic and non-biodegradable products, which negatively affect aquatic life and, thus, a human food source. Most dyes composed of inorganic compounds are easily produced compared to non-toxic organic dyes, which are highly valuable but less cost efficient to a business. Current methods of research are working to develop quick and effective dyes that adhere to various types of fabric while also being cost efficient, less harmful to the environment, and bright in pigment. In this experiment, Rhodamine B, which is a bright-red color used for fluorescent staining, was synthesized at different temperatures in order to observe the subsequent effect on dyeing quality and fluorescence. Three trials were conducted per variable group. While heating in a sand bath, the control group maintained a temperature between 180-200°C, the second group between 160-180°C, and the third group between 140-160°C. To quantify the effect of the variable, results were assessed based on the following: purity of sample through Ultraviolet-visible spectroscopy and melting point, fluorescence on fabrics, yield, and percent yield. Higher temperature when synthesizing this dye may result in higher yield and purity that would cause the dye to not wash out after being absorbed into a fabric, thus decreasing the impact on environment and aquatic life.

Various modern methods of chemical analysis require sample manipulation prior to introducing samples into instrumentation. Desorption Electrospray Ionization Mass Spectrometry (DESI-MS) is a method of analyzing a chemical substance directly from a sample surface without any prior sample preparation. This advantage provides a much-needed solution to the challenges faced in conducting trace chemical analysis in remote or field locations, where laboratory capabilities for sample preparation are inaccessible. In DESI-MS, sample concentrations are limited to the amount that can be acquired through direct contact with the sample surface (which can be either a swab, card, or specialized chemical collection pen). In most cases, chemicals of interest will be found in trace amounts on sample surfaces. In order to improve instrument reliability, methods of increasing the amount of desorbed analyte are of interest. Ultrasonic waves pose a likely candidate in increasing the amount of desorbed analyte from sample surface and therefore improve the reliability of the instrument. Ultrasonic waves, produced by inexpensive electrical components, were used in an attempt to directly agitate sample surfaces to increase sample desorption. Two types of piezoelectric ultrasonic transducers, one high power and another low power, were directly placed on sample surfaces. Analysis was conducted using a FLIR Ambient Ionization (AI) Mass Spectrometer, with ambient ionization capability for both Electrospray Ionization (ESI) and DESI. In the experiment, the DESI configuration was used, and samples were prepared and introduced under control conditions (no agitation), and with ultrasonic agitation. Abundance (overall signal strength) was then compared between the two measurements, as well as chemical peak strengths.

Thermal conductivity is generally the tool of choice for quantification of fixed gases, particularly lighter-than-air gases. Unfortunately, gas chromatography-thermal conductivity detectors (GC-TCDs) are difficult to introduce in first- and second-year chemistry courses where the cost and number of instruments, as well as the space required, is impractical. In this presentation, the co-presenters describe the development of a small, inexpensive microcontroller-based thermal conductivity detector (TCD) for undergraduate teaching and research lab experiments which utilizes a matched pellistor pair to quantify lighter-than-air gases. The total cost of materials is under $200 including the microcontroller, electronics, TCD pellistor pair, and the mechanical parts which serve as the housing and analysis chamber.