Comparison of solid state and solution photoreactivity of a tertiary alkyl azide

Solid-state photochemical reactions have been shown to be useful synthetic tools for their remarkable stereo and regiospecificity. Decreased solvent use also gives these reactions green chemistry appeal. One of the limitation of using solid-state photoreactions in synthetic applications is understanding how the crystal lattice controls the reactivity. Until recently, elucidation of solid-state reactions has been limited to structure reactivity correlations. With the aid of laser flash photolysis of nanocrystals in water slurry it is possible to determine solid-state kinetics, which makes it possible to correlate the kinetics with the structure. We have investigated dimerization of 1,4-naphthoquinone derivatives in the solid-state, which has allowed us to determine how the crystal packing of a molecule influence the solid-state kinetics of product formation. The correlation was established through X-ray crystallography of the 1,4-naphthoquinone derivatives and their transient kinetics spectroscopy. 12. Liposome-Nanoparticle Substrates for Surface Enhanced Raman Spectroscopy Russell Anthony, William Lum, Ian Bruzas, and Dr. Laura B. Sagle University of Cincinnati, Department of Chemistry, Cincinnati, Ohio, 45220, United States Raman scattering is an inefficient optical phenomenon that occurs when incident photons inelastically scatter from an atom or molecule. Surface-enhanced Raman Scattering (SERS) spectroscopy uses noble metal surfaces such as Au to greatly increase Raman scattering thus producing a highly sensitive and selective technique, which can analyze single molecules (SM). In order to create more biologically compatible SERS substrates, we propose to encapsulate probe molecules into liposomes to mimic the native environment. As proof of concept, crystal violet was encapsulated into biotinylated liposomes, the liposomes are tethered to a gold surface and finally gold nanoparticles are bound to maximize the signal. 13. Azido Modified NTP as Chemical Handles for Multiplex Analysis of tRNA Digestion Products Kayla Borland and Patrick A. Limbach Department of Chemistry, University of Cincinnati Liquid chromatography tandem mass spectrometry (LC-MS/MS) is the gold standard in transfer ribonucleic acid (tRNA) modification identification and mapping. A common practice in LCMS/MS in the field of proteomics is the use of multiplexing, which allows multiple biological samples to be analyzed simultaneously. We are exploring the use of poly adenosine polymerase (PAP), which – under optimized conditions – can add one 2’ azido modified nucleotide to the 3’terminus of tRNA digest products. The addition of this azido-modified nucleotide can allow for the use of click chemistry to uniquely tag each sample. Here we report preliminary studies focused on click reaction conditions. 14. Synthesis of a pyridyl disulfide functionalized RAFT copolymer for conjugation with Polypropylene fumarate through thiol-ene click reactions. Mario Perera, Neil Ayres Department of Chemistry, University of Cincinnati Poly(N,N-dimethyl aminoethyl methacrylate-co-pyridyldisulfide ethyl methacrylate) (poly(DMAEMA-co-PDSMA) was synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. The number average molecular weight (Mn= 7800 g/mol) and dispersity (Đ= 1.3) were determined using gel permeation chromatography and the PDSMA content in the polymer was determined using the 1H nuclear magnetic resonance (NMR) spectroscopy. Post polymerization modifications reduced the pyridyl disulfide groups to thiols using (tris(2-carboxyethyl)phosphine) (TCEP), this was confirmed by the disappearance of the pyridyl protons in the 1H NMR spectra. Thiol-ene click reactions are an efficient tool for polymer synthesis and modification. Polypropylene fumarate (PPF) is a hydrophobic polyester that has been investigated as a potential scaffold material for bone tissue engineering. In this work, thiolene click reactions were attempted as a strategy to graft PPF with modified poly(DAMAEMA-coPDSMA). However the expected copolymer was unable to be isolated. Control thiol-ene reactions of PPF with propane thiol and diethyl fumarate with modified poly(N,N-dimethyl acrylamide) were successfully performed, and the 1H and 13C NMR spectroscopy confirmed the products. Hence, this study proves that polymer/polymer thiol-ene reactions are not an appropriate strategy to conjugate PPF and poly(DAMAEMA-co-PDSMA). We speculate that this is due to a combination of steric and reptation effects. 15. Quantitative SERS measurement of trichloroethylene with Au-core/Ag-shell nanoparticles Zhao Yu, Yan Zhou, Peng Zhang* Department of Chemistry, University of Cincinnati, OH 45221, United States Abstract: Trichloroethylene (TCE) has been used for cleaning and degreasing metal-based equipment, and it is known to be a human carcinogen. Surface-enhanced Raman scattering (SERS) is introduced to determine the concentration of TCE in water. We use Au-core/Ag-shell nanoparticles with 4-mercaptophenylboronic acid (4MPBA) as embedded internal reference as a new strategy to measure TCE with a high sensitivity. 4-mercaptopyridine (4-MPy) can react with TCE through Fujiwara Reaction. We monitor the consumption of 4-MPy by the SERS signals change of Au@4MPBA@Ag nanoparticles to determine the concentration of TCE in water indirectly. Trichloroethylene (TCE) has been used for cleaning and degreasing metal-based equipment, and it is known to be a human carcinogen. Surface-enhanced Raman scattering (SERS) is introduced to determine the concentration of TCE in water. We use Au-core/Ag-shell nanoparticles with 4-mercaptophenylboronic acid (4MPBA) as embedded internal reference as a new strategy to measure TCE with a high sensitivity. 4-mercaptopyridine (4-MPy) can react with TCE through Fujiwara Reaction. We monitor the consumption of 4-MPy by the SERS signals change of Au@4MPBA@Ag nanoparticles to determine the concentration of TCE in water indirectly. 16. Fenton Chemistry of Acetophenones in Water: Evidence of Ipso Substitution Jennifer L. Meyer1, Richard P. Hotz1, Allan R. Pinhas2 1Department of Chemistry, Mount St. Joseph University 2Department of Chemistry, University of Cincinnati Using Fenton’s reagent, the coupling of two radicals formed by hydrogen atom abstraction from the -carbon of acetophenone, in its keto form, results in the generation of a 1,4-diketone. However, because the enol form predominates under acidic conditions in water, the major reaction products derive from attack of the hydroxyl radical on the aromatic ring. A small percentage of these compounds, including phenol, are formed by ipso substitution. Identification of ipso substitution products from several substituted acetophenones and possible mechanisms for their formation will be presented. 17. Comparing Photosensitization of Azido-Butyrophenone Derivatives using UV Light and Acetophenone as a Built-in Triplet Sensitizer and Visible Light and Inorganic Photocatalysts DeVonna M. Gatlin, Anntonette Perry, Anna D. Gudmundsdóttir* Department of Chemistry, University of Cincinnati Photocatalyst make it possible to use visible light for sustainable organic photosynthesis. To explore the difference between the inorganic photocatalyst and built-in triplet sensitizer, we investigated the photoreactivity of alkyl azide 1. Photolysis of alkyl azide 1 with UV light above 300 nm, results in product A through formation of triplet alkylnitrenes intermediates. Irradiation with 400 nm light and photocatalyst X also yields the same product presumably through the same mechanism as UV irradiation. However, photolysis with photocatalyst Y (with 460 nm irradiation) results in product B. We will use theoretical calculations and transient spectroscopy to further understand how the photoreactivity differ for each photocatalyst.