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ProfYunPic

Yun Lu

Professor, Organic Chemistry
Department of Chemistry
Southern Illinois University Edwardsville
College of Arts and Sciences
SL 3210 (Office) | 3015 (Lab)
Edwardsville, Illinois 62026-1652.
Tel: (618) 650-3563 (Office) | (618) 650-3568 (Lab)
Fax: (618) 650-3556
E-mail: yulu@siue.edu

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Education:

Research Interests:

H-transfer reactions have drawn chemists and physicists particular attention in the mechanistic studies since H is the lightest atom and has pronounced quantum mechanical wave properties. Much evidence has shown that H-transfer likely takes place by a H-tunneling mechanism in which H wave packet tunnels through the energy barrier. To date, a few H-tunneling models have been proposed but none has been universally accepted. Two contemporary models are the vibrationally assisted activated H-tunneling model and the multidimensional H-tunneling model within the variational transition state theory. Both contain the important concept that the donor-acceptor distance (DAD) is shorter in the tunneling ready state (TRS) for the transfer of a heavier isotope than that of H-transfer. While the cause appears to be that H has the longest de Broglie wavelength among its isotopes, there have been very few studies to examine the important isotopically different DAD concept. We use physical organic mechanistic analysis methods to distinguish the isotopically different TRS structures for various H- vs. D-transfer reactions in solution. We study (1) the primary isotope dependence of the secondary kinetic isotope effects (KIEs) to distinguish the isotopically different TRS conformations, and (2) the primary isotope dependence of Hammett correlations (equivalent to the substituent effect on the primary KIEs) to differentiate the isotopically different TRS electronic structures. Both the conventional spectroscopic kinetic measurement methods and competitive KIE measurement method are used. Computational replication of the observed secondary KIEs are carried out to help search for the TRS structures.

Students involved in the project will learn organic synthesis, mechanistic analysis techniques, computational chemistry methods, quantum chemistry, the use of analytical instrumentation, as well as H-transfer mechanism in enzymes.

Hydrogen transfer transition state diagram
Donor-acceptor distance (DAD) and energetic comparison of the potential activated reactive complexes involved in a H-transfer reaction to show isotopically different tunneling-ready-state (TRS) structures. The oval-shaped areas in the non-classical TRS represent H/D wave packets. The wave packet of the heavier D isotope is less diffuse than that of H; thus a shorter DAD is required for tunneling. The DAD of the TRS is longer than that of the classical TS for that same reaction. The relative energies of the three activated complexes are in the order depicted. The different trajectories of the H/D-transfer in TRS and TS are not shown.

Selected Publications:

  • Mortaza Derakhshani-Molayousefi, Sadra Kashefolgheta, James E. Eilers, and Yun Lu*, "Computational Replication of the Primary Isotope Dependence of Secondary Kinetic Isotope Effects in Solution Hydride-Transfer Reactions: Supporting the Isotopically Different Tunneling Ready State Conformations" J. Phys. Chem. A 2016, 120, 4277−4284.
  • Binita Maharjan, Mahdi Raghibi Boroujeni, Jonathan Lefton, Ormacinda R. White, Mortezaali Razzaghi, Blake A. Hammann, Mortaza Derakhshani-Molayousefi, James E. Eilers, Yun Lu* "Steric Effects on the Primary Isotope Dependence of Secondary Kinetic Isotope Effects in Hydride Transfer Reactions in Solution: Caused by the Isotopically Different Tunneling Ready State Conformations?" J. Am. Chem. Soc. 2015, 137, 6653-6661.
  • Sadra Kashefolgheta, Mortezaali Razzaghi, Blake Hammann, James E. Eilers, Daniel Roston, Yun Lu* "Computational Replication of the Abnormal Secondary Kinetic Isotope Effects in a Hydride Transfer Reaction in Solution with a Motion Assisted H-Tunneling Model" J. Org. Chem. 2014, 79, 1989-1994.
  • Blake Hammann, Mortezaali Razzaghi, Sadra Kashefolgheta, Yun Lu* "Imbalanced Tunneling Ready States in Alcohol Dehydrogenase Model Reactions: Rehybridization Lags behind H-Tunneling†" Chemical Communications, 2012, 48, 11337-11339.
  • Qi Liu, Yu Zhao, Blake Hammann, James E. Eilers, Yun Lu*, Amnon Kohen* "A Model Reaction Assesses Contribution of H-Tunneling and Coupled Motions to Enzyme Catalysis" J. Org. Chem. 2012, 77 , 6825-6833.
  • Yun Lu*, Joshua Bradshaw, Yu Zhao, William Kuester, Daniel Kabotso "Structure - Reactivity Relationship for Alcohol Oxidations via Hydride Transfer to a Carbocationic Oxidizing Agent" J. Phys. Org. Chem. 2011, 24, 1172-1178.
  • Yun Lu* ,Fengrui Qu, Yu Zhao, Ashia Small, Joshua Bradshaw, Brian Moore "Kinetics of the Hydride Reduction of an NAD+ Analogue by Isopropyl Alcohol in Aqueous and Acetonitrile Solutions: Solvent Effects, Deuterium Isotope Effects and Mechanism" J. Org. Chem. 2009, 74, 6503-6510.
  • Yun Lu* , Fengrui Qu, Brian Moore, Donald Endicott, William Kuester "Hydride Reduction of NAD+ Analogues by Isopropyl Alcohol: Kinetics, Deuterium Isotope Effects and Mechanism" J. Org. Chem. (Featured Article) 2008, 73, 4763-4770.
  • Yun Lu* , Donald Endicott, William Kuester "Effective Oxidation of Isopropanol by an NAD+ Model." Tetra Lett 2007, 48, 6356-6359.
  • Yun Lu* , Jiancheng Liu, Garry Diffee, Diansheng Liu, Bo Liu* "Reduction of Nitroarenes by Hydroxide Ion in Water Catalyzed by β-Cyclodextrin: Enhanced Reactivity of Hydroxide Ion." Tetra Lett 2006, 47, 4597-4599.
  • Martin Newcomb*, Runnan Shen, Yun Lu, Minor J. Conn, Paul F. Hollenberg, Daniel A. Kopp, Stephen J. Lippard "Evaluation of norcarane as a probe for radicals in cytochrome P-450 and soluble Methane Monooxygenase- catalyzed hydroxylation reactions" J. Am. Chem. Soc. 2002, 124, 6879-6886.
  • Yun Lu , Yixing Zhao, Vernon D. Parker* "Proton-transfer reactions of methylarene radical cations with pyridine bases under non-steady-state conditions. Real kinetic isotope effect evidence for extensive tunneling" J. Am. Chem. Soc. 2001, 123, 5900-5907.
  • Jin-Pei Cheng*, Yun Lu, Xiaoqing Zhu, Linjing Mu "Energetics of Multi-step vs. One-step Hydride Transfer Reactions of Reduced Nicotinamide Adenine Dinucleotide (NADH) Models with Organic Cations and p-Quinones" J. Org. Chem. 1998, 63, 6108-6114.
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