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Planar Cyclopenten‐4‐Yl Cations: Highly Delocalized Π Aromatics
Angewandte Research Articles Chemie How to cite: Angew.Chem. Int. Ed. 2020, 59,18809–18815 Carbocations International Edition: doi.org/10.1002/anie.202009644 German Edition: doi.org/10.1002/ange.202009644 Planar Cyclopenten-4-yl Cations:Highly Delocalized p Aromatics Stabilized by Hyperconjugation Samuel Nees,Thomas Kupfer,Alexander Hofmann, and Holger Braunschweig* 1 B Abstract: Theoretical studies predicted the planar cyclopenten- being energetically favored by 18.8 kcalmolÀ over 1 (MP3/ 4-yl cation to be aclassical carbocation, and the highest-energy 6-31G**).[11–13] Thebishomoaromatic structure 1B itself is + 1 isomer of C5H7 .Hence,its existence has not been verified about 6–14 kcalmolÀ lower in energy (depending on the level experimentally so far.Wewere now able to isolate two stable of theory) than the classical planar structure 1C,making the derivatives of the cyclopenten-4-yl cation by reaction of bulky cyclopenten-4-yl cation (1C)the least favorable isomer.Early R alanes Cp AlBr2 with AlBr3.Elucidation of their (electronic) solvolysis studies are consistent with these findings,with structures by X-raydiffraction and quantum chemistry studies allylic 1A being the only observable isomer, notwithstanding revealed planar geometries and strong hyperconjugation the nature of the studied cyclopenteneprecursor.[14–18] Thus, interactions primarily from the C Al s bonds to the empty p attempts to generate isomer 1C,orits homoaromatic analog À orbital of the cationic sp2 carbon center.Aclose inspection of 1B,bysolvolysis of 4-Br/OTs-cyclopentene -
On the Harmonic Oscillator Model of Electron Delocalization (HOMED) Index and Its Application to Heteroatomic Π-Electron Systems
Symmetry 2010, 2, 1485-1509; doi:10.3390/sym2031485 OPEN ACCESS symmetry ISSN 2073-8994 www.mdpi.com/journal/symmetry Article On the Harmonic Oscillator Model of Electron Delocalization (HOMED) Index and its Application to Heteroatomic π-Electron Systems Ewa D. Raczyñska 1, *, Małgorzata Hallman 1, Katarzyna Kolczyñska 2 and Tomasz M. Stêpniewski 2 1 Department of Chemistry, Warsaw University of Life Sciences (SGGW), ul. Nowoursynowska 159c, 02-776 Warszawa, Poland 2 Interdisciplinary Department of Biotechnology, Warsaw University of Life Sciences (SGGW), ul. Nowoursynowska 166, 02-776 Warszawa, Poland * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +48-22-59-37623; Fax: +49-22-59-37635. Received: 23 April 2010; in revised form: 19 May 2010 / Accepted: 7 July 2010 / Published: 12 July 2010 Abstract: The HOMA (Harmonic Oscillator Model of Aromaticity) index, reformulated in 1993, has been very often applied to describe π-electron delocalization for mono- and polycyclic π-electron systems. However, different measures of π-electron delocalization were employed for the CC, CX, and XY bonds, and this index seems to be inappropriate for compounds containing heteroatoms. In order to describe properly various resonance effects (σ-π hyperconjugation, n-π conjugation, π-π conjugation, and aromaticity) possible for heteroatomic π-electron systems, some modifications, based on the original HOMA idea, were proposed and tested for simple DFT structures containing C, N, and O atoms. An abbreviation HOMED was used for the modified index. Keywords: geometry-based index; π -electron delocalization; σ - π hyperconjugation; n-π conjugation; π-π conjugation; aromaticity; heteroatomic compounds; DFT 1. -
Aldrichimica Acta
VOLUME 51, NO. 1 | 2018 ALDRICHIMICA ACTA The Spectacular Resurgence of Electrochemical Redox Reactions in Organic Synthesis Carbon–Carbon π Bonds as Conjunctive Reagents in Cross-Coupling The life science business of Merck KGaA, Darmstadt, Germany operates as MilliporeSigma in the U.S. and Canada. MakInG sTrIDes In Genome EDITInG: THe DIGITaL, CHemIcaL, anD BIoLogIcaL Dear Fellow Researchers: You may not know that MilliporeSigma can make DNA from scratch, using 100% synthetic chemical methods—no living cells and no fermentation necessary. Our DNA synthesis facilities in The Woodlands (Texas) and Haverhill (U.K.) receive thousands of DNA orders daily from scientists all over the world. A small piece of DNA, one hundred bases long, gives scientists 4100 possibilities using only the fundamental letters of our genetic code (A,C,G,T). Included within these options is the opportunity for a researcher to open a common text editor on his or her PC and design a 100-base piece of DNA. This piece of DNA could help study diseases ranging from sickle cell anemia and blindness to cystic fibrosis by using CRISPR. To get started, scientists cut this 100-base DNA text from the text editor and paste it into MilliporeSigma’s online ordering system. The corresponding DNA piece that likely has never existed before is then delivered to them in 24–48 hours. Once received, this piece of DNA is mixed with CRISPR and living cells, and, with a “blast” of electricity, these synthetic chemical pieces activate the cell to edit the genome. Learn more about our CRISPR gene editing portfolio at SigmaAldrich.com/CRISPR Sincerely yours, Udit Batra, Ph.D. -
Preparation and Characterization of Iridium Hydride and Dihydrogen Complexes Relevant to Biomass Deoxygenation
Preparation and Characterization of Iridium Hydride and Dihydrogen Complexes Relevant to Biomass Deoxygenation Jonathan M. Goldberg A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 2017 Reading Committee: D. Michael Heinekey, Chair Karen I. Goldberg, Chair Brandi M. Cossairt Program Authorized to Offer Degree: Department of Chemistry © Copyright 2017 Jonathan M. Goldberg University of Washington Abstract Preparation and Characterization of Iridium Hydride and Dihydrogen Complexes Relevant to Biomass Deoxygenation Jonathan M. Goldberg Chairs of the Supervisory Committee: Professor D. Michael Heinekey Professor Karen I. Goldberg Department of Chemistry This thesis describes the fundamental organometallic reactivity of iridium pincer complexes and their applications to glycerol deoxygenation catalysis. These investigations provide support for each step of a previously proposed glycerol deoxygenation mechanism. Chapter 1 outlines the motivations for this work, specifically the goal of using biomass as a chemical feedstock over more common petroleum-based sources. A discussion of the importance of transforming glycerol to higher value products, such as 1,3-propanediol, is discussed. Chapter 2 describes investigations into the importance of pincer ligand steric factors on the coordination chemistry of the iridium metal center. Full characterization of a five-coordinate iridium-hydride complex is presented; this species was previously proposed to be a catalyst resting state for glycerol deoxygenation. Chapter 3 investigates hydrogen addition to R4(POCOP)Ir(CO) R4 3 t i R4 R4 3 [ POCOP = κ -C6H3-2,6-(OPR2)2 for R = Bu, Pr] and (PCP)Ir(CO) [ (PCP) = κ -C6H3-2,6- t i (CH2PR2)2 for R = Bu, Pr] to give cis- and/or trans-dihydride complexes. -
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COORDINATION COMPOUNDS OF ALKYL GALLIUM HYDRIDES by VICTOR GRAHAM WIEBE B.Sc. (Hons.) University of British Columbia 1966 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE In The Department of Chemistry We accept this thesis as conforming to the required standard The University of British Columbia June 1968 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and Study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by hits representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver 8, Canada - ii - Abstract Although the organo hydride derivatives of boron and aluminum are well characterized^little work has been reported on the corresponding gallium systems. The present study was initiated to determine the relative stabilities and reactivity of organo gallium hydride derivatives as compared with the stabilities and reactions of the corresponding compounds of boron and aluminum. Various preparative routes to this new class of gallium compounds have been investigated. These include the use of organo-mercury, organo-lithium and lithium hydride derivatives in reactions with gallium hydride and gallium alkyl compounds and their halogen substituted derivatives: Me3NGaH3 + HgR2 >- Me3NGaH2R + l/2Hg + 1/2H2 Me3NGaH2Cl + LiR y Me3NGaH2R + LiCl Me3NGaR2Cl + LiH • Me3NGaHR2 + LiCl A fourth preparative method involves disproportionation reactions between gallium hydride compounds and organo gallium compounds to yield the mixed organo hydride derivatives. -
The Lowest-Energy Isomer of C2si2h4 Is a Bridged Ring: Reinterpretation of the Spectroscopic Data Based on DFT and Coupled-Cluster Calculations
Air Force Institute of Technology AFIT Scholar Faculty Publications 4-11-2019 The Lowest-Energy Isomer of C2Si2H4 Is a Bridged Ring: Reinterpretation of the Spectroscopic Data Based on DFT and Coupled-Cluster Calculations Jesse J. Lutz ORISE Fellow Larry W. Burggraf Air Force Institute of Technology Follow this and additional works at: https://scholar.afit.edu/facpub Part of the Inorganic Chemistry Commons Recommended Citation Lutz, J. J., & Burggraf, L. W. (2019). The Lowest-Energy Isomer of C2Si2H4 Is a Bridged Ring: Reinterpretation of the Spectroscopic Data Based on DFT and Coupled-Cluster Calculations. Inorganics, 7(4), 51. https://doi.org/10.3390/inorganics7040051 This Article is brought to you for free and open access by AFIT Scholar. It has been accepted for inclusion in Faculty Publications by an authorized administrator of AFIT Scholar. For more information, please contact [email protected]. inorganics Article The Lowest-Energy Isomer of C2Si2H4 Is a Bridged Ring: Reinterpretation of the Spectroscopic Data Based on DFT and Coupled-Cluster Calculations Jesse J. Lutz 1,* and Larry W. Burggraf 2 1 ORISE fellow residing at Department of Engineering Physics, Air Force Institute of Technology, Wright-Patterson Air Force Base, Dayton, OH 45433-7765, USA 2 Department of Engineering Physics, Air Force Institute of Technology, Wright-Patterson Air Force Base, Dayton, OH 45433-7765, USA; Larry.Burggraf@afit.edu * Correspondence: jesse.lutz.ctr@afit.edu Received: 28 February 2019; Accepted: 3 April 2019; Published: 11 April 2019 Abstract: The lowest-energy isomer of C2Si2H4 is determined by high-accuracy ab initio calculations to be the bridged four-membered ring 1,2-didehydro-1,3-disilabicyclo[1.1.0]butane (1), contrary to prior theoretical and experimental studies favoring the three-member ring silylsilacyclopropenylidene (2). -
Binuclear Copper(I) Borohydride Complex Containing Bridging Bis
crystals Article Binuclear Copper(I) Borohydride Complex Containing Bridging Bis(diphenylphosphino) Methane Ligands: Polymorphic Structures of 2 [(µ2-dppm)2Cu2(η -BH4)2] Dichloromethane Solvate Natalia V. Belkova 1 ID , Igor E. Golub 1,2 ID , Evgenii I. Gutsul 1, Konstantin A. Lyssenko 1, Alexander S. Peregudov 1, Viktor D. Makhaev 3, Oleg A. Filippov 1 ID , Lina M. Epstein 1, Andrea Rossin 4 ID , Maurizio Peruzzini 4 and Elena S. Shubina 1,* ID 1 A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences (INEOS RAS), 119991 Moscow, Russia; [email protected] (N.V.B.); [email protected] (I.E.G.); [email protected] (E.I.G.); [email protected] (K.A.L.); [email protected] (A.S.P.); [email protected] (O.A.F.); [email protected] (L.M.E.) 2 Inorganic Chemistry Department, Peoples’ Friendship University of Russia (RUDN University), 117198 Moscow, Russia 3 Institute of Problems of Chemical Physics, Russian Academy of Sciences (IPCP RAS), 142432 Moscow, Russia; [email protected] 4 Istituto di Chimica dei Composti Organometallici Consiglio Nazionale delle Ricerche (ICCOM CNR), 50019 Sesto Fiorentino, Italy; [email protected] (A.R.); [email protected] (M.P.) * Correspondence: [email protected]; Tel.: +7-495-135-5085 Academic Editor: Sławomir J. Grabowski Received: 18 September 2017; Accepted: 17 October 2017; Published: 20 October 2017 Abstract: Bis(diphenylphosphino)methane copper(I) tetrahydroborate was synthesized by ligands exchange in bis(triphenylphosphine) copper(I) tetrahydroborate, and characterized by XRD, FTIR, NMR spectroscopy. According to XRD the title compound has dimeric structure, [(µ2-dppm)2Cu2(η2-BH4)2], and crystallizes as CH2Cl2 solvate in two polymorphic forms (orthorhombic, 1, and monoclinic, 2) The details of molecular geometry and the crystal-packing pattern in polymorphs were studied. -
Bsc Chemistry
Subject Chemistry Paper No and Title Paper 1: ORGANIC CHEMISTRY- I (Nature of Bonding and Stereochemistry) Module No and Module 3: Hyper-Conjugation Title Module Tag CHE_P1_M3 CHEMISTRY PAPER No. 1: ORGANIC CHEMISTRY- I (Nature of Bonding and Stereochemistry) Module No. 3: Hyper-Conjugation TABLE OF CONTENT 1. Learning outcomes 2. Introduction 3. Hyperconjugation 4. Requirements for Hyperconjugation 5. Consequences and Applications of Hyperconjugation 6. Reverse Hyperconjugation 7. Summary CHEMISTRY PAPER No. 1: ORGANIC CHEMISTRY- I (Nature of Bonding and Stereochemistry) Module No. 3: Hyper-Conjugation 1. Learning Outcomes After studying this module you shall be able to: Understand the concept of hyperconjugation. Know about the structural requirements in a molecule to show hyperconjugation. Learn about the important consequences and applications of hyperconjugation. Comprehend the concept of reverse hyperconjugation. 2. Introduction In conjugation, we have studied that the electrons move from one p orbital to other which are aligned in parallel planes. Is it possible for electron to jump from p orbital to sp3 orbital that are not parallelly aligned with one another? The answer is yes. This type of conjugation is not normal, it is extra-ordinary. Hence, the name hyper-conjugation. It is also know as no-bond resonance. Let us study more about it. 3. Hyperconjugation The normal electron releasing inductive effect (+I effect) of alkyl groups is in the following order: But it was observed by Baker and Nathan that in conjugated system, the attachment of alkyl groups reverse their capability of electron releasing. They suggested that alkyl groups are capable of releasing electrons by some process other than inductive. -
Structure, Stability, and Substituent Effects in Aromatic S-Nitrosothiols: the Crucial Effect of a Cascading Negative Hyperconjugation/Conjugation Interaction
Marquette University e-Publications@Marquette Chemistry Faculty Research and Publications Chemistry, Department of 10-23-2014 Structure, Stability, and Substituent Effects in Aromatic S-Nitrosothiols: The Crucial Effect of a Cascading Negative Hyperconjugation/Conjugation Interaction Matthew Flister Marquette University, [email protected] Qadir K. Timerghazin Marquette University, [email protected] Follow this and additional works at: https://epublications.marquette.edu/chem_fac Part of the Chemistry Commons Recommended Citation Flister, Matthew and Timerghazin, Qadir K., "Structure, Stability, and Substituent Effects in Aromatic S-Nitrosothiols: The Crucial Effect of a Cascading Negative Hyperconjugation/Conjugation Interaction" (2014). Chemistry Faculty Research and Publications. 360. https://epublications.marquette.edu/chem_fac/360 Marquette University e-Publications@Marquette Chemistry Faculty Research and Publications/College of Arts and Sciences This paper is NOT THE PUBLISHED VERSION; but the author’s final, peer-reviewed manuscript. The published version may be accessed by following the link in the citation below. Journal of Physical Chemistry : A, Vol. 18, No. 42 (October 23, 2014): 9914–9924. DOI. This article is © American Chemical Society Publications and permission has been granted for this version to appear in e-Publications@Marquette. American Chemical Society Publications does not grant permission for this article to be further copied/distributed or hosted elsewhere without the express permission from American Chemical Society Publications. Structure, Stability, and Substituent Effects in Aromatic S-Nitrosothiols: The Crucial Effect of a Cascading Negative Hyperconjugation/Conjugation Interaction Matthew Flister Department of Chemistry, Marquette University, Milwaukee, Wisconsin Qadir K. Timerghazin Department of Chemistry, Marquette University, Milwaukee, Wisconsin Abstract Aromatic S-nitrosothiols (RSNOs) are of significant interest as potential donors of nitric oxide and related biologically active molecules. -
Contribution of Quantum Chemistry to the Study of Dienes and Polyenes
The Chemistry of Dienes and Polyenes. Volume 1 Edited by Zvi Rappoport Copyright ¶ 1997 John Wiley & Sons, Ltd. ISBN: 0-471-96512-X CHAPTER 1 Contribution of quantum chemistry to the study of dienes and polyenes V. BRANCHADELL, M. SODUPE, A. OLIVA and J. BERTRAN´ Departament de Qu´ımica, Universitat Autonoma` de Barcelona, 08193 Bellaterra, Spain Fax: (34)35812920; e-mail: [email protected] I. INTRODUCTION ..................................... 2 II. SURVEY OF THEORETICAL METHODS .................... 2 III. GROUND STATE STRUCTURE AND VIBRATIONAL SPECTRA .... 4 A. Butadiene ........................................ 4 1. Geometry ...................................... 4 2. Vibrational frequencies and force field ................... 5 3. Conformational equilibrium .......................... 6 B. Trienes and Tetraenes ................................ 7 1. Geometries and conformations ........................ 7 2. Vibrational frequencies and force constants ................ 9 C. Longer Polyenes .................................... 9 IV. EXCITED STATES .................................... 10 A. Butadiene ........................................ 11 B. Hexatriene ........................................ 13 C. Octatetraene ...................................... 14 D. Longer Polyenes .................................... 14 V. MOLECULAR ELECTRIC PROPERTIES ..................... 15 VI. CHEMICAL REACTIVITY .............................. 17 A. The Diels Alder Reaction ............................. 17 1. Reaction mechanism .............................. -
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Journal of Chemistry, Vol. 47 (6), P. 779 - 785, 2009 The Interaction of BH2NH2 with HNZ (Z: O, S) in the Gas Phase: Theoretical Study of the Blue Shift of N-H...H-B Dihydrogen Bonds and the Red Shift of N-H...O and N-H...S Hydrogen Bonds Received 13 September 2007 Nguyen Tien Trung1, Tran Thanh Hue2 1Faculty of Chemistry, Quy Nhon University 2Faculty of Chemistry, Hanoi National University of Education Abstract Theoretical calculations at the MP2/6-311++G(2d,2p) level were performed to study the origin of the B-H...H-N blue-shifting dihydrogen bonds in the complexes of BH2NH2...HNZ (Z = O, S). The stably optimized cyclic structures of the complexes are displayed in figure 1, with interaction energies as table 1. The blue shift of the N5-H7 bond stretching frequencies is observed in the B9-H4...H7-N5 dihydrogen bonds for BH2NH2...HNO and BH2NH2...HNS, corresponding to contraction of the N5-H7 bonds (except for slight elongation of the N5-H7 bond found in the complex BH2NH2...HNS), increase of stretching frequencies and decrease of infrared intensities respectively. I - Introduction chemical processes was studied [4, 5]. The authors have pointed out that similar processes Very recently, the 1990s, a new type of were observed for biological systems such as interaction named dihydrogen bond was the enzyme hydrogenate in bacteria and algae. detected for metal organic crystal structure [1, To increase the understanding of dihydrogen 2] which was coined to describe an interaction bonds, Thomas et al. [6] carried out an ab-initio of the type X-H...H-E; where X is a typical theoretical study on the dimmer (BH3NH3)2. -
The Digallane Molecule, Ga2h6: Experimental Update Giving an Improved Structure and Estimate of the Enthalpy Change for the Reaction Ga2h6(G) 2Gah3(G)
Edinburgh Research Explorer The digallane molecule, Ga2H6: experimental update giving an improved structure and estimate of the enthalpy change for the reaction Ga2H6(g) 2GaH3(g) Citation for published version: Downs, AJ, Greene, TM, Johnsen, E, Pulham, CR, Robertson, HE & Wann, DA 2010, 'The digallane molecule, Ga H : experimental update giving an improved structure and estimate of the enthalpy change for the reaction2 Ga6 H (g) 2GaH (g)', Dalton Transactions, vol. 39, no. 24, pp. 5637-5642. https://doi.org/10.1039/c000694g2 6 3 Digital Object Identifier (DOI): 10.1039/c000694g Link: Link to publication record in Edinburgh Research Explorer Document Version: Publisher's PDF, also known as Version of record Published In: Dalton Transactions General rights Copyright for the publications made accessible via the Edinburgh Research Explorer is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Take down policy The University of Edinburgh has made every reasonable effort to ensure that Edinburgh Research Explorer content complies with UK legislation. If you believe that the public display of this file breaches copyright please contact [email protected] providing details, and we will remove access to the work immediately and investigate your claim. Download date: 02. Oct. 2021 PAPER www.rsc.org/dalton | Dalton Transactions The digallane molecule, Ga2H6: experimental update giving an improved structure and estimate of the enthalpy change for the reaction Ga2H6(g) → 2GaH3(g)†‡ Anthony J. Downs,*a Tim M. Greene,a Emma Johnsen,a Colin R.