George Andrew Olah Across Conventional Lines
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The Influence of Electronegativity on Linear and Triangular Three-Centre Bonds
The Free Internet Journal Review for Organic Chemistry Archive for Arkivoc 2020, part iv, 12-24 Organic Chemistry The influence of electronegativity on linear and triangular three-centre bonds Christopher A. Ramsden Lennard-Jones Laboratories, School of Chemical and Physical Sciences, Keele University, Keele, Staffordshire ST5 5BG, United Kingdom Email: [email protected] Received 03-24-2020 Accepted 04-19-2020 Published on line 04-30-2020 Abstract Electronegativity differences between bonding atoms have major effects on the strengths of chemical bonds but they affect two-centre and three-centre bonds in different ways and with different consequences. The effect on two-centre bonds was recognised almost 100 years ago but the influence of electronegativity difference on three-centre bonding has received less attention. Molecular orbital models of three-centre bonding are discussed and their application to the understanding of the properties of three-centre bonded species illustrated. -2.5 X -3.0 + Y Y Ea -3.5 -4.0 -4.5 X Binding Energy Binding + -5.0 Y Y -5.5 -6.0 -4 -2 0 2 4 h (b units) Keywords: Three-centre bonding, electronegativity, hypervalent, nonclassical carbocations, 2-norbornyl cation, xenon difluoride DOI: https://doi.org/10.24820/ark.5550190.p011.203 Page 12 ©AUTHOR(S) Arkivoc 2020, iv, 12-24 Ramsden, C. A. Table of Contents 1. Introduction 2. Linear Three-Centre Bonds (Hypervalent Bonds) (X-Y-X) X 3. Triangular Three-Centre Bonds (Y Y) 4. The Localised Bond Model of Two- and Three-Centre Bonds 5. Conclusions References -
(T = C/Si/Ge): the Uniqueness of Carbon Bonds in Tetrel Bonds
Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 13 September 2018 doi:10.20944/preprints201809.0228.v1 Inter/intramolecular Bonds in TH5+ (T = C/Si/Ge): The Uniqueness of Carbon bonds in Tetrel Bonds Sharon Priya Gnanasekar and Elangannan Arunan* Department of Inorganic and Physical Chemistry Indian Institute of Science, Bangalore. 560012 INDIA * Email: [email protected] Abstract Atoms in Molecules (AIM), Natural Bond Orbital (NBO), and normal coordinate analysis have been carried out at the global minimum structures of TH5+ (T = C/Si/Ge). All these analyses lead to a consistent structure for these three protonated TH4 molecules. The CH5+ has a structure with three short and two long C-H covalent bonds and no H-H bond. Hence, the popular characterization of protonated methane as a weakly bound CH3+ and H2 is inconsistent with these results. However, SiH5+ and GeH5+ are both indeed a complex formed between TH3+ and H2 stabilized by a tetrel bond, with the H2 being the tetrel bond acceptor. The three-center-two-electron bond (3c-2e) in CH5+ has an open structure, which can be characterized as a V-type 3c-2e bond and that found in SiH5+ and GeH5+ is a T-type 3c-2e bond. This difference could be understood based on the typical C-H, Si-H, Ge-H and H-H bond energies. Moreover, this structural difference observed in TH5+ can explain the trend in proton affinity of TH4. Carbon is selective in forming a ‘tetrel bond’ and when it does, it might be worthwhile to highlight it as a ‘carbon bond’. -
Is There an Acid Strong Enough to Dissolve Glass? – Superacids
ARTICLE Is there an acid strong enough to dissolve glass? – Superacids For anybody who watched cartoons growing up, the word unit is based on how acids behave in water, however as acid probably springs to mind images of gaping holes being very strong acids react extremely violently in water this burnt into the floor by a spill, and liquid that would dissolve scale cannot be used for the pure ‘common’ acids (nitric, anything you drop into it. The reality of the acids you hydrochloric and sulphuric) or anything stronger than them. encounter in schools, and most undergrad university Instead, a different unit, the Hammett acidity function (H0), courses is somewhat underwhelming – sure they will react is often preferred when discussing superacids. with chemicals, but, if handled safely, where’s the drama? A superacid can be defined as any compound with an People don’t realise that these extraordinarily strong acids acidity greater than 100% pure sulphuric acid, which has a do exist, they’re just rarely seen outside of research labs Hammett acidity function (H0) of −12 [1]. Modern definitions due to their extreme potency. These acids are capable of define a superacid as a medium in which the chemical dissolving almost anything – wax, rocks, metals (even potential of protons is higher than it is in pure sulphuric acid platinum), and yes, even glass. [2]. Considering that pure sulphuric acid is highly corrosive, you can be certain that anything more acidic than that is What are Superacids? going to be powerful. What are superacids? Its all in the name – super acids are intensely strong acids. -
The Problem the Diols, Such As Ethane-1,2-Diol, Which Are The
The problem The diols, such as ethane-1,2-diol, which are the products of the reaction with cold dilute potassium manganate(VII), are themselves quite easily oxidised by manganate(VII) ions. That means that the reaction won't stop at this point unless the potassium manganate(VII) solution is very dilute, very cold, and preferably not under acidic conditions. If you are using hot concentrated acidified potassium manganate(VII) solution, what you finally end up with depends on the arrangement of groups around the carbon-carbon double bond. Writing a structural formula to represent any alkene The formula below represents a general alkene. In organic chemistry, the symbol R is used to represent hydrocarbon groups or hydrogen in a formula when you don't want to talk about specific compounds. If you use the symbol more than once in a formula (as here), the various groups are written as R1, R2, etc. In this particular case, the double bond is surrounded by four such groups, and these can be any combination of same or different - so they could be 2 hydrogens, a methyl and an ethyl, or 1 hydrogen and 3 methyls, or 1 hydrogen and 1 methyl and 1 ethyl and 1 propyl, or any other combination you can think of. In other words, this formula represents every possible simple alkene: The first stage of the extended oxidation The acidified potassium manganate(VII) solution oxidises the alkene by breaking the carbon-carbon double bond and replacing it with two carbon-oxygen double bonds. 1 The products are known as carbonyl compounds because they contain the carbonyl group, C=O. -
The Strongest Acid Christopher A
Chemistry in New Zealand October 2011 The Strongest Acid Christopher A. Reed Department of Chemistry, University of California, Riverside, California 92521, USA Article (e-mail: [email protected]) About the Author Chris Reed was born a kiwi to English parents in Auckland in 1947. He attended Dilworth School from 1956 to 1964 where his interest in chemistry was un- doubtedly stimulated by being entrusted with a key to the high school chemical stockroom. Nighttime experiments with white phosphorus led to the Headmaster administering six of the best. He obtained his BSc (1967), MSc (1st Class Hons., 1968) and PhD (1971) from The University of Auckland, doing thesis research on iridium organotransition metal chemistry with Professor Warren R. Roper FRS. This was followed by two years of postdoctoral study at Stanford Univer- sity with Professor James P. Collman working on picket fence porphyrin models for haemoglobin. In 1973 he joined the faculty of the University of Southern California, becoming Professor in 1979. After 25 years at USC, he moved to his present position of Distinguished Professor of Chemistry at UC-Riverside to build the Centre for s and p Block Chemistry. His present research interests focus on weakly coordinating anions, weakly coordinated ligands, acids, si- lylium ion chemistry, cationic catalysis and reactive cations across the periodic table. His earlier work included extensive studies in metalloporphyrin chemistry, models for dioxygen-binding copper proteins, spin-spin coupling phenomena including paramagnetic metal to ligand radical coupling, a Magnetochemi- cal alternative to the Spectrochemical Series, fullerene redox chemistry, fullerene-porphyrin supramolecular chemistry and metal-organic framework solids (MOFs). -
FULL PAPER (CF3)3Au As a Highly Acidic Organogold(III) Fragment
FULL PAPER (CF3)3Au as a Highly Acidic Organogold(III) Fragment Alberto Pérez-Bitrián,[a] Miguel Baya,[a] José M. Casas,[a] Larry R. Falvello,[b] Antonio Martín,[a] and Babil Menjón*[a] Dedicated to Professor Juan Forniés on the occasion of his 70th birthday Abstract: The Lewis acidity of perfluorinated trimethylgold, (CF3)3Au, was soon realized that fluorination of the organic group R has been assessed by theoretical and experimental methods. It has resulted in enhancement of the Lewis acidity in the F [9–11] been found that the (CF3)3Au unit is much more acidic than its non- corresponding R 3B derivatives. In fact, the most widely fluorinated homologue (CH3)3Au, probably setting the upper limit in used borane is by far (C6F5)3B, which exhibits a considerable [12] the acidity scale for any neutral R3Au organogold(III) species. The Lewis acidity. The perfluoromethyl-derivative (CF3)3B would significant acidity increase upon fluorination is in line with the CF3 be expected to exhibit even stronger Lewis acidity. Although this group being in fact more electron-widthdrawing than CH3. The compound has not yet been isolated as such, its derivatives [13] solvate (CF3)3Au·OEt2 (1) is presented as a convenient synthon of (CF3)3B·L and, especially the singular carbonyl compound [14] the unsaturated, 14-electron species (CF3)3Au. Thus, the weakly (CF3)3BCO, evidence a greatly enhanced acidity of the [15,16] coordinated ether molecule in 1 is readily replaced by a variety of (CF3)3B moiety. neutral ligands affording a wide range of (CF3)3AuL compounds, The trifluoromethyl group, CF3, exhibits properties departing which have been isolated and conveniently characterized. -
Fluorosulfonic Acid
Fluorosulfonic acid sc-235156 Material Safety Data Sheet Hazard Alert Code EXTREME HIGH MODERATE LOW Key: Section 1 - CHEMICAL PRODUCT AND COMPANY IDENTIFICATION PRODUCT NAME Fluorosulfonic acid STATEMENT OF HAZARDOUS NATURE CONSIDERED A HAZARDOUS SUBSTANCE ACCORDING TO OSHA 29 CFR 1910.1200. NFPA FLAMMABILITY0 HEALTH3 HAZARD INSTABILITY2 W SUPPLIER Santa Cruz Biotechnology, Inc. 2145 Delaware Avenue Santa Cruz, California 95060 800.457.3801 or 831.457.3800 EMERGENCY ChemWatch Within the US & Canada: 877-715-9305 Outside the US & Canada: +800 2436 2255 (1-800-CHEMCALL) or call +613 9573 3112 SYNONYMS FSO3H, H-F-O3-S, HSO3F, "fluorosulphonic acid", "fluosulfonic acid", "fluorosulfuric acid" Section 2 - HAZARDS IDENTIFICATION CHEMWATCH HAZARD RATINGS Min Max Flammability 0 Toxicity 2 Body Contact 4 Min/Nil=0 Low=1 Reactivity 2 Moderate=2 High=3 Chronic 2 Extreme=4 CANADIAN WHMIS SYMBOLS 1 of 17 CANADIAN WHMIS CLASSIFICATION CAS 7789-21-1Fluorosulfonic acid E-Corrosive Material 1 F-Dangerously Reactive Material 2 EMERGENCY OVERVIEW RISK Reacts violently with water. Harmful by inhalation. Causes severe burns. Risk of serious damage to eyes. POTENTIAL HEALTH EFFECTS ACUTE HEALTH EFFECTS SWALLOWED ■ The material can produce severe chemical burns within the oral cavity and gastrointestinal tract following ingestion. ■ Accidental ingestion of the material may be damaging to the health of the individual. ■ Ingestion of acidic corrosives may produce burns around and in the mouth, the throat and oesophagus. Immediate pain and difficulties in swallowing and speaking may also be evident. ■ Fluoride causes severe loss of calcium in the blood, with symptoms appearing several hours later including painful and rigid muscle contractions of the limbs. -
Organogold Chemistry: I Structure and Synthesis
Organogold Chemistry: I Structure and Synthesis R V Parish Department a/Chemistry, UMIST, Manchester, M60 1QD, UK Organogold chemistry is enjoying a resurgence of interest as useful applications, largely physical or medicinal, are being found. There is also a wide range of novel molecules, some with curious structures. This article reviews the structures and syntheses of recently discovered gold compounds. A later article will describe their reactions and applications. Organogold derivatives have been known for almost example, reference 2), and deals with the preparation, 100 years. Many fascinating compounds and reactions structures, properties and applications of some of the have been discovered but, until recently, they have more interesting organogold systems; the examples found little practical application. However, the last ten given are drawn principally from those reported during to fifteen years have seen the development of new the last ten years (a more comprehensive treatment is materials with potential applications in non-linear found in reference 3). The intention is to exemplify optics, conjugated linear polymers (potential molecular rather than to be comprehensive, and no mention at all wires), liquid crystals, chemical vapour deposition and is made of cluster compounds. Complexes in which anti-tumour agents (see Box 1). On the other hand, in carbonyl, cyano, or isonitrile ligands provide the only marked contrast to the neighbouring noble metals, Au-C bonds are also ignored. For convenience, the compounds of gold have been very little used in review is divided into two parts: this part deals with homogeneous catalysis (but see reference 1). This the wide variety of organic ligands now available and review attempts to update previous treatments (see, for the structure and synthesis of the gold compounds derived from them; the second part treats the reactions and applications of these compounds. -
Superacid Chemistry
SUPERACID CHEMISTRY SECOND EDITION George A. Olah G. K. Surya Prakash Arpad Molnar Jean Sommer SUPERACID CHEMISTRY SUPERACID CHEMISTRY SECOND EDITION George A. Olah G. K. Surya Prakash Arpad Molnar Jean Sommer Copyright # 2009 by John Wiley & Sons, Inc. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. -
Bun)Mo(Pme3)(Η -C2H4) (6) Through Etmgbr Reduction of (Arn)( Bun)Mocl2(DME) in the Presence of Pme3
Synthesis, Catalysis and Stoichiometric Reactivity of Mo Imido Complexes Nicolas A. McLeod BSc. in Chemistry Chemistry Thesis submitted to the Faculty of Graduate Studies In the partial fulfillment of the requirements For the MSc. degree in chemistry Chemistry Department Faculty of Mathematics and Science Brock University St. Catharines, Ontario © Nicolas A. McLeod, 2014 Abstract The current thesis describes the syntheses, catalytic reactivity and mechanistic investigations of novel Mo(IV) and Mo(VI) imido systems. Attempts at preparing mixed bis(imido) Mo(IV) complexes of the type (RN)(R′N)Mo(PMe3)n (n = 2 or 3) derived from the t mono(imido) complexes (RN)Mo(PMe3)3(X)2 (R = Bu (1) or Ar (2); X = Cl2 or HCl, Ar=2,6- i Pr2C6H3) are also described. The addition of lithiated silylamides to 1 or 2 results in the 2 unexpected formation of the C-H activated cyclometallated complexes (RN)Mo(PMe3)2(η - t CH2PMe2)(X) (R = Ar, X = H (3); R = Bu, X = Cl (4)). Complexes 3 and 4 were used in the activation of R′E-H bonds (E = Si, B, C, O, P; R′ = alkyl or aryl), which typically give products of addition across the M-C bond of the type (RN)Mo(PMe3)3(ER′)(X) (4). In the case of 2,6- dimethylphenol, subsequent heating of 4 (R = Ar, R′ = 2,6-Me2C6H3, E = O) to 50 °C results in 2 C-H activation to give the cyclometallated complex (ArN)Mo(PMe3)3(κ -O,C-OPh(Me)CH2) (5). An alternative approach was developed in synthesizing the mixed imido complex t 2 t (ArN)( BuN)Mo(PMe3)(η -C2H4) (6) through EtMgBr reduction of (ArN)( BuN)MoCl2(DME) in the presence of PMe3. -
The Legacy of George Olah Chemical Engineering
PP Periodica Polytechnica The Legacy of George Olah Chemical Engineering 61(4), pp. 301-307, 2017 https://doi.org/10.3311/PPch.11352 Creative Commons Attribution b Miklós Simonyi1* research article Received 27 June 2017; accepted after revision 11 August 2017 Abstract 1 Introduction The life of George Olah exemplifies the fate of Hungarian The New York Times wrote on March 14, 2017: „George scientific excellence in the 20th century. He was talented and A. Olah, a Hungarian-born scientist who won the Nobel Prize a hard worker, but he could not remain in his country and had in Chemistry in 1994 for his study of the chemical reactions of to seek a new life in the West. His life-long scientific interests carbon compounds, died on Wednesday at his home in Beverly developed in the Budapest Technical University helped him Hills, Calif. He was 89.” to overcome obstacles and he became a leading chemist of Once again, a man of outstanding excellence with world- worldwide fame. His qualities and flexibility in both scientific wide fame died abroad. Olah’s studies and career started in research and practical applications serve as a brilliant example Budapest, as vividly described in his autobiography [1]. He for generations to come. obtained a diploma in chemical engineering at the Budapest Technical University (BTU) in 1949 and joined the Organic Keywords Chemistry Institute founded by Professor Géza Zemplén in early achievements, accommodating to foreign norms, scientific 1913, as the first University Department for Organic Chemistry breakthrough, the super-acids, in the service of mankind in Hungary. -
Nonclassical Carbocations: from Controversy to Convention
Nonclassical Carbocations H H C From Controversy to Convention H H H A Stoltz Group Literature Meeting brought to you by Chris Gilmore June 26, 2006 8 PM 147 Noyes Outline 1. Introduction 2. The Nonclassical Carbocation Controversy - Winstein, Brown, and the Great Debate - George Olah and ending the discussion - Important nonclassical carbocations 3. The Nature of the Nonclassical Carbocation - The 3-center, 2-electron bond - Cleaving C-C and C-H σ−bonds - Intermediate or Transition state? Changing the way we think about carbocations 4. Carbocations, nonclassical intermediates, and synthetic chemistry - Biosynthetic Pathways - Steroids, by W.S. Johnson - Corey's foray into carbocationic cascades - Interesting rearrangements - Overman and the Prins-Pinacol Carbocations: An Introduction Traditional carbocation is a low-valent, trisubstituted electron-deficient carbon center: R superacid R R LG R R R R R R "carbenium LGH ion" - 6 valence e- - planar structure - empty p orbital Modes of stabilization: Heteroatomic Assistance π-bond Resonance σ-bond Participation R X H2C X Allylic Lone Pair Anchimeric Homoconjugation Hyperconjugation Non-Classical Resonance Assistance Stabilization Interaction Outline 1. Introduction 2. The Nonclassical Carbocation Controversy - Winstein, Brown, and the Great Debate - George Olah and ending the discussion - Important nonclassical carbocations 3. The Nature of the Nonclassical Carbocation - The 3-center, 2-electron bond - Cleaving C-C and C-H σ−bonds - Intermediate or Transition state? Changing the way we think about carbocations 4. Carbocations, nonclassical intermediates, and synthetic chemistry - Biosynthetic Pathways - Steroids, by W.S. Johnson - Corey's foray into carbocationic cascades - Interesting rearrangements - Overman and the Prins-Pinacol The Nonclassical Problem: Early Curiosities Wagner, 1899: 1,2 shift OH H - H+ Meerwein, 1922: 1,2 shift OH Meerwin, H.