The Effect of Stabilizing Groups on the Extent of Long-Range ΀ Electron
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Topological Analysis of the Metal-Metal Bond: a Tutorial Review Christine Lepetit, Pierre Fau, Katia Fajerwerg, Myrtil L
Topological analysis of the metal-metal bond: A tutorial review Christine Lepetit, Pierre Fau, Katia Fajerwerg, Myrtil L. Kahn, Bernard Silvi To cite this version: Christine Lepetit, Pierre Fau, Katia Fajerwerg, Myrtil L. Kahn, Bernard Silvi. Topological analysis of the metal-metal bond: A tutorial review. Coordination Chemistry Reviews, Elsevier, 2017, 345, pp.150-181. 10.1016/j.ccr.2017.04.009. hal-01540328 HAL Id: hal-01540328 https://hal.sorbonne-universite.fr/hal-01540328 Submitted on 16 Jun 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Topological analysis of the metal-metal bond: a tutorial review Christine Lepetita,b, Pierre Faua,b, Katia Fajerwerga,b, MyrtilL. Kahn a,b, Bernard Silvic,∗ aCNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, BP 44099, F-31077 Toulouse Cedex 4, France. bUniversité de Toulouse, UPS, INPT, F-31077 Toulouse Cedex 4, i France cSorbonne Universités, UPMC, Univ Paris 06, UMR 7616, Laboratoire de Chimie Théorique, case courrier 137, 4 place Jussieu, F-75005 Paris, France Abstract This contribution explains how the topological methods of analysis of the electron density and related functions such as the electron localization function (ELF) and the electron localizability indicator (ELI-D) enable the theoretical characterization of various metal-metal (M-M) bonds (multiple M-M bonds, dative M-M bonds). -
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 -
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. -
Course No: CH15101CR Title: Inorganic Chemistry (03 Credits)
Course No: CH15101CR Title: Inorganic Chemistry (03 Credits) Max. Marks: 75 Duration: 48 Contact hours (48L) End Term Exam: 60 Marks Continuous Assessment: 15 Marks Unit-I Stereochemistry and Bonding in the Compounds of Main Group Elements (16 Contact hours) Valence bond theory: Energy changes taking place during the formation of diatomic molecules; factors affecting the combined wave function. Bent's rule and energetics of hybridization. Resonance: Conditions, resonance energy and examples of some inorganic molecules/ions. Odd Electron Bonds: Types, properties and molecular orbital treatment. VSEPR: Recapitulation of assumptions, shapes of trigonal bypyramidal, octahedral and - 2- 2- pentagonal bipyramidal molecules / ions. (PCl5, VO3 , SF6, [SiF6] , [PbCl6] and IF7). Limitations of VSEPR theory. Molecular orbital theory: Salient features, variation of electron density with internuclear distance. Relative order of energy levels and molecular orbital diagrams of some heterodiatomic molecules /ions. Molecular orbital diagram of polyatomic molecules / ions. Delocalized Molecular Orbitals: Butadiene, cyclopentadiene and benzene. Detection of Hydrogen Bond: UV-VIS, IR and X-ray. Importance of hydrogen bonding. Unit-II Metal-Ligand Equilibria in Solution (16 Contact hours) Stepwise and overall formation constants. Inert & labile complexes. Stability of uncommon oxidation states. Metal Chelates: Characteristics, Chelate effect and the factors affecting stability of metal chelates. Determination of formation constants by pH- metry and spectrophotometry. Structural (ionic radii) and thermodynamic (hydration and lattice energies) effects of crystal field splitting. Jahn -Teller distortion, spectrochemical series and the nephleuxetic effect. Evidence of covalent bonding in transition metal complexes. Unit-III Pi-acid Metal Complexes (16 Contact hours) Transition Metal Carbonyls: Carbon monoxide as ligand, synthesis, reactions, structures and bonding of mono- and poly-nuclear carbonyls. -
Aromaticity Sem- Ii
AROMATICITY SEM- II In 1931, German chemist and physicist Sir Erich Hückel proposed a theory to help determine if a planar ring molecule would have aromatic properties .This is a very popular and useful rule to identify aromaticity in monocyclic conjugated compound. According to which a planar monocyclic conjugated system having ( 4n +2) delocalised (where, n = 0, 1, 2, .....) electrons are known as aromatic compound . For example: Benzene, Naphthalene, Furan, Pyrrole etc. Criteria for Aromaticity 1) The molecule is cyclic (a ring of atoms) 2) The molecule is planar (all atoms in the molecule lie in the same plane) 3) The molecule is fully conjugated (p orbitals at every atom in the ring) 4) The molecule has 4n+2 π electrons (n=0 or any positive integer Why 4n+2π Electrons? According to Hückel's Molecular Orbital Theory, a compound is particularly stable if all of its bonding molecular orbitals are filled with paired electrons. - This is true of aromatic compounds, meaning they are quite stable. - With aromatic compounds, 2 electrons fill the lowest energy molecular orbital, and 4 electrons fill each subsequent energy level (the number of subsequent energy levels is denoted by n), leaving all bonding orbitals filled and no anti-bonding orbitals occupied. This gives a total of 4n+2π electrons. - As for example: Benzene has 6π electrons. Its first 2π electrons fill the lowest energy orbital, and it has 4π electrons remaining. These 4 fill in the orbitals of the succeeding energy level. The criteria for Antiaromaticity are as follows: 1) The molecule must be cyclic and completely conjugated 2) The molecule must be planar. -
Fundamental Studies of Early Transition Metal-Ligand Multiple Bonds: Structure, Electronics, and Catalysis
Fundamental Studies of Early Transition Metal-Ligand Multiple Bonds: Structure, Electronics, and Catalysis Thesis by Ian Albert Tonks In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2012 Defended December 6th 2011 ii 2012 Ian A Tonks All Rights Reserved iii ACKNOWLEDGEMENTS I am extremely fortunate to have been surrounded by enthusiastic, dedicated, and caring mentors, colleagues, and friends throughout my academic career. A Ph.D. thesis is by no means a singular achievement; I wish to extend my wholehearted thanks to everyone who has made this journey possible. First and foremost, I must thank my Ph.D. advisor, Prof. John Bercaw. I think more so than anything else, I respect John for his character, sense of fairness, and integrity. I also benefitted greatly from John’s laissez-faire approach to guiding our research group; I’ve always learned best when left alone to screw things up, although John also has an uncanny ability for sensing when I need direction or for something to work properly on the high-vac line. John also introduced me to hiking and climbing in the Eastern Sierras and Owens Valley, which remain amongst my favorite places on Earth. Thanks for always being willing to go to the Pizza Factory in Lone Pine before and after all the group hikes! While I never worked on any of the BP projects that were spearheaded by our co-PI Dr. Jay Labinger, I must also thank Jay for coming to all of my group meetings, teaching me an incredible amount while I was TAing Ch154, and for always being willing to talk chemistry and answer tough questions. -
FAROOK COLLEGE (Autonomous)
FAROOK COLLEGE (Autonomous) M.Sc. DEGREE PROGRAMME IN CHEMISTRY CHOICE BASED CREDIT AND SEMESTER SYSTEM-PG (FCCBCSSPG-2019) SCHEME AND SYLLABI 2019 ADMISSION ONWARDS 1 CERTIFICATE I hereby certify that the documents attached are the bona fide copies of the syllabus of M.Sc. Chemistry Programme to be effective from the academic year 2019-20 onwards. Date: Place: P R I N C I P A L 2 FAROOK COLLEGE (AUTONOMOUS) MSc. CHEMISTRY (CSS PATTERN) Regulations and Syllabus with effect from 2019 admission Pattern of the Programme a. The name of the programme shall be M.Sc. Chemistry under CSS pattern. b. The programme shall be offered in four semesters within a period of two academic years. c. Eligibility for admission will be as per the rules laid down by the College from time to time. d. Details of the courses offered for the programme are given in Table 1. The programme shall be conducted in accordance with the programme pattern, scheme of examination and syllabus prescribed. Of the 25 hours per week, 13 hours shall be allotted for theory and 12 hours for practical; 1 theory hour per week during even semesters shall be allotted for seminar. Theory Courses In the first three semesters, there will be four theory courses; and in the fourth semester, three theory courses. All the theory courses in the first and second semesters are core courses. In the third semester there will be three core theory courses and one elective theory course. College can choose any one of the elective courses given in Table 1. -
The Chemistry of Alkynes
14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 644 14 14 The Chemistry of Alkynes An alkyne is a hydrocarbon containing a carbon–carbon triple bond; the simplest member of this family is acetylene, H C'C H. The chemistry of the carbon–carbon triple bond is similar in many respects toL that ofL the carbon–carbon double bond; indeed, alkynes and alkenes undergo many of the same addition reactions. Alkynes also have some unique chem- istry, most of it associated with the bond between hydrogen and the triply bonded carbon, the 'C H bond. L 14.1 NOMENCLATURE OF ALKYNES In common nomenclature, simple alkynes are named as derivatives of the parent compound acetylene: H3CCC' H L L methylacetylene H3CCC' CH3 dimethylacetyleneL L CH3CH2 CC' CH3 ethylmethylacetyleneL L Certain compounds are named as derivatives of the propargyl group, HC'C CH2 , in the common system. The propargyl group is the triple-bond analog of the allyl group.L L HC' C CH2 Cl H2CA CH CH2 Cl L L LL propargyl chloride allyl chloride 644 14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 645 14.1 NOMENCLATURE OF ALKYNES 645 We might expect the substitutive nomenclature of alkynes to be much like that of alkenes, and it is. The suffix ane in the name of the corresponding alkane is replaced by the suffix yne, and the triple bond is given the lowest possible number. H3CCC' H CH3CH2CH2CH2 CC' CH3 H3C CH2 C ' CH L L L L L L L propyne 2-heptyne 1-butyne H3C CH C ' C CH3 HC' C CH2 CH2 C' C CH3 L L L L 1,5-heptadiyneLL L "CH3 4-methyl-2-pentyne Substituent groups that contain a triple bond (called alkynyl groups) are named by replac- ing the final e in the name of the corresponding alkyne with the suffix yl. -
Chemical Bonding Valence Electrons Are the Outer Shell Electrons of an Atom
Chapter 8 Chemical Bonding Valence electrons are the outer shell electrons of an atom. The valence electrons are the electrons that participate in chemical bonding. Group e- configuration # of valence e- 1 ns1 1 2 ns2 2 13 ns2np1 3 14 ns2np2 4 15 ns2np3 5 16 ns2np4 6 17 ns2np5 7 Lewis Dot Symbols for the Representative Elements & Noble Gases Lewis dot symbol consists of the symbol of the element and one dot for each valence electron in an atom of each element The Ionic Bond Ionic bond = the electrostatic force that holds ions Li + F Li+ F - together in an 2 1 2 2 5 [He]2[Ne]2 2 6 ionic compound 1s 2s1s 2s 2p 1s1s 2s 2p Li Li+ + e- e- + F F - Lithium fluoride, LiF Li+ + F - Li+ F - Ionic Bonds 3Mg (s) + N2 (g) → Mg3N2 (s) .. .. 2 3 3 Mg2 N 3Mg 2: N : (Mg3N2 ) . .. Electrostatic (Lattice) Energy Lattice energy (E) is the energy required to completely separate one mole of a solid ionic compound into gaseous ions. Coulomb’s Law: the potential energy between 2 ions is directly proportional to the product of their charges and inversely proportional to the distance of separation between them Q+ is the charge on the cation Q Q E = k + - Q is the charge on the anion r - r is the distance between the ions cmpd lattice energy MgF2 2957 Q= +2,-1 Lattice energy (E) increases MgO 3938 Q= +2,-2 as Q increases and/or as r decreases. LiF 1036 r F- < r Cl- LiCl 853 Born-Haber Cycle for Determining Lattice Energy The Born-Haber cycle relates lattice energies of ionic compounds to ionization energies, electron affinities, and other atomic & molecular properties o o o o o o DHoverall = DH1 + DH2 + DH3 + DH4 + DH5 Born-Haber cycle for lithium fluoride 1. -
Basic Concepts of Chemical Bonding
Basic Concepts of Chemical Bonding Cover 8.1 to 8.7 EXCEPT 1. Omit Energetics of Ionic Bond Formation Omit Born-Haber Cycle 2. Omit Dipole Moments ELEMENTS & COMPOUNDS • Why do elements react to form compounds ? • What are the forces that hold atoms together in molecules ? and ions in ionic compounds ? Electron configuration predict reactivity Element Electron configurations Mg (12e) 1S 2 2S 2 2P 6 3S 2 Reactive Mg 2+ (10e) [Ne] Stable Cl(17e) 1S 2 2S 2 2P 6 3S 2 3P 5 Reactive Cl - (18e) [Ar] Stable CHEMICAL BONDSBONDS attractive force holding atoms together Single Bond : involves an electron pair e.g. H 2 Double Bond : involves two electron pairs e.g. O 2 Triple Bond : involves three electron pairs e.g. N 2 TYPES OF CHEMICAL BONDSBONDS Ionic Polar Covalent Two Extremes Covalent The Two Extremes IONIC BOND results from the transfer of electrons from a metal to a nonmetal. COVALENT BOND results from the sharing of electrons between the atoms. Usually found between nonmetals. The POLAR COVALENT bond is In-between • the IONIC BOND [ transfer of electrons ] and • the COVALENT BOND [ shared electrons] The pair of electrons in a polar covalent bond are not shared equally . DISCRIPTION OF ELECTRONS 1. How Many Electrons ? 2. Electron Configuration 3. Orbital Diagram 4. Quantum Numbers 5. LEWISLEWIS SYMBOLSSYMBOLS LEWISLEWIS SYMBOLSSYMBOLS 1. Electrons are represented as DOTS 2. Only VALENCE electrons are used Atomic Hydrogen is H • Atomic Lithium is Li • Atomic Sodium is Na • All of Group 1 has only one dot The Octet Rule Atoms gain, lose, or share electrons until they are surrounded by 8 valence electrons (s2 p6 ) All noble gases [EXCEPT HE] have s2 p6 configuration. -
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. -
Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc
Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc Richard H. Duncan Lyngdoh*,a, Henry F. Schaefer III*,b and R. Bruce King*,b a Department of Chemistry, North-Eastern Hill University, Shillong 793022, India B Centre for Computational Quantum Chemistry, University of Georgia, Athens GA 30602 ABSTRACT: This survey of metal-metal (MM) bond distances in binuclear complexes of the first row 3d-block elements reviews experimental and computational research on a wide range of such systems. The metals surveyed are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, representing the only comprehensive presentation of such results to date. Factors impacting MM bond lengths that are discussed here include (a) n+ the formal MM bond order, (b) size of the metal ion present in the bimetallic core (M2) , (c) the metal oxidation state, (d) effects of ligand basicity, coordination mode and number, and (e) steric effects of bulky ligands. Correlations between experimental and computational findings are examined wherever possible, often yielding good agreement for MM bond lengths. The formal bond order provides a key basis for assessing experimental and computationally derived MM bond lengths. The effects of change in the metal upon MM bond length ranges in binuclear complexes suggest trends for single, double, triple, and quadruple MM bonds which are related to the available information on metal atomic radii. It emerges that while specific factors for a limited range of complexes are found to have their expected impact in many cases, the assessment of the net effect of these factors is challenging.