DOCSLIB.ORG

Arrow Pushing Guide

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Arrow Pushing Guide Arrow Pushing Guide The rules of arrow pushing Interpretation Generic Example Molecular Example An arrow pointing from a single bond to an atom means that the bond breaks and a lone pair forms on A B A B H Cl H Cl the target atom. An arrow pointing from a lone pair to an atom means that the lone pair electrons form a new bone to the B A A B Cl H H Cl target atom. An arrow pointing from a double or triple bond to an atom means that one of the bonds break, and those O O electrons form a new lone pair on the target atom. A B A B H H H H An arrow pointing from a lone pair to a bond means the lone pair electrons are used to increase the bond O O A B order of the target bond (e.g., a single bond becomes A B a double bond). H H H H Additional examples Interpretation Example The arrow pointing from the bromine lone pair to the methyl group means that those electrons will be used to form a new Br-C bond. Since carbon can only have four bonds, H Br H it must lose a bond in order to form the new Br-C bond. The second arrow, which points O O Br from the O-C bond to oxygen, tells us that carbon will lose its bond to oxygen, and H H oxygen will keep those electrons as a lone pair. Therefore, the O-C bond breaks, and a new lone pair is formed on oxygen. The arrow pointing from the oxygen lone pair to the O-C bond means that the elec- H H H H trons from that lone pair will be used to form a new O-C bond. Since a single bond N N already exists between oxygen and carbon, a double bond will be formed. Since carbon can only form four bonds, carbon must lose a bond in order to form the new bond to O O oxygen. The second arrow, which points from the C-N double bond to nitrogen, tells us that one of the C-N bonds will break, and the electrons from that bond will form a new lone pair on nitrogen. The arrow that points from the C-C double bond to the hydrogen atom means that the H double bond will break (leaving a single bond), and the electrons from that broken H bond will form a new bond between one of the carbon atoms and hydrogen. Since Br hydrogen can only form one bond at a time, it must lose its bond to bromine. The other Br arrow, which points from the H-Br bond to the bottom carbon atom, tells us that the electrons from the broken H-Br bond will be used to form a new bond between bromine and the bottom carbon atom. In order for the bottom carbon atom to form this bond to bromine, it must be true that the top carbon atom is the atom that forms the new bond to hydrogen. The arrow that points from the oxygen lone pair to the O-S bond means that the lone O pair of electrons on oxygen will be used to form a new O-S bond. The second arrow, O S which points from the other O-S bond to the hydrogen ion, tells us that this O-S bond S H O H will break, and the electrons from it will be used to form a new bond between the O O oxygen and the hydrogen. O H H.
Load more

Recommended publications
  • No Rabbit Ears on Water. the Structure of the Water Molecule
    No Rabbit Ears on Water The Structure of the Water Molecule: What Should We Tell the Students? Michael Laing University of Natal. Durban, South Africa In the vast majority of high school (I)and freshman uni- He also considers the possibility of s character in the bond- versity (2) chemistry textbooks, water is presented as a bent ing orbitals of OF2 and OH2 to improve the "strength" of the molecule whose bonding can be described bv the Gilles~ie- orbital (p 111) from 1.732 for purep to 2.00 for the ideal sp3. Nyholm approach with the oxygen atomsp3 Gyhridized. The Inclusion of s character in the hybrid will be "resisted in the lone uairs are said to he dominant causine the H-O-H anele case of atoms with an nnshared pair.. in the s orbital, to beieduced from the ideal 1091120to 104' and are regul&ly which is more stable than the p orbitals" (p 120). Estimates shown as equivalent in shape and size even being described of the H-E-H angle range from 91.2 for AsH3 to 93.5O for as "rabbit ears" (3). Chemists have even been advised to Hz0. He once again ascribes the anomalies for Hz0 to "re- wear Mickey Mouse ears when teaching the structure and uulsion of the charzes of the hvdroaeu atoms" (D 122). bonding of the H20molecule, presumably to emphasize the - In his famous hook (6)~itac~oro&kii describks the bond- shape of the molecule (and possibly the two equivalent lone ing in water and HzS (p 10).
    [Show full text]
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • Early- Versus Late-Transition-Metal-Oxo Bonds: the Electronlc Structure of VO' and Ruo'
    J. Phys. Chem. 1988, 92, 2109-2115 2109 Early- versus Late-Transition-Metal-Oxo Bonds: The Electronlc Structure of VO' and RuO' Emily A. Cartert and William A. Goddard III* Arthur Amos Noyes Laboratory of Chemical Physics,$ California Institute of Technology, Pasadena, California 91125 (Received: July 9, 1987; In Final Form: November 3, 1987) From all-electron ab initio generalized valence bond calculations (GVBCI-SCF) on VO+ and RuO', we find that an accurate description of the bonding is obtained only when important resonance configurations are included self-consistently in the wave function. The ground state of VO+('Z-) has a triple bond similar to that of CO, with D,""(V-O) = 128.3 kcal/mol [DFptl(V-O) = 1.31 * 5 kcal/mol], while the ground state of RuO+(~A)has a double bond similar to that of Oz, with D,CS'cd(Ru-O) = 67.1 kcal/mol. Vertical excitation energies for a number of low-lying electronic states of VO+ and RuO' are also reported. These results indicate fundamental differences in the nature of the metal-oxo bond in early and late metal oxo complexes that explain the observed trends in reactivity (e.g., early metal oxides are thermodynamically stable whereas late metal oxo complexes are highly reactive oxidants). Finally, we have used these results to predict the ground states of MO' for other first-row transition-metal oxides. I. Introduction TABLE I: First-Row Transition-Metal-Oxo Bond Strengths While the electronic structure of neutral transition-metal oxides (kcal/mol)' has been examined by several authors,' the only cationic tran- metal Do(M+-O) Do(M-0) metal Do(M+-O) Do(M-0) sition-metal oxide (TMO) which has been studied with correlated 3 Mn 3 wave functions is2 CrO+.
    [Show full text]
  • 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.
    [Show full text]
  • Variation of Aromaticity by Twisting Or Expanding the Ring Content*
    Pure Appl. Chem., Vol. 82, No. 4, pp. 769–800, 2010. doi:10.1351/PAC-CON-09-11-07 © 2010 IUPAC, Publication date (Web): 26 March 2010 Variation of aromaticity by twisting or expanding the ring content* Remi Chauvin‡, Christine Lepetit, Valérie Maraval, and Léo Leroyer Laboratory of Coordination Chemistry (LCC), CNRS, 205, Route de Narbonne, F-31077 Toulouse, France; Université de Toulouse; UPS, INPT; LCC; F-31077 Toulouse, France Abstract: Generalization of the Hückel rule predicts that the (anti)aromaticity of a neutral ring is qualitatively reverted upon a single twist of the π-orbital array (Möbius interconver- sion), and is preserved upon expansion of all the bonds by single C2 units (ring carbo-mer- ization). These opposite effects are addressed from quantitative theoretical and experimental standpoints, respectively. (i) According to most resonance energy (RE) schemes, the RE value of a Möbius ring is not the opposite of that of the Hückel version. This also applies to the Aihara’s and Trinajstic’s topological resonance energy (TRE), where a non-aromatic ref- erence in the topological limit is defined as being “as identical as possible” to the parent ring but just “acyclic”. In spite of its conceptual merits, the computing complexity and fictitious character of the TRE acyclic reference resulted in a disuse of TRE as a current energetic aro- maticity index. Both the calculation and interpretation of TRE have been revisited in light of a cross-reference between the Hückel and Möbius rings within the Hückel molecular orbital (HMO) framework. Whereas the topological influence of triple bonds is currently neglected in the first-level HMO treatment of π-conjugated systems, a graph-theoretical analysis allows one to differentiate the TRE value of a [3n]annulene from those of the corresponding carbo- [n]annulene.
    [Show full text]
  • Alkenes and Alkynes
    02/21/2019 CHAPTER FOUR Alkenes and Alkynes H N O I Cl C O C O Cl F3C C Cl C Cl Efavirenz Haloprogin (antiviral, AIDS therapeutic) (antifungal, antiseptic) Chapter 4 Table of Content * Unsaturated Hydrocarbons * Introduction and hybridization * Alkenes and Alkynes * Benzene and Phenyl groups * Structure of Alkenes, cis‐trans Isomerism * Nomenclature of Alkenes and Alkynes * Configuration cis/trans, and cis/trans Isomerism * Configuration E/Z * Physical Properties of Hydrocarbons * Acid‐Base Reactions of Hydrocarbons * pka and Hybridizations 1 02/21/2019 Unsaturated Hydrocarbons • Unsaturated Hydrocarbon: A hydrocarbon that contains one or more carbon‐carbon double or triple bonds or benzene‐like rings. – Alkene: contains a carbon‐carbon double bond and has the general formula CnH2n. – Alkyne: contains a carbon‐carbon triple bond and has the general formula CnH2n‐2. Introduction Alkenes ● Hydrocarbons containing C=C ● Old name: olefins • Steroids • Hormones • Biochemical regulators 2 02/21/2019 • Alkynes – Hydrocarbons containing C≡C – Common name: acetylenes Unsaturated Hydrocarbons • Arene: benzene and its derivatives (Ch 9) 3 02/21/2019 Benzene and Phenyl Groups • We do not study benzene and its derivatives until Chapter 9. – However, we show structural formulas of compounds containing a phenyl group before that time. – The phenyl group is not reactive under any of the conditions we describe in chapters 5‐8. Structure of Alkenes • The two carbon atoms of a double bond and the four atoms bonded to them lie in a plane, with bond angles of approximately 120°. 4 02/21/2019 Structure of Alkenes • Figure 4.1 According to the orbital overlap model, a double bond consists of one bond formed by overlap of sp2 hybrid orbitals and one bond formed by overlap of parallel 2p orbitals.
    [Show full text]
  • Reactions of Aromatic Compounds Just Like an Alkene, Benzene Has Clouds of  Electrons Above and Below Its Sigma Bond Framework
    Reactions of Aromatic Compounds Just like an alkene, benzene has clouds of electrons above and below its sigma bond framework. Although the electrons are in a stable aromatic system, they are still available for reaction with strong electrophiles. This generates a carbocation which is resonance stabilized (but not aromatic). This cation is called a sigma complex because the electrophile is joined to the benzene ring through a new sigma bond. The sigma complex (also called an arenium ion) is not aromatic since it contains an sp3 carbon (which disrupts the required loop of p orbitals). Ch17 Reactions of Aromatic Compounds (landscape).docx Page1 The loss of aromaticity required to form the sigma complex explains the highly endothermic nature of the first step. (That is why we require strong electrophiles for reaction). The sigma complex wishes to regain its aromaticity, and it may do so by either a reversal of the first step (i.e. regenerate the starting material) or by loss of the proton on the sp3 carbon (leading to a substitution product). When a reaction proceeds this way, it is electrophilic aromatic substitution. There are a wide variety of electrophiles that can be introduced into a benzene ring in this way, and so electrophilic aromatic substitution is a very important method for the synthesis of substituted aromatic compounds. Ch17 Reactions of Aromatic Compounds (landscape).docx Page2 Bromination of Benzene Bromination follows the same general mechanism for the electrophilic aromatic substitution (EAS). Bromine itself is not electrophilic enough to react with benzene. But the addition of a strong Lewis acid (electron pair acceptor), such as FeBr3, catalyses the reaction, and leads to the substitution product.
    [Show full text]
  • Resonance 1. Lone Pair Next to Empty 2P Orbital
    1 Lecture 5 Resonance 1. Lone pair next to empty 2p orbital electron pair acceptors - lack of electrons C C CC sp2 R+ is more common sp R+ is less common R+ needs electrons, has to overlap with a. an adjacent 2p lone pair with electrons b. an adjacent pi bond a. an adjacent 2p lone pair with electrons on a neutral atom (+ overall, delocalization of positive charge) R R X = neutral atom with lone pair R R C C R X 2D resonance R X C C R X R X R R R R C R C R CX CX R N R N R 3D resonance R R R R R R R C R C R CX R O CX 3D resonance R O R R R R C better, more bonds, full octets C R F R F b. an adjacent 2p lone pair with electrons on a negative atom (neutral overall, delocalization of electrons) R R X =anion with lone pair R R C C R X 2D resonance R X C C R X R X R R R R C R C R CX CX R C R C R 3D resonance R R R R R R R C R C R CX R N CX 3D resonance R N R R R R C C better, more bonds, full octets R O R O 2 Lecture 5 Problem 1 – All of the following examples demonstrate delocalization of a lone pair of electrons into an empty 2p orbital. Usually in organic chemistry this is a carbocation site, but not always.
    [Show full text]
  • Effect of Lone Pairs on Hybridization
    EFFECT OF LONE PAIRS ON HYBRIDIZATION We have discussed the effect of ghost lone pairs on the shape of a molecule in the post about VSEPR theory. The effect lone pairs exert is the same in VBT as it was in VSEPR. In this post we will study a few examples in which central atom possess lone pairs. First, we will take the example of NH3 molecule. When you draw its Lewis dot structure, you will find three bonding pairs of electrons and one lone pair on N. Now write the ground state configuration of N. 7N: 1s2, 2s2, 2p3 N already has 3 unpaired electrons in ground state to make bond with 3 H atoms. You may think why does N need hybridization in this case when it has 3 unpaired electrons of the same orbital p? Because hybridized orbitals are more competent in overlapping which results in a stronger bond. 3 In NH3 molecule, N chooses sp hybridization. This may get you puzzled again, if N has 3 unpaired electrons in p why does it include s orbital which has paired electrons? You know that the atoms follow Hund’s rule for filling electrons in orbitals, similarly they have to consider energy order of orbitals in hybridization also. When an atom undergoes hybridization, it has to pick orbitals in the increasing order of their energies. In NH3, N has to first pick 2s then 2px, 2py and then 2pz. N can’t ignore 2s even if it is filled because 2s has the lowest energy and N has to include all three 2p orbitals because it needs them for bonding with three H atoms.
    [Show full text]
  • How Do We Know That There Are Atoms
    Chemistry 11 Fall 2010 Discussion – 12/13/10 MOs and Hybridization 1. a. [:C N:]- Bond order = (8 – 2) / 2 = 3 *2p * 2p C 2p N 2p 2p 2p *2s C 2s N 2s 2s CN- b. Comparison of Lewis and MO models of CN- CN- Consistent: Both have triple bond (B.O. = 3) Inconsistent: - Lewis structure shows lone pairs on each atom rather than all e- being shared (MO) - Lewis structure indicates a negative formal charge on C, whereas MO suggests more electron density on N, which is consistent with EN considerations c. Both molecules exhibit sp mixing, and the MOs should reflect this. In N2, the molecular orbitals would be distributed equally between the two N atoms, whereas in CN-, the bonding orbitals have greater electron density on the more electronegative atom (N). The antibonding orbitals have more electron density on the less electronegative atom (C). - 1 - Chemistry 11 Fall 2010 2. a. Completed structure of guanine (carbons at each intersection are implied): * * * * b. 17 sigma bonds; 4 pi bonds. c. All carbons are sp2 hybridized; trigonal planar; with 120˚ bond angles. d. We predict that the three N’s marked with * are sp3 hybridized, with 109.5˚ bond angles. The remaining N atoms are sp2 hybridized, with 120˚ bond angles. e. i. Benzene: ii. For the structure drawn in (a), the bond angles in the six membered ring would be expected to be 120˚ for each atom except for the N§, which is predicted to have bond angles of 109.5˚. However, it is not possible to form a planar six-membered ring unless ALL the angles are 120˚.
    [Show full text]