Vibrational bond

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A vibrational bond is a chemical bond that happens between two very large atoms, like bromine, and a very small atom, like hydrogen, at very high energy states. Vibrational bonds only exist for a few milliseconds. This bond is detectable through modern analytic chemistry and is significant because it affects the rate at which other reactions can occur.

Chemical bond lasting attraction between atoms that enables the formation of chemical compounds

A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the electrostatic force of attraction between oppositely charged ions as in ionic bonds or through the sharing of electrons as in covalent bonds. The strength of chemical bonds varies considerably; there are "strong bonds" or "primary bonds" such as covalent, ionic and metallic bonds, and "weak bonds" or "secondary bonds" such as dipole–dipole interactions, the London dispersion force and hydrogen bonding.

Atom smallest unit of a chemical element

An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small; typical sizes are around 100 picometers.

Bromine Chemical element with atomic number 35

Bromine is a chemical element with symbol Br and atomic number 35. It is the third-lightest halogen, and is a fuming red-brown liquid at room temperature that evaporates readily to form a similarly coloured gas. Its properties are thus intermediate between those of chlorine and iodine. Isolated independently by two chemists, Carl Jacob Löwig and Antoine Jérôme Balard, its name was derived from the Ancient Greek βρῶμος ("stench"), referencing its sharp and disagreeable smell.

Contents

History

Vibrational bonds were mathematically predicted almost thirty years before they were experimentally observed. The original theoretical calculations had been carried out by D.C. Clary and J.N.L Connor during the early 1980s. Together they hypothesized that with very large atoms and small atoms at high energy states, the elements would stabilize and create temporary bonds for very short periods of time. The vibrational bond would be weaker than any currently known bond, like the commonly known ionic or covalent bonds. [1]

Mathematics Field of study concerning quantity, patterns and change

Mathematics includes the study of such topics as quantity, structure, space, and change.

A theory is a contemplative and rational type of abstract or generalizing thinking, or the results of such thinking. Depending on the context, the results might, for example, include generalized explanations of how nature works. The word has its roots in ancient Greek, but in modern use it has taken on several related meanings.

David Clary Professor of Chemistry

Sir David Charles Clary, FRS is a British theoretical chemist. He has been president of Magdalen College, Oxford, since 2005.

One year after the theoretical discovery of vibrational bonds, J. Manz and his team confirmed the calculations that were previously made, and elaborated on them by showing that the vibrational bonds were most likely to occur during symmetric reactions, but stated that vibrational bonds may also be possible with asymmetric reactions. [2] Their team explained that although vibrational bonding theories proved to be correct they found some inconsistencies with the 'classic model' and found that symmetric reactions will show resonance, but only in certain transition states. However, the classic model would still be viable to use to predict vibrational bonds. [2]

In chemistry, resonance is a way of describing bonding in certain molecules or ions by the combination of several contributing structures into a resonance hybrid in valence bond theory. It has particular value for describing delocalized electrons within certain molecules or polyatomic ions where the bonding cannot be expressed by one single Lewis structure.

Transition state set of states (each characterized by its own geometry, energy) in which an assembly of atoms, when randomly placed there, would have an equal probability of forming the reactants or of forming the products of that elementary reaction

The transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the state corresponding to the highest potential energy along this reaction coordinate. At this point, assuming a perfectly irreversible reaction, colliding reactant molecules always go on to form products. It is often marked with the double dagger ‡ symbol.

In 1989, Donald Fleming noticed that a reaction between bromine and muonium slowed down as temperature increased. This phenomenon was known as a "vibrational bond" and would capture the attention of Donald Fleming again in 2014. In 1989 the technology did not exist to collect sufficient data on the reaction, and Donald Fleming and his team moved away from the research. [3]

Donald George Fleming is a Canadian chemist. He attended the University of British Columbia and earned a Bachelor of Science degree in 1961 and a Master of Science degree in 1961. He earned a Ph.D. at the University of California, Berkeley in 1967. He is currently a professor emeritus of chemistry at the University of British Columbia. In 1989 he published a paper theorizing a new kind of chemical bond, which he referred to as vibrational bonding. The existence of such a short-lived bond was confirmed using a reaction between bromine and the exotic atom muonium in January 2015. Fleming is also known for his work in utilizing muon beams in studies of physical chemical sciences.

Muonium exotic atoms made up of an antimuon and an electron

Muonium is an exotic atom made up of an antimuon and an electron, which was discovered in 1960 by Vernon W. Hughes and is given the chemical symbol Mu. During the muon's 2.2 µs lifetime, muonium can enter into compounds such as muonium chloride (MuCl) or sodium muonide (NaMu). Due to the mass difference between the antimuon and the electron, muonium is more similar to atomic hydrogen than positronium. Its Bohr radius and ionization energy are within 0.5% of hydrogen, deuterium, and tritium, and thus it can usefully be considered as an exotic light isotope of hydrogen.

Discovery

Donald Fleming and his team recently began their investigation of vibrational bonds, and as they had expected from the results of their experiments in 1989, the BrLBr reaction slowed at high temperatures, now using modern instrumental analysis from photo detachment electron spectroscopy, the vibrational bond was detected but lasted only a few milliseconds. [4] The vibrational bond acted differently than van der Waals forces reactions because the energy was balanced differently.

Electron spectroscopy is an analytical technique to study the electronic structure and its dynamics in atoms and molecules. In general an excitation source such as x-rays, electrons or synchrotron radiation will eject an electron from an inner-shell orbital of an atom. Detecting photoelectrons that are ejected by x-rays is called x-ray photoelectron spectroscopy (XPS) or electron spectroscopy for chemical analysis (ESCA). Detecting electrons that are ejected from higher orbitals to conserve energy during electron transitions is called Auger electron spectroscopy (AES).

Bond

In chemistry it is known that increased temperature increases the rate or reaction of an experiment, however vibrational bonds are not formed like covalent bonds where electrons are shared between the two bonding atoms. Vibrational bonds are created at high energy where the muonium bounces to and from bromine atoms "like a ping pong ball bouncing between two bowling balls," according to Donald Fleming. [5] This bouncing action lowers the potential energy of the BrMuBr molecule, and therefore slows the rate of the reaction. [3]

Chemistry is the scientific discipline involved with elements and compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a reaction with other substances.

Temperature physical property of matter that quantitatively expresses the common notions of hot and cold

Temperature is a physical quantity expressing hot and cold. It is measured with a thermometer calibrated in one or more temperature scales. The most commonly used scales are the Celsius scale, Fahrenheit scale, and Kelvin scale. The kelvin is the unit of temperature in the International System of Units (SI), in which temperature is one of the seven fundamental base quantities. The Kelvin scale is widely used in science and technology.

This type of bond has been confirmed in the BrMuBr molecules but in the heavier isotopes of hydrogen (protium, deuterium, and tritium), the vibrational bonding can only occur as the van der Waals forces are overcome and the vibrational bond is formed.

Relevance

This discovery changes the understanding of chemical bonds, with van der Waals interactions, and recently discovered vibrational bonding will show that there are different mechanisms and energies for different bonds, and the experimental discovery of the vibrational bonding has the potential to encourage more research in isotopic interactions. [3]

Related Research Articles

Covalent bond chemical bond that involves the sharing of electron pairs between atoms

A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they share electrons, is known as covalent bonding. For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration.

Halogen group in the periodic table

The halogens are a group in the periodic table consisting of five chemically related elements: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). The artificially created element 117 may also be a halogen. In the modern IUPAC nomenclature, this group is known as group 17. The symbol X is often used generically to refer to any halogen.

Hydrogen bond form of association between an electronegative atom and a hydrogen atom attached to a second,relatively electronegative atom;electrostatic interaction,heightened by the small size of hydrogen which permits proximity of the interacting dipoles/charges

A hydrogen bond is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative atom or group, particularly the second-row elements nitrogen (N), oxygen (O), or fluorine (F)—the hydrogen bond donor (Dn)—and another electronegative atom bearing a lone pair of electrons—the hydrogen bond acceptor (Ac). Such an interacting system is generally denoted Dn–H···Ac, where the solid line denotes a fully covalent bond, and the dotted line indicates the hydrogen bond. There is general agreement that there is actually a minor covalent component to hydrogen bonding, especially for moderate to strong hydrogen bonds, although the importance of covalency in hydrogen bonding is debated. At the opposite end of the scale, there is no clear boundary between a weak hydrogen bond and a van der Waals interaction. Weaker hydrogen bonds are known for hydrogen atoms bound to elements such as sulfur (S) or chlorine (Cl); even carbon (C) can serve as a donor, particularly when the carbon or one of its neighbors is electronegative. The hydrogen bond is responsible for many of the anomalous physical and chemical properties of compounds of N, O, and F.

Ionic bonding chemical bond involving electron transfer

Ionic bonding is a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions, and is the primary interaction occurring in ionic compounds. It is one of the main bonds along with Covalent bond and Metallic bonding. Ions are atoms that have gained one or more electrons and atoms that have lost one or more electrons. This transfer of electrons is known as electrovalence in contrast to covalence. In the simplest case, the cation is a metal atom and the anion is a nonmetal atom, but these ions can be of a more complex nature, e.g. molecular ions like NH+
4
or SO2−
4
. In simpler words, an ionic bond is the transfer of electrons from a metal to a non-metal in order to obtain a full valence shell for both atoms.

Molecule Electrically neutral entity consisting of more than one atom (n > 1); rigorously, a molecule, in which n > 1 must correspond to a depression on the potential energy surface that is deep enough to confine at least one vibrational state

A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge. However, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions.

Molecular geometry Study of the 3D shapes of molecules

Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that determine the position of each atom.

In physical organic chemistry, a kinetic isotope effect (KIE) is the change in the reaction rate of a chemical reaction when one of the atoms in the reactants is replaced by one of its isotopes. Formally, it is the ratio of rate constants for the reactions involving the light (kL) and the heavy (kH) isotopically substituted reactants (isotopologues):

An interhalogen compound is a molecule which contains two or more different halogen atoms and no atoms of elements from any other group.

The bond-dissociation energy (BDE, D0, or DH°) is one measure of the strength of a chemical bond A–B. It can be defined as the standard enthalpy change when A–B is cleaved by homolysis to give fragments A and B, which are usually radical species. The enthalpy change is temperature dependent, and the bond-dissociation energy is often defined to be the enthalpy change of the homolysis at 0 K (absolute zero), although the enthalpy change at 298 K (standard conditions) is also a frequently encountered parameter. As a typical example, the bond-dissociation energy for one of the C–H bonds in ethane (C2H6) is defined as the standard enthalpy change of the process

In chemistry, bond energy (E) or bond enthalpy (H) is the measure of bond strength in a chemical bond. IUPAC defines bond energy as the average value of the gas-phase bond dissociation energies (usually at a temperature of 298 K) for all bonds of the same type within the same chemical species. For example, the carbon–hydrogen bond energy in methane H(C–H) is the enthalpy change involved with breaking up one molecule of methane into a carbon atom and four hydrogen radicals, divided by 4. Tabulated bond energies are generally values of bond energies averaged over a number of selected typical chemical species containing that type of bond. Bond energy (E) or bond enthalpy (H) should not be confused with bond-dissociation energy. Bond energy is the average of all the bond-dissociation energies in a molecule, and will show a different value for a given bond than the bond-dissociation energy would. This is because the energy required to break a single bond in a specific molecule differs for each bond in that molecule. For example, methane has four C–H bonds and the bond-dissociation energies are 435 kJ/mol for D(CH3–H), 444 kJ/mol for D(CH2–H), 444 kJ/mol for D(CH–H) and 339 kJ/mol for D(C–H). Their average, and hence the bond energy, is 414 kJ/mol, even though not a single bond required specifically 414 kJ/mol to be broken.

In chemistry, heterolysis or heterolytic fission is the process of cleaving a covalent bond where one previously bonded species takes both original bonding electrons from the other species. During heterolytic bond cleavage of a neutral molecule, a cation and an anion will be generated. Most commonly the more electronegative atom keeps the pair of electrons becoming anionic while the more electropositive atom becomes cationic.

A non-covalent interaction differs from a covalent bond in that it does not involve the sharing of electrons, but rather involves more dispersed variations of electromagnetic interactions between molecules or within a molecule. The chemical energy released in the formation of non-covalent interactions is typically on the order of 1-5 kcal/mol. Non-covalent interactions can be classified into different categories, such as electrostatic, π-effects, van der Waals forces, and hydrophobic effects.

Molecular solid

A molecular solid is a solid consisting of discrete molecules. The cohesive forces that bind the molecules together are van der Waals forces, dipole-dipole interactions, quadrupole interactions, π-π interactions, hydrogen bonding, halogen bonding, London dispersion forces, and in some molecular solids, coulombic interactions. Van der Waals, dipole interactions, quadrupole interactions, π-π interactions, hydrogen bonding, and halogen bonding are typically much weaker than the forces holding together other solids: metallic, ionic, and network solids. Intermolecular interactions, typically do not involve delocalized electrons, unlike metallic and certain covalent bonds. Exceptions are charge-transfer complexes such as the tetrathiafulvane-tetracyanoquinodimethane (TTF-TCNQ), a radical ion salt. These differences in the strength of force and electronic characteristics from other types of solids give rise to the unique mechanical, electronic, and thermal properties of molecular solids.

Physical organic chemistry, a term coined by Louis Hammett in 1940, refers to a discipline of organic chemistry that focuses on the relationship between chemical structures and reactivity, in particular, applying experimental tools of physical chemistry to the study of organic molecules. Specific focal points of study include the rates of organic reactions, the relative chemical stabilities of the starting materials, reactive intermediates, transition states, and products of chemical reactions, and non-covalent aspects of solvation and molecular interactions that influence chemical reactivity. Such studies provide theoretical and practical frameworks to understand how changes in structure in solution or solid-state contexts impact reaction mechanism and rate for each organic reaction of interest.

This glossary of chemistry terms is a list of terms and definitions relevant to chemistry, including chemical laws, diagrams and formulae, laboratory tools, glassware, and equipment. Chemistry is a physical science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions; it has an extensive vocabulary and a significant amount of jargon.

Chemical compound Substance composed of multiple elements

A chemical compound is a chemical substance composed of many identical molecules composed of atoms from more than one element held together by chemical bonds. A chemical element bonded to an identical chemical element is not a chemical compound since only one element, not two different elements, is involved.

Fluorine forms a great variety of chemical compounds, within which it always adopts an oxidation state of −1. With other atoms, fluorine forms either polar covalent bonds or ionic bonds. Most frequently, covalent bonds involving fluorine atoms are single bonds, although at least two examples of a higher order bond exist. Fluoride may act as a bridging ligand between two metals in some complex molecules. Molecules containing fluorine may also exhibit hydrogen bonding. Fluorine's chemistry includes inorganic compounds formed with hydrogen, metals, nonmetals, and even noble gases; as well as a diverse set of organic compounds. For many elements the highest known oxidation state can be achieved in a fluoride. For some elements this is achieved exclusively in a fluoride, for others exclusively in an oxide; and for still others the highest oxidation states of oxides and fluorides are always equal.

References

  1. D.C. Clary and J.N.L. Connor, 'Isotope and Potential energy surface effects in Vibrational Bonding.' Journal of Physical Chemistry. 1984
  2. 1 2 J. Manz, E. Pollak, J. Romelt 'A classical analysis of quantum resonances in isotopic collinear H + H2 Reactions' Chemical Physics letters, 1982.
  3. 1 2 3 Donald G. Fleming, Jorn Manz, Kazuma Sato, and Toshiyuki Takayanagi 'Fundamental Change in the Nature of Chemical Bonding by Isotopic Substitution' Angewandte communications 2014
  4. Tibi Puiu 'A new type of chemical bond has been confirmed- the vibrational bond' ZMEscience.com 2015
  5. Amy Nordrum 'Chemists confirm the Existence of New Type of Bond' Scientific American. Jan 20, 2015