Isolobal principle - Wikipedia
Carbonyl clusters-LNCCS and HNCCS, Isoelectronic and isolobal analogy, Wade-Mingos rules, cluster valence electrons. Linear free energy relationships . Isolobal compounds are analogues to isoelectronic compounds that share the . Figure 7: Isolobal relationship between octahedral and square planar complexes. .. welding, cathode ray tubes, electron microscopes, radiation therapy, lasers. The bioinorganic and medicinal chemistry of carboranes: From new drug discovery to molecular imaging and therapy. Article. Full-text available.
An object has symmetry if it can be simultaneously translated and rotated in three-dimensional space along a line known as a screw axis. An object has symmetry if it does not change shape when it is expanded or contracted. Fractals also exhibit a form of symmetry, where small portions of the fractal are similar in shape to large portions.
Other symmetries include glide reflection symmetry and rotoreflection symmetry, a dyadic relation R is symmetric if and only if, whenever its true that Rab, its true that Rba. Thus, is the age as is symmetrical, for if Paul is the same age as Mary. Symmetric binary logical connectives are and, or, biconditional, nand, xor, the set of operations that preserve a given property of the object form a group.
In general, every kind of structure in mathematics will have its own kind of symmetry, examples include even and odd functions in calculus, the symmetric group in abstract algebra, symmetric matrices in linear algebra, and the Galois group in Galois theory. In statistics, it appears as symmetric probability distributions, and as skewness, symmetry in physics has been generalized to mean invariance—that is, lack of change—under any kind of transformation, for example arbitrary coordinate transformations.
This concept has one of the most powerful tools of theoretical physics. See Noethers theorem, and also, Wigners classification, which says that the symmetries of the laws of physics determine the properties of the found in nature.
Important symmetries in physics include continuous symmetries and discrete symmetries of spacetime, internal symmetries of particles, in biology, the notion of symmetry is mostly used explicitly to describe body shapes. Bilateral animals, including humans, are more or less symmetric with respect to the plane which divides the body into left 2.
Quantum mechanical properties of the include a intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant. As it is a fermion, no two electrons can occupy the same state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of particles and waves, they can collide with other particles and can be diffracted like light. Since an electron has charge, it has an electric field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law, electrons radiate or absorb energy in the form of photons when they are accelerated.
Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields, special telescopes can detect electron plasma in outer space.
Electrons are involved in applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors. Interactions involving electrons with other particles are of interest in fields such as chemistry.
The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms, ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system.
The exchange or sharing of the electrons between two or more atoms is the cause of chemical bonding. InBritish natural philosopher Richard Laming first hypothesized the concept of a quantity of electric charge to explain the chemical properties of atoms.
Irish physicist George Johnstone Stoney named this charge electron inelectrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of isotopes and in high-energy collisions.
The antiparticle of the electron is called the positron, it is identical to the electron except that it carries electrical, when an electron collides with a positron, both particles can be totally annihilated, producing gamma ray photons. The ancient Greeks noticed that amber attracted small objects when rubbed with fur, along with lightning, this phenomenon is one of humanitys earliest recorded experiences with electricity.
Nobel Prize — The Nobel Prize is a set of annual international awards bestowed in a number of categories by Swedish and Norwegian institutions in recognition of academic, cultural, or scientific advances.
The will of the Swedish inventor Alfred Nobel established the prizes inthe prizes in Chemistry, Literature, Peace, Physics, and Physiology or Medicine were first awarded in Medals made before were struck in 23 carat gold, between andthe Nobel Prizes and the Prize in Economic Sciences were awarded times to people and organisations.
With some receiving the Nobel Prize more than once, this makes a total of 23 organisations, the prize ceremonies take place annually in Stockholm, Sweden. Each recipient, or laureate, receives a medal, a diploma. The Nobel Prize is widely regarded as the most prestigious award available in the fields of literature, medicine, physics, chemistry, peace, and economics.
The prize is not awarded posthumously, however, if a person is awarded a prize and dies before receiving it, though the average number of laureates per prize increased substantially during the 20th century, a prize may not be shared among more than three people.
Alfred Nobel was born on 21 October in Stockholm, Sweden and he was a chemist, engineer, and inventor. InNobel purchased the Bofors iron and steel mill and this invention was a precursor to many smokeless military explosives, especially the British smokeless powder cordite.
As a consequence of his patent claims, Nobel was eventually involved in a patent infringement lawsuit over cordite, Nobel amassed a fortune during his lifetime, with most of his wealth from his inventions, of which dynamite is the most famous. InNobel was astonished to read his own obituary, titled The merchant of death is dead, as it was Alfreds brother Ludvig who had died, the obituary was eight years premature.
The article disconcerted Nobel and made him apprehensive about how he would be remembered and this inspired him to change his will. Because of skepticism surrounding the will, it was not until 26 April that it was approved by the Storting in Norway. The executors of Nobels will, Ragnar Sohlman and Rudolf Lilljequist, formed the Nobel Foundation to take care of Nobels fortune, Nobels instructions named a Norwegian Nobel Committee to award the Peace Prize, the members of whom were appointed shortly after the will was approved in April Soon thereafter, the other prize-awarding organisations were designated or established and these were Karolinska Institutet on 7 June, the Swedish Academy on 9 June, and the Royal Swedish Academy of Sciences on 11 June.
The Nobel Foundation reached an agreement on guidelines for how the prizes should be awarded, and, ininthe personal union between Sweden and Norway was dissolved 4.
He has also published plays and poetry and he is the Frank H. After Germany invaded Poland and occupied the town, his family was placed in a camp where his father. His father remained at the camp, but was able to occasionally visit. While in hiding his mother kept Hoffmann entertained by teaching him to read and having him memorize geography from textbooks stored in the attic and he referred to the experience as having been enveloped in a cocoon of love.
Most of the rest of the family perished in the Holocaust, though one grandmother and they migrated to the United States on the troop carrier Ernie Pyle in Ina monument to Holocaust victims was built in Zolochiv on Hoffmanns initiative, Hoffmann graduated in from New York Citys Stuyvesant High School, where he won a Westinghouse science scholarship.
He received his bachelor of degree at Columbia University in This method was extended by Hoffmann. He went to Cornell in and has remained there, becoming professor emeritus, Hoffmanns research and interests have been in the electronic structure of stable and unstable molecules, and in the study of transition states in reactions.
He has investigated the structure and reactivity of organic and inorganic molecules, and examined problems in organo-metallic and solid-state chemistry. They realized that chemical transformations could be predicted from subtle symmetries and asymmetries in the electron orbitals of complex molecules. Their rules predict differing outcomes, such as the types of products that will be formed when two compounds are activated by heat compared with those produced under activation by light. For this work Hoffmann received the Nobel Prize in chemistry, sharing it with Japanese chemist Kenichi Fukui, in his Nobel Lecture, Hoffmann introduced the isolobal analogy for predicting the bonding properties of organometallic compounds 5.
Molecular geometry — Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It determines several properties of a substance including its reactivity, polarity, phase of matter, color, magnetism and biological activity. The angles between bonds that an atom forms depend only weakly on the rest of molecule, i.
IR, microwave and Raman spectroscopy can give information about the molecule geometry from the details of the vibrational and rotational absorbance detected by these techniques. Further removal of hydrogen results in the formation of a second frontier orbital. This process can be repeated until only one bond remains to the molecule's central atom. Figure 2 demonstrates this example of step-by-step generation of isolobal fragments.
Isolobal principle - WikiVisually
Construction of frontier orbitals from methane. The isolobal fragments of octahedral complexes, such as ML6, can be created in a similar fashion. Transition metal complexes should initially satisfy the eighteen electron rulehave no net charge, and their ligands should be two electron donors Lewis bases. Consequently, the metal center for the ML6 starting point must be d6. Removal of a ligand is analogous to the removal of hydrogen of methane in the previous example resulting in a frontier orbital, which points toward the removed ligand.
In order to satisfy the zero-charge criteria the metal center must be changed. For example, a MoL6 complex is d6 and neutral. To remedy this, Mo can be exchanged for Mn, which would form a neutral d7 complex in this case, as shown in Figure 3. This trend can continue until only one ligand is left coordinated to the metal center. Production of a frontier orbital in an octahedral complex. Addition and elimination reactions-1,2 additions to double bonds, carbonylation and decarbonylation, oxidative addition and reductive elimination, insertion migration and elimination reactions.
Rearrangement reactions, redistribution reactions, fluxional isomerism. Reactions of carbon monoxide and hydrogen-the water gas shift reaction, the Fischer-Tropsch reaction synthesis of gasoline.
Hydroformylation of olefins using cobalt or rhodium catalyst. Polymerization by organometallic initiators and templates for chain propagation-Ziegler Natta catalysts. Carbonylation reactions-Monsanto acetic acid process, carbonylation of butadiene using Co2 CO 8 catalyst in adipic ester synthesis. Palladium catalysed oxidation of ethylene-the Wacker process. Role of calcium in muscle contraction, blood clotting mechanism and biological calcification.
Oxygen carriers and oxygen transport proteins-haemoglobins, myoglobins and haemocyanin, haemerythrins and haemevanadins, cooperativity in haemoglobin. Iron storage and transport in biological systems-ferritin and transferrin. Redox metalloenzymes-cytochromes, peroxidases and superoxide dismutase and catalases. Nonredox metalloenzymes-CarboxypeptidaseA-structure and functions.
Nitrogen Fixation-nitrogenase, vitamin B12 and the vitamin B12 coenzymes. Metals in medicine-therapeutic applications of cis-platin, radio-isotopes and MRI agents. Toxic effects of metals Cd, Hg, Cr and Pb. Neutron capture cross section and critical size. Nuclear fusion reactions and their applications.
Chemical effects of nuclear transformations. Positron annihilation and autoradiography. Principles of counting technique such as G. Synthesis of transuranic elements such as Neptunium, Plutonium, Curium, Berkelium, Einsteinium, Mendelevium, Nobelium, Lawrencium and elements with atomic numbers to Analytical applications of radioisotopes-radiometric titrations, kinetics of exchange reactions, measurement of physical constants including diffusion constants, Radioanalysis, Neutron Activation Analysis, Prompt Gama Neutron Activation Analysis and Neutron Absorptiometry.
Applications of radio isotopes in industry, medicine, autoradiography, radiopharmacology, radiation safety precaution, nuclear waste disposal.
Radiation chemistry of water and aqueous solutions. Measurement of radiation doses. Relevance of radiation chemistry in biology, organic compounds and radiation polymerization.
Cotton, G Wilkinson, C. Kotz, Inorganic Chemistry, Holt-Saunders, Powell, Principles of Organometallic Chemistry, 2nd Edn. Goshal, Nuclear Physics, S. Chand and Company, Bonding weaker than covalent bonds. The formalism of curved arrow mechanisms. Practicing of line diagram drawing. NMR as a tool for aromaticity. Anti-and homo-aromatic systems — Fullerenes, Carbon nanotubes and Graphene.
Mechanism of electrophilic and nucleophilic aromatic substitution reactions with examples. Kinetic versus thermodynamic control of product formation,Hammond postulate, kinetic isotope effects with examples, Hammet equation, Taft equation.
Linear free energy relationships.