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Nobel Prize in Chemistry 2010: Palladium-Catalyzed Cross

Palladium-Catalyzed Cross Couplings in Organic Synthesis

Three researchers share this year’s Nobel Prize in Chemistry, Professor Richard F. Heck, who has been working at University of Delaware, Newark, Delaware, USA, Professor Ei-ichi Negishi, Purdue University, West Lafayette, Indiana, USA, and Professor (emeritus) Akira Suzuki, Hokkaido University, Sapporo, Japan. The Royal Swedish Academy of Sciences is rewarding the three chemists for: “palladium-catalyzed cross couplings in organic synthesis”. The discoveries by the three organic chemists have had a great impact on academic research, the development of new drugs and materials,
and are used in many industrial chemical processes for the synthesis of pharmaceuticals and other biologically active compounds. A background and description of their discoveries are given below.

Introduction

This year’s Nobel Prize in Chemistry concerns the development of methods for palladiumcatalyzed formation of carbon-carbon bonds via so-called cross-coupling reactions. The formation of new carbon-carbon bonds is of central importance in organic chemistry and a prerequisite for all life on earth. Through the assembly of carbon atoms into chains, complex molecules, e.g. molecules of life, can be created. The importance of the synthesis of carboncarbon bonds is reflected by the fact that Nobel Prizes in Chemistry have previously been given to this area: The Grignard reaction (1912), the Diels-Alder reaction (1950), the Wittig reaction (1979), and olefin metathesis to Y. Chauvin, R. H. Grubbs, and R. R. Schrock (2005). 

Transition metals in synthetic organic chemistry

During the second half of the 20th century, transition metals have come to play an important role in organic chemistry and this has led to the development of a large number of transition metal-catalyzed reactions for creating organic molecules. Transition metals have a unique ability to activate various organic compounds and through They CAN catalyze this activation the formation of new bonds ...

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COUPLINGS IN ORGANIC SYNTHESIS Nobel Prize in Chemistry 2010: Tools for Molecular Architect

Life on Earth is built out of carbon. Chains of carbon atoms arranged in different ways, are the backbone of most of the molecules that form and regulate the living systems. These molecules, large and small, of course contain other elements. But the greatest challenge for chemists, when they try to replicate and even improve the ability of nature to build molecules derived Carbon (organic) has long been finding ways to create and break the chemical bonds between carbon atoms. Over the years, chemists synthetic organic chemistry have accumulated a vast array of these reactions used to build new molecular structures.

However, many organic reactions tend to form undesired side products, due to the conditions or highly activated molecules used. The Nobel Prize in Chemistry, 2010 reward for three chemicals that have developed new methods to build links between atoms carbon, very selective and relatively mild conditions. All three have developed reactions as they are called. Heck reactions, Negishi and Suzuki used palladium, silver metal, joining two molecules, using a single link between them. Over the past thirty years, these reactions have become basic tools and very valuable to any organic chemist.

Richard Heck developed its addition reaction based on palladium for the 60, running a series of scientific papers on this subject, before stipulating what would become the standard protocol for Heck reaction in 1972. In this standard, palladium acts as a catalyst, first "grabbing" one molecule, then another and then joining them and "dropping" the couple together, leaving himself unchanged by the process, something akin to a marriage bureau. In the Heck reaction, the first molecule always contains a link between a carbon atom and a halogen such as chlorine, and the second always contains a double bond between carbon atoms. Surprisingly, the reaction occurs at room temperature.

Ei-ichi Negishi and Akira Suzuki, who had worked casually with Herbert Brown, Nobel Nobel in Chemistry in 1979, expanded the range of application of the Heck reaction, mainly to develop new ways to change the second molecule involved. The molecule containing a carbon double bond is replaced by a molecule in the reaction of organozinc Negishi and organoborane molecule in the Suzuki reaction. Together, these three reactions, and variants that have been created from them, have dramatically improved both the potential and the efficiency of synthetic organic chemistry and contributed substantially to the construction of complex molecules that contribute to multiple areas of our lives daily, from agriculture to medicine.

Translation of original article written by Adam Smith, Editor in Chief, Nobelprice.org

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Graphene, new material developed by Andre Geim and Novoselov Konstantin: Nobel Prize in Physics

Graphene

Graphene is a flat sheet structure of an atom thick, composed by atoms of carbon densely packed in a crystal lattice in the form of honeycomb by covalent would be formed from the superposition of the hybrid sp ² bonded carbons.

Sp hybridization 2 is best explained the bond angles, 120 °, the hexagonal structure. As each carbon has four electrons of valence in the hybridized state, three of those electrons will stay in the hybrid sp 2 , forming the skeleton of simple covalent structure and extra electron is accommodated in a p-type atomic orbital perpendicular to the plane of the hybrids. The overlap is side of these orbitals is what would lead to the formation of π-type orbitals. Some of these combinations, among others, would Instead of a giant molecular orbital delocalized among all carbon atoms that form the graphene layer.

The structure of graphite can be considered as a stack of a large number of overlapping graphene sheets. The links between the different layers of graphene stacked is because Van der Waals forces and interactions between the π orbital of carbon atoms.

Graphene is constituted entirely perfect hexagonal cells, the cells are pentagonal and heptagonal defects.

Properties

· High thermal and electrical conductivity (due to its dimensional structure on a honeycomb).

· High elasticity.

· High hardness (almost like the diamond).

· resistance (200 times greater than steel)

· Graphene can react chemically with other substances to form compounds with different properties.

· Supports ionizing radiation .

· is very light, as carbon fiber , but more flexible.

· Minor Joule , unless the lead is heated electrons.

· consumes less power than silicon .

· is almost completely transparent and so thick that neither the helium atom (the atoms are smaller than present) can pass through it.

The discovery of Andre Geim and Novoselov Konstantin

The Nobel Prize in Physics 2010 has been awarded to Andre Geim and Novoselov Konstantin, not for his discovery of graphene, since this was already nearly half a century, but because they discovered how carbon is presented in a way that becomes the material of the future.

Novoselov The finding came about four years ago, when he intuitively with an imaginative approach to isolate graphitic layers of a single atom thick. Graphite, the material from the mines of pencils, is made of layers of carbon atoms arranged like a honeycomb. In this sense, graphene is actually one of these layers that the teacher got Novoselov staining a strip of graphite deposited zeal, painting with a pencil on paper and then using that zeal as a seal on a clean surface.

Kostya Novoselov first manufactured graphene in laboratory in 2004, and July 2008, the scientists had just concluded that it was the toughest material known.

A graphene mesh one atom thick demonstrates its strength to bear the pressure of a diamond stylus.

In March 2007 Professor Andre Geim present a transistor made of graphene. The transistor was more than four times smaller than the smallest made of silicon, as well as more efficient. Was used for making them a sheet of graphene tenth nanometer thick, ie the thickness of a single atom.

Improvements relative to silicon

processors could reach speeds of hundreds of gigahertz (in silicon, the maximum-NonCommercial-is 100 GHz) will take a little more, because graphene is very good driver and passes all the electrons. Silicon, however, is a semiconductor that is, admits that he "tell" when transmitting current and power the millions of transistors that form the processor, and when not.

spoken to "control the conductivity of graphene using two layers of this material, one above another, and in a particular orientation." To fix this problem could also be used graphane, a derivative of graphene: graphane has the same honeycomb structure of graphene, except that it is "sprayed" with hydrogen atoms attached to carbon. The resulting links between the atoms of hydrogen and carbon "bind" the electrons effectively to make such a good driver to graphene. Graphane still retains the thinness, the enormous strength, flexibility and density of its old chemical cousin.

Because graphene is consisting of a single layer thick, the transistors are very sensitive to any molecule that is deposited on its surface. Therefore, it is an ideal material for making chemical and biological sensors.

Some of the future inventions combine "sensitivity" of graphene with the "ability" of silicon, since they complement not replace.

Jorge García Paredes

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