Accurate Molecular Structures

Modern experimental and computational techniques are capable of determining bond lengths and angles with precisions of a few thousandths of an angstrom and a few tenths of a degree. Such precisions are meaningful only if they are coupled with rigorous error analysis and careful evaluation ofthe physical meaning of the parameters. Here, internationally respected authors present all modern experimental and computational techniques for the determination of accurate molecular structures for the first time in one volume. They establish guidelines for accuracy requirements in answering broadly varying questions in currentchemical research.

This book presents a detailed look at experimental and computational techniques for accurate structure determination of free molecules. The most fundamental property of a molecule is its structure – it is a prerequisite for determining and understanding most other important properties of molecules. The determination of accurate structures is hampered by a myriad of factors, subjecting the collected data to non-negligible systematic errors. This book explains the origin of these errors and how to mitigate and even avoid them altogether. It features a detailed comparison of the different experimental and computation methods, explaining their interplay and the advantages of their combined use. Armed with this information, the reader will be able to choose the appropriate methods to determine – to a great degree of accuracy – the relevant molecular structure.

Molecular structure is the most basic information about a substance, determining most of its properties. Determination of accurate structures is hampered in that every method applies its own definition of "structure" and thus results from different sources can yield significantly different results. Sophisticated protocols exist to account for these

The principal focus of this volume is to illustrate the level of accuracy currently achievable by ab initio quantum chemical calculations. While new developments in theory are discussed to some extent, the major emphasis is on a comparison of calculated properties with experiment. This focus is similar to the one taken in a book, Comparison of Ab Initio Quantum Chemistry with Experiment for Small Molecules, edited by Rodney Bartlett (Reidel, 1984). However, the phenomenal improvement in both theoretical methods and computer architecture have made it possible to obtain accurate results for rather large molecular systems. This is perhaps best illustrated in this volume by the chapter entitled `Spectroscopy of Large Organic Molecules' by Bjorn Roos and coworkers. For example, the electronic spectra of the nucleic acid base monomer structures shown on the front cover have been obtained using a fully correlated ab initio study. For researchers, teachers and students in chemistry and physics.

A guide to analyzing the structures and properties of organic molecules Until recently, the study of organic molecules has traveled down two disparate intellectual paths—the experimental, or physical, method and the computational, or theoretical, method. Working somewhat independently of each other, these disciplines have guided research for decades, but they are now being combined efficiently into one unified strategy. Molecular Structure delivers the essential fundamentals on both the experimental and computational methods, then goes further to show how these approaches can join forces to produce more effective analysis of the structure and properties of organic compounds by: Looking at experimental structures: electron, neutron, X-ray diffraction, and microwave spectroscopy as well as computational structures: ab initio, semi-empirical molecular orbital, and molecular mechanics calculations Discussing various electronic effects, particularly stereoelectronic effects, including hyperconjugation, negative hyperconjugation, the Bohlmann and anomeric effects, and how and why these cause changes in structures and properties of molecules Illustrating complex carbohydrate effects such as the gauche effect, the delta-two effect, and the external anomeric torsional effect Covering hydrogen bonding, the CH bond, and how energies, especially heats of formation, can be affected Using molecular mechanics to tie all of these things together in the familiar language of the organic chemist, valence bond pictures Authored by a founding father of computational chemistry, Molecular Structure broadens the scope of the subject by serving as a pioneering guide for workers in the fields of organic, biological, and computational chemistry, as they explore new possibilities to advance their discoveries. This work will also be of interest to many of those in tangential or dependent fields, including medicinal and pharmaceutical chemistry and pharmacology.

Advances in Molecular Structure Research

Chemistry and chemical engineering have changed significantly in the last decade. They have broadened their scopeâ€"into biology, nanotechnology, materials science, computation, and advanced methods of process systems engineering and controlâ€"so much that the programs in most chemistry and chemical engineering departments now barely resemble the classical notion of chemistry. Beyond the Molecular Frontier brings together research, discovery, and invention across the entire spectrum of the chemical sciencesâ€"from fundamental, molecular-level chemistry to large-scale chemical processing technology. This reflects the way the field has evolved, the synergy at universities between research and education in chemistry and chemical engineering, and the way chemists and chemical engineers work together in industry. The astonishing developments in science and engineering during the 20th century have made it possible to dream of new goals that might previously have been considered unthinkable. This book identifies the key opportunities and challenges for the chemical sciences, from basic research to societal needs and from terrorism defense to environmental protection, and it looks at the ways in which chemists and chemical engineers can work together to contribute to an improved future.

Specialist Periodical Reports provide systematic and detailed review coverage of progress in the major areas of chemical research. Written by experts in their specialist fields the series creates a unique service for the active research chemist, supplying regular critical in-depth accounts of progress in particular areas of chemistry. For over 80 years the Royal Society of Chemistry and its predecessor, the Chemical Society, have been publishing reports charting developments in chemistry, which originally took the form of Annual Reports. However, by 1967 the whole spectrum of chemistry could no longer be contained within one volume and the series Specialist Periodical Reports was born. The Annual Reports themselves still existed but were divided into two, and subsequently three, volumes covering Inorganic, Organic and Physical Chemistry. For more general coverage of the highlights in chemistry they remain a 'must'. Since that time the SPR series has altered according to the fluctuating degree of activity in various fields of chemistry. Some titles have remained unchanged, while others have altered their emphasis along with their titles; some have been combined under a new name whereas others have had to be discontinued. The current list of Specialist Periodical Reports can be seen on the inside flap of this volume.