The lecturers as well as the participants came from varied scientific backgrOlUldsfor the NATO -Advanced Study Institute (ASDheld atAltinoluk, Edremit. Turkey during the period of July 31 -August 12 1989. The lecturers were University Professors from the USA, Canada, England, C'-.ermany, France and Spain and they covered a broad spectrwn of specialities from methodology t.o appications. On the other hand students coming from the various NATO countries arrived with an inhomogeneous background to absorb the broad spectnUIl of material covered by the lecturers. However, by the end of the two week period of the ASI, that initial difference in scientific background had been reduced substantially . The lecturers had covered subject matters from the most fundamental to the most applied aspects of theoretical and computational organic chemistry. The lectures were argnmented with tutorial sessions and computational laboratory led by a small group of carefnlly selected tutors. Overall, this NATO -ASI was a ~at success and the Editors are hopeful that the present volume will communicate the scientific success and will radiate the intellectual spirit of the meeting.

People who attended the NATO Advanced Study Institute (ASI) entitled NEW THEORETICAL CONCEPTS FOR UNDERSTANDING ORGANIC REAC TIONS held at Sant Feliu de Gufxols on the Costa Brava of Spain had a unique experience. They have seen the evolution of the field from qualitative arguments through the generation of Potential Energy Surfaces (PES) to the use of PES in molecular dynamics. The excellent lectures that were dedicated to the various aspects of Potential Energy Surfaces clearly revealed a colossal amount of ma terial that represents our current understanding of the overall problem. It is our hope that the present volume will recreate the excitement in the readers that we all experienced during the meeting in Spain. One can say, without too much exaggeration, that chemistry has become and exercise on potential energy surfaces (PES). Structural (position of the energy minima), spectroscopic (vicinity around the minima), and reactivity (reaction path along the surface) properties may be determined from the analysis of PES. New theoretical tools, together with recent developments in computer technology and programming, have allowed to obtain a better knowledge of these surfaces, and to extract further chemical information from them, so new horizons have been added to Theoretical Organic Chemistry."

Organophosphorus Chemistry presents a groundbreaking resource in this branch of organic chemistry that demonstrates how phosphorus-containing compounds can be manipulated in a variety of organic reactions. The authors give an overview of the newest trends and synthesis strategies, introduce bioactive and environmentally friendly organophosphorus compounds and show their importance in mainstream organic chemistry.

The lecturers as well as the participants came from varied scientific backgrOlUldsfor the NATO -Advanced Study Institute (ASDheld atAltinoluk, Edremit. Turkey during the period of July 31 -August 12 1989. The lecturers were University Professors from the USA, Canada, England, C'-.ermany, France and Spain and they covered a broad spectrwn of specialities from methodology t.o appications. On the other hand students coming from the various NATO countries arrived with an inhomogeneous background to absorb the broad spectnUIl of material covered by the lecturers. However, by the end of the two week period of the ASI, that initial difference in scientific background had been reduced substantially . The lecturers had covered subject matters from the most fundamental to the most applied aspects of theoretical and computational organic chemistry. The lectures were argnmented with tutorial sessions and computational laboratory led by a small group of carefnlly selected tutors. Overall, this NATO -ASI was a ~at success and the Editors are hopeful that the present volume will communicate the scientific success and will radiate the intellectual spirit of the meeting.

The papers in this volume were presented at the NATO Advanced Study Institute held in Porto Novo, Portugal, August 26 - September 8, 1990. The Institute has been able to cover a wide spectrum of the Theoretical and Computational Models for organic molecules and organic reactions, ranging from the ab initio to the more empirical approaches, in the tradition established in the previous Institutes at S. Feliu de Guixols (Spain) and Altinoluk (Turkey). The continuity with this work was achieved by inviting half of the lecturers present in those meetings. But other important subjects were also covered at Porto Novo by new lecturers, both from universities and the industry. Molecular Mechanics, Protein Structure and Unidimensional Models were introduced by the first time. The concept of building on the expertise already acquired and available, both in terms of methods and contents, to develop in new directions, was appreciated by participants and lecturers. The Institute first considered the fundamentals of molecular orbital computations and ab initio methods and the construction of Potential Energy Surfaces. These subjects were further explored in several applications related with optimization of equilibrium geometries and transition structures. Practical examples were studied in Tutorial sessions and solved in the computational projects making use of the Gaussian 88 and Gaussian 90 programs. Empirical models can be complementary to the quantum-mechanical ones in equilibrium geometry optimizations.

As a general rule any interdisciplinary subject and that includes Computational Theoretical Organic Chemistry (CTOC) incorporates people from the two overlaping areas. In this case the overlaping areas are Computational Theoretical Chemistry and Organic Chemistry. Since CTOC is a relatively young science, people continue to shift from their major discipline to this area. At this particular time in history we have to accept in CTOC people who were trained in Computational Theoretical Chemistry and do not know very much about Organic Chemistry, but more often the opposite case is operative Experimental Organic Chemistry who have not been exposed to Computational Theoretical Chemistry. This situation made NATO Advanced Study Institute in the field of CTOC necessary. The inhomogenity outlined above was present in the NATO Advanced Study Institute, held at Menton in July 1980, and to some degree it is noticable from the content of this volume. This book contains 20 contributions. The first contribution is an Introduc tion chapter in which the initiated experimental chemists are briefed about the subject matter. The last chapter describes very briefly the "Computational Laboratory" that was designed to help people with an experimental back ground in order to obtain some first hand experience. Between the first and the last chapters there are 18 contributions. These contributions were arranged in a spectrum from the exclusively method oriented papers to the applications of existing computational methods to problems of interest in Organic Chemistry."

People who attended the NATO Advanced Study Institute (ASI) entitled NEW THEORETICAL CONCEPTS FOR UNDERSTANDING ORGANIC REAC TIONS held at Sant Feliu de Gufxols on the Costa Brava of Spain had a unique experience. They have seen the evolution of the field from qualitative arguments through the generation of Potential Energy Surfaces (PES) to the use of PES in molecular dynamics. The excellent lectures that were dedicated to the various aspects of Potential Energy Surfaces clearly revealed a colossal amount of ma terial that represents our current understanding of the overall problem. It is our hope that the present volume will recreate the excitement in the readers that we all experienced during the meeting in Spain. One can say, without too much exaggeration, that chemistry has become and exercise on potential energy surfaces (PES). Structural (position of the energy minima), spectroscopic (vicinity around the minima), and reactivity (reaction path along the surface) properties may be determined from the analysis of PES. New theoretical tools, together with recent developments in computer technology and programming, have allowed to obtain a better knowledge of these surfaces, and to extract further chemical information from them, so new horizons have been added to Theoretical Organic Chemistry."