developing very sensitive arrays of chemical detectors, sometimes called artificial noses, that can detect and identify volatile components of explosives in very small amounts. Other problems are learning to detect chemical and biological warfare agents, both on the battlefield and in civilian areas, and to detect trace components in our environment, either anthropogenic or of natural origin, that offer health risks to living organisms: human, beast, insect, fungus, and plant.

A vital activity of the chemical sciences is the determination of structure. Detailed molecular structure determinations require identifying the spatial locations of all of the atoms in molecules, that is, the atomic distances and bond angles of a species. It is important to realize that the three-dimensional architecture of molecules very much defines their reactivity and function. However, molecules are dynamic, a feature that is not reflected by static pictures. This last point requires further explanation. Because the atoms in all molecules move, even in the limit of the lowest temperatures obtainable, molecular structures really describe the average position about some equilibrium arrangement. In addition, rotations about certain bonds occur freely at common temperatures. Consequently, some molecules exist in more than one structure (conformation). Some molecules are so floppy that structural characterizations really refer to averages among several structures. Yet other molecules are sufficiently rigid that molecular structures can be quite precisely determined.

The techniques available to achieve molecular structure determinations are limited. They include structural analysis with diffraction techniques—such as electron, neutron, and x-ray diffraction—and various absorption and emission techniques of electromagnetic radiation—such as microwave spectroscopy and nuclear magnetic resonance (NMR). For molecules with unpaired spins a companion technique of electron spin resonance spectroscopy (ESR) is highly informative.

A number of other spectroscopies provide information that is related to molecular structure, such as coordination symmetry, electronic splitting, and/or the nature and number of chemical functional groups in the species. This information can be used to develop models for the molecular structure of the system under study, and ultimately to determine the forces acting on the atoms in a molecule for any arbitrary displacement of the nuclei. According to the energy of the particles used for excitation (photons, electrons, neutrons, etc.), different parts of a molecule will interact, and different structural information will be obtained. Depending on the relaxation process, each method has a characteristic time scale over which the structural information is averaged. Especially for NMR, the relaxation rate may often be slower than the rate constant of a reaction under study.

Front Matter (R1-R14)

Executive Summary (1-10)

1 Introduction (11-15)

2 The Structures and Cultures of the Disciplines: The Common Chemical Bond (16-21)

3 Synthesis and Manufacturing: Creating and Exploiting New Substances and New Transformations (22-40)

4 Chemical and Physical Transformations (41-54)

5 Isolating, Identifying, Imaging, and Measuring Substances and Structures (55-70)

6 Chemical Theory and Computer Modeling: From Computational Chemistry to Process Systems Engineering (71-94)

7 The Interface with Biology and Medicine (95-122)

8 Materials by Design (123-147)

9 Atmospheric and Environmental Chemistry (148-159)

10 Energy: Providing for the Future (160-170)

11 National and Personal Security (171-179)

12 How To Achieve These Goals (180-194)

Appendix A: Biographical Sketches of Steering Committee Members (195-201)

Appendix B: Statement of Task (202-202)

Appendix C: Contributors (203-208)

Index (209-224)