Chemical problems

The suitability of a buffer system for any particular application depends on many factors, the first of which is the p a value of the buffer acid or base. For a buffer to be effective, its pH must be within the range pA a 1, or preferably, within pATa 0.5. The former scarcity of buffer substances with a pH range 6 to 8 frequently led to the use of buffers such as phosphate or Tris in pH regions where they had little buffer capacity. 

Not only must the buffer species be appreciably soluble in water, but it is also important that they do not react with ions or molecules present in the solution. For example, phosphate and pyrophosphate buffers are unsuitable if a solution contains calcium or certain other di- and trivalent cations which form insoluble phosphates, or if reaction progress is to be followed by the change in phosphate content. Similarly, carbonate buffers can precipitate calcium ion. 

Borate buffers should not be used in the presence of polyols, including carbohydrates and their derivatives, with which they may form chelate compounds they react in this way with many respiratory intermediates. Use of borate buffers in gel electrophoresis of proteins can result in spreading of the zones if fructose, ribose, sorbitol, catechol or other appropriate polyols are present to form borate complexes (Lerch and Stegemann, 1969). The increased solubility of adrenalin in borate buffers is due to complex formation as is also the improved separation of sugar phosphates chromatographically in the presence of borate buffers. Likewise, complexation of carbohydrates in german-ate or borate buffers is the basis of a suggested method for 

A difficulty in using bicarbonate/C02 buffers is that pH constancy requires the use of closed systems equilibrated with a controlled level of CO2 in the gas phase. Otherwise, loss of CO2 from the solution can lead to a progressive and undesirable rise in pH. 

The storage of alkalis and alkaUne buffer solutions presents problems because of the avidity with which CO2 is absorbed 

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On the environmental side, it turns out that the surfaces of oceans and lakes are usually coated with natural films, mainly glycoproteins [8]. As they are biological in origin, the extent of such films seems to be seasonal. Pollutant slicks, especially from oil spills, are of increasing importance, and their cleanup can present interesting surface chemical problems. 

Apart from the development of imaging and force measurement devices, an important biophysico-chemical problem is... 

A vital biophysico-chemical problem is to understand how chemical energy (released by ATP or GTP hydrolysis... 

Chemoinformatics is the application of informatics methods to solve chemical problems. 

Since then, the application of methods of computer science, or informatics as it is called in many languages, to the solution of chemical problems has ventured into many more areas of chemistry. So broad are the applications of informatics, and its foundation, mathematics, in chemistry that no longer can any single conference cover the entire field. 

In this book, we want to build on the long history of applying infonnatics methods to chemical problems, and to pay tribute to the scientists who started out decades ago to develop this interdisciplinary field. 

The DENDRAL project initiated in 1964 at Stanford was the prototypical application of artificial intelligence techniques - or what was understood at that time under this name - to chemical problems. Chemical structure generators were developed and information from mass spectra was used to prune the chemical graphs in order to derive the chemical structure associated with a certain mass spectrum. 

Further prerequisites depend on the chemical problem to be solved. Some chemical effects have an undesired influence on the structure descriptor if the experimental data to be processed do not account for them. A typical example is the conformational flexibility of a molecule, which has a profound influence on a 3D descriptor based on Cartesian coordinates. In particular, for the application of structure descriptors with structure-spectrum correlation problems in... 

Thus, computers will continue to penetrate every aspect of chemistry and we have to prepare the next generation of chemists for this process. In fact, we will see that the various types of computer applications in chemistry will increasingly be used in concert to solve chemical problems. Therefore, a unified view of the entire field is needed the various approaches to using computers in chemistry have to be ordered into a common framework, into a disdpline of its own Chemoinfor-matics. 

In applying quantum mechanics to real chemical problems, one is usually faced with a Schrodinger differential equation for which, to date, no one has found an analytical solution. This is equally true for electronic and nuclear-motion problems. It has therefore proven essential to develop and efficiently implement mathematical methods which can provide approximate solutions to such eigenvalue equations. Two methods are widely used in this context- the variational method and perturbation theory. These tools, whose use permeates virtually all areas of theoretical chemistry, are briefly outlined here, and the details of perturbation theory are amplified in Appendix D. 

Davidsou-Fletcher-Powell (DFP) a geometry optimization algorithm De Novo algorithms algorithms that apply artificial intelligence or rational techniques to solving chemical problems density functional theory (DFT) a computational method based on the total electron density... 

C. Boyars, "Sensitivity and Desensitization of Nitroglycerin," ia Proceedings of 2nd Symposium on Chemical Problems Connected with the Stability of... 

H. J. Reitsma, in J. Hansen ed. Symposium on Chemical Problems Connected with Stability ofiExplosives, Bastad, Sweden, 1979. 

Annual Proceedings of the Safety Seminars, Dept, of Defense, Explosive Safety Board, Washington, D.C. International symposia on explosives and closely related subjects are excellent sources of information, ie, international symposia on detonation symposia on combustion symposia on chemical problems connected with the stabiUty of explosives international pyrotechnics seminars symposia on compatibiUty of plastics and other materials with explosives, propellants, and pyrotechnics, and processing of explosives, propellants, and ingredients and symposia on explosives and pyrotechnics Mineral Industy Surveys, U.S. Bureau of Mines, Pittsburgh, Pa. Periodic pubhcations dedicated primarily to explosive studies in Propellants and Explosives Journal of Ha yardous Materials, and apparent consumption of industrial explosives and blasting agents in the United States. 

Belarusian State University, Research Institute for Physical Chemical Problems, 220050 Leningradskaya st.l4, Minsk, Belarus, egorvv bsu.by... 

Belarusian State University Research Institute for Physical Chemical Problems ... 

Neglect of electrons means that molecular mechanics methods cannot treat chemical problems where electronic effects predominate. For example, they cannot describe processes which involve bond formation or bond breaking. Molecular properties which depend on subtle electronic details are also not reproducible by molecular mechanics methods. 

Experimental research chemists with little or no experience with computational chemistry may use this work as an introduction to electronic structure calculations. They will discover how electronic structure theory can be used as an adjunct to their experimental research to provide new insights into chemical problems. 

Part 3, Applications, discusses electronic structure calculations in the context of real-life research situations, focusing on how it can be used to illuminate a variety of chemical problems. 

Part 3, Applications, begins with Chapter 8, Studying Chemical Reactions and Reactivity, which discusses using electronic structure theory to investigate chemical problems. It includes consideration of reaction path features to investigate the routes between transition structures and the equilibrium structures they connect on the reaction s potential energy surface. 

Non-electrolytic sources of hydrogen have also been studied. The chemical problem is how to transfer the correct amount of free energy to a water molecule in order to decompose it. In the last few years about I0(X)0 such thermochemical water-splitting cycles have been identified, most of them with the help of computers, though it is significant that the most promising ones were discovered first by the intuition of chemists. 

The ready reduction of Sn02 by glowing coals accounts for the knowledge of Sn and its alloys in the ancient world. Modem technology uses a reverberatory furnace at 1200-1300°. The main chemical problem in reducing Sn02 comes... 

If Dirac was warning us that solution of the equations of quantum mechanics was going to be horrendous for everyday chemical problems, then history has proved him right. Fifty years on from there, Enrico dementi (1973) saw things differently ... 

The potential due to a point charge falls off as 1 /r, the potential due to a dipole falls off as /r, and so on, and the expectation in that the series will quickly terminate for chemical problems. 

The aim of the series is to present the latest fundamental material for research chemists, lecturers and students across the breadth of the subject, reaching into the various applications of theoretical techniques and modelling. The series concentrates on teaching the fundamentals of chemical structure, symmetry, bonding, reactivity, reaction mechanism, solid-state chemistry and applications in molecular modelling. It will emphasize the transfer of theoretical ideas and results to practical situations so as to demonstrate the role of theory in the solution of chemical problems in the laboratory and in industry. 

Joining one metal to itself or to another has frequently presented many metallurgical and chemical problems. For a number of years palladium-containing brazing alloys have found widespread applications, as they offer several advantages over other conventionally used materials ... 

The major chemical problem met in ion-exchange practice is the fouling or poisoning of the anion resins by organic matter. The various counter measures deployed include pre-flocculation, oxidation of the organic material, the use of specially developed resins, and treatment of the fouled resins by brine and/or hypochlorite. 

This short book is intended for students who lack confidence and/or competency in the essential mathematical skills necessary to survive in general chemistry. Each chapter focuses on a specific type of skill and has worked-out examples to show how these skills translate to chemical problem solving. 

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