Chemical concept

Furthermore, here we emphasize the chemical concepts and aspects in chemoin-formatics. We had to refrain from introducing those aspects that are more concerned with the informatics side, such as... 

Specinfo, from Chemical Concepts, is a factual database information system for spectroscopic data with more than 660000 digital spectra of 150000 associated structures [24], The database covers nuclear magnetic resonance spectra ( H-, C-, N-, O-, F-, P-NMR), infrared spectra (IR), and mass spectra (MS). In addition, experimental conditions (instrument, solvent, temperature), coupling constants, relaxation time, and bibliographic data are included. The data is cross-linked to CAS Registry, Beilstein, and NUMERIGUIDE. 

Speclnfo Chemical Concepts GmbH, Germany spectral data nu- meric, struc- ture 150000 subst., 80000 C-NMR, 850 N-NMR, 670 O-NMR, 1750 F-NMR, 2000 P-NMR, 17000IR, 65 000 MS Chemical Concepts GmbH online periodi- cally www.chemicaJ- conctpts.com/ products.htm... 

Commercial implementations of this general approach are ACD/I-Lab [36], Specinfo (Chemical Concepts) [37], WINNMR (Bruker), and KnowItAll (Bio-Rad) [38]. Figure 10.2-3 shows the workspace generated by ACD/I-Lab after predicting a H NMR spectrum. ACD calculations are currently based on over 1 200 000 experimental chemical shifts and 320 000 experimental coupling constants [36]. 

H.F. Schaefer III, P. R. Schreiner (Eds.), John Wiley Sons, Chichester, 1998, pp. 1845-1857. pq ACD/lLab - Interactive Laboratory, http //wwiv.acdlab5.com/ilab p7] Chemical Concepts (Whey-VCH), http //www.chemicalconcepts.com p ] Bio-Rad Laboratories, Inc., kttp //wmv.bio-rad.com P9] M. Tusar, L. Tusar, S. Bohanec,... 

The course instructors or professors have not tried to intentionally deceive their students. Most individuals cannot grasp the full depth and detail of any chemical concept the first time that it is presented to them. It has been found that most people learn complex subjects best when first given a basic description of the concepts and then left to develop a more detailed understanding over time. Despite the best elforts of educators, a few misconceptions are at times possibly introduced in the attempt to simplify complex material for freshmen students. The part of this process that perpetuates any confusion is the fact that texts and instructors alike often do not acknowledge the simplifications being presented. 

SPECINEO Chemical Concepts GmbH spectral data for a representative section of organic chemistry... 

A PC-based H-nmr database, which includes fiiU spectmm search capabiHty, is being constmcted by the Toyohashi University of Technology (67). Speclnfo, owned by Chemical Concepts, offers a 150,000 spectra Hbrary and database system for mainframe computers, which includes H, F, "O,... 

Speclnfo Chemical Concepts 13/ C-nmr 100,000 13,000 STN (vendor) Bremser-BASE collection Nn th, Munich... 

CA File, CAPlus, CA Previews STN Chemical Abstracts Service international, chemistry limited bibhographic data comprehensive English language abstracts deep indexing of chemical concepts stmcture-searchable compound registry chemical stmcture drawings... 

Two resin systems based on this chemical concept are commercially available from Shell Chemical Company/Technochemie under the COMPIMIDE trademark COMPIMIDE 183 (34) [98723-11-2], for use in printed circuit boards, and COMPIMIDE 796 [106856-59-1], as a resin for low pressure autoclave mol ding (35). Typical properties of COMPIMIDE 183 glass fabric—PCB laminates are provided in Table 8. COMPIMIDE 183 offers a combination of advantageous properties, such as a high glass transition temperature, low expansion coefficient, and flame resistance without bromine compound additives. 

Some of the solvent assignments seem capricious, such as CCU in ARP, CF3COOH in AD, and CHCI3 and CftHjNHi in MISC. From one point of view, it is a triumph that a purely statistical treatment, devoid of chemical experience or intuition, can generate a scheme more or less in accord with chemical concepts. However, it does not seem to be superior to the simple application of chemical ideas. 

In standard quantum-mechanical molecular structure calculations, we normally work with a set of nuclear-centred atomic orbitals Xi< Xi CTOs are a good choice for the if only because of the ease of integral evaluation. Procedures such as HF-LCAO then express the molecular electronic wavefunction in terms of these basis functions and at first sight the resulting HF-LCAO orbitals are delocalized over regions of molecules. It is often thought desirable to have a simple ab initio method that can correlate with chemical concepts such as bonds, lone pairs and inner shells. A theorem due to Fock (1930) enables one to transform the HF-LCAOs into localized orbitals that often have the desired spatial properties. 

The total energy, for example, may be written as a sum of atomic energies, and these atomic energies are again almost constant for the same structural units in different molecules. The atomic basins are probably the closest quantum mechanical analogy to the chemical concepts of atoms within a molecule. 

Hummel Infrared Standards Surfactants, Electronic Data, Chemical Concepts, Weinheim, 1994. 

Thus, two interpretations based on two different concepts of the effect of temperature on dipole orientation have been put forward. The two views clash with each other on physical as well as chemical grounds. However, the view based on the correlation of Fig. 25 introduces chemical concepts that are absent in the other, which ignores some definite facts. For instance, although a value for dEa=0/dT is not available for Ga, the temperature coefficient of C is apparently small.905 Ga is universally recognized as a strongly hydrophilic metal. Therefore, according to the simple model of up-and-down dipoles, the effect of temperature should be major, which is in fact not the case. 

This chapter applies the physical chemistry taught in the first year of undergraduate chemistry to chemical problems in the natural environment and introduces key chemical concepts to use and keep in mind for the rest of this book. The material in this chapter is especially important to consider when utilizing the modeling techniques presented in Chapter 4. 

There are two principal chemical concepts we will cover that are important for studying the natural environment. The first is thermodynamics, which describes whether a system is at equilibrium or if it can spontaneously change by undergoing chemical reaction. We review the main first principles and extend the discussion to electrochemistry. The second main concept is how fast chemical reactions take place if they start. This study of the rate of chemical change is called chemical kinetics. We examine selected natural systems in which the rate of change helps determine the state of the system. Finally, we briefly go over some natural examples where both thermodynamic and kinetic factors are important. This brief chapter cannot provide the depth of treatment found in a textbook fully devoted to these physical chemical subjects. Those who wish a more detailed discussion of these concepts might turn to one of the following texts Atkins (1994), Levine (1995), Alberty and Silbey (1997). 

Be aware of, anticipate and avoid the Normal Chemistiy Education reflex, i.e. the introduction into design and teaching of more chemical concepts than are needed for the chosen curriculum emphasis. Alternatively, deal in time with any difficulties related to the dominant school chemistiy curriculum at all stages of development, starting with the initial vision and the first design of the curriculum. 

Devetak, L, Urbancic, K., Grm, W., Krnel, D., Glazar, S. (2004). Submicroscopic representations as a tool for evaluating students chemical conceptions. Acta Chimica Slovenica, 51, 799-814. 

Krajcik, J. S. (1991). Developing students understanding of chemical concepts. In S. M. Glynn, R. H. Yeany, B. K. Britton (Eds.), The psychology of learning science (pp. 117-147). Hillsdale, NJ Eawrence Erlbaum Associates. 

Rotgieter, M., Davidowitz, B., Blom, B. (2005). Chemical concepts inventory of first year students at two tertiary institutions in South Africa. In the conference proceedings of the 13th Annual Conference Southern African Association of Research in Mathematics, Science and Technology Education. Namibia, pp. 664-675. 

The content of a curriculum must be functional when dealing with societal activities necessary chemical concepts, skills and attitudes with respect to macro-micro thinking must be included. This can be derived from representative authentic tasks. The content of the curriculum should be considered as a chemical toolbox. The traditional content of the present chemistry curriculum, such as the stmcture of atoms, ionic theoiy, fundamental acid-base calculations, are not necessarily part of the chemical toolbox when addressing chemical and technological tasks. The validity of the toolbox (philosophical substmcture) is determined by the representative practices and tasks related to chemistry (cf need-to-know principle in context-based approaches). 

Ever since Johnstone (1993) addressed the three levels of chemistry (symbolic, macro, and microscopic, called submicro currently), many studies have investigated how multimedia could support the constraction, development, and evaluation of students mental representations of chemistiy at the three levels. The studies in the previous chapters mention that the representations of the macro-submicro-symbolic relationship play important roles in chemical concept learning. 

Russell, J. W., Kozma, R. B., Jones, T., Wykoff, J., Marx, N., Davis, J. (1997). Use of simultaneous-synchronized macroscopic, microscopic, and symbolic representations to enhance the teaching and learning of chemical concepts. Journal of Chemical Education, 74(3), 330-334. 

The necessity of the statistical approach has to be stressed once more. Any statement in this topic has a definitely statistical character and is valid only with a certain probability and in certain range of validity, limited as to the structural conditions and as to the temperature region. In fact, all chemical conceptions can break dovra when the temperature is changed too much. The isokinetic relationship, when significantly proved, can help in defining the term reaction series it can be considered a necessary but not sufficient condition of a common reaction mechanism and in any case is a necessary presumption for any linear free energy relationship. Hence, it does not at all detract from kinetic measurements at different temperatures on the contrary, it gives them still more importance. 

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