Number chemical examples

CAS Number - Chemical Abstracts Service Registry Number A CAS (Chemical Abstracts Service) Registry Number is a unique identifier that tells you, for example, that aeetone and dimethyl ketone are actually the same substance. The Chemical Abstracts Service is a division of the American Chemical Society. OSHA only requires certain items on an MSDS and a CAS number is not one of them. However, authors of MSDS s are allowed to add additional information, such as the CAS number, if they desire. The numbers you see on trucks on the highway are not CAS Numbers, butU.S. Department of Transportation (DOT) codes, which are not necessarily specific to each chemical. Their aim is to assist emergency responders. 

The optical rotatory dispersion curves of steroidal ketones permit a distinction to be made between the conformations, and assignment of configuration is possible without resorting to chemical methods (see, e.g. ref. 36) which are often tedious. The axial halo ketone rule and, in the more general form, the octant rule summarize this principle and have revealed examples inconsistent with the theory of invariable axial attack in ketone bromination. 2-Methyl-3-ketones have been subjected to a particularly detailed analysis. There are a considerable number of examples where the products isolated from kinetically controlled brominations have the equatorial orientation. These results have been interpreted in terms of direct equatorial attack rather than initial formation of the axial boat form. 

A number of examples of the use of molten pyridinium chloride (mp 144 °C) in chemical synthesis are known, dating back to the 1940 s. Pyridinium chloride can act both as an acid and as a nucleophilic source of chloride. These properties are exploited in the deallcylation reactions of aromatic ethers [4]. An example involving the reaction of 2-methoxynaphthalene is given in Scheme 5.1-2 [16, 18], and a mechanistic explanation in Scheme 5.1-3 [18]. 

Some reductions with silanes have already been described in previous chapters (in Section 4.8 reaction of 356 to give 359 in Section 5.4 reaction of 121 to give 717, 718 to 719 in Section 12.1 reaction of 1790 to give 1791). Because of the many applications of such reductions with silanes in the chemical literature only a selected number of examples can be given in this chapter. 

In an ionic compound, each ion is an individual chemical species with its own set of oxidation numbers. For example, we treat ammonium nitrate, NH4 NO3, as NHq cations and NO3 anions. 

The rate is thus the number of collisions between A and B - a very large number - multiplied by the reaction probability, which may be a very small number. For example, if the energy barrier corresponds to 100 kj mol , the reaction probability is only 3.5 x lO l at 500 K. Hence, only a very small fraction of all collisions leads to product formation. In a way, a reaction is a rare event For examples of the application of collision theory see K.J. Laidler, Chemical Kinetics 3 Ed. (1987), Harper Row, New York. 

This chapter focuses on heterogeneous catalysis, which is most important in fine chemicals production. Table 3.1 presents a number of examples of catalysis in fine chemistry. These examples are divided in heterogeneously catalysed processes and homogeneously catalysed processes. A detailed treatment of heterogeneously catalysed processes for the production of fine chemicals is also given in the book edited by Sheldon and van Bekkum (2001). 

Downing et al. (1997) have reported a number of examples, including isomerization of 2,3-dimethyl-2,3-epoxide to methyl-rer/-butyl ketone, which is required for the production of photographic and crop-protection chemicals. 

Thus, we considered a number of examples of application of the sensor technique in experiments on heterogeneous recombination of active particles, pyrolysis and photolysis of chemical compounds in gas phase and on the surface of solids, such as oxides of metals and glasses. The above examples prove that, in a number of cases, compact detectors of free atoms and radicals allow one to reveal essential elements of the mechanisms of the processes under consideration. Moreover, this technique provides new experimental data, which cannot be obtained by other methods. Sensors can be used for investigations in both gas phase and adsorbed layers. This technique can also be used for studying several types of active particles. It allows one to determine specific features of distribution of the active particles along the reaction vessel. The above experiments demonstrate inhomogeneity of the reaction mixture for the specified processes and, consequently, inhomogeneity of the... 

The abbreviation log stands for logarithm. In mathematics, a logarithm is the power (also called an exponent) to which a number (called the base) has to be raised to get a particular number. In other words, it is the number of times the base (this is the mathematical base, not a chemical base) must be multiplied times itself to get a particular number. For example, if the base number is 10 and 1,000 is the number trying to be reached, the logarithm is 3 because 10 x 10 x 10 equals 1,000. Another way to look at this is to put the number 1,000 into scientific notation ... 

Hie possibility that a particle with energy Jess than the barrier height can penetrate is a quantum-mechanical phenomenon known as the tunnel effect. A number of examples are known in physics and chemistry. The problem illustrated here with a rectangular barrier was used by Eyring to estimate the rates of chemical reactions. ft forms the basis of what is known as the absolute reaction-rate theory. Another, more recent example is the inversion of the ammonia molecule, which was exploited in the ammonia maser - the fbiemnner of the laser (see Section 9.4,1). 

Proton nuclear magnetic resonance (NMR) chemical shifts of 1,2,3-thiadiazoles give another indication of the aromatic character of these compounds. Compiled in Table 4 are a number of examples of proton chemical shifts for ring-substituted 1,2,3-thiadiazoles. 

It is fortunate that we do not have to consider the dependent reactions. Given Nj secondary species, there are just Nj reactions with the basis, but (Nj — Nj )/2 reactions could be written among the secondary species. The formula for the latter number, for example, is the number of handshakes if everyone in a group shook everyone else s hand. This is practical at a small party, but impossible at a convention. In chemical systems with many hundreds of species, taking the dependent reactions into account might tax even the most powerful computers. 

Comments on some trends and on the Divides in the Periodic Table. It is clear that, on the basis also of the atomic structure of the different elements, the subdivision of the Periodic Table in blocks and the consideration of its groups and periods are fundamental reference tools in the description and classification of the properties and behaviour of the elements and in the definition of typical trends in such characteristics. Well-known chemical examples are the valence-electron numbers, the oxidation states, the general reactivity, etc. As far as the intermetallic reactivity is concerned, these aspects will be examined in detail in the various paragraphs of Chapter 5 where, for the different groups of metals, the alloying behaviour, its trend and periodicity will be discussed. A few more particular trends and classification criteria, which are especially relevant in specific positions of the Periodic Table, will be summarized here. 

Abstract This chapter describes a number of examples of kinetic isotope effects on chemical reactions of different types (simple gas phase reactions, Sn2 and E reactions in solution and in the gas phase, a and 3 secondary isotope effects, etc.). These examples are used to illustrate many aspects of the measurement, interpretation, and theoretical calculation of KIE s. The chapter concludes with an example of an harmonic semiclassical calculation of a kinetic isotope effect. 

The CNIC does not deny the right of a discoverer to propose a name for a new chemical element. However, the approved names of the elements should differ as little as possible in different languages the names should be based on practicality and prevailing usage and finally the choice of the name carries no implication at all about the priority of discovery. A number of examples of this last point will be seen in the element review. 

A research area in which obvious applications are to be found include the design of new catalysts and a number of examples have nowbeen reported of the catalysis of chemical reactions by designed folded polypeptides [11 -13]. So far, enzyme-like selectivities and efficiencies have not been achieved but, eventual-... 

The first part of this chapter (Section 15.2) discusses the value of and challenges involved in implementing NIR technology in the chemical industry. It also describes a process for successful process analyzer implementation. Similar issues as they relate to the pharmaceutical industry are covered in Chapter 2. The second part of this chapter (Section 15.3) gives a number of examples of actual NIR applications in the chemical industry, which serve both to illustrate the points from the first part and to demonstrate the range of applications for NIR technology. 

In addition to the CIEEL mechanism, peroxides and endoperoxides are key intermediates in a number of chemical and biological processes. There are a growing number of examples where ET to the 0-0 bond in these systems is accepted as an important step in their activity. For example, it is now generally agreed that the first step in the bioactivity of the recently discovered potent antimalarial, artemisinin, involves an ET from Fe-heme to the 0-0 bond, leading to fragmentation and a number of psytotoxic radical intermediates. " In contrast to the enormous amount of literature on the thermal and photochemical reactivity of peroxides, there is relatively little known about their ET chemistry. It is this lack of kinetic data on ET to peroxides and endoperoxides and the possible relationship of this data to Saveant s model for dissociative ET that initiated our own interest in this chemistry.22 23 2 - - - ... 

---