The Abstracts

Chemical Abstracts (CA) is the world s best-known and most comprehensive reference periodical for all areas of chemistry and chemical engineering. It consists of two parts the abstracts and the indexes. 

Each publication containing new information of importance to chemistry or chemical engineering is abstracted in Chemical Abstracts. The individual abstracts are divided into two parts the first part comprises all the important bibliographic particulars, the second the abstract text. The latter is organized as follows the first sentence summarizes the new research results reported in the publication. The rest of the abstract highlights the following information  

The terminology, e.g. the substance names, employed in the abstract is taken over from the original document and does not necessarily correspond to the systematic nomenclature of the Chemical Abstracts Service. 

The Chemical Abstracts Service divides the original publications into seven different categories  

Congress and symposia proceedings and edited collections of the papers presented, 

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In Chapter 2 we discuss briefly the thermodynamic functions whereby the abstract fugacities are related to the measurable, real quantities temperature, pressure, and composition. This formulation is then given more completely in Chapters 3 and 4, which present detailed material on vapor-phase and liquid-phase fugacities, respectively. 

Finally, it should also be clear that ER reactions do not necessarily yield a gas-phase product. The new molecule may be trapped on the surface. There is evidence for an ER mechanism in the addition of incident Ft atoms to ethylene and benzene on Cii(l 11) [91], and in the abstraction of Ft atoms from cyclohexane by incident D atoms [92], and the direct addition of Ft atoms to CO on Rii(OOl) [93]. 

At low energies the abstraction process dominates and at higher energies the exchange mechanism becomes more important. The cross-sections for the two processes crossing at 10 eV. The END calculations yield absolute cross-sections that show the same trend as the experimentally determined relative cross-sections for the two processes. The theory predicts that a substantial fraction of the abstraction product NHjD, which are excited above the dissociation threshold for an N—H bond actually dissociates to NH2D" + H or NH3 during the almost 50-ps travel from the collision chamber to the detector, and thus affects the measured relative cross-sections of the two processes. 

The conical parameters describe the topography of the conical intersection. The directions for g, h, and h relate the abstract x, y, z directions to actual molecular... 

If the query provides thousands of hits, the analyze features are particularly advantageous. One method is to analyze the results by any of the criteria that arc listed, c.g., by language (default), author names, journals, puhlication year, and so on. If one specification is selected and the choice is modified, the hit list will be updated. A more specific analysis is available with the Refine" option. where the user has the opportunity to choose one of eight criteria (including the search topics above) with further individual input. Several refinements of the hit list can reduce the result to a concise list of literature. To read the abstract of an article, the microscope button (to the right of the citation) has to be pressed (Figure 5-15). 

The removal of the two alkyl groups comprises the two primai y steps, the abstraction of the ethyl group being the dominant one. These products show up first, as can be seen on the left-hand side of Figure 10.3-14, It can also be seen that it is expected that after one year an apprceiable amount of s-triazine eom-pounds will still be found in the soil. 

British Chemicai Abstracts. These were commenced in the year 1871 and were included in the Journal of the Chemical Society. In 1926 the abstracting was taken over by the Bureau of Chemical Abstracts abstracts were then published in two parts Part A Pure Chemistry (formerly issued by the Chemical Society) and Part B Applied Chemistry ... 

Chemical Abstracts. These were commenced by the American Chemical Society in 1907. The abstracts are very comprehensive (particularly in recent years) from the standpoint of subject matter and journals covered. Four decennial indexes have appeared—1917, 1927, 1937 and 1947—and these are widely used for locating information pub lished during the period 1907-1947. The annual indexes cover the period 1948 to date. 

Chemisches Zentrallblatt. This periodical, published by the Deutsche Chemische Gesellschaft to 1945, originated in 1830 as the Phar-maceutisches Zentrallblatt, the name was changed in 1850 to Chemisches-Pharmaceutisches Centrallblatt, again in 1856 to Chemisches Centrall-blatt, and in 1907 to Chemisches Zentrallblatt. Collective indexes are available from 1870. The abstracts, particularly for organic chemistry, are very detailed to 1939. 

If one of the groups R is Ph or SR, the abstraction of the second proton is much faster. Allenes give the same dilithium compounds as their acetylenic isomers . 

The mass-spectrometric fragmentation of 2-aminothiazole-3-oxides is characterized by the abstraction of O and OH out of the molecule ion. Variations observed in the mass spectra suggest an equilibrium between tautomers 354a and 354b in the gas phase (Scheme 203). 

With the exception of the nuclear amination of 4-methylthiazole by sodium amide (341, 346) the main reactions of nucleophiles with thiazole and its simple alkyl or aryl derivatives involve the abstraction of a ring or substituent proton by a strongly basic nucleophile followed by the addition of an electrophile to the intermediate. Nucleophilic substitution of halogens is discussed in Chapter V. 

A primary isotope effect /ch/ d of 6.4 (extrapolated for 35 C) is observed for the metalation and the methylation of 171b when the C-5 position is deuterated. This value is in excellent agreement with the primary isotope effect of 6.6 reported for the metalation of thiophene (392) and it confirms that the rate-determining step is the abstraction by the base of the acidic proton. 

Substitution Reactions. Substitution reactions can occur on the methyl group by free-radical attack. The abstraction of an aHybc hydrogen is the most favored reaction, followed by addition to that position. 

In order for the cyclooxygenase to function, a source of hydroperoxide (R—O—O—H) appears to be required. The hydroperoxide oxidizes a heme prosthetic group at the peroxidase active site of PGH synthase. This in turn leads to the oxidation of a tyrosine residue producing a tyrosine radical which is apparendy involved in the abstraction of the 13-pro-(5)-hydrogen of AA (25). The cyclooxygenase is inactivated during catalysis by the nonproductive breakdown of an active enzyme intermediate. This suicide inactivation occurs, on average, every 1400 catalytic turnovers. 

Apphcations of the thermodynamic postulates necessarily involve the abstract quantities internal energy and entropy The solution of any problem in apphed thermodynamics is therefore found through these quantities. 

If the spectra of the k relevant components are known, the abstract matrices can be transformed into interpretable spectra and concentration matrices, respectively, and as a final result, one obtains the required component depth profile. If one or more of the spectra of the k relevant components are not known, a quantified component depth profile cannot be constructed. 

Radical substitution reactions by iodine are not practical because the abstraction of hydrogen from hydrocarbons by iodine is endothermic, even for stable radicals. The enthalpy of the overall reaction is also slightly endothermic. Thus, because of both the kinetic problem excluding a chain reaction and an unfavorable equilibrium constant for substitution, iodination cannot proceed by a radical-chain mechanism. 

The efficiency of reduction of benzophenone derivatives is greatly diminished when an ortho alkyl substituent is present because a new photoreaction, intramolecular hydrogen-atom abstraction, then becomes the dominant process. The abstraction takes place from the benzylic position on the adjacent alkyl chain, giving an unstable enol that can revert to the original benzophenone without photoreduction. This process is known as photoenolization Photoenolization can be detected, even though no net transformation of the reactant occurs, by photolysis in deuterated hydroxylic solvents. The proton of the enolic hydroxyl is rapidly exchanged with solvent, so deuterium is introduced at the benzylic position. Deuterium is also introduced if the enol is protonated at the benzylic carbon by solvent ... 

Consider the effect of the abstraction of individual solvents on consequent solute concentration. Let the volume fraction of ethanol, ethyl acetate and n-hexane in the original mobile phase mixture be (ae), (cxea) and (an), respectively. If a given solute is placed on the TLC plate at a concentration (cs) then, assuming for the... 

Other key issues include the selection ol the appropriate model and the abstraction of the physical problem for that model. 

In these CRGT plants, efficiency increase is obtained mainly through the abstraction of more heat from the exhaust gases rather than reduction in combustion irreversibility. 

According to a detailed mechanistic study, the first step is the abstraction of the relatively acidic hydrazone proton (93- 97). This is followed by hydride attack on the trigonal carbon of the C=N bond, mainly from the a-side at C-3, together with the concomitant loss of the tosylate anion (97 -> 98). Expulsion of nitrogen from the resulting intermediate (98) yields a fairly insoluble anion-metal complex (99) which upon decomposition with water provides the methylene derivative (100). 

A mechanism which is consistent with the various experimental results for olefin formation involves the initial abstraction of the hydrazone proton (103->106) In this case, however, expulsion of the tosylate anion is associated with the abstraction of a second hydrogen from C-16 instead of hydride attack on the C=N bond (compare 97 98 and 106 107). Ex-... 

This force field was developed primarily for protein and nucleic acid applications. It is a united atom force field, and there are many versions. Once again, you might like to see the Abstract of the original Paper. 

I am conscious that I have missed many sets of acronyms from my guided tour of the differential overlap models, and I will just tell you that MINDO, MINDO/1, MINDO/2 all appeared but have now been consigned to oblivion. With MINDO/3, Dewar thought that he had at last developed a reliable model for use by organic chemists. The abstract to the landmark MINDO/3 paper is terse ... 

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