Failed Reactions database

The reasons for this lack of work are manifold The problem is quite complex and difficult to tackle. The information in reaction databases is inherently biased only known reactions, no reactions that failed, are stored. However, any learning also needs information on situations where a certain event will not happen or will fad. The quality of information stored in reaction databases often leaves something to be desired reaction equations are incomplete, certain detads on a reaction are often incomplete or missing, the coverage of the reaction space is not homogeneous, etc. Nevertheless, the challenge is there and the merits of success should be great ... 

Obviously, use of such databases often fails in case of interaction between additives. As an example we mention additive/antistat interaction in PP, as observed by Dieckmann et al. [166], In this case analysis and performance data demonstrate chemical interaction between glycerol esters and acid neutralisers. This phenomenon is pronounced when the additive is a strong base, like synthetic hydrotalcite, or a metal carboxylate. Similar problems may arise after ageing of a polymer. A common request in a technical support analytical laboratory is to analyse the additives in a sample that has prematurely failed in an exposure test, when at best an unexposed control sample is available. Under some circumstances, heat or light exposure may have transformed the additive into other products. Reaction product identification then usually requires a general library of their spectroscopic or mass spectrometric profiles. For example, Bell et al. [167] have focused attention on the degradation of light stabilisers and antioxidants... 

Despite elaims in some books and reviews, an extensive literature search failed to find any experimental or clinical evidence for an alleged disulfiram-like reaction between alcohol and nitrofurantoin. A study in healthy subjects failed to demonstrate any such interaction and a survey of the reports in the manufacturer s database also failed to find good evidence for alcohol intolerance. It is concluded that this interaction is erroneous. ... 

During batch processing of databases, the program recognises potentially poor solutions. With nearly 90,000 reactions, it would be prohibitively expensive to examine all of them while searching for the 1-5 per cent which failed. 

However, if your reactions contain aqueous species, the Maier-KeUey formulation does not apply, and a, b, and c values are not available because they don t work. The Cp of HC ag) shown in Figure 9.8 is fairly typical of aqueous species, which are convex upward and have a maximum somewhere around 50-100 °C (see also Figures 10.12 15.10). If the aqueous and mineral species in your reaction are all in the supcrt92 database, you should use that program, which incorporates the HKF model, introduced in 13.6.2, and discussed more fully in Chapter 15. Failing that you must estimate your equilibrium constant as a function of T and P, and there are only a couple of ways of doing that. 

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