DISCUSSION OF AUXILIARY DATA SELECTION

Note that the values in Table IV-1 and Table IV-2 may contain more digits than those listed in either [89COX/WAG] or in the discussions on auxiliary data selection of NEA-TDB reviews, because the data in the present chapter are retrieved directly from the computerised data base and rounded to three digits after the decimal point throughout. 

Chapter IV contains, for auxiliary compounds and complexes that do not contain selenium, a table of the thermodynamic data for individual species (Table IV-1) and a table of reaction data (Table IV-2). Most of these values are the CODATA Key Values [89COX/WAG]. The selection of the remaining auxiliary data is discussed in [92GRE/FUG], and other preceding volumes of this series. As just mentioned, Appendix E contains a table. Table E-1, of the adopted thermodynamic data for individual selenium compounds calculated with auxiliary data not contained in Chapter IV. The non-TDB auxiliary data, usually from [82WAG/EVA], are presented in Table E-2 and the evaluations are discussed in Chapter V and Appendix A. 

The enthalpies of formation reported in [68TAN/GOR] are -7401.1 and - 1978.2 kJ-moP respectively. An analysis of the evaluation there shows that the difference from the present results is mainly caused by the different selections of the standard enthalpy of formation of BaSe04(cr), see Appendix A. The values calculated by the review are adopted, although the experimental difficulties with highly hydrated salts are well known. This matter is further discussed in Appendix A, [68TAN/GOR]. Since the calculation of the formation enthalpies from the experiments involved non-TDB auxiliary data, they are included in Appendix E. 

Table E-l lists the values of the properties for a large number of selenium species which have been evaluated using auxiliary data (themselves listed in Table E-2) that have not been critically reviewed following the NEA-TDB Guidelines. The original experimental sources reporting the thermodynamic cycles leading to the values listed in Table E-l have been submitted to a critical review following the NEA-TDB Guidelines, as discussed in Chapter V, and have been found to be acceptable according to such criteria. While the data contained in Tables E-l and E-2 are not selected values, it is considered that they are the best values currently available, and further critical reviews would benefit from the information they provide.

Ibis chapter will discuss various reliability issues. The discussion will kept at a philosophical level rather than getting into a statistical analy The statistical analysis is best left to others equipped with the training, toi and the data. Hopefully, this material will give the reader some comn sense insight into the various considerations involved in the selection applicadon of reliable compressors, their drivers, and auxiliary systems. 

The Ivanov reaction (Scheme 5.1) is an early example of an aldol addition reaction that proceeded selectively. There has been an enormous amount of work done in this area, and only a small amount of the developmental work will be covered here. A large number of chiral auxiliaries and catalysts have been developed, but we will concentrate on only a few, which suffice to provide an understanding of the structural factors that influence selectivity. The transition structures presented in the following discussion are oversimplifications, in that the enolate and its metal are represented as monomers, when in fact they are not [2-4]. On the other hand, much of the available data may be rationalized on the basis of these structures, so the simplification is justified in the absence of detailed structural and configurational information about mixed aggregate transition structures. 

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