Broad applicability

Another, probably more broadly applicable, technique is to represent a chemical compound by some of its properties. Figure 8-15 is an extension of Figure 8-1 and shows that when no structure descriptors can be derived because the structure is not known, thcji a compound can be represented by a second property (2) or. better, a series of properties, in order to predict the property 1 of interest. 

The function/c is a smoothing function with the value 1 up to some distance Yy (typically chosen to include just the first neighbour shell) and then smoothly tapers to zero at the cutoff distance, by is the bond-order term, which incorporates an angular term dependent upon the bond angle 6yk- The Tersoff pofenfial is more broadly applicable than the Stillinger-Weber potential, but does contain more parameters. 

A catalytic enantio- and diastereoselective dihydroxylation procedure without the assistance of a directing functional group (like the allylic alcohol group in the Sharpless epox-idation) has also been developed by K.B. Sharpless (E.N. Jacobsen, 1988 H.-L. Kwong, 1990 B.M. Kim, 1990 H. Waldmann, 1992). It uses osmium tetroxide as a catalytic oxidant (as little as 20 ppm to date) and two readily available cinchona alkaloid diastereomeis, namely the 4-chlorobenzoate esters or bulky aryl ethers of dihydroquinine and dihydroquinidine (cf. p. 290% as stereosteering reagents (structures of the Os complexes see R.M. Pearlstein, 1990). The transformation lacks the high asymmetric inductions of the Sharpless epoxidation, but it is broadly applicable and insensitive to air and water. Further improvements are to be expected. 

Thionyl chloride and phosphorus tribromide are specialized reagents used to bring about particular functional group transformations For this reason we won t present the mechanisms by which they convert alcohols to alkyl halides but instead will limit our selves to those mechanisms that have broad applicability and enhance our knowledge of fundamental principles In those instances you will find that a mechanistic understand mg IS of great help m organizing the reaction types of organic chemistry... 

Although the present chapter includes the usual collection of topics designed to acquaint us with a particular class of compounds its central theme is a fundamental reaction type nucleophilic addition to carbonyl groups The principles of nucleophilic addition to aide hydes and ketones developed here will be seen to have broad applicability m later chap ters when transformations of various derivatives of carboxylic acids are discussed... 

There are several types of nomenclature systems that are recognized. Which type to use is sometimes obvious from the nature of the compound. Substitutive nomenclature, in general, is preferred because of its broad applicability, but radicofunctional, additive, and replacement nomenclature systems are convenient in certain situations. 

Nitrile mbber finds broad application in industry because of its excellent resistance to oil and chemicals, its good flexibility at low temperatures, high abrasion and heat resistance (up to 120°C), and good mechanical properties. Nitrile mbber consists of butadiene—acrylonitrile copolymers with an acrylonitrile content ranging from 15 to 45% (see Elastomers, SYNTHETIC, NITRILE RUBBER). In addition to the traditional applications of nitrile mbber for hoses, gaskets, seals, and oil well equipment, new applications have emerged with the development of nitrile mbber blends with poly(vinyl chloride) (PVC). These blends combine the chemical resistance and low temperature flexibility characteristics of nitrile mbber with the stability and ozone resistance of PVC. This has greatly expanded the use of nitrile mbber in outdoor applications for hoses, belts, and cable jackets, where ozone resistance is necessary. 

The synthesis of 2-hydroxycyclobutanone was chosen as a model for the use of a trapping agent because diethyl succinate was the most accessible of 1,2-diesters and because the hydrolysis step for this compound is more difficult than most. Procedures developed for succinoin have been found broadly applicable in preparation of other sensitive acy loins. 

Both types of tapes have found broad applicability throughout the industry. Some of the major uses for single-coated tapes include packaging, masking, electrical, office and medical related applications. Double-coated tapes are quite commonly used in assembly type of operations. 

Resins currently available exhibit a range of selectivity s and thus have broad application. As an example, for a strong acid resin, the relative preference for divalent calcium ions (Ca ) over divalent copper ions (Cu ) is approximately 1.5... 

It is not surprising that multistep synthesis of challenging and complex target molecules is an engine for the discovery of new synthetic principles and novel methodology which may have very broad application. Just as each component of structural complexity can signal a strategy for synthesis, each obstacle to the realization of a chemical synthesis presents an opportunity for scientific discovery. 

Study of transverse shearing stress effects is divided in two parts. First, some exact elasticity solutions for composite laminates in cylindrical bending are examined. These solutions are limited in their applicability to practical problems but are extremely useful as checl oints for more broadly applicable approximate theories. Second, various approximations for treatment of transverse shearing stresses in plate theory are discussed. 

There are no clearly discernable, broadly applicable, correlations between the 6-inch and 1 S-inch deflagration and detonation experiments. Therefore, comparisons were done on a parameter-byparameter basis. However, comparisons of data taken during experiments with the two pipe sizes reveal that enough scale-related differences exist that interpolation between the two scales for an intermediate size should be done only where conditions are very similar. Then, overpressure and specific impulse can be estimated based on L/D. 

This chapter describes the use of three commercially available SEC column types for the characterization of nonionic, anionic, and cationic, synthetic water-soluble polymers. These include TSK-PW, Synchropak, and CATSEC columns. Specific examples and experimental procedures are discussed for each type of column. Elowever, the major emphasis is on the use of TSK-PW columns due to their broad applicability for a variety of water-soluble polymers. 

The world of science is a deliciously excruciating blend of the general and the specific. There are general laws and rules of broad application (E=mc, opposite charges attract), but the precise way in which these laws combine in any particular instance always depends on the specifics of the situation. 

Because of the mild reaction conditions, and its broad applicability, the Knoevenagel reaction is an important method for the synthesis of a ,/3-unsaturated carboxylic acids. Comparable methods are the Reformatsky reaction, the Perkin reaction, as well as the Claisen ester condensation. The Knoevenagel reaction is of greater versatility however the Reformatsky reaction permits the preparation of a ,/3-unsaturated carboxylic acids that are branched in a-position. 

Ideal chiral selectors to be used in preparative separations should fulfil certain properties. In general, high loadability is one of the most interesting features for large-scale purposes, but high enantioselectivity, high chemical stability, low cost and broad applicability are also very important issues. None of these properties can be considered independently. 

Although very efficient, the broad application of the direct preparation is restricted due to the limited number of pure starting enantiomers. The design of a multistep process that includes asymmetric synthesis is cumbersome and the development costs may be quite high. This approach is likely best suited for the multi-ton scale production of commodity enantiomers such as the drugs ibuprofen, naproxen, atenolol, and albuterol. However, even the best asymmetric syntheses do not lead to products in an enantiomerically pure state (100 % enantiomeric excess). Typically, the product is enriched to a certain degree with one enantiomer. Therefore, an additional purification step may be needed to achieve the required enantiopurity. 

To demonstrate the excellent correlation (r- = 0.99) between the luminance of the images and molecular diversity, we plotted the luminance values of the map versus the mean similarity values of data sets (Fig. 4-13). From this plot, a scoring scheme for the classification of CSPs from specific to broad application range can be well established Crownpak CR > Pirkle DNBPG > Whelk > Chiralpak AD > Chiralcel OD. 

Cole and Davidson s continuous distribution of correlation times [9] has found broad application in the interpretation of relaxation data of viscous liquids and glassy solids. The corresponding spectral density is ... 

An example of how information from fragmentation patterns can be used to solve structural problems is given in Worked Example 12.1. This example is a simple one, but the principles used are broadly applicable for organic structure determination by mass spectrometry. We ll see in the next section and in later chapters that specific functional groups, such as alcohols, ketones, aldehydes, and amines, show specific kinds of mass spectral fragmentations that can be interpreted to provide structural information. 

According to the Hiickel criteria for aromaticity, a molecule must be cyclic, conjugated (that is, be nearly planar and have ap orbital on each carbon) and have 4n + 2 tt electrons. Nothing in this definition says that the number of p orbitals and the number of nr elections in those orbitals must be the same. In fact, they can he different. The 4n + 2 rule is broadly applicable to many kinds of molecules and ions, not just to neutral hydrocarbons. For example, both the cydopentadienyl anion and the cycloheptatrienyl cation are aromatic. 

The very extensive changes that have taken place over recent years and the broad application to organic separations necessitated a major revision of Part C covering solvent extraction and chromatographic procedures. These particular... 

A rather broadly applicable method leading to products which can be further modified starts from 3,8-diaryl-l,2-diazacycloocta-2,8-dienes 4.23,24 With /V-bromosuccinimide dihalogenation occurs which, after a double dehydrohalogenation, gives 3,8-diphenyl-1,2-di-azocine (5 Ar = Ph, X = H) in low yield. The reaction with sulfuryl chloride to give tetra-... 

The sulfur ylide-mediated epoxidation of aldehydes has been thoroughly investigated [70, 71]. The chiral sulfur ylides reported by Aggarwal have been most broadly applicable, and a catalytic, asymmetric process yielding aromatic transepoxides has been developed [72]. In this process, the sulfur ylides are produced in situ from diazo compounds, generated in turn from tosylhydrazone salts (Scheme 9.15) [73],... 

The great interest in the methods of modification of polymers which has increased during the past decades does not result only from the practical significance of this problem, but also from the fact that, due to the broad application of these methods, potentialities of the modem chemistry of polymers have expanded considerably and it has become possible to create polymers with required properties. 

Copolymers of AN with diene monomers and, in particular, with butadiene and isoprene, deserve special attention. These copolymers with a predominating content of monomeric units of dienes are known to have been produced in the form of rubbers for a long time and are finding a broad application in various branches of technology. 

---