Principal properties

The principal advantages of anthraquinone dyes are brightness and good fastness properties, including lightfastness, but they are both expensive and tinctorially weak. However, they are still used to some extent, particularly for red and blue shades, because other dyes cannot provide the combination of properties offered by anthraquinone dyes, albeit at a price. Metallization would deteriorate the brightness and fastness properties, and there is no need to improve the lightfastness. Consequently, metallized anthraquinone dyes are of very little importance. 

Here comes the important point The variations of measured macroscopic molecular properties can reasonably be assumed to be reflections of variations of the intrinsic properties at the molecular level. Descriptors which depend on the same molecular property are most likely to be correlated to each other. The principal components describe the systematic variation of the descriptors over the set of compounds. Descriptors which are correlated to each other will be described by the same principal component. The principal component vectors are mutually orthogonal, and different component will therefore describe independent and uncorrelated variations of the descriptors. Hence, different components will portray a variation in the data due to different intrinsic properties. These intrinsic properties, which manifest themselves as a variation of the macroscopic descriptors, are called the principal properties.[3] 

The variation of the principal properties over the set of compounds is measured by the corresponding scores, fy. The important result of this is that we can now describe the systematic variation using fewer variables (the scores) than the K original descriptors. This is a considerable simplification without loss of systematic information. 

A graphic illustration of how the principal properties vary over the set of compounds is obtained by plotting the scores against each other, see Fig. 15.7. 

Such score plots provide a tool by which it is possible to select test compounds to ensure a desired variation of the intrinsic (principal) molecular properties. 

As principal components modelling is based on projections it can take any number of descriptors into account. Projections to principal components models offer a means of simultaneously considering the joint variation of all property descriptors. By means of the score values it is therefore possible to quantify the axes of the reaction space to describe the variation of substrates, reagent(s) and solvents. When there are more than one principal component to consider for each type of variation, the axes will be multidimensional. Quantification of the axes of the reaction space offers an opportunity to pay attention to all available back-ground information prior to selecting test compounds. 

To allow for a systematic search of the reaction space it is necessary to quantify the axes . One problem is that discrete variation will change a number of molecular properties. A change of a substituent in the substrate will alter several properties, e.g. electron distribution, steric concestion, lipophilicity, hydrogen bond ability, etc. It is such intrinsic properties of the molecule which determine its chemical behaviour. By the concept of principal properties it is possible to obtain quantitative measures of the intrinsic properties. The principal properties can therefore be used to quantify the axes of the reaction space. 

When a molecule takes part in a reaction, it is properties at the molecular level which determine its chemical behaviour. Such intrinsic properties cannot be measured directly, however. What can be measured are macroscopic molecular properties which are likely to be manifestations of the intrinsic properties. It is therefore reasonable to assume that we can use macroscopic properties as probes on intrinsic properties. Through physical chemical models it is sometimes possible to relate macroscopic properties to intrinsic properties. For instance 13C NMR shifts can be used to estimate electron densities on different carbon atoms in a molecule. It is reasonable to expect that macroscopic observable properties which depend on the same intrinsic property will be more or less correlated to each other. It is also likely that observed properties which depend on different intrinsic properties will not be strongly correlated. A few examples illustrate this In a homologous series of compounds, the melting points and the boiling points are correlated. They depend on the strengths of intermolecular forces. To some extent such forces are due to van der Waals interactions, and hence, it is reasonable to assume a correlation also to the molar mass. Another example is furnished by the rather fuzzy concept nucleophilicity . What is usually meant by this term is the ability to donate electron density to an electron-deficient site. A number of measurable properties are related to this intrinsic property, e.g. refractive index, basicity as measured by pK, ionization potential, HOMO-LUMO energies, n — n  

Organic chemistry is often described in terms of functional groups. Compounds are naturally grouped into classes which share a common functional group. Synthetic reactions usually involve transformations due to the presence of specific functionalities. Within a class of functionally related compounds, the compounds are in some respect similar to each other and it is reasonable to assume that a gradual variation of measured properties corresponds to a gradual variation of the intrinsic molecular properties. 

Instrumental methods in chemistry make it possible to characterize any chemical compound by a very large number of different kind of measurements. Such data can be called observables. Examples are provided by Spectroscopy (absorbtions in IR, NMR, UV, ESCA. ..) chromatography (retentions in TLC, HPLC, GLC. ..) thermodynamics (heat capacity, standard Gibbs energy of formation, heat of vaporization. ..) physical propery measures (refractive index, boiling point, dielectric constant, dipole moment, solubility. ..) chemical properties (protolytic constants, ionzation potential, lipophilicity (log P)...) structural data (bond lengths, bond angles, van der Waals radii...) empirical structural parameters (Es, x ct+.). 

For any given problem in which we have to consider the properties of a molecule, it is reasonable to assume that, at least, some of the observables will be related to the pertinent intrinsic properties. Analyzing the problem will make it possible to make certain a priori assumptions as to the relevance of the observables and those which we believe to be relevant to our problem will hereafter be called descriptors. 

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Chlorine, a member of the halogen family, is a greenish yellow gas having a pungent odor at ambient temperatures and pressures and a density 2.5 times that of air. In Hquid form it is clear amber SoHd chlorine forms pale yellow crystals. The principal properties of chlorine are presented in Table 15 additional details are available (77—79). The temperature dependence of the density of gaseous (Fig. 31) and Hquid (Fig. 32) chlorine, and vapor pressure (Fig. 33) are illustrated. Enthalpy pressure data can be found in ref. 78. The vapor pressure P can be calculated in the temperature (T) range of 172—417 K from the Martin-Shin-Kapoor equation (80) ... 

Although thermal performance is a principal property of thermal insulation (13—15), suitabiHty for temperature and environmental conditions compressive, flexure, shear, and tensile strengths resistance to moisture absorption dimensional stabiHty shock and vibration resistance chemical, environmental, and erosion resistance space limitations fire resistance health effects availabiHty and ease of appHcation and economics are also considerations. 

Pure carbon disulfide is a clear, colorless Hquid with a deHcate etherHke odor. A faint yellow color slowly develops upon exposure to sunlight. Low-grade commercial carbon disulfide may display some color and may have a strong, foul odor because of sulfurous impurities. Carbon disulfide is slightly miscible with water, but it is a good solvent for many organic compounds. Thermodynamic constants (1), vapor pressure (1,2), spectral transmission (3,4), and other properties (1,2,5—7) of carbon disulfide have been deterrnined. Principal properties are Hsted in Table 1. 

Styrene is a colourless mobile liquid with a pleasant smell when pure but with a disagreeable odour due to traces of aldehydes and ketones if allowed to oxidise by exposure to air. It is a solvent for polystyrene and many synthetic rubbers, including SBR, but has only a very limited mutual solubility in water. Table 16.1 shows some of the principal properties of pure styrene. 

Typical values for the principal properties of cellulose acetate compounds are tabulated in Table 22.2 in comparison with other cellulosic plastics. Since cellulose acetate is seldom used today in applications where detailed knowledge of physical properties are required these are given without further comment. 

Although there will be specific requirements for specific applications, the principal properties of importance with the thermoplastic elastomers are ... 

Different filter media, regardless of the specific application, are distinguished by a number of properties. The principal properties of interest are the permeability of the medium relative to a pure liquid, its retention capacity relative to solid particles of known size and the pore size distribution. These properties are examined in a laboratory environment and are critical for comparing different filter media. 

Sedimentary deposits are usually carried to the region of deposition by water and are deposited in water. (In some cases deposits are carried by wind or ice.) It is within these water leposited sediments that hydrocarbons are likely generated from the plant and animal life that exists in these environments. Two principal properties of the sedimentary rocks that form from such deposits are porosity and permeability. 

The production process and the principal properties of this system have been described in detail in the section on traction battery separators (see Sec. 9.2.3.1). The outstanding properties, such as excellent porosity (70 percent) and resulting very low acid displacement and electrical resistance, come into full effect when applied in open stationary batteries. Due to the good inherent stiffness the backweb may even be reduced to 0.4 mm, reducing acid displacement and electrical... 

Conditions (30) and (31) are sufficient to discuss the principal properties of the critical state of a one-component system. We observe that the existence of a critical state for such a system cannot be inferred from a j)riori considerations, because it is not necessary that the two branches of the connodal curve should ultimately coalesce that such is the case must be regarded as established for systems containing liquid and vapour by the experiments of Andrews ( 86), and the following discussion is limited to such systems (cf. 103). 

The investigation above is due initially to Gibbs (Scient. Papers, I., 43—46 100—134), although in many parts we have followed the exposition of P. Saurel Joum. Phys. diem., 1902, 6, 474—491). It is chiefly noteworthy on account of the ease with which it permits of the deduction, from purely thermodynamic considerations, of all the principal properties of the critical point, many of which were rediscovered by van der Waals on the basis of molecular hypotheses. A different treatment is given by Duhem (Traite de Mecanique chimique, II., 129—191), who makes use of the thermodynamic potential. Although this has been introduced in equation (11) a the condition for equilibrium, we could have deduced the second part of that equation directly from the properties of the tangent plane, as was done by Gibbs (cf. 53). 

A distinguishing feature of electronically excited atoms and molecules is that they have one or a few excited orbitals of an electron. The principal properties of these particles are represented by a high internal energy potential localized on the excited orbitals and the structure of electron shell essentially different from the electron ground state. 

It is through the solid state characteristics of polymers that we - as users - primarily interact with them. For convenience, we can divide the principal properties of polymers into five categories mechanical, optical, surface contact, barrier, and electrical. Weather resistance is a sixth category that can influence each of the other five categories. In order to understand these properties we must be able to quantify them. In this chapter we shall concentrate on measurement techniques, since it is through these methods that we learn how a polymer will behave during use. 

Catalysts may be metals, oxides, zeolites, sulfides, carbides, organometallic complexes, enzymes, etc. The principal properties of a catalyst are its activity, selectivity, and stability. Chemical promoters may be added to optimize the quality of a catalyst, while structural promoters improve the mechanical properties and stabilize the particles against sintering. As a result, catalysts may be quite complex. Moreover, the state of the catalytic surface often depends on the conditions under which it is used. Spectroscopy, microscopy, diffraction and reaction techniques offer tools to investigate what the active catalyst looks like. 

We can summarize the principal properties of these aggregates, saying they form spontaneously at a well-defined concentration, the CMC (see p. 516) and adding more monomer to the solution yields more micelles, each colloidal particle having the same size, and ensuring the concentration of free monomer does not change. 

Six ZSM-5 samples were synthesized from gels containing the whole series of alkali cations, added in form of chloride, as described in procedure B. Synthesis data, principal properties and analyses are summarized in Tables VI and VII. 

It should be recalled that one of the principal properties of transition metals is their aptitude to accede to multiple oxidation states. Thus, the main scope of an electrochemical study is to ascertain whether a metal complex, prepared in a certain oxidation state, is stable also in different oxidation states, or whether the lifetimes of these oxidation states are too short to observe stable products. Whenever stable oxidation states are identified, the chemist might be able to prepare and fully characterize these new complexes. 

Zhi Gan Cao is sweet and slightly warm, which are the principal properties of herbs that can tonify the Qi. It enters all the ordinary meridians, can tonify the Qi, moderate the speed of Qi and blood, and harmonize the functions of the internal organs. It is particularly selected in the formula with a large dosage as chief to calm the mind and relieve the palpitations and restlessness caused by Heart-Qi deficiency. 

Physical and Chemical Properties. While the principal properties of diazinon are well characterized, (ASTER 1995 Howard 1991 HSDB 1996 Merck 1989) there are data gaps for melting point, odor and taste thresholds, autoignition temperature, flash point, and explosive limits for the compound. Additional information on these properties would be helpful in assessing the compound s environmental fate. There are also data gaps for some spontaneously-produced degradation products some of which may be as toxic or more toxic than diazinon. 

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