Chemically identical components

2 Blends of two molecular weight fractions and defined distributions 

The dependence of the crystallization rate on molecular weights was discussed in Chapter 9. The profound influence of molecular weight fractions on the rate raises the interesting question as to the role of polydispersity in governing the crystallization kinetics. Studies of the crystallization kinetics of polydisperse homopolymers 

There is a question whether during the course of isothermal crystallization of binary blends, as well as other polydisperse systems, molecular weight fractionation 

Spherulite growth rates of blends of linear polyethylene, M = 66000/M = 2500, plotted as a function of the crystallization temperature for different 

The spherulite growth rates of poly(ethylene oxide) blends, M = 5000/M = 270 000, display a qualitatively similar behavior. (39) In this case, both components co-crystallize in a common lattice at large undercoolings. At the low undercoolings separate phases result. There is no indication of this fractionation in the growth rate-temperature plots. Morphological studies demonstrate the fractionation. 

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Chemical identity Component A 70-80% Common name Solvent A... 

Complementary measurements have been made of the dehydration kinetics of three distinct lithium potassium tartrate hydrates those containing the d and dt anions were monohydrates and the meso salt was a dihydrate. These reactants were of interest because they contained chemically identical components, but had different crystal structures and reactivities [150]. 

Reactive scattering or a chemical reaction is characterized by a rearrangement of the component particles within the collision system, thereby resulting in a change of the physical and chemical identity of the original collision reactants A + B into different collision products C + D. Total mass is conserved. The reaction is exothemiic when rel(CD) > (AB) and is endothermic when rel(CD) < (AB). A threshold energy is required for the endothemiic reaction. 

One way to describe this situation is to say that the colligative properties provide a method for counting the number of solute molecules in a solution. In these ideal solutions this is done without regard to the chemical identity of the species. Therefore if the solute consists of several different components which we index i, then nj = S nj j is the number of moles counted. Of course, the total mass of solute in this case is given by mj = Sjnj jMj j, so the molecular weight obtained for such a mixture is given by... 

Synthetics. The lack of spice products to satisfy demand and the wide variation in price and availabihty have caused the manufacture of selected synthetics, chemically identical to the component in the natural spice, to replace the vital components of some spices. However, synthetic organic chemistry is not yet able to manufacture economically the many homologous piperine [94-62-2] components in black pepper or those capsaicin [404-86-4] amides in... 

Table 3-3 contains information regarding the chemical identity of principal components of hydraulic fluids. Trade names are included when the component constitutes 100% (or nearly 100%) of the product. Information has also been included for several representative types of mineral oil. It should be noted, however, that the term "mineral oil" encompasses a wide variety of petroleum-based products. Several phosphate esters used as hydraulic fluid additives are also included in Table 3-3. 

Hazardous Components (Specific Chemical identity Common Name(s)) Other limits OSHA PEL ACGlH TlV Recommended o-o (optionan... 

These are the only ranges of precursor products in the Colour Index that are still commercially significant. Azoic dyes have a close formal relationship to those monoazo pigments derived from BON acid or from acetoacetanilides (section 2.3.1) and some are chemically identical with them, although they are used in a totally different way. Azoic components are applied to produce insoluble azo dyes within the textile substrate, which is almost always cotton. Corresponding azoic components for the dyeing of cellulose acetate, triacetate and polyester fibres were once commercially important, but are now obsolete because of environmental hazards and the time-consuming application procedure. 

Correct chemical identity including molecular formula, Chemical Abstracts Service (CAS) Registry number, common synonyms, trade names, and a structural diagram. Gosselin et al. (1984) and Ash and Ash (1994, 1995) are excellent sources of information on existing commercial products, their components and uses ... 

The arenium ion/(R)-(— )-2-chlorobutane adducts. A crucial question concerns the chemical identity and the relative spatial arrangement of the components of a microsolvated system, two features of paramount importance to assess the kinetic and the mechanistic role of the corresponding ion-dipole pairs in solution. In the example reported in this section, Cacace and coworkers consider the ion-molecule complexes involved in the classical Friedel-Crafts alkylation of arenes." " At 300 K and under FT-ICR conditions, the benzenium ion CeH reacts with 2-chlorobutane C4H9CI to give the CloHj5 ion with a rate constant of 5 X 10 cm molecule corresponding to a collision efficiency of 2.5% (equations (33) or (34)). ... 

The components of the sample that are to be determined are often referred to as analytes. While qualitative analysis reveals the chemical identity of the species in the sample, quantitative analysis establishes the relative amount of one or more of these species, the analytes, in numerical terms. Often separation is required as a necessary part of either qualitative or quantitative analysis. 

Figure 3 shows several examples of 13C chemical shift tensors of carbe-nium ions oriented in the molecular frame as indicated. If the molecule or ion has a rotational axis of C3 or higher order that passes through the nucleus in question, symmetry demands that the two components perpendicular to the C3 or higher order rotational axes be identical in such cases the identical components are designated SL. The unique component that lies along the... 

Immediately on entering the body, a chemical begins changing location, concentration, or chemical identity. It may be transported independently by several components of the circulatory system, absorbed by various tissues, or stored the chemical may effect an action, be detoxified, or be activated the parent compound or its metabo-lite(s) may react with body constituents, be stored, or be eliminated—to name some of the more important actions. Each of these processes may be described by rate constants similar to those described earlier in our discussion of first-order rate processes that are associated with toxicant absorption, distribution, and elimination and occur... 

It is obvious that independently of the rate of exchange the NMR spectrum of a system subject to a dynamic equilibrium depends on the relative concentrations of the components present. These may be expressed as mole fractions or, in the case of intramolecular exchange, as conformer populations. Sometimes the populations are governed by symmetry effects alone and are independent of the experimental conditions. This is always the case for mutual exchange when the process does not alter the chemical identity of a molecule. Examples of such exchange may be drawn from rotations of the t-butyl group in (CH3)3C-C(R1)(R2)(R3), and those about the CO-N bond in N,N-dimethyl-substituted amides (CH3)2N-C(=0)R. Other examples include ring inversions such as those in 1,2-ds-dimethylcyclohexane, 1,3-trans-... 

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