Physical property!ies

Physical Properties, (i) Aromatic. Colourless when freshly prepared, but usually brown. MonomethylaniUne, CgHjNHCH, b.p. 193°, and monoethylaniline, CgHjNHCjHj, b.p. 206 , diphenylamine,(C6H5)2NH, m.p. 54 , are all insoluble in water, the two alkylanilines having well-marked basic properties, diphenylamine being feebly basic and insoluble in dilute mineral acids. 

Physical Properties, (i) Triethylamine, b.p. 90 , tri-n-propylamine, b.p. 156 , tri biitylamine, b.p. 212 ", are liquids with a fishy odour, and with decreasing solubility in water. 

Solvents exert their influence on organic reactions through a complicated mixture of all possible types of noncovalent interactions. Chemists have tried to unravel this entanglement and, ideally, want to assess the relative importance of all interactions separately. In a typical approach, a property of a reaction (e.g. its rate or selectivity) is measured in a laige number of different solvents. All these solvents have unique characteristics, quantified by their physical properties (i.e. refractive index, dielectric constant) or empirical parameters (e.g. ET(30)-value, AN). Linear correlations between a reaction property and one or more of these solvent properties (Linear Free Energy Relationships - LFER) reveal which noncovalent interactions are of major importance. The major drawback of this approach lies in the fact that the solvent parameters are often not independent. Alternatively, theoretical models and computer simulations can provide valuable information. Both methods have been applied successfully in studies of the solvent effects on Diels-Alder reactions. 

After determining the relevant physical properties (i.e., particle size, solids particle density and bulk density), the next step is to evaluate some of the existing techniques of powder classification. 

In the gas phase species are isolated, far from each other. It follows that their behaviour is not influenced by solvation, as occurs in solution, or by reticular forces, as in the crystalline state. Thus, the gas phase allows the study of the intrinsic properties of a given species, that are only dependent on its chemico-physical properties, i.e. its molecular weight, type of atoms (C, N, O,...) involved, connections between them, etc. 

Another approach is to consider petroleum constituents in terms of transportable materials, the character of which is determined by several chemical and physical properties (i.e., solubility, vapor pressure, and propensity to bind with soil and organic particles). These properties are the basis of measures of teachability and volatility of individual hydrocarbons. Thus, petroleum transport fractions can be considered by equivalent carbon number to be grouped into 13 different fractions. The analytical fractions are then set to match these transport... 

Isotope One of two or more atoms with the same atomic number (the same chemical element) but with different atomic weights isotopes usually have very nearly the same chemical properties but somewhat different physical properties, i. v. Abbreviation for intravenous (administration). 

In the process of translation into English, I tried to introduce these compounds as examples of non-stoichiometric compounds, adding a new section. I had to decide, however, to stop my trial, because many papers on these compounds have been published from the viewpoint of the relation between the non-stoichiometry and physical properties, i.e. it is too early to adopt these compounds in a textbook. 

Polymer Selection. The selection of corn starch as the starting material was made due to its low cost, ready availability, multitude of previous derivatization literature work and favorable chemical and physical properties (i.e., inert, readily deriva-tized homopolysaccharide capable of forming high solids content aqueous dispersions with relatively low viscosities). The corn starch used in this study was purchased in bulk from a local food cooperative. Table I gives the proximate analysis of a typical corn starch. 

Diastereomcrs have different physical properties (i.e. rotation of plane-polarized light, melting points, boiling points, solubilities, etc...). Their chemical properties also differ. 

It was at the turn of the twentieth century that the importance of lipid solubility in drug action was also independently described by Meyer and Overton (the significance of the oil/water partition coefficient was discussed in Chapter 2). The importance of lipid solubility in drug action subsequently became manifested in the lipoid theory of cellular depression. In essence, this theory correlated a pharmacological effect (e.g., CNS depression) with a physical property (i.e., lipid solubility) rather than a structure-activity relationship. In the process, the theory was attempting to explain the diverse chemical structures that exist within the hypnotic and general anesthetic classes of drugs (see Chapter 11). Today, we realize the limitations of the lipoid theory and appreciate that the distinction between physical and chemical factors is illusory, since chemical structure is a determinant of physical properties. 

Distinction should be made at this time between diastereoisomers and enantiomers. The former are characterized by the presence of at least two closely associated asymmetric centers in the molecular structure, either of which can epimerize. Altogether then there are two pairs of enantiomers for a total of four stereochemically unique individuals. Diastereoisomers have different physical properties and as a result discriminations, and even separations, can be done relatively easily. Enantiomers on the other hand differ in only one physical property, i.e. the direction of rotation of polarized light. Reaction of an enantiomeric racemic mixture with a third chiral species will produce a mixture of diastereomers therefore facilitating their identification or their separation. Early examples of this were the separations done by fractional crystallization of salts produced by a derivatization reaction with, for example, the alkaloid (-)-brucine. Fractional crystallization would never seem to be an effective analytical method yet it was used with some success in a forensic sciences context to confirm the presence of (L)-cocaine by a carefully contrived microcrystalline test. The physical properties... 

Mochida et al. (76) report that in carbonizations of several heterocyclic compounds containing nitrogen, sulphur and oxygen, the presence of the heteroatoms markedly affects optical texture of resultant cokes. When co-carbonized with aluminium chloride the heteroatoms exert a less marked effect where heteroatom evolution becomes important. Again, Mochida et al. (76) emphasise that the rate of the carbonization process, by influencing viscosity, is dominant in determining optical textures of cokes and related physical properties, i.e. CTE. 

Isotopes are atoms of the same element with the same number of protons (same atomic number) but different number mass numbers (due to a different number of neutrons). Isotopes have identical chemical properties (the same reactivity) but different physical properties (i.e., some are radioactive, while others are stable). Consider the three isotopes of hydrogen in Table 2.1. 

Me Cabe-Thiele assumptions apply for the fractionation column Physical properties = i-butane n-butane... 

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