Physical properties Melting point Solubility

The factors which Influence the choice of formulation are pesticide physical properties (melting point, solubility, volatility), pesticide chemical properties (hydrolytic stability, thermal stability), soil application vs. foliar application, crop and cultural practice, pesticide biological properties (crop selectivity, transport), and economics. 

The physical properties—melting point, solubility, high dipole moment—are just what would be expected of such a salt. The acid-base properties also become... 

Individual pure enantiomers are identical to each other in most respects in that they have tire same physical properties, melting point (m.p.), boiling point (b.p.), refractive index, polarity, and solubility. The only difference between individual enantiomers is that they behave differently in chiral environments. For example, each enantiomer of an enantiomeric pair produces a rotation of the plane of plane-polarized light to an equal but opposite extent. This is because plane-polarized light is itself chiral and each enantiomer interacts differently with tire light (Figure 6.1). 

Two enantiomers have identical physical properties— melting point, boiling point, solubility— except for how they interact with plane-polarized light. 

First, wc purify the compound and determine its physical properties melting point, boiling point, density, refractive index, and solubility in various solvents. In the laboratory today, we would measure various spectra of the compound (Chap. 13), in particular the infrared spectrum and the nmr spectrum indeed, because of the wealth of information to be gotten in this way, spectroscopic examination might well be the first order of business after purification. From the mass spectrum we would get a very accurate molecular weight. 

Physical properties Melting point and purity Solubility Hygroscopicity... 

Clearly, an early task in organic chemistry was to isolate pure compovmds from natural sources and then attempt to identify them. Initially, the compounds were purified (usually by crystallization) and characterized as to their physical properties (melting point, boiling point, solubility in water, etc.). It was not until much later (mid- to late nineteenth century and even into the early twentieth century) that the structures of most of these compovmds were known absolutely. Justus Liebig (Germany 1803-1873) perfected the science of analysis of organic compounds, based on the early work of Antoine Lavoisier (France 1743-1794). 

Physical properties Melting point (mp), boiling point (bp), solubility, color, odor, refractive index. 

Chemical development Proof of structure and configuration are required as part of the information on chemical development. The methods used at batch release should be validated to guarantee the identity and purity of the substance. It should be established whether a drug produced as a racemate is a true racemate or a conglomerate by investigating physical parameters such as melting point, solubility and crystal properties. The physicochemical properties of the drug substance should be characterized, e.g. crystallinity, polymorphism and rate of dissolution. 

Some physical properties of the three stereoisomers are listed in Table 9.3. The (+)- and (-j-tartaric acids have identical melting points, solubilities, and densities but differ in the sign of their rotation of plane-polarized light. The meso isomer, by contrast, is diastereomeric with the (+) and (-) forms. As such, it has no mirror-image relationship to (+)- and (-)-tartaric acids, is a different compound altogether, and has different physical properties. 

Meso compounds contain chirality centers but are achiral overall because they have a plane of symmetry. Racemic mixtures, or racemates, are 50 50 mixtures of (+) and (-) enantiomers. Racemic mixtures and individual diastereomers differ in their physical properties, such as solubility, melting point, and boiling point. 

Fluoran compounds have an optically active spiro-carbon atom. Consequently, some fluoran compounds, especially those having an alkylamino group of four or more carbon atoms at 3 -position, have been found to exhibit crystal modifications as determined by X-ray diffraction. Each crystal modification reveals different physical properties such as melting point, solubility, and affinity with acidic compounds, resulting in different characteristics regarding use for carbonless copying papers, thermosensitive recording papers, and the like. 

Enantiomers have identical chemical and physical properties in the absence of an external chiral influence. This means that 2 and 3 have the same melting point, solubility, chromatographic retention time, infrared spectroscopy (IR), and nuclear magnetic resonance (NMR) spectra. However, there is one property in which chiral compounds differ from achiral compounds and in which enantiomers differ from each other. This property is the direction in which they rotate plane-polarized light, and this is called optical activity or optical rotation. Optical rotation can be interpreted as the outcome of interaction between an enantiomeric compound and polarized light. Thus, enantiomer 3, which rotates plane-polarized light in a clockwise direction, is described as (+)-lactic acid, while enantiomer 2, which has an equal and opposite rotation under the same conditions, is described as (—)-lactic acid. 

PHYSICAL PROPERTIES Boiling point 26°C Melting point -13°C Relative density (water = 1) 0.69 Solubility in water miscible Vapour pressure, kPa at 20°C 82.6 Relative vapour density (air = 1) 0.94 Flash point -18°C c.c. 

Diastereomers are nonenantiomeric isomers that result when more than one stereocenter is present in a molecule. The distinction between diastereomers and enantiomers is not always clear but, in general, enantiomers have mirror images, whereas diastereomers are not mirror images of one another. As such diastereomers have different physical properties such as boiling and melting points, solubilities, etc. 

Can be used to detect polymorphs of drugs (polymorphs are different crystal forms of a molecule that have different physical properties such as solubility and melting point which may be important in the manufacturing process). 

D. Amino-1,2,4-thiadiazoles 1. 3- and 5-Amino-1,2,4-thiadiazoles a. Physical Properties. 3-Substituted 5-amino-1,2,4-thiadiazoles are generally stable, colorless, odorless compounds.6,88,86,128 Their thermal stability (as reflected by their melting points), solubility, and resistance to acids are influenced by the nature of the 3-substituent. 5-Alkoxy-3-amino-l,2,4-thiadiazoleB sublime without decomposition.83... 

The physical properties (C, H, and N analysis, melting point, solubility, etc.) of Dexedrine and Benzedrine were identical. The recommended oral dosage of Dexedrine (which is still available) was 5 mg/day, but the recommended dosage of Benzedrine (no longer available) was twice that. Apparently it required considerably more Benzedrine than Dexedrine to yield the same physiological response. Explain this apparent contradiction. 

Physical properties such as solubility, melting point, and electrical conductivity, and chemical properties such as flammability of substances indicate bonding types. 

Comprehensive coverage of thermodynamic aspects for the 1,4-diazocines was presented in CHEC-II(1996) and included discussion on physical properties, such as melting points, solubility, and chromatographic behavior,... 

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