Organic compounds, crystalline

T. Norris, PK. Aldridge and S.S. Sekulic, Determination of end-points for polymorph conversions of crystalline organic compounds using on-line near-infrared spectroscopy. Analyst, 122, 549-552 (1997). 

Wise et al. investigated a number of crystalline organic compounds polynuclear aromatics, polyphenols, diacids, phthalein salts and phenolphthalein etc. as a substitute for charcoal in pyrotechnic formulations. Charcoal in black powder was substituted by these compounds in order to probe the chemical functionality of charcoal required for combustion. The data indicate that polynuclear aromatics which do not contain any oxygen do not sustain... 

Crystalline organic compounds typically have a characteristic melting point. In some cases, a compound may have more than one arrangement in the crystal and such polymorphs will exhibit differences in melting behavior. For the most part, however, the melting point of a compound is characteristic and invariant for a pure sample. When contaminated by a second substance, however, the melting (or freezing) point is typically lowered. 

Norris, T. Aldridge, P.K. Sekulic, S.S., Determination of End-Points for Polymorph Conversions of Crystalline Organic Compounds Using On-Line Near-Infrared Spectroscopy Analyst 1997, 122, 549-552. 

A professor once received from a chemical supply house a specimen of a crystalline organic compound needed in her research. This compound was optically active, with a positive rotation (i.e., it was dextrorotatory). The professor wanted to check that the sample was not contaminated by the other (levorotatory) optical isomer. Such contamination would decrease the magnitude of the positive rotation. Therefore she gave a small amount of the material to a graduate student with instructions to determine its specific rotation at 25°C with the highly precise polarimeter available in the laboratory (see Exp. 28 and Chapter XIX). 

The equilibrium solubility of the nonsol-vated form of a crystalline organic compound which does not dissociate in the solvent (for... 

Crystalline organic compounds containing OH, COOH, CO. NH, NH2, and other polar groups containing H atoms provide many further examples of all the above types of structure. 

Compounds with high internal mobility, such as adamantane, can have line widths as narrow as 0.01 ppm. This is why in solid-state NMR, adamantane is used not only as a chemical shift standard, but also for optimizing experimental variables and for shimming probes. A typical line width encountered in crystalline organic compounds is of the order of 0.5 ppm, but the exact value will be strongly dependent on the mobility of the compound. It is not unusual to resolve the majority of carbon resonances in compounds containing 40 or more carbons. 

K, the temperature and pressure at which there is no longer any distinction between liquid and gas), p rises to 0.17, while solid methane at 0 K exhibits a p value of 0.67. In occupancy terms, then, the intracavity environment is akin to a supercritical fluid. Translated to the macroscopic scale, one molecule of methane in the cavity of cryptophane-A is equivalent to one mole of methane in 49 mL, exerting a pressure of 610 atm at 298 K. In contrast, for CHCI3 the occupancy factor of 0.89 is akin to a very densely packed crystal, and indeed the entropic and enthalpic changes on binding are similar to those that occur in the formation of crystalline organic compounds. 

DDT /dee-dee-tee/ (dichlorodiphenyl-trichloroethane (ClCgH4)2CH(CCl3)) A colorless crystalline organic compound, once widely used as an insecticide. Its use is now restricted or banned in many countries because it is stable and remains unchanged in the soil, and passes up the food chain to accumulate in the fatty tissues of carnivorous animals. 

C6IT4O2) A yellow crystalline organic compound with a pungent odor. Its molecules contain a non-aromatic six-carbon ring and it behaves as an unsaturated diketone with conjugated double bonds. It is used in making dyestuffs. A platinum electrode in an equimolar solution of quinone and hydroquinone (benzene-l,4-diol, CgH4(OH)2) is used as a standard electrode in electrochemistry. The reaction is ... 

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