Camphor theory

The theory of sublimation, t.e. the direct conversion from the vapour to the sohd state without the intermediate formation of the liquid state, has been discussed in Section 1,19. The number of compounds which can be purified by sublimation under normal pressure is comparatively small (these include naphthalene, anthracene, benzoic acid, hexachloroethane, camphor, and the quinones). The process does, in general, yield products of high purity, but considerable loss of product may occur. 

Substituted norbomanes, such as camphor, aTe found widely in nature, and many have been important historically in developing organic structural theories. 

Lowry is best known to chemistry students through the tradition of eponymony, since the proton theory of acidity is known as the "Bronsted/Lowry theory" of proton donors. His most important experimental investigation likely was a long series of studies on optical rotatory dispersion.49 For our purposes, there is special interest in his discovery of mutarotation in camphor derivatives and his theory of dynamic tautomerism, which led him to an ionic theory of organic reaction mechanisms. 

FLAME EXTINCTION FROM THE UPSTREAM PORTION OF A DROP IN MOTION. In his studies of the influence of relative air velocity on the combustion of liquid fuel spheres, Spalding (51, 56) noted a critical velocity above which flame could not be supported at the upstream portion of the sphere. He observed that the flame blew off and resided solely in the sphere s wake. In tests with kerosine, the air (20° C.) velocity at extinction varied linearly with sphere diameter (range 0.7 to 2.6 cm.), and the ratio Ubi2n was about 100 seconds-1. A similar result is obtained from the data on flame extinction of burning camphor spheres (15, 59). The near proportionality between extinction velocity and diameter was taken as supporting evidence for a theory on flame extinction advanced by Spalding (59). More recent experimental work with porous spheres and n-butyl alcohol as fuel does not support this relationship (1), because it was found that the extinction velocity is proportional to the square root of the drop diameter. 

T. Money, Remote Functionalization of Camphor Application to Natural Product Synthesis, in Organic Synthesis Theory and Applications (T. Hudlicky, Ed.), 1996, 3, JAI, Greenwich, CT. 

An understanding of the three-dimensional structures of molecules has played an important part in the development of organic chemistry. The first experiments of importance to this area were reported in 1815 by the French physicist J. B. Biot, who discovered that certain organic compounds, such as turpentine, sugar, camphor, and tartaric acid, were optically active that is, solutions of these compounds rotated the plane of polarisation of plane-polarized light. Of course, the chemists of this period had no idea of what caused a compound to be optically active because atomic theory was just being developed and the concepts of valence and stereochemistry would not be discovered until far in the future. 

Schoneboom JC, S Cohen, H Lin, S Shaik, W Thiel (2004) Quantum mechanical/molecular mechanical investigation of the mechanism of C-H hydroxylation of camphor by cytochrome P450(cam) Theory supports a two-state rebound mechanism. J. Am. Chem. Soc. 126 (12) 4017-4034... 

I write what he dictates, but I am not happy with the idea of phlogiston. I think that the results of our experiment support Stahl s theory to an extent but don t prove it. I wish we could catch the air inside the glass and do more experiments to see how it really differs in quality from what Stahl would call the dephlogisticated air around us, but I say nothing of this to my father. I do as he says, and after a while I feel peaceful again. I love the flow of ink from my pen, the smells of sulfur and camphor, dusty wig and tobacco, and the satisfaction of watching an experiment go as predicted. Out of the comer of my eye, I notice that my father s hands are trembling more than ever and that after a little while his knees sag and he perches on a stool. 

The practice and theory of enantioselective CGC was comprehensively reviewed. Racemic oxygen-, nitrogen- and sulfur-containing selectands can be separated without prior derivatization into enantiomers by CGC on optically active metal(II) bis[3-(perfluoro-acyl)-(lR)-camphorate] (61) selectors. Peak inversion is obtained when the selectors with opposite configuration are employed. Applications pertain to chiral analysis in asymmetric synthesis, enzymatic reactions, pheromone and flavor chemistry. ... 

A review appeared on the practice and theory of enantioselective CGC with optically active selectors, e.g. 3-(perfluorobutyryl)-(17 )-camphorate residues forming complexes on a functionalized polysiloxane stationary phase (e.g. Chirasil, 65) SEC operates at temperatures lower than those of CGC, thus allowing better resolution, especially of thermally unstable enantiomers (e.g. those based on restricted free rotation, as is the case of dimethyl l,l -binaphthyl-2,2 -dicarboxylate, 66 ). Various analytical problems were addressed, such as determination of enantiomeric excess, assignment of absolute configuration, the elusive separation of protio- and deuterio-substituted enantiomers and the semipreparative separation of enantiomers. The following chromatographic parameters are related to the chemical and thermodynamic properties enclosed in parentheses of the enantiomeric system (i) peak retention (chemoselectivity, —AG), (ii) peak separation... 

As noted above (Section 1.4.2.2) reduction of carbonyl compounds under these conditions proceeds with hydrogen transfer to afford an equimolar mixture of alkoxide and enolate, plus varying quantities of dimeric reduction products. As a consequence, at least in theory, this procedure should afford an equimolar mixture of recovered ketone and reduction product. This appears to be the case if less than one equivalent of metal is used however, with excess metal, camphor, " some 12-keto steroids2 and several 1 -decalones2 afforded 70-99% yields of secondary alcohols. The explanation which has been offered is that the product enolate is protonated by NH3 to regenerate the starting ketone, which is recycled through the reduction process. ... 

S—H groups, presumably another manifestation of the relative weakness of H bonds in this group. Sack (1768) has developed a theory of high dielectric losses in terms of the number of states of the molecule. Other solid organic materials that have been studied less extensively include cyclohexanol (1515, 1128, 793), in which the H bonding apparently differs in various crystal phases camphor and some related materials (793) and palmitamide (1075). 

Theories abound, which relate those two vocabularies, but no one of them has emerged as predominant. Many of the theories suppose the existence of specific receptor sites on the surface of the receptor neurons. One hypothesis posits a set of odors of specific objects (e.g., camphor, sperm, urine, fish) that correspond to pure compounds and represent fundamental submodalities (Beets, 1982). Another (based on molecular biology) proposes dozens—perhaps hundreds—of different types of cell surface receptor proteins, each of which is tuned to a specific odorant compound or class of compounds (Buck, 1996 Zhao et al., 1998). 

According to stereochemical theory, the mechanism of smell depends on the binding of an odor molecule to a specific receptor site, which resembles the lock-and-key mechanism of enzyme catalysis. If two substances fit the same receptor, they should have the same odor, even if they differ in chemical composition. There are seven different kinds of olfactory receptors, each of which will accept a molecule that has the appropriate geometry. For putrid molecules such as hydrogen sulfide (H2S), however, polarity is more important than shape in linking up with a receptor. In addition, if different portions of a molecule fit different receptors, the molecule should have a mixed odor. For example, portions of benzaldehyde fit the camphor-like, floral, and peppermint receptors we recognize the resulting aroma as almond. 

The theory of sublimation will become clear by reference to Figure 2.7, which is the vapour pressure-temperature diagram for camphor. The vapour pressure of a solid increases with temperature in much the same way that the vapour pressure of a liquid does. 

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