Early Observations

Initial reports leading to speculation about non-linear or branched polymeric connectivity were provided by researchers such as Zincke,121 who isolated an insoluble hydrocarbon-based material upon the treatment of benzyl chloride with copper. Later, in 1885, reaction of benzyl chloride with aluminium chloride led Friedel and Crafts131 to report similar observations. When benzyl chloride was subjected to the action of a zinc-copper couple analogous materials were obtained.141 

The key observation in the case of 152 is that photolysis in benzene conforms to the expected a-cleavage and decarbonylation reactions to form diphenylmethyl (A ) and benzyl radicals (B ), which are free to diffuse apart. The statistical combination of free radicals A and B gives a 1 2 1 mixture of products 154,155, and 156. In contrast, photochemical excitation in the crystalline phase led to the exclusive formation of 153 by combination of the geminate radical pair A B with a 100% cage effect. 

The experimental observations in the case of 1,3-diphenyl-2-indanones 157 and 158 demonstrate convincingly that the stereochemical integrity of the two radical centers is maintained to high levels when reactions are carried out in the solid state. Crystals 

The next important realization was that bile from different species 

Although alkaline hydrolysis of glycocholic and taurocholic acid was known to yield a crystalline, non-nitrogenous product (24), it was several decades before this procedure was applied to the verification and extension of the experiments that had yielded different bile acids. Thudichum (25), in 1881, observed an isomer of cholic acid in ox bile. Latschinoff (26), in 1885, isolated choleic acid from ox bile and determined its approximate ratio to cholic acid. Mylius (27, 28), in 1886, isolated deoxycholic acid from putrefied ox bile. The co-identity of these preparations was accepted for many years, but it was not until 1916 (29), when the molecular complexes of deoxycholic were described by Wieland and Sorge, that the apparent inconsistencies were resolved. 

By 1900, only deoxycholic acid and cholic acid had been obtained in pure crystalline form. In 1911, Fischer (30) isolated lithocholic acid from a gallstone in the course of his classical studies on the bile pigments. Hyodeoxy-cholic acid was purified by Windaus and Bohne in 1923 (31) and chenodeoxy-cholic acid was rediscovered almost simultaneously by Wieland and Reverey (32) and by Windaus et al. (33) in 1924. 

A typical procedure for the isolation of the free bile acids included precipitation of the bile protein with alcohol and hydrolysis of the conjugated acids for long periods of time in from 5 to 10 percent aqueous sodium hydroxide. Different methods were then applied for the isolation of each individual acid from the resulting crude mixture of free bile acids. Cholic and deoxycholic acid could be separated from each other by the addition of concentrated barium chloride to an ammoniacal solution of the hydrolyzed acids, since most of the barium deoxycholate is precipitated with the fatty acids, whereas barium cholate remains in solution (34). The greater solubility of chenodeoxycholic acid in ether was used by Wieland for its isolation lithocholic acid, the weakest of the acids, was obtained by fractional precipitation 

As the result of the efforts of a number of investigators, a wealth of information accumulated concerning the occurrence of bile acids in a large number of species, but it must be emphasized that the procedures used until about 1950 allowed the isolation of only the predominant bile acids. Minor constituents were isolated from mother liquors when large amounts of bile were examined. 

There is no clear distinction between comets and asteroids. Very old comets have lost all their volatiles and the nucleus resembles to asteroids. There are more than 3500 reported known comets which certainly is only a tiny fraction of the whole comet population in the solar system. The main reservoir of comets is in the Oort cloud and there may be several 10 cometary like objects there. 

Most of the comets observed are unspectacular. Some are very bright and some are famous because they return periodically like Halley s comet. 

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Some early observations on the catalytic oxidation of SO2 to SO3 on platinized asbestos catalysts led to the following observations (1) the rate was proportional to the SO2 pressure and was inversely proportional to the SO3 pressure (2) the apparent activation energy was 30 kcal/mol (3) the heats of adsorption for SO2, SO3, and O2 were 20, 25, and 30 kcal/mol, respectively. By using appropriate Langmuir equations, show that a possible explanation of the rate data is that there are two kinds of surfaces present, 5 and S2, and that the rate-determining step is... 

Our understanding of the development of oscillations, multi-stability and chaos in well stirred chemical systems and pattern fonnation in spatially distributed systems has increased significantly since the early observations of these phenomena. Most of this development has taken place relatively recently, largely driven by development of experimental probes of the dynamics of such systems. In spite of this progress our knowledge of these systems is still rather limited, especially for spatially distributed systems. 

The history of iaclusion compounds (1,2) dates back to 1823 when Michael Faraday reported the preparation of the clathrate hydrate of chlorine. Other early observations iaclude the preparation of graphite iatercalates ia 1841, the P-hydroquiaone H2S clathrate ia 1849, the choleic acids ia 1885, the cyclodexthn iaclusion compounds ia 1891, and the Hofmann s clathrate ia 1897. Later milestones of the development of iaclusion compounds refer to the tri-(9-thymotide benzene iaclusion compound ia 1914, pheaol clathrates ia 1935, and urea adducts ia 1940. 

A close study of the chronology of this episode teaches another lesson. The early observation on irradiation-induced growth of uranium was purely phenomeno-... 

Since Pressman s early observation that antibiotics of the nigericin type complexed cations there has been considerable effort expended to mimic this action using simple, readily synthesized molecules. Simon and his collaborators have been especially active in this approach and have reviewed this area . They have devised a number of struc-... 

These early observations on the correlation of structure and pharmacological action in the morphine group have been greatly extended as a result of chemical, pharmacological and clinical work done under the auspices of the American National Committee on Drug Addiction. In addition to numerous papers, contributed by experts serving this Committee, to chemical and pharmacological journals, two important reports have been published —... 

Pharmacological Action. Most of the early observations on the gelse-mium alkaloids were made on amorphous preparations, and the results reeorded are probably further confused by the faet that while in English journals the first erystalline alkaloid obtained was ealled gelsemine and the residual amorphous fraction gelseminine, these two names were used in the opposite sense in some German publieations. 

Recently, many investigators have extended the early observations that the ultraviolet spectra of - and y-hydroxypyridines resemble those of their A -methyl (not the 0-methyl) derivatives. This spectral resemblance is found both in aqueous solutions and in solutions of solvents with low dielectric constants, e.g., quinol-4-one in benzene, indicating that these compounds exist predominantly in the oxo form under all conditions. These data are summarized in Table I. In contrast, 4-hydroxyquinoline-3-carboxylic acid has been tentatively concluded to exist in the hydroxy form %- pjTid-2-one-4-carboxylic acid has also been formulated as a hydroxy compound, but this has been disputed. ... 

The reaction is based on an early observation by Angeli and Ahrens that Piloty s acid converted aldehydes to hydroxamic acids, and this has formed the basis of the Angeli-Rimini aldehyde test. Di Maio and Tardella propose the above reaction sequence, consistent with the observed second-order kinetics. The possibility that benzenesulfon-hydroxamic acid would decompose in alkali to give nitroxyl (HNO)... 

In the isolation process of glucobrassicin hydrolysis products, early observations led to file suggestion fiiat 227 was one of the major metabolites, and the most potent... 

It was the early observation by Cope et al. that treatment of epoxides of mediumsized cydoalkenes with strong base results in the generation of new carbon skeletons, which prompted the initial interest in the chemistry of metalated epoxides [61-... 

Sometimes two discharge voltage plateaus are seen on nickel oxide electrodes. Early observations are documented in previous reviews [2, 9]. Normally, nickel oxide electrodes have a voltage plateau on discharge in the potential range of 0.25-0.35V vs. Hg/HgO. The second plateau, which in some cases can account for up to 50% of the capacity, occurs at -0.1 to - 0.6 V. At present there is a general consensus that this second plateau is not due to the presence of a new, less-active, compound [91-94]. Five interfaces have been identified for a discharging NiOOH electrode [93]. These are... 

Amino Acids. Early observations on the liberation of amino acids by plant roots were reviewed by Loehwing (94), Rademacher (121), and Borner (12). Free amino acids have been isolated from soil fractions (119), and the excretion of a variety of ninhydrin-positive compounds by plant roots has been demonstrated under controlled conditions by Katznelson et al. (18), Rovira (121), and Pearson and Parkinson (115). 

An early observation that 2 -d-3 -AMP was a more potent inhibitor of adenylyl cyclases than 2 -d-Ado suggested that the enzyme would accept substitutions at the 3 -ribose position and that phosphate was particularly well tolerated. This led to the generation of a family of 3 -phosphoryl derivatives of 2, 5 -dideoxyadenosine exhibiting ever greater inhibition with the addition of an increasing number of 3 -phosphoryl groups, the most potent of which is 2, 5 -dideoxyadenosine-3 -tetraphosphate (2, 5 -dd-3 -A4P Table 4) [5]. These constitute a class of inhibitors historically referred to as P -site ligands that caused inhibition of adenylyl... 

There is, however, another possible explanation. For relatively weak complexes, as in these cases, a complex other than one of the insertion type may form in solution, for example a charge-transfer complex. An early observation which may indicate the formation of other types of complexes was reported by Bartsch and Juri (1980), but not interpreted the dediazoniation rate for 4-tert-butylbenzenediazonium tetra-fluoroborate in 1,2-dichloroethane decreases by 12% in the presence of one equivalent of 15-crown-5, a host compound which does not form insertion complexes. Kuokkanen and Virtanen (1979) also observed some stabilization towards dediazoniation of 2-toluenediazonium ion by 18-crown-6, even though, for steric reasons, an insertion-type complex is hardly possible in this case. 

These early observations have evolved into the branch of chemistry called electrochemistry. This subject deals not only with the use of spontaneous chemical reactions to produce electricity but also with the use of electricity to drive non-spontaneous reactions forward. Electrochemistry also provides techniques for monitoring chemical reactions and measuring properties of solutions such as the pK, of an acid. Electrochemistry even allows us to monitor the activity of our brain and heart (perhaps while we are trying to master chemistry), the pH of our blood, and the presence of pollutants in our water supply. 

A method has recently been described for wrapping polymers around metal atoms and very small metal clusters using both matrix and macroscale metal vapor-fluid polymer synthetic techniques. Significant early observations are that (i) the experiments can be entirely conducted at, or close to room temperature, (ii) the resulting "pol5aner stabilized metal cluster combinations are homogeneous liquids which are stable at or near room temperature, and (,iii) the methodology is easily extended to bimetallic and trimetallic polymer combinations. ... 

The drying protoplast will be subjected to tension as the result of volume contraction and its adherence to the cell wall. Early observations (Steinbrick, 1900) on desiccation tolerant species showed that the protoplasm does not separate from the wall, but rather that it folds and cavities develop in the wall. Where there are thick-walled cells, localised separation of the plasmalemma from the wall may occur. It seems unlikely, however, that rupture of the plasmalemma normally occurs during desiccation. A more subtle form of membrane damage may arise from dehydration-induced conformational changes. Certainly it is relatively easy to demonstrate that dehydrated membranes exhibit a loss of functional integrity... 

Seeligmann, Torrilhon, and Falconnet, in a treatise on rubber published in France in 1896, recorded interesting early observations on the sol and gel components now known to be present in most specimens of undegraded raw rubber. They referred to them as the two isomeric hydrocarbides of rubber, one being the adhesive principle and the other the nervous principle. It was observed that the latter refused to dissolve on repeated treatment with fresh portions of solvent and that the approximate percentage of this constituent was roughly the same when different solvents were used to extract the soluble portion. The authors called attention also to the enormous swelling capacity of the nervous hydrocarbide. Vulcanization was attributed to a reaction of sulfur with the adhesive principle whereby the adhesive characteristics are suppressed or eliminated. 

SCAVENGING FROM SEAWATER 3.1. Early observations of Th scavenging... 

The raw data in the more comprehensive study (61) were conversions, determined in duplicate, when each of 104 coals selected from three geological provinces was heated with tetralin under standard conditions, together with the results of 14 commonly made analytical determinations for each coal. An early observation in this study was that when data for all 104 samples were plotted against volatile matter, a steady decrease of conversion with decreasing volatile matter was apparent. But there was a great deal of scatter (r=0.85). In any case, the formal requirements that make possible the employment of valid statistical analyses were not met by the data matrix, as evidenced by skewed and bimodal relationships between the variables the sample set was heterogeneous. ... 

Although the anhydrous nitrate is relatively stable and can be distilled under partial pressure, as is remarked in most recent text books, these do not tell that the hydrate actually obtainable by purchase or by normal preparations is among the least stable and most oxidising of main valence nitrates. It was early observed that paper contaminated with it ignited easily [1],... 

The biosynthetic origin of the depolymerization-resistant core of cutin (cutan) remains to be established. The early observation that linoleic acid and linolenic acid were preferentially incorporated into the non-depolymerizable core of cutin in apple skin slices suggested that the ether-linked or C-C-linked core might arise preferentially from the czs-l,4-pentadiene system [31]. The insoluble residue, that contained the label from the incorporated polyunsaturated C18 acids, released the label upon treatment with HI, supporting the notion that some of those aliphatic chains were held together by ether bonds. More recently,... 

The data of Fig. 20 also point out an interesting phenomenon—while the heat transfer coefficients at bed wall and bed centerline both correlate with suspension density, their correlations are quantitatively different. This strongly suggests that the cross-sectional solid concentration is an important, but not primary parameter. Dou et al. speculated that the difference may be attributed to variations in the local solid concentration across the diameter of the fast fluidized bed. They show that when the cross-sectional averaged density is modified by an empirical radial distribution to obtain local suspension densities, the heat transfer coefficient indeed than correlates as a single function with local suspension density. This is shown in Fig. 21 where the two sets of data for different radial positions now correlate as a single function with local mixture density. The conclusion is That the convective heat transfer coefficient for surfaces in a fast fluidized bed is determined primarily by the local two-phase mixture density (solid concentration) at the location of that surface, for any given type of particle. The early observed parametric effects of elevation, gas velocity, solid mass flux, and radial position are all secondary to this primary functional dependence. 

While secondary metabolites of plants and animals have been the subject of many chemical investigations, their associations and roles in their host organism are at times controversial this is particularly so, when insufficient observations exist. Nevertheless, natural products provide fruitful areas of research [69]. There is little doubt that chemical defense against predators is an important aspect of survival. In the marine environment, early observations of nudi-branch- sponge relationships were reported and those relating to isocyano compounds are summarized in Table 6. 

Following the above and other early observations on the photobehavior of Euglena and a large number of other motile and non-motile unicellular organisms7 52 67 , attention... 

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