Synthetic preparation

With my European background, I was when I came to America and still am impressed by the rather loosely organized, more decentralized way of research support. Of course, even in a great country like ours resources are not limitless and inevitably prevailing trends of research set priorities. In my field of interest the 1970s and 1980s were a period when, after two oil crises, research on hydrocarbon fuels and their synthetic preparation had significant public interest and support. Catalytic research in its many aspects was heavily pursued and considered a national priority. 

Until the 1920s the major source of methanol was as a byproduct m the production of charcoal from wood—hence the name wood alcohol Now most of the more than 10 billion lb of methanol used annually m the United States is synthetic prepared by reduc tion of carbon monoxide with hydrogen... 

The purity of a synthetic preparation of methylethyl ketone (C4H8O) can be determined by reacting the ketone with hydroxylamine hydrochloride, liberating HCl (see Table 9.10). In a typical analysis, a 3.00-mL sample was diluted to 50.00 ml and treated with an excess of hydroxylamine hydrochloride. The liberated HCl was titrated with 0.9989 M NaOH, requiring 32.68 ml to reach the end point. Report the percent purity of the sample, given that the density of methylethyl ketone is 0.805 g/mL. 

Vitamins aie specific organic compounds that are essential for normal metabolism. Many participate as cofactors or coen2ymes ia mammalian biochemical reactions. The common thread for the diverse chemical stmctures of the vitamins is that they ate micronutrients. Micronutrients are compounds that are requited ia only small amounts and are not synthesized by humans, either at all or, at least, ia sufficient quantity for metaboHc needs. Vitamins are obtained from the diet or as synthetic preparations used ia food fortification or supplements. 

Synthetic Iron Oxide. This colorant is one or a combination of various synthetically prepared iron oxides, including the hydrated forms. The naturally occurring oxides are unacceptable as color additives because of the difficulties frequendy encountered ia purifyiag them. 

Only synthetically prepared Ti02 can be used as a color additive. It is permitted ia foods to 1% and is used to color such products as confectionary paimed goods, cheeses, and icings. It is also widely used ia tableted dmg products and ia numerous cosmetics such as Upsticks, nail enamels, face powder, eye makeup, and rouges, ia amounts consistent with good manufactuting practice (42). 

Bismuth citrate [813-93-4]—The synthetically prepared crystalline salt of bismuth and citric acid, principally BiC H O. ... 

Bismuth oxychloride [7787-59-9]—Cl Pigment White 14, Cl No. 77163. A synthetically prepared white or nearly white amorphous or finely crystalline, odorless powder consisting principally of BiOCl. Bismuth oxychloride is synthetic pearl essence. It is used in Upstick, nail poHsh, eye makeup, and other cosmetics to produce a lustrous, pearly effect. 

Calcium carbonate [471-34-1]—Cl Pigment White 18, Cl No. 77220, EEC No. E 170. A fine, white, synthetically prepared powder consisting essentially of precipitated calcium carbonate, CaCO. ... 

These researches on the synthesis of the terpenes were commenced in 1900, and has been carried on with considerable success and conspicuous ability ever since. It was considered necessary to synthesise terpineol, and BO establish the formula which analytic reactions supported. The first necessary step was to synthetically prepare the l-methyl-A -cyclo-hexene-4-earboxylic acid, of the formula—... 

There appear to exist two very closely allied terpenes, which have so similar constitutions and characters that it is almost impossible, if not quite so, to separate them when existing together naturally. The synthetically prepared sylvestrene is, of course a distinct individual, the constitution of which will be dealt with directly. 

Mentho-citronellol or menthonyl alcohol, CjjHjoO, is an alcohol of delicate rose odour, and is synthetically prepared as follows —... 

Adrenergic dru mimic the activity of the sympathetic nervous system. These dragp also are called sympathomimetic druc s. Epinephrine and norepinephrine are neurohormones produced naturally by the body. Synthetic preparations of these two neurohormones,... 

One of the longest known synthetically prepared surfactants are the fatty alcohol sulfates, which were prepared on technical scale before 1940. Along with their ethoxylated counterparts, the fatty alcohol ether sulfates, which appeared on the stage shortly after, their use in toiletries is very popular but they can also be found in products for textile industry and auxiliaries in emulsion polymerization. With the exception of soaps, the mentioned anionic surfactants all have a sulfur-containing functional group. Denying the differences between these, their skin irritancy potential is remarkably high. 

The synthetic preparation of 2,8-dichlorodibenzo-p-dioxin was facilitated in that the chemical precursor, 2,4,4 -trichloro-2 -hydroxydiphenyl ether, was available as a pure material. Condensation was induced by heating the potassium salt at 200 °C for 15 hours in bis (2-ethoxyethyl) ether. Product analysis by GLC and mass spectrometry revealed an unexpected dichlorophenol and a monochlorodibenzo-p-dioxin. Further, the product initially isolated by crystallization from the reaction mixture was 2,7-dichlorodibenzo-p-dioxin, rather than the expected 2,8-isomer. Cooling of the mother liquor yielded crystalline plates which were shown to be 2,8-dichlorodibenzo-p-dioxin by x-ray diffraction (Reaction 2). 

The most convenient and successful synthetic preparation of octa-chlorodibenzo-p-dioxin has been described by Kulka (13). The procedure involves chlorination of pentachlorophenol in refluxing trichlorobenzene to give octachlorodibenzo-p-dioxin in 80% yield. Kulka has explained the reaction as coupling between two pentachlorophenoxy radicals. Large amounts (5—15%) of heptachlorodibenzo-p-dioxin were observed in the unpurified product. Since the pentachlorophenol used in this study contained 0.07% tetrachlorophenol, we feel that tetrachloro-phenol may be produced in situ (Reaction 4). Such a scheme would be analogous to the formation of 2,4-dichlorophenol and 3-chlorophenol produced from 2,4,4 -trichloro-2 -hydroxydiphenyl ether (Reaction 2). The solubility of octachlorodibenzo-p-dioxin was determined in various solvents data are presented in Table II. 

It Is hoped that current work being carried out on the amino acid sequence of human PTH (1-4) will be successful, so that synthetic preparations of Important regions of the hormone can become commercially available. This would partially... 

Reagents and diy solvents were purchased from Aldrich or VWR and used without further treatment. Synthetic preparation of the complexes was done using standard Schlenk techniques (diy aigon) unless otherwise stated. Standard rathenium(ll) precursors were prepared as described in the literature or via internal routes. 

Intramolecular hydrogen abstraction has been successfully utilized in a number of interesting synthetic preparations. In general the recombination of the biradical resulting from intramolecular hydrogen abstraction to form a cyclobutanol has received more attention from the point of view of photo-... 

Two more examples of the use of photoreduction as a step in a synthetic preparation are<79-80)... 

In order to determine whether these surfactant vesicles were of polymerized vesicle forms, a 25% V/V ethanol (standard grade) was added to the three year old sample solution. Alcohols are known (34) to destroy surfactant vesicles derived from natural phospholipids, however, synthetically prepared polymerized vesicles are stable in as much as 25% (V/V) alcohol addition. Photomicrographs shown in Figures 7c and 7d indicate that these vesicles partially retain their stability (being mesomorphic) and therefore are suspected to be polymerized surfactants. Whether surfactant molecules of these vesicles are single or multipla bonds in tail, or in head groups remains to be seen. 

At the end of 2003, new research results led to sensational headlines Minerals Cooked Up in the Laboratory Call Ancient Microfossils Into Question was the title chosen by Richard A. Kerr for his article in Science dealing with synthetically prepared silicate carbonates. Their microstructures show morphologies which look exactly like those of filaments which had been assigned as cyanobacterial microfossils of the Precambrian Warrawoona chert formation in western Australia. The synthetic structures consist of silicate-encapsulated carbonate crystals, and in part have a helically twisted morphology reminiscent of biological objects. Simple... 

By contrast, a given synthetic preparation of a major phospholipid possesses fatty acid constituents all of identical chain length and unsaturation. A synthetic PC derivative can be purchased that contains only, for instance, 1,2-dimyristoyl (C14) fatty acid substitutions on its glyceryl... 

The main disadvantage of incorporating sphingolipids in liposomes is their high cost. Purified phosphodiglyceride derivatives may be obtained in bulk quantities and in highly defined synthetic preparations, whereas sphingolipid derivatives are not so readily available in similar purity. 

One difficulty with many synthetic preparations of semiconductor NCs that complicates any interpretation of NMR results is the inevitable distribution of sizes (and exact shapes or surface morphologies). Therefore attempts to make semiconductors as a sort of molecular cluster having a well-defined stoichiometry are of interest to learn potentially about size-dependent NMR parameters and other properties. One approach is to confine the semiconductor inside a template, for instance the cuboctahedral cages of the sodalite framework or other zeolite structures, which have been characterized by multinuclear NMR methods [345-347], including the mesoporous channel material MCM-41 [341, 348]. 

---