Source natural

Twenty-three radioactive isotopes of iodine have been identified. The only naturally-occurring radioisotope, I, has a half-life of 1.57 X 10 years (Walker et o/., 1977). It is produced in nature by the interaction of high-energy particles with xenon in the upper atmosphere and, to a lesser extent, by neutron-initiated reactions Te(n, 7) and Te(n, 2n) and spontaneous fission (Kohman and Edwards, 1966). Edwards (1962) estimated that these natural reactions would produce a global steady state atom ratio of of lO , which 

Kohman and Edwards (1966) estimated should result in a ratio of about 2 X 10 in the oceans. More recently, analyses of samples of a natural silver iodide deposit in Australia (Srinivasan et aL, 1971) have led to an estimate that the equilibrium terrestrial ratio was bounded as follows  

Kohman and Edwards (1966) also estimated that natural production resulted in a steady state inventory of 8.7 x 10 atoms of I in the hydrosphere (primarily oceans), equivalent to 31 Ci( 1.8 X 10 g) and that the transfer rate fi m oceans to sediments of I is 2.3 x 10 g 

The quantity of I in the lithosphere is more difficult to estimate. Based only on the spontaneous fission of U widely dispersed at 3 /ig g , a content of 0.01 Ci can be obtained. However, from the atom 

Since the atmosphere can be treated, on a large scale, as if it were in steady state, we have a model that views the atmosphere as having sources, a reservoir (i.e. the atmosphere itself) and removal processes, all in delicate balance. The sources need to be quite stable over the long term. If they are not, then the balance will shift. In terms of our earlier analogy, the level in the leaking bucket will change. 

The best-known, and most worrying, example of such a shift is the increasing magnitude of the C02 source because of the consumption of vast amounts of 

The world-wide demand for vanillin amounts to 15,000-16,000 tonnes annually. Its main customer is the flavoms industry, which accounts for 84% 13 % find application in drug preparation e.g. (L)-DOPA and papaverine), but only 3 % in perfumery. With a price of 10-15 Emo per kilogram, the market is worth around 180 million Euro per annmn. Only 20-40 tonnes of vanillin come directly from natural sources. [153, 157] This corresponds approximately to 1,500-2,000 tonnes of dried vanilla pods. 

337 Un BoisVanill isa valuable perfume from the absolue of Mexican vanilla. 

38 Since 1973, the musk deer has been a protected species In all parts of East Asia, and the black market has shrunk to a minimum. In recent times, attempts have been made to obtain musk by curettage (scraping out of the scent glands) of live animals raised on farms. 

Civet is a yellowish viscous secretion of the Large Indian civet (Viverra zibetha) and African civet (Civettictis civetta) (Fig. 3.39). Both sexes use it for the marking of their roaming area. For centuries the scented material is obtained by curettage of the perineal glands, located near the sexual organs of the civets. 

The muskrat (Ondatra zibethicus) is a rodent, around 30 cm long, belonging to the family of voles it is valued especially for its fur (Fig. 3.40). Originally native to North America, the muskrat is also found nowadays in central Europe. The muskrat has pockets near its sexual organs, which produce a musk-like scent. A chemical process of extracting it was developed in the 1940s, but it did not prove commercially worthwhile. [158] 

The total amount of mercury in various global reservoirs is estimated at 334.17 billion metric tons almost all of this amount is in oceanic sediments (98.75%) and oceanic waters (1.24%), and most of the rest is in soils. Living aquatic organisms are estimated to contain only 7.0 metric tons of mercury. 

The largest pool of methylmercury in freshwater biota is found in fish tissues, and fly larvae are alleged to play an important role in mercury cycling from feeding on beached fish carcasses, as judged by observations on 

Mercury is emitted from volcanoes into the atmosphere, along with large quantities of lead, cadmium, and bismuth. About 6000 tons of mercury is discharged into the atmosphere every year from all sources, and from all volcanoes about 60 tons or about 1% of the total. 

Virtually all mercury in the Florida Everglades from natural sources (39% of the total mercury deposited) is attributed to release from the soil through natural processes, including microbial transformations of inorganic 

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Several substances having vitamin K. activity have been isolated from natural sources. Vitamin Ki from alfalfa oil, is 2-methyl-3-phytyl-1,4-naphthoquinone. 

The chief uses of chromatographic adsorption include (i) resolution of mixtures into their components (Li) purification of substances (including technical products from their contaminants) (iii) determination of the homogeneity of chemical substances (iv) comparison of substances suspected of being identical (v) concentration of materials from dilute solutions (e.g., from a natural source) (vi) quantita tive separation of one or more constituents from a complex mixture and (vii) identi-1 ig- II, 16, 3. gcajjQij and control of technical products. For further details, the student is referred to specialised works on the subject. ... 

Hydrocarbons are divided into two mam classes aliphatic and aromatic This classifi cation dates from the nineteenth century when organic chemistry was devoted almost entirely to the study of materials from natural sources and terms were coined that reflected a substance s origin Two sources were fats and oils and the word aliphatic was derived from the Greek word aleiphar meaning ( fat ) Aromatic hydrocarbons irre spective of their own odor were typically obtained by chemical treatment of pleasant smelling plant extracts... 

Cyclopentane and cyclohexane are present m petroleum but as a rule unsubsti tuted cycloalkanes are rarely found m natural sources Compounds that contain rings of various types however are quite abundant... 

Cholesterol when isolated from natural sources is obtained as a single enantiomer The observed rotation a of a 0 3 g sample of cholesterol in 15 ml of chloroform solution contained in a 10 cm polarimeter tube is -0 78° Cal culate the specific rotation of cholesterol... 

Steroids are another class of natural products with multiple chirality centers One such compound is cholic acid which can be obtained from bile Its structural formula IS given m Figure 7 12 Cholic acid has 11 chirality centers and so a total (including cholic acid) of 2" or 2048 stereoisomers have this constitution Of these 2048 stereoiso mers how many are diastereomers of cholic acid s Remember Diastereomers are stereoisomers that are not enantiomers and any object can have only one mirror image Therefore of the 2048 stereoisomers one is cholic acid one is its enantiomer and the other 2046 are diastereomers of cholic acid Only a small fraction of these compounds are known and (+) cholic acid is the only one ever isolated from natural sources... 

Beginning in the 1980s research directed toward the isolation of new drugs derived from natural sources identified a family of tumor inhibitory antibiotic substances characterized by novel struc tures containing a C C—C=C—C C unit as part of a nine or ten membered ring With one double bond and two triple bonds (-ene + di- + -yne) these com pounds soon became known as enediyne antibiotics The simplest member of the class is dynemian A most of the other enediynes have even more compli cated structures... 

NMR IR UVVIS and MS) were obtained using pure substances It is much more common however to encounter an organic substance either formed as the product of a chemical reaction or iso lated from natural sources as but one component of a mixture Just as the last half of the twentieth cen tury saw a revolution in the methods available for the identification of organic compounds so too has it seen remarkable advances in methods for their separation and purification... 

For a review of the isolation of chitin from natural sources and some of its uses see the November 1990 issue of the Journal of Chemical Education (pp 938-942)... 

Following the movement of airborne pollutants requires a natural or artificial tracer (a species specific to the source of the airborne pollutants) that can be experimentally measured at sites distant from the source. Limitations placed on the tracer, therefore, governed the design of the experimental procedure. These limitations included cost, the need to detect small quantities of the tracer, and the absence of the tracer from other natural sources. In addition, aerosols are emitted from high-temperature combustion sources that produce an abundance of very reactive species. The tracer, therefore, had to be both thermally and chemically stable. On the basis of these criteria, rare earth isotopes, such as those of Nd, were selected as tracers. The choice of tracer, in turn, dictated the analytical method (thermal ionization mass spectrometry, or TIMS) for measuring the isotopic abundances of... 

However, the quantity of Pa produced in this manner is much less than the amount (more than 100 g) that has been isolated from the natural source. The methods for the recovery of protactinium include coprecipitation, solvent extraction, ion exchange, and volatility procedures. AH of these, however, are rendered difficult by the extreme tendency of protactinium(V) to form polymeric coUoidal particles composed of ionic species. These caimot be removed from aqueous media by solvent extraction losses may occur by adsorption to containers and protactinium may be adsorbed by any precipitate present. 

Artificial materials include aUphatic, aromatic, and terpene compounds that are made synthetically as opposed to those isolated from natural sources. As an example, ben2aldehyde may be made synthetically or obtained from oil of bitter almond (51) and t-menthol may be made synthetically or isolated from oil of Mentha arvensis var. to give Bra2iUan mint oil or com mint oil. 

Fluorine, which does not occur freely in nature except for trace amounts in radioactive materials, is widely found in combination with other elements, accounting for ca 0.065 wt % of the earth s cmst (4). The most important natural source of fluorine for industrial purposes is the mineral fluorspar [14542-23-5] CaF2, which contains about 49% fluorine. Detailed annual reports regarding the worldwide production and reserves of this mineral are available (5). A more complete discussion of the various sources of fluorine-containing minerals is given elsewhere (see Fluorine compounds, inorganic). 

Aroma. Chemicals. Specialty chemicals produced either by extraction from natural sources or by synthesis, such as vanillin [121 -33-5],... 

Magnesium sulfate heptahydrate may be prepared by neutralization of sulfuric acid with magnesium carbonate or oxide, or it can be obtained directly from natural sources. It occurs abundantly as a double salt and can also be obtained from the magnesium salts that occur in brines used for the extraction of bromine (qv). The brine is treated with calcium hydroxide to precipitate magnesium hydroxide. Sulfur dioxide and air are passed through the suspension to yield magnesium sulfate (see Chemicals frombrine). Magnesium sulfate is a saline cathartic. 

Imperial Chemical Industries (ICI) operated a coal hydrogenation plant at a pressure of 20 MPa (2900 psi) and a temperature of 400—500°C to produce Hquid hydrocarbon fuel from 1935 to the outbreak of World War II. As many as 12 such plants operated in Germany during World War II to make the country less dependent on petroleum from natural sources but the process was discontinued when hostihties ceased (see Coal conversion PROCESSES,liquefaction). Currentiy the Fisher-Tropsch process is being used at the Sasol plants in South Africa to convert synthesis gas into largely ahphatic hydrocarbons at 10—20 MPa and about 400°C to supply 70% of the fuel needed for transportation. 

Occurrence. S(—)-Mahc acid occurs widely in biological systems. It is the predominant acid in many fmits (Table 4). However, malic acid occurs in relatively low concentrations, thus making its isolation from natural sources expensive and impractical. 

Iron Porphyrins. Porphyrias (15—17) are aromatic cycHc compouads that coasist of four pyrrole units linked at the a-positions by methine carbons. The extended TT-systems of these compounds give rise to intense absorption bands in the uv/vis region of the spectmm. The most intense absorption, which is called the Soret band, falls neat 400 nm and has 10. The TT-system is also responsible for the notable ring current effect observed in H-nmr spectra, the preference for planar conformations, the prevalence of electrophilic substitution reactions, and the redox chemistry of these compounds. Porphyrins obtained from natural sources have a variety of peripheral substituents and substitution patterns. Two important types of synthetic porphyrins are the meso-tetraaryl porphyrins, such as 5,10,15,20-tetraphenylporphine [917-23-7] (H2(TPP)) (7) and P-octaalkylporphyrins, such as 2,3,7,8,12,13,17,18-octaethylporphine [2683-82-1] (H2(OEP)) (8). Both types can be prepared by condensation of pyrroles and aldehydes (qv). 

AH metals come originally from natural deposits present in the earth s cmst. These ore deposits result from a geological concentration process, and consist mainly of metallic oxides and sulfides from which metals can be extracted. Seawater and brines are another natural source of metals, eg, magnesium (see Chemicals frombrine Magnesium and magnesium alloys Ocean raw materials). Metal extracted from a natural source is called primary metal. 

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