Hydrogen occurrence

Synonyms sulfur hydride sulfureted hydrogen Occurrence and Uses... 

KhisinaN. R., Wirth R., Andrut M., and Ukhanov A. V. (2001) Extrinsic and intrinsic mode of hydrogen occurrence in natural olivines FTIR and TEM investigation. Phys. Chem. Mineral. 28, 291-301. 

The present-day sediments of the Atlantic do not contain a substantial amount of zeolite (Elderfield, 1976). Clinoptilolite has been found, however, in association with sepiolite, quartz, and mont-morillonite (Hathaway and Sachs, 1965 Bonatti and Joensuu, 1968). The clay minerals palygorskite and sepiolite are usually minor constituents of marine sediments (Hathaway, 1979), and may be detrital (Weaver and Beck, 1977) or authigenic. Their hydrogenous occurrences are usually in basal sediment sections exposed to fluids of elevated temperarnres (Bonatti and Joensuu, 1968 Church and Velde, 1979 see below). 

Scherbakov, A.V. and Kozlova, N.D., 1986. Hydrogen occurrence in underground fluids and the relation of anomalously high concentrations to deep faults in the USSR. Geotectonics, N2 56-66 (in Russian). 

Tartaric acid is noteworthy for a) the excellent way in which the majority of its salts Crystallise, and h) the frequent occurrence of salts having mixed cations. Examples of the latter are sodium potassium tartrate (or Rochelle salt), C4H40 NaK, used for the preparation of Fehling s solution (p. 525), sodium ammonium tartrate, C4H OaNaNH4, used by Pasteur for his early optical resolution experiments, and potassium antimonyl tartrate (or Tartar Emetic), C4H404K(Sb0). The latter is prepared by boiling a solution of potassium hydrogen tartrate (or cream of tartar ) with antimony trioxide,... 

The occurrence of a hydrogen isotope effect in an electrophilic substitution will certainly render nugatory any attempt to relate the reactivity of the electrophile with the effects of substituents. Such a situation occurs in mercuration in which the large isotope effect = 6) has been attributed to the weakness of the carbon-mercury bond relative to the carbon-hydrogen bond. The following scheme has been formulated for the reaction, and the occurrence of the isotope effect indicates that the magnitudes of A j and are comparable ... 

Many artificial (likely radioactive) isotopes can be created through nuclear reactions. Radioactive isotopes of iodine are used in medicine, while isotopes of plutonium are used in making atomic bombs. In many analytical applications, the ratio of occurrence of the isotopes is important. For example, it may be important to know the exact ratio of the abundances (relative amounts) of the isotopes 1, 2, and 3 in hydrogen. Such knowledge can be obtained through a mass spectrometric measurement of the isotope abundance ratio. 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Xanthine, 8-ethyl-synthesis, 5, 574 Xanthine, 9-hydroxy-8-methyl-synthesis, S, 596 Xanthine, 1-methyl-deuterium-hydrogen exchange, S, 527 methylation, S, 533 occurrence, S, 598 reduction, 5, 541 synthesis, S, 589 Xanthine, 3-methyl-deuterium-hydrogen exchange, S, 528 methylation, S, 533 reduction, S, 541 synthesis, S, 595 Xanthine, 7-methyl-deuterium-hydrogen exchange alkylation, S, 527 reduction, S, 541 synthesis, S, 587 Xanthine, 8-methyl-synthesis, S, 574 Xanthine, 9-methyl-methylation, S, 533 nitration, 5, 538... 

Ammodendrine, C jH oONj, HjO (No. 1, table, p. 116). The base has m.p. 73 °, becomes anhydrous at 70-80°, and then melts at 50-60°, Wd i 0°. The salts are amorphous and deliquescent except the hydriodide B. HI, which forms a crystalline precipitate, m.p. 218-20°, from alcohol, and the perchlorate, m.p. 199-200°. An amorphous A-benzoyl derivative was obtained. With methyl iodide ammodendrine behaves as a secondary base, yielding first A-methylammodendrine hydriodide (a crystalline precipitate, m.p. 183-5°, from a mixture of alcohol and acetone), and at the second stage iV-methylammodendrine methiodide, m.p. 163-5°. On hydrogenation ammodendrine furnishes a dihydro-base, which is hydrolysed into acetic acid and 2 3 -dipiperidyl, C oHjoNj, and must be dZ-A-acetyl-3-a-piperidylpiperidine. Ammodendrine should therefore be acetyltetrahydroanabasine and is of biological interest as the first recorded occurrence of this type of alkaloid in the Leguminoss. ... 

As pointed out in the introduction, if one of the substituents on the nitrogen atom is a hydrogen atom, tautomeric equilibrium between enamino and imino forms strongly favors the latter form 18,140,141). According to physiochemical measurements, the occurrence of simply substituted /1 -pyrrolines and zl -piperideines is very improbable. The formulation of this type of compound with a double bond in the position (used mainly by early authors) was of formal meaning only, having no experimental evidence (142-144). 

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