Hydration photochemical

Post-column in-line photochemical derivatization permits fluorescence detection of the common aflatoxins Bl, B2, Gl, and G2 (60). Chromatographic evidence indicates that photolysis causes the hydration of the nonfluorescent Bl and Gl components to B2a and G2a components, respectively. Analysis of naturally contaminated com samples show no interfering peaks and permits the deterrnination of 1 and 0.25 ppb for Bl and B2, respectively. 

IR spectra, 3, 395 mass spectra, 3, 396 photochemical hydration, 3, 400 reactions... 

Triazin-3-one, 5-amino-acylation, 3, 408 photochemical hydration, 3, 400 synthesis, 3, 433... 

A. Shafferman and G. Stein, The effect of aromatic amino acids on the photochemistry of a disulfide Energy transfer and reaction with hydrated electrons, Photochem. Photobiol. 20, 399-406 (1974). 

In attempts to isolate the aforementioned irradiated products of thymine derivatives at lower temperature, the photochemical reactions were carried out in frozen aqueous solutions containing either thymine or 1,3-dimethylthymine. The resulting products were not hydrates, but had elementary analyses corresponding to the starting material. Molecular weight determination indicated that the products were dimers, and infrared and ultraviolet spectral data suggested cyclo addition across the 5,6-double bond to form a cyclobutane system... 

Compounds 217 and 218, which are the hydrated forms of 118 and 182, give the same products when treated with 8% NaOH (Equation 16 see Equation 3 for comparison) <1992T4545>. The ring expansion of 201 (Equation 17) <2007S225> and photochemical ring contractions of benzothiazines (Scheme 23) <1994TL3365> have also been reported. 

Freshly prepared [Cr(en)3] Br3 is a yellow solid which slowly turns violet-blue, probably because of some photochemically induced reaction (cf. Reference 9). The compound is sparingly soluble in water, from which it can be recrystallized as the hydrate. The resolution of [Cr(en)3]3+ salts by means of tartrate has been described in a previous volume of Inorganic Syntheses.11... 

Classical precedents for these hydration reactions are far fewer than those of the dimerization process, and reveal more complexity in the reaction. Water has been observed to add photochemically to crotonic acid21a>b and to ergotamine.21b Methanol, ethanol, ammonia, and aniline were also found to add photochemically to crotonic acid.21a More recently, methanol and propanol-2 have been observed to add... 

Conditions 5% CH3CH-H2O, = 0.5 (NaC104), T = 20°C, unless otherwise indicated. If and are reported, the rate constants were directly measured from photochemically generated ions. If only log 5 is reported, the selectivity was measured by the azide clock procedure. X is the observed [azide adduct]/[hydration product] ratio extrapolated to 1 M NJ. 

Complexes containing ethylenediamine and related bidentate N donor ligands which are new since 1969, or have been prepared by new methods, are listed in Tables 49 and 50. Water of hydration has not been specified. In general, the complexes have been prepared for kinetic and photochemical investigations. The list is restricted to solids which have been characterized at least by analyses. Cations obtained only in solution have not been included. Most complexes have also been characterized by conductance measurements, and IR, UV and visible spectroscopy. Spectroscopic methods have been used to distinguish between cis and trans isomers, and where cis isomers have been resolved this is indicated in the tables. 

Other cations (Cu2+, Pd2+, Ru3+, Ni2+, Rh3+) incorporated into Nafion-H have been found to promote hydration.36 Other metals that catalyze hydration of alkynes include gold(III),37 ruthenium(in),38 and platinum(II) (Zeise s salt39 40 and halides40), p-Methoxybenzenetellurinic acid is very effective in the hydration of terminal alkynes 41 Similar to the hydration of alkenes, photochemical acid-catalyzed hydration of alkynes is possible ... 

Many 1,2,4-triazine derivatives undergo photochemical hydration reactions, e.g. (174) — (175). Such reactions with 1,2,4-triazine 2-oxides are followed by loss of hydroxide ion to give overall substitution (176) — (177). 

Photochemical reactions of the purines and pyrimidines assume special significance because of the high molar extinction coefficients of the nucleic acids present in cells. Light is likely to be absorbed by nucleic acids and to induce photoreactions that lead to mutations.190 Both pyrimidines and purines undergo photochemical alterations, but purines are only about one-tenth as sensitive as pyrimidines. Photohydration of cytidine (Eq. 23-25) is observed readily. The reaction is the photochemical analog of the hydration of a,P-unsaturated carboxylic acids. Uracil derivatives also undergo photohydration. 

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