Kinetics of the Exchange of Oxygen between Benzoic Acid and Water

Equilibrium 2H/1H fractionations in organic molecules: I. Experimental calibration of ab initio calculations

“…Isotope exchange reactions between an organic molecule and water can be described by the first-order rate equation (Roberts and Urey, 1939;Wedeking and Hayes, 1983):…”

“…At natural 2 H abundances, d 2 H values can be approximately substituted for F's (Roberts and Urey, 1939;Sessions et al, 2004). Therefore by regressing ln[(d 2 H t À d 2 H e )/ (d 2 H i À d 2 H e )] versus time, the apparent first-order rate constant (k obsd ) can be obtained as the negative slope.…”

Isotopic exchange of carbon-bound hydrogen over geologic timescales 1 1Associate editor: J. Horita

“…where F is the fractional abundance of D [ϭ D/(D ϩ H)] in the organic molecule initially, at time t, and at equilibrium, and k is the reaction rate constant (Roberts and Urey, 1939;Wedeking and Hayes, 1983;Criss, 1999). Eqn.…”

HPLC-MS technique for radiopharmaceuticals analysis and quality control

“…However, when the peroxide, methyl or ethylene groups were excluded, just four combinations of fluorinated compounds and their acetonitrile (MeCN) associates ionised by association with HCO2-or C1-or by H § removal were found by mathematical combinations ( Table 2, C6H11Os18F ~ C6H1105180 (-) + H20----~ C6H1205180 + OHSuch a scheme can be proposed by analogy with the chemical consequences of/3-decay [13]. Oxygen isotope exchange between 2-[180]glucose and water molecules should occur only with aldehyde groups of the open chain isomer of glucose that is not abundant and has slow exchange [14,15]. Further, the presence of isobaric sorbitol was excluded either by its retention time (V R 1.9 niL) or the mass spectra that did not yield the specific fragments m/z +183 (M +H § § and -363 (2M-H § -in addition to m/z -227 (M.HCO2-).…”