The Chemistry of the Isotopes of Oxygen.

Unexpected regioselective carbon–hydrogen bond activation/cyclization of indolyl aldehydes or ketones with alkynes to benzo-fused oxindoles

“…Dialkyl alkynes exhibited slightly lower reactivity than diaryl alkynes ( O-3n), which showed that the oxygen of the carbonyl group in the product originated from the initial material ( Fig. 3a) [35][36][37] . Further investigation demonstrated that 18 O could also be incorporated into benzo-fused oxindole 3n when extra 18 O-labelled water was added into the reaction system, which suggested that water might be produced and then participate in an apparent oxygen transposition in the cascade reaction (Fig.…”

Oxygen isotope fractionation of dissolved oxygen during reduction by ferrous iron

“…Isotope analyses were compared against internal O 2 gas standards using MassLynx software, and d 18 O values are reported in the usual d notation relative to the VSMOW standard with a reproducibility of ±0.2&. d 18 O of air-O 2 (d 18 O = +23.5&) (Kroopnick and Craig, 1972) (Dole, 1952;Holser et al, 1979;Hoefs, 1987). The isotope fractionation factor associated with dissolution at varying ionic strengths is unknown, and it is assumed that any such isotope frac- Two lines of evidence suggest that the rate of oxygen dissolution and oxygen isotope equilibration are relatively fast vs. the rate of oxygen reduction: firstly, experimental measurements of the oxygen transfer coefficient, K L a, indicate that the rate of oxygen dissolution is relatively fast (e.g.…”

“…Dissolved Fe 2+ can form complexes with HFO or various organic compounds in solutions, those of which would have a catalytic effect to accelerate the rate of Fe(II) oxidation (Tamura et al, 1976;Sung and Morgan, 1980;Wehrli, 1990;Liang et al, 1993a,b;Santana-Casiano et al, 2000;Park and Dempsey, 2005). The isotopic composition of dissolved oxygen gas (d 18 O) will be an efficient tracer to better understand biogeochemical processes in water, because O 2 does not readily undergo isotope exchange with water (Dole, 1952;Hoefs, 1987). Hence, d 18 O-O 2 has been applied to the study of oxygen behavior during diffusive transport (Kroopnick and Craig, 1976;Aggarwal and Dillon, 1998;Lee et al, 2003;Wassenaar and Hendry, 2007) and biogeochemical processes such as microbial respiration and photosynthesis (Guy et al, 1993;Quay et al, 1995;Angert and Luz, 2001;Lee et al, 2003;Parker et al, 2005).…”

The determination of total body exchangeable O2 stores

“…The correction factor applied to peak 36 due to isotopic Ar' (mass 36) was 0.0033 of the 40 peak (amounting to approximately 1% of the total peak 36) ; peak 20 due to Ar++ (mass 40) was approximately 0.140 of the 40 peak; peak 28 due to CO+ (mass 28) was approximately 0.106 of the 44 peak. 6 The natural abundance of 180 (18018O) is 0.000004 (4). As this was beyond detection by the methods used in this investigation, no additional background corrections of the 36 peak were required for either gas or blood samples.…”