The origin of hydrogen generated from formaldehyde in basic solutions Page: 3 of 6
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from the head space was then transferred to a mass spectrometer for analysis. Results are
summarized in Table 1. The short period of time from initiation to quenching of the reaction
ensures very little isotopic exchange between dihydrogen and hydroxide.7 The last line in Table 1
shows that, indeed, little exchange occurs in 30 minutes in the system used when D2 is injected
into basic H20 solution. Our kinetic results presented elsewhere8 indicate that only a very small
fraction of the formaldehyde (<1%) is converted to dihydrogen under the experimental conditions
The results for dihydrogen generation from deuterated water containing NaOD and proteated
glyoxylate (Exp. 6 Table 1) agree with a mechanism requiring one water (or water exchangeable)
hydrogen and one hydrogen from the aldehyde. The -7% H2 in this experiment probably reflects a
reaction with the ~1% proteated water impurity. The preeminent result from the experiments on
formaldehyde is the high percentage of mono isotopic dihydrogen, D2 in Exp. 1 to 3 and H2 in
Exp. 4,5 of Table 1, that was obtained from the corresponding aldehyde. In particular, the high
yield of D2 from the parent CD20 is outstanding. Nonetheless, a pathway involving an hydrogen
atom from water is also required, to explain the significant percentage of HD. Quantitative analysis
of the results in Table 1 would need to consider the isotopic dependence of the two acid-base
equilibria of methylene glycol, and the kinetic isotope effect on the dihydrogen generating
reactions; the margin of error in the results of Table 1 is too large to attempt such an analysis.
The mono isotopic dihydrogen may originate either from a single or two different
formaldehyde molecules. The former is probably the case. A reaction between two formaldehyde
molecules is inconsistent with the dependence of the yield on formaldehyde concentrations that has
been previously reported and was confirmed in this study. In such a bimolecular reaction the
conversion ratio of formaldehyde to H2 would be independent of [CH20] because the rates of both
reactions, the H2 evolution and the Cannizzaro reaction, would have the same concentration
dependence. A reaction between two aldehyde molecules to generate 112 is possible for glyoxylate,
as well as formaldehyde, but no significant amount of mono isotopic product was obtained in the
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Kapoor, S.; Barnabas, F.; Jonah, C.D.; Sauer, M.C. Jr. & Meisel, D. The origin of hydrogen generated from formaldehyde in basic solutions, report, March 1, 1996; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc669675/m1/3/: accessed March 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.