Temperature dependent near-UV molar absorptivities of glyoxal and gluteraldehyde in aqueous solution

Molar absorptivities have been determined for glyoxal and gluteraldehyde in aqueous solution. Absorptivities are reported at eight temperatures in the range 5-70 degrees C for wavelengths greater than 200 nm. For glyoxal the data indicate did less than 0.02% of the glyoxal molecules exist in the free dialdehyde form, and that at 25 degrees C approximately 98% of the molecules are hydrated at both carbonyl groups, results that are consistent with previous experiments. For gluteraldehyde hydration of the two carbonyl groups occurs in an independent manner. The following thermodynamic data are found for gluteraldehyde hydration: deltaH = - 35.8+/-1.3 kJ mole(-1), deltaS = 103+/-7 J (mole K)(-1), and K = 7.5+/-2.0. The results for gluteraldehyde are compared with previous results obtained for the hydration of aliphatic aldehydes.