The Reversible Hydration of Carbonyl Compounds in Aqueous Solution. Part I, The Keto/Gem‐diol Equilibrium

Abstract

H.-J. Buschmann et al.: The Reversible Hydration of Carbonyl Compounds in Aqueous Solution, Part I 41 T h e same is true with respect to the theoretical approach concerning the stability of W/O microemulsions within the validity range of this model (wo > 20). The surprising validity of the applied equipartition principle as concluded from the excellent coincidence between measured and calculated points, appears noteworthy. T h e latter observation certainly points to a remarkable monodispersity of the discussed W/O microemulsions.The equilibrium constants of hydration (given in parenthesis) have been determined for the aliphatic aldehydes acetaldehyde (1.2), propionaldehyde (1.24), butyraldehyde (0.58), pentanal (0.34), and hexanal (0.41), for the halogenated acetones chloracetone (0.091), fluoroacetone (0.167), and l,l,l-trifluoroacetone (35), and for the 1,2-dicarbonyl compounds 2.3-butanedione (2.1) and 2,3-pentanedione (1.7). Comparing the constants shows, that the equilibrium of hydration of carbonyl compounds is determined mainly by the inductive effects of the substituents.Die Hydratations-Gleichgewichtskonstanten (in Klammern angegeben) wurden fiir die aliphatischen Aldehyde Acetaldehyd (1,2), Propionaldehyd (1,24), Butyraldehyd (0,58), Pentanal (0,34) und Hexanal (0,41), fur die halogenierten Acetone Chloraceton (0.091), Fluoraceton (0,167) und 1,l,l-Trifluoraceton (35) und fur die 1,2-Dicarbonylverbindungen 2,3-Butandion (2,l) und 2.3-Pentandion (1,7) bestimmt. EinVergleich der Konstanten zeigt, daD das Hydratationsgleichgewicht von Carbonylverbindungen vorwiegend durch den induktiven Effekt der Substituenten bestimmt wird. 0 OD 11 I I 00 KI J I + O i O c CHI-CH~--C-C-CHI .J i 1 i , , , , , 483 280 2.33 185 1MA 28, 162 (1974).Czech. Chem. Commun. 31, 388 (1966).

Photochemistry of aqueous pyruvic acid

“…Aldehydes and, to a lesser degree, ketones are known to hydrate in aqueous solution (43)(44)(45)(46)(47)(48)(49)(50). It is known that PA is reversibly hydrated in aqueous solution to its gem-diol and that the equilibrium is both pH-and temperature-dependent, with lower pH and lower temperature both favoring the hydrate (51,52).…”

“…It is known that PA is reversibly hydrated in aqueous solution to its gem-diol and that the equilibrium is both pH-and temperature-dependent, with lower pH and lower temperature both favoring the hydrate (51,52). In aqueous solution at 298 K, ∼35% of PA exists in its keto form, with the majority existing as its gem-diol (13,45,46). The keto form contains a UV chromophore, which can be excited in the near-UV state to induce photolysis.…”

Quantification of Carboxylic and Carbonyl Functional Groups in Organic Aerosol Infrared Absorbance Spectra

“…Particularly for the region between 4000 and 2000 cm −1 , these values were chosen from observations of the detrended spectra (Figure 2) but can be modified according to requirements of individual samples (for instance, higher loadings may require applying the baseline over a wider region). Detrending by differencing is a method commonly used in time series analysis (Box et al 2008) and spectroscopic analysis (Griffiths and Haseth 2007); a gradual variation is removed from sequential observations (over successive wavenumbers in this case). The positions of onset of perturbations in the signal due to analyte absorbance can then be located in the differenced spectrum.…”

“…Compounds such as glyceraldehyde (included in this study) have strongly electron withdrawing substituents with low steric hindrance, leading to high equilibrium constants for hydration (K Hydr 1; Wasa and Musha 1970;Lewis and Wolfenden 1973;Creighton et al 1988). Propionaldehyde, acetaldehyde, and possibly other aldehydic compounds expected to be present in atmospheric particles (De Andrade et al 1993;Yu et al 1999) have lower hydration equilibrium constants (K Hydr < ∼ 1; Lewis and Wolfenden 1973;Guthrie 1975), which can be due to stabilizing electronic, symmetry, or steric effects of the unhydrated molecule (Guthrie 1975;Buschmann et al 1980;Wiberg et al 1994). Therefore, caution is warranted when interpreting spectra from ambient aerosol (and also smog chamber) samples.…”

The occurrence of bisulfite-aldehyde addition products in fog- and cloudwater

“…The hydrolysis constant alone, KH, is 2530, 1.2, and 1.2 for CH20, CH3CHO, and C2HsCHO, respectively (Buschmann et al, 1980). In the hydrated form, aldehydes are less sensitive to photodecomposition (NRC, 1981).…”