Glyoxal identity and physical/chemical properties

Glyoxal (CAS No. 107-22-2; C2H2O2) is also known as ethanedial, diformyl, ethanedione, biformal, and oxal. At room temperature, anhydrous glyoxal is a liquid, with a melting point of about 15 °C. It crystallizes in its monomeric form to yield yellow, irregular to prism-like crystals. However, it is generally employed as an aqueous solution (typically containing 30-50% glyoxal), in which hydrated oligomers are present due to nucleophilic addition.

Glyoxal can undertake rotational isomerization between the planar cis and trans conformations, with trans-glyoxal being the more stable isomer.

glyoxal

trans-glyoxal           cis-glyoxal

Some of the most important hydrated derivatives of glyoxal formed by nucleophilic addition in aqueous solution are shown below (Whipple, 1970; Chastrette et al., 1983). These include the monomer ethane-1,1,2,2-tetraol (I), the dimer 2-dihydroxymethyl-(1,3)dioxolane-4,5-trans-diol (II), and the trimer bis(dioxolane) (i.e., 2,2′-bi-1,3-dioxolanyl-4,4′,5,5′-tetraol) (III) — both cis and trans configurations. However, the proportion of the different structures varies with concentration and pH.

glyoxal-1

Physicochemical properties of glyoxal and its commercially employed aqueous solution (40%)

Property Value Reference
Glyoxal
Relative molecular mass 58.04
Density (g/cm3) 1.14 (20 °C) Lide (1995)
Refractive index 1.3826 (20 °C) Lide (1995)
Melting point (°C) 15 Brabec (1993)
Boiling point (°C) 50.4 (101.3 kPa) Lide (1995)
Vapour pressure (kPa) 29.33 (~20 °C) Brabec (1993)
n-Octanol/water partition coefficient (log Kow) -1.65 (calculated) This reporta
-0.85 (measured) BASF AG (1988)
Water solubility (g/litre) 600 (25 °C) Hoechst AG (1994)
Henry’s law constant Betterton & Hoffmann (1988)
(Pa·m3/mol) <3.38 × 10-4 (25 °C, measured)
(dimensionless) <1.36 × 10-7
40% aqueous solution of glyoxal
Vapour pressure (kPa) 2.03 (20 °C) BASF AG (personal communication, 2003)
Density (g/cm3) 1.27 (20 °C) Hoechst AG (1993)
Viscosity (mPa·s) 5-10 (23 °C) BASF AG (1991)
Setting point (°C) ~ -10 Hoechst AG (1993)
pH of aqueous solution 2.1-2.7 Lundberg (1995)

 

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