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Glyoxal identity and physical/chemical properties

Release date:2016-11-17 11:37:48 Browsing times:1072

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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.gif

                       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.gif


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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