The Subpction d Glutaraldehyde to the Fehling Test and to the Corrected Benedict Test A solution containing 200 ml of distilled water, 32 g (0.20 mole) of anhydrous eopper(II) sulfate, 12 g (.04 mole) of sodium potassium tartrate tetrahydrate, 200 ml of glutaraldehyde, and 1000 ml of potassium hydroxide was heated on a hot plate until a brick red precipitate was formed. A solution containing 200 ml of distilled water, 0.20 moleof anhydrous copper(I1) sulfate, 15 g (0,051 mole) of sodium eitrate dihydrate, 200 ml of glutaraldehyde, and 1000 ml of potassium carbonate also was heated on a hot olate. Fizzine or effervescence. indieatine the evolution of carbon dioxide, took olace and ceased after several minutes of heating but th;? characteristic hiue color remained. The addition of 400 ml of pota&um hydroxide after a few extra minutes of beating caused the desired hriek red precipitate to form. The above reactions were executed so that redox equations1could be established for the Fehlingtest2and for the corrected Benedict test3 with respect to compounds containing two aldehyde groups such as glutaraldehyde. The molecular and the ionic redax equations with respect to the Fehling test are 0 0 0 0
11
HC-(CHh-CH
11
A
+ 4CuSOa + 10 KOH NaK -ate
0
0
II
II
HC-(CHZ)~-CH
11
11
0
11
11
0
I
II + 4CuZ+ + 10 OH- d -oL-(cH2)3-co+ 6HzO + 2Cu20 NeK tartrate A
hut the equations with respect to the corrected Benedict test are n n n
HC-(CHd-CH
+ 4KzS04 + 6H20 + 2CuzO
KOC-(CH2)bCOK
A
n
11
+ 4Cu2+ + Cog2-+ SOH-+-OC-(CHdsCON. citrate
i
+ COz + 5H20 + 2Cu20
Balancing these equations was simplified after the total valence of carbon in glutaraldehyde and in potassium glutarate was obtained. The Fehling test and the Benedict test correded with respect to glutaraldehyde should apply to other compounds having two or more aldehyde groups in the molecule hut the total valence of carhon in that aldehyde and in the potassium or sodium salt formed must be found in order to simplify the halancing of these equations given that a brick red precipitate is also obtained in these cases.
'
Hogwss, Johnson. and Armsmng. "(Xlalitative Analysis and Chemical Equilibrium," Holt. Rinehari and Winston Inc.. New York. 1966, pp. 92-105 and 217. McElvain, "The Characterization of Organic Compounds." The Macmillan Company, New York. 1965, pp. 92 and 133. Hill, Jr., William 0.. J. CHEM. E m . , 59, 334(1982). William D. HIII, Jr. North Carolina Central Universihl Durham. NC 27707
Volume 61
Number 12
December 1984
1085
