LCAR49405
LCAR_024_001
Techset Composition Ltd, Salisbury, U.K.
3/24/2005
C. H. Hamann and T. Ro¨pke
14
According to this principle, sugar anions are produced in our case.
electrocatalyst
1
NaHgx þ ROH ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ! ROꢀNaþ þ H2 þ xHg
2
EXPERIMENTAL
Experiments were carried out at 248C in a conventional beaker with a volume
of 200 cm3. Two hundred grams of sodium amalgam (NaHgX) containing
0.24 wt. % sodium was brought into contact with 20 g catalyst grains (ca.
10 mm diameter; see end of experimental section). Next, 7.77 g of methyl
a-D-glucopyranoside (Fluka) was dissolved in 100 mL N,N-dimethylformamide
¨
(Riedel-de Haen), with a remaining water concentration of 450 ppm. This
solution was added while the reaction mixture was continuously stirred. The
resulting increase of the conductivity (formation of anions and cations in
the solution) was measured with a conductivity meter (Radiometer CDM 83).
The reaction ended after 10 min. This was indicated by reading a constant
final conductivity amounting to 240 mScm21
.
In a further experiment under the same conditions the conductivity
increase during the reaction of NaHgx with water traces in the solvent
without methyl a-D-glucopyranoside led to a final conductivity of 21 mScm21
.
The N,N-dimethylformamide containing the dissolved reaction products
was decanted from mercury and catalyst. Benzylbromide (Fluka) was added
in 1.1 mol equivalents (3.9 g) as scavenger. The addition was calculated from
the amount of electrons (20.9 mmol), which resulted from the complete decompo-
sition of sodium amalgam. The end of the reaction was reached after approxi-
mately 3 hr of stirring at room temperature. In this time the pH value
decreased constantly from pH 9 to 7. After removing of the solvent, the resulting
product mixture was acetylated for easier separation and identification. The
product mixture was dissolved in 160 mL pyridine (Fluka) and 80 mL acetic
¨
anhydride (Riedel-de Haen). After 1 hr of stirring at room temperature the
mixture was hydrolyzed with ice water followed by extraction with four times
40mL dichlormethane (Merck). The combined organic phases were washed
with deionized water, with saturated sodium hydrogencarbonate (Sigma-
Aldrich) solution, and afterwards with deionized water. After drying over
sodium sulphate (Sigma-Aldrich) for 24 hr and removal of dichlormethane, a
product mixture (syrup) of 13.9 g was obtained. Five grams were further separ-
ated by chromatography on a silicagel column (KG 60, 450 mm ꢁ 50 mm) with a
mixture of n-hexane and ethyl acetate (1:1, both Fluka) as eluent.
The catalyst grains used consisted of coal coated with molybdenum carbide,
prepared according to Hamann and Schmittinger.[7] For laboratory purposes
it may be more convenient to use platinum-activated carbon.