2.2 Trans-cyclooctene preparation
The general procedure to produce trans -cyclooctene (TCO) was
followed by using the setup which was applied in case 3 (section 4.5.1).
In the photoisomerisation of cis into trans -cyclooctene,
0.06 g (0.55 mmol) of TCO and 0.136 g (1mmol) of methyl benzoate were
dissolved in 25 ml of (1: 99 diethyl ether: n-hexane) solvent. The
solution was stirred in the inlet vessel and pumped through the micro
flow setup (case 3). On average, each 70 minutes the packed bed was
changed to a fresh bed. Prior to discharge of the used column, the bed
was flushed with solvent (1% ether in n-hexane), dried with compressed
air and stored in an Erlenmeyer flask. Each packed bed approximately
contained 200-220 mg of AgNO3 impregnated silica gel and
was mixed with 1 mm borosilicate glass beads in a mass ratio 1.66:1. The
experiment was carried out for about 3 hours and the final yield was
above 80% (using n-dodecane as internal standard).
Trans -cyclooctene adsorbed on packing powder was extracted by the
following procedure. First, the powder was stirred with a mixture of 10
ml ammonium hydroxide solution (28% NH3 in
H2O) and 10 ml of dichloromethane for about 5 min. Then,
the powder was filtered and the filtrate was transferred to a separating
funnel. The organic layer was separated and the aqueous phase was
extracted by dichloromethane three times (each time 10 ml). The organic
layers were combined, washed with water and dried by using
MgSO4. After filtration, the residue was concentrated
under reduced pressure to provide concentrated trans -cyclooctene.
The yield (80%) was determined by 1H-NMR using 1,3,5
trimethoxybenzene as an internal standard.