Reaction setup

Figure 8.5. Schematic view of continuous flow reaction setup for IL/scCC>2 systems (adapted from reference [81]). C compressor, CT cold trap, D dosimeter, DP depressuriser, F flowmeter, M mixer, MF metal filter, P HPLC pump, PT pressure transducer and thermocouple, R reactor, S styrene...

Stopped after 180 h time on stream and the reaction setup was evacuated for 10 min at 100 °C. When the experiment was continued after this procedure, the activity had indeed increased by 80% from TOFs of initially 60 h to 108 h Within the next 20 h of reaction the TOFs decreased again from 108 h to 76 h and the selectivity re-estabhshed at 95% n-butanal. A second vacuum period of 10 min resulted in improved TOFs, as depicted in Fig. 4. hi both cases the observed overshooting of the activity directly after evacuation might be caused by either simultaneous removal of CO ligand of the Rh-3-complex leading to higher activity or a rearrangement of the active surface due to sudden evaporation of dissolved heavies. In the first case, a lower selectivity would be expected, which was indeed observed directly after the evacuation. Thereafter, the catalyst solution was re-saturated with CO gas and both the activity and the selectivity approached the initial levels. 

Reactions were conducted at 80°C and at different CO pressures with a reaction time of 29 to 30 minutes. Two different carbonyl compounds were produced by a three-component reaction setup. The yields were determined by GC analysis from the outlet flow. 

Figure 2.1.6 shows the results of such a continuous synthesis process. It shows the variation of the mean particle size during the experiment. The error bars indicate the standard deviation of the particle size distribution of each sample based on the transmission electron micrographs (number distribution). The experiment was performed under the following conditions (A) ammonia, water, and TEOS concentrations were 0.8, 8.0, and 0.2 mol dm-3 7", = 273 K, T2 = 313 K total flow rate was 2.8 cm3 min-1 100 m reaction tube of 3 mm diameter residence time 4 h and (B) ammonia, water, and TEOS concentrations were 1.5,8.0, and 0.2 mol dm- 3 Tx = 273 K, T2 = 313 K total flow rate was 8 cm3 min-1 50 m reaction tube of 6 mm diameter, residence time 3 h. Further details and other examples are described elsewhere (38). Unger et al. (50) also described a slightly modified continuous reaction setup in another publication. 

Similar to the chromatographic selection step, the enrichment of undesired RNA molecules, which may bind to the filter, strep tavidin, or other components of the reaction setup, must be prevented by preselection. For preselection, the RNA pool is passed through a cellulose filter. Unbound RNA is washed from the filter in a small volume of selection buffer. 

The desired weight of diisocyanate is added to the flask plus any ingredients to either adjust the acidity or catalyze the reactions. See Appendix 5 for the required calculations. The diisocyanate is heated to the start temperature with gentle agitation. It is best to provide a complete blanket of nitrogen in the reaction setup from this point on. 

Intramolecular radical cyclization of an aryl bromide and an alkyne can be used to produce dihydroquinolines (Equation 57) <1998TL2965>. An analogous reaction setup utilizes a Lewis acid-catalyzed novel one-pot domino pathway using silver catalysis in high regioselectivity (Scheme 26) <2005OL2675>. Three mole equivalents of the alkyne are used with the final cyclization step arising from alkynic addition. 

The setup and amplification section of a protocol also contains specific recommendations for the prevention of carryover of aerosolized DNA into the new reaction. Dedicated hoods or dead-air boxes are recommended in this step of the procedure. All pipets should be of the positive-displacement type. They should be kept in a dedicated setup hood and should never have previously been used to pipet amplified target. No amplified DNA should ever be brought into this area. During the reaction setup, either dUTP and UNG or isopsoralens may be added. 

Kit manufacturers provide instmctions on measures used to prevent and monitor potential issues during sample preparation and analysis. To prevent carryover contamination, one of the companies recommends the use of separate areas for DNA preparation, reaction setup, and amplification, encouraging that manipulation of PCR products never be performed in the PCR setup or DNA extraction dedicated labs. Also, this kit includes dUTP instead of dTTP, which allows the use of uracil A-glycosylate to prevent PCR product carryover contamination (see Section 9.5.5). 

Figure 6 Schematic view of continuous-flow reaction setup for IL-SCCO2 systems (adapted from po]).

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