5 A molecular sieve trap

After addition of suitable internal standards the fractions are concentrated by rotary evaporation to > 1 mL. The rotary evaporator should be fitted with a solvent trap as shown in Fig. 18-2 to prevent refluxing solvent to flow back into the attached flask. The rotary evaporator air inlet should either be connected to a tank of compressed nitrogen or be fitted with a 5 A molecular sieve trap. The concentrated samples are transferred with a 100-250 mL syringe into glass ampoules as shown in Fig. 18-3 which are flushed with nitrogen and flame-sealed while being cooled to well below room temperature with a mixture of crushed ice cubes and table salt. 

After partial evaporation the pressure inside the rotary evaporator is equilibrated with the atmosphere through a 5 A molecular sieve trap. The solution is transferred into a 10 mL volumetric flask with a Pasteur pipette and made up to volume. This solution is ready for measurement in the UV spectrofluorimeter. Should volumetric flasks not be available, the voliunes of individual extracts may be determined by weighing on a top-loading balance. The densities are 0.6603 g/cm (n-hexane) and 0.77855 g/cm (cyclohexane), both at 20 °C. 

Temperature-programmed reduction (TPR) experiments were carried out in a quartz-made microreactor connected to a thermal conductivity detector (TCD) equipped with active charcoal column, using 0.2 g calcined catalysts from 373 K to 1073 K. The gas stream, 5 % H2 diluted by nitrogen as reducing gas, was fed via a mass flow controller. After the reactor, the effluent gas was led via a 3 A molecular sieve trap to remove the produced water. 

Rotary evaporator. With solvent trap (Fig. 18-2) and 5 A molecular sieve at the air inlet. 

TPR has been carried out in a Micromeritics Autochem 2910 instrument equipped with the CryoCooler system for reaching subambient temperature by means of liquid nitrogen. A molecular sieve trap has been put between the sample holder and the detector in order to absorb water that is formed dining the rednction process. 100 mg of wet sample has been introduced in the sample holder, dried in situ by a nitrogen flow at 393 K for two h. Then the sample was cooled down to 153 K under Ar flow (50 cm min" ) after which, the flow was switched to 5% H2 in Ar (50 cm min ) and maintained throughout the analysis. After a baseline had been established, the temperature was started at a rate of 5 K min up to 623 K. A TPR experiment on sample Pduns reference was carried out on 10 mg of sample following the same procedure described above for the catalysts. 

Figure 5. Effect of adsorbent mass in the molecular sieve trap on the ethylene, ethane and total C2 selectivity at a fixed methane conversion of 15%. Recirculation flowrate 220 cm3 STP/min...

Into a 3-L three-neck round-bottom flask equipped with a thermometer, a KPG stirrer and a 20-cm Vigreux column linked to a distillation apparatus with three cooled traps (MeOH/dry ice) were placed rw-4.5-(thiocarbonyldioxy)spiro[2.3]hexane (50 98.2 g, 0.63 mol) and freshly distilled tributyl phosphite (472 g, 1.89 mol). The mixture was heated at 115 120 0C/17 Torr for 44 h. The condensed distillates in the traps were combined, dried over 4 A molecular sieves and fractionally distilled through a 40-cm Vigreux column to give the product 51 yield 40 g (80%) bp 66.5 nC (760 Torr). 

The methods reported for the preparation of the oxazaborolidine include the reaction of diphenylprolinol with methylboronic acid 1) in toluene at 23°C for 1.5 hr with 4 A molecular sieves present and 2) in toluene at reflux for 3 hr using a Dean-Stark trap, bolh followed by evaporation of solvent and molecular distillation (0.1 mm, 170°C).5( An alternate method involved heating a toluene solution of 2-naphthylprolinol and methylboronic acid at reflux for 10 hr using a Soxhlet extractor containing 4 A molecular sieves.5 These methods afforded erratic results. The submitters therefore developed an alternate synthesis. 

In a 100-mL dry Schlenk flask were added 2.0 mmol amino alcohol, 2.1 mmol phenyl-boronic acid, and 40 mL dry toluene. The suspension mixture was heated to reflux in an atmosphere of argon for 24 h with azeotropic removal of water, which was trapped by 10 g 4-A molecular sieves placed in a pressure-equalizing dropping funnel between the flask and the condenser. The toluene was then removed in vacuo, and the residue was purified by Kugelrohr distillation (215-220°C, 0.5 mbar) to give 93% pure (5)-l,3,3-triphenylperhydropyrrolo[ 1,2-c] [ 1,2,3] oxazaborole. 

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