Microscale distillation

An instrument used to measure melting point. A microscale distillation apparatus. 

Some stages in the evolution of microscale distillation equipment from alchemical equipment (dates represent approximate time of popular use). 

Basic microscale distillation (external monitoring of temperature). Do not use a mercury thermometer. 

Basic microscale distillation using thermometer adapter (internal monitoring of temperature). 

Reduced-pressure microscale distillation (internal monitoring of... 

Microscale Distillation. Microscale organic chemistry, with a history that spans more than a century, is not a new concept to research scientists however, the traditional 5- to 100-gram macroscale of student laboratories was reduced one hundred to one thousand times by the introduction of microscale glassware in the 1980 s to reduce the risk of fire and explosion, limit exposure to toxic substances, and minimize hazardous waste. Microscale glassware comes in a variety of configurations, such as Mayo-Pike or Williamson styles. Distillation procedures are especially troublesome in microscale because the ratio of wetted-glass... 

The volume of distillate in microscale distillations is typically less than 500 xL (0.5 mL), so it is important to minimize the surface area of glass to avoid unnecessary loss of material. This is accomplished by combining the stillhead and collector in a single piece called a Hickman stillhead, which has a reservoir for containing distillate and may have a port to facilitate removal of distillate (Fig. 2.38). 

Another common method for removing solvent is by simple microscale distillation (Sec. 2.13). Discontinue heating when only a small amount of solvent remains, and do not overheat the stillpot, as your product may decompose if heated too strongly. The stillpot should be cooled to room temperature. Remove the Hickman stillhead and water condenser and insert an air condenser into the vial. Attach a thermometer adapter fitted with a glass tube to the top of the condenser and attach the tube to a vacuum source (Fig. 2.73). If you use a water aspirator, be sure to place... 

Setting Up Place a spinvane in the conical vial. Using a calibrated Pasteur pipet, add 1 mL of cyclohexanol and 0.5 mL of 9 AT sulfuric acid to the vial. Thoroughly mix the contents by briefly stirring or swirling the liquid for a few seconds. Equip the vial for microscale distillation and circulate cold water through the condenser. 

Distillation Using a filter-tip pipet. transfer the dried organic layer into a clean 5-mL conical vial equipped with a stirbar. Attach the vial to a Hickman stillhead equipped with a water-cooled condenser (Fig. 2.38) and perform a microscale distillation. The first fraction should contain solvent and unchanged 1-hexene and should distill at a bath temperature below 110 °C. Remove this fraction from the still, and collect a second fraction, using a bath temperature of 165 °C. This fraction should mainly consist of the desired product. Transfer this distillate to a fared screw-cap vial. 

The most powerful microscale distillation system currently available is the 2.5-in. vacuum-jacketed microscale spinning-band distillation column (see Fig. 3.16 and Experiment [3C] for description and details).This still is designed for convention downward distillate collection and nonstopcock reflux control. The column is rated at 10 theoretical plates. 

Why is it very important that the hot vapor in microscale distillations climb the column very slowly ... 

The spinning band overcomes two major problems of microscale distillations by wiping the liquid condensate rapidly from the column walls. What are these problems ... 

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