Spinning band fractionating columns

A mixture of 314 g, (1.89 moles) of triethyl phosphitef and 200 g. (1.05 moles) of 1,2-dibromoethane is placed in a two-necked, 500-ml., round-bottomed flask equipped with a thermometer well. The flask is attached to a Nester-Faust 24-in. intermediate-model spinning-band distillation column with a column bore of 8 mm.J The pot temperature is maintained at 145-150°C. After its contents are heated at this temperature for lj-2 hours, ethyl bromide commences to distill. Approximately 130 ml. (180-190 g., 1.6-1.7 moles) of ethyl bromide is collected. After the removal of ethyl bromide is completed, the reaction mixture is cooled to ambient temperature and subsequently fractionated under reduced pressure. The following fractions are obtained ... 

Product Evaluation. Gaseous products were analyzed by gas chromatography (GC) using an alumina column. Liquid products were evaluated by physical properties, elemental analysis, liquid chromatographic separation (9), and simulated distillation (10). Distillation to produce a gasoline fraction was accomplished with a spinning band distillation column. Gasoline analysis and evaluation was obtained from an industrial analysis laboratory. 

In the following set of experiments, we wiU examine the applications of a variety of distillation techniques to the purification of liquid mixtures. In Experiments [3A] and [3B] you will conduct simple distillations. In Experiment [3A] a volatile liquid component is separated from a nonvolatile solid. Experiment [3B] illustrates the use of the Hickman still in the separation of hexane and toluene, which have boiling points 42 °C apart. The composition of the fractions is analyzed by refractive index and boiling point. Experiments [3C] and [3D] introduce the use of micro spinning-band distillation columns for the separation of cyclohexane (bp 80.7 °C) and 2-methylpentane (bp 60.3 °Q. The composition of the distillate fractions are determined by gas chromatography. The number of theoretical plates is determined for the spinning-band column used. In Experiment [3D] you wiU be introduced to one of the simplest yet most efficient and powerful distillation techniques for the separation of liquid mixtures at the semimicroscale level, the Hickman-Hinkle stiU. 

In this experiment, the separation of a 2-mL mixture of 2-methylpentane and cyclohexane using a 15-in. spinning-band distillation column is described. The purity of the fractions is determined by gas chromatography and by measurement of the refractive index. Finally, the number of theoretical plates is estimated. You will separate a 50 50 mixture of 2-methylpentane and cyclohexane using the spinning band distillation column shown in Figure 6.4. 

Explain why packed and spinning-band fractional distillation columns are more efficient at separating two liquids with close boiling points than are unpacked columns. 

Cyclobutanone [1191-95-3] M 70.1, b 96-97 , d 0.931, n 1.4189. Treated with dilute aqueous KMn04, dried with molecular sieves and fractionally distd. Purified via the semicarbazone, then regenerated, dried with CaS04, and distd in a spinning-band column. Alternatively, purified by preparative gas chromatography using a Carbowax 20-M column at 80°. (This treatment removes acetone). 

Fractionated through a 90cm Monel spiral column, or other efficient fractionating or spinning band column and collecting the middle fraction. 

Ethyl stearate [111-61-5] M 312.5, m 33 , b 213-215 /15mm. The solid portion was separated from the partially solid starting material, then crystd twice from EtOH, dried by azeotropic distn with benzene, and fractionally distd in a spinning-band column at low pressure [Welsh Trans Faraday Soc 55 52 1959]. 

Methyl-2-butanone (methyl isopropyl ketone) [563-80-4] M 86.1, b 93-94 /752mm, d 0.818, n 1.410, pK -7.1 (aq H2SO4). Refluxed with a little KMn04. Fractionated on a spinning-band column, dried with CaS04 and distd. 

Pentyl acetate (n-amyl acetate) [628-63-7] M 130.2, b 147-149 /atm, 149.55 , 149.2 /atm, d4 0.8753, n 1.4028. Purified by repeated fractional distn through an efficient column or spinning band column. [Timmermann and Hennant-Roland J Chim Phys 52 223 7955 Mumford and Phillips J Chem Soc 75 1950 H NMR Crawford and Foster Can J Phys 34 653 7956.]... 

VinyInaphthaIene [826-74-4] M 154.2, b 124-12S /lSnim. Fractionally distd under reduced pressure on a spinning-band column, dried with CaH2 and again distd under vacuum. Stored in sealed ampoules in a freezer. 

The drying agent is removed by filtration, and the filtrate is distilled under nitrogen through a spinning band column (Notes 6 and 7). The fraction, boiling at 92-93° (725 mm.), is collected to yield 54.2-60.0 g. (66-73%, based on chloroform) of lerf-butyl isocyanide (Notes 8 and 9). 

The pentane solution is dried over anhydrous magnesium sulfate and fractionated with an efficient spinning-band column (Note 10). After foreruns of pentane and glyme containing f-nitrosobutane are removed (Note 11), 26-27 g. (42-43%) of red di-/-butyl nitroxide, b.p. 59-60° (11 mm.), is obtained. 

The reaction mixture is then cooled to 35-40° and poured into a stirred solution of 230 g. of sodium chloride and 6.0 g. of sodium acetate in 600 ml. of water at 40°. The mixture is stirred for 15 minutes and then is transferred to a separatory funnel the layers are separated, and the lower, aqueous layer is discarded. The crude product is distilled at reduced pressure through a stainless steel spinning-band column (Note 5). The yield of the /3-lactone dimer of dimethylketene is 122-132 g. (61-67%) b.p. 69-71.5° (14 mm.) (Note 6). The product may be redistilled and the fraction boiling at 119.5-120° (150 mm.), 20d 1.4380, collected. 

A 45-cm. spinning band column was employed by the submitter, but any distillation column with a low holdup may be used. Since the products have widely different boiling points, careful fractionation during distillation is not needed. Because the phenylsulfur trifluoride and benzenesulfinyl fluoride slowly attack glass, all equipment should be rinsed with water and acetone immediately after use to minimize etching. 

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