Short Path Evaporator

N hydrochloric acid, aqueous 10% sodium hydroxide, and water. The organic layer is dried over anhydrous magnesium sulfate, filtered, and the solvent is removed by rotary evaporation. Short path distillation of the crude product yields methyl 6-oxohexanoate, (7.0-7.8 g, 65-72%),bp 83-86 C/1.5 mm (Note 13). 

After dilution with 225 ml of dichloromethane the flask is cooled to 0 C and 16 ml of triethylamine (0.113 mol) and 21.24 ml of acetic anhydride (0.225 mol) are added via syringe (Note 12), and the solution is stirred under a nitrogen atmosphere for 15 min. The ice bath is removed and stirring is continued for 4 hr. The solution is washed with 150-mL portions of aqueous 0.1 N hydrochloric acid, aqueous 10% sodium hydroxide, and water. The organic layer is dried over anhydrous magnesium sulfate, filtered, and the solvent Is removed by rotary evaporation. Short path distillation of the crude product yields methyl 6-oxohexanoate, (7.0-7.8 g, 65-72%),bp 33-86"C/1.5 mm (Note 13). 

Consider short-path evaporator (SPE) (internal condenser) when pressure must be in 0.013—0.00013 kPa (0.1—0.001 torr) range for larger-scale production, 0.013—0.0007 kPa (0.01 to 0.005 torr) is practical lower pressure limit. 

After dilution with 200 ml. of benzene, the solution is transferred to a 2-1. separatory funnel containing 800 ml. of ice water and shaken thoroughly. The aqueous layer is separated, acidified to pH 3-4 with 2-3 ml. of concentrated hydrochloric acid, and extracted with three 100-ml. portions of benzene. All the organic layers are then combined and dried over anhydrous sodium sulfate. Filtration and concentration of the solution with a rotary evaporator, followed by exposure to high vacuum for 2-3 hours, affords 17.3-19.3 g. of the crude product (Note 3). Low-boiling impurities are removed by vacuum distillation (Note 4), the residual oil (14-15 g.) is transferred to a 50-ml. flask equipped with a short-path distillation apparatus, and vacuum distillation is continued. A forerun is taken until no rise in boiling point is observed, and then 7.2-8.6 g. (23-27%) of dimethyl nitrosuccinate is collected as a colorless oil, b.p. 85° (0.07 mm.), 1.4441 (Note 5). 

A solution of quinoline 1-oxide (0.29 g, 2 mmol) in cyclohexane (1 L) was dehydrated by azeotropic distillation in the reaction vessel. The solution was purged with dry N2 and irradiated with a Hanau high-pressure Hg lamp. The resulting solution was evaporated and the residue was extracted with a little cyclohexane. The insoluble part contained carbostyril (3). The cyclohexane extract was evaporated and the residue purified by short-path distillation at 50°C/0.1 Torr yield 0.174g (60%) moisture-sensitive oil. 

To a stirred solution of 2.0 mmol of LDA in 3.3 mL of a 60 40 mixture of THF/hexane at — 78 °C under a nitrogen atmosphere is added 264 mg (2.0 mmol) of tert-butyl propanoatc in 2 mL of THF. After 30 min stirring a solution of 168 mg (1.5 mmol) of ethyl (t)-2-butenoalein 1.5 mL of THE is added and the mixture is stirred for an additional hour at — 78 °C. The reaction is quenched by addition of sat. NH4C1. Extraction with diethyl ether, drying over NiiCl followed by evaporation of the solvent and short path distillation gives the adduct yield 378 mg (1.2 mmol, 84%). 

If long distillation time is a problem, one can move to continuous distillation with conventional shell and tube heaters accompanied by a typical column bottom (often called a sump) which is a high temperature holdup, or better yet a short path evaporator (falling film, thin film, or wiped film) with usually a smaller receiver (called an accumulator in this case). The most chemical damage is in the thin liquid film at the heat transfer surface, so the short path evaporators do the least thermal damage. 

The precipitate of triphenylphosphine oxide is filtered and washed with 50 ml. of pentane. The solvent is removed from the combined filtrate at the rotary evaporator under water aspirator pressure at room temperature. Distillation of the residue through a 2-cm. Vigreux column attached to a short-path distillation apparatus (Note 4) provides 13.0-14.0 g. (75-81%) of geranyl chloride, b.p. 47-49° (0.4 mm.), w2Sd = 1.4794 (Note 5). 

The combined organic phases are washed with two 200-mL portions of water, four 200-mL portions of saturated sodium bicarbonate solution, and two 200-mL portions of saturated sodium chloride. The organic phase is dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure at room temperature using a rotary evaporator. The crude product is distilled through a short-path distillation apparatus under reduced pressure to give 45.2 g (0.318 mol, 71% yield) of 4-(trimethyls11yl)-3-butyn-l-ol, bp 78-79°C (10 mm), as a colorless liquid (Notes 4 and 5). 

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