Boiling points of residue and distillate

In series II and III the differences between the boiling points of residue and distillate agree very fairly weU together, except for two observations in II, where there are apparently two mistakes of a whole degree each but these differences do not agree at all well with those derived from the first series. 

As a model system which represents an impure methacrylate, MMA doped with n-propyl alcohol (NPA) was chosen. This combination was arrived at due to the relative hydrophilicity and availability of MMA, and more importantly, the very close boiling points of NPA and MMA (97 and 100 C, respectively). Thus, no possibility existed for separation by simple distillation. A stock solution was prepared which contained 96% MMA and 4% NPA. The heterogeneous purification agents were allowed to interact with an aliquot of this stock solution for one week. After filtration (when necessary) the solution was distilled under vacuum and the resulting product was slowly added to a solution of DPHL in THF at -78 C. The distillate was also checked for residual NPA using a GOW-MAC gas liquid chromatograph (GLC). The results are listed in Table 2. 

Purification. Tellurium can be purified by distillation at ambient pressure in a hydrogen atmosphere. However, because of its high boiling point, tellurium is also distilled at low pressures. Heavy metal (iron, tin, lead, antimony, and bismuth) impurities remain in the still residue, although selenium is effectively removed if hydrogen distillation is used (21). 

When extraction is complete the ether solution of 2-furylcarbinol is distilled until the temperature of the liquid (not the vapor) reaches 95°. Then the residue is distilled under diminished pressure. Some ether and water come over first and the temperature then rises rapidly to the boiling point of 2-furylcarbinol. The yield of 2-furylcarbinol boiling at 75-77°/iS mm. is 310-325 g. (61-63 psr cent of the theoretical amount) (Note 5). 

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). 

After twice washing with 100 ml of diethyl ether, the aqueous phase is made alkaline with 50% caustic soda solution. The liberated base Is twice extracted with 150 ml of diethyl ether. After the ether has been evaporated, the residue Is distilled under reduced pressure and has a boiling point of 184°C/0.1 mm, np70 = i. 5539. 77 g of the pure base in the form of a viscous liquid is thus obtained. The hydrochloride, which is prepared in conventional manner, has a melting point of 128°C. 

Chloro-4-Carbethoxy-6-Ethyl-Pyridine 26 grams of the product just obtained are treated with 81 grams of phosphorus pentachloride in 45 cc of phosphorus oxychloride. The phosphorus oxychloride is distiiled off in a vacuum and the residue is treated with absoiute aicohoi. After distillation there are obtained 24 grams of product having a boiling point of 127° to 131°C/8 mm. 

Distill a small quantity each day to obtain relatively pure o-xylene from a mixture of ortho and para xylene, having boiling points of 142.7°C and 138.4°C, respectively. The feed is 15 Ib-mols (about 225 gallons) per batch, at 0.20 mol fraction para. The desired residue product is 0.020 in the kettle, while the distillate is to be 0.400 mol fraction para. A distillation column equivalent to 50 theoretical plate is to be used. 

Primary amine (0.5 mol) and triethylamine (111.2 g, 1.2 mol) are dissolved in CH2CI2 (500 mL) and slowly mixed with TiC (1 mL). After stirring for 45 min at room temperature Me3SiCl 14 (119.45 g, 1.1 mol) is added dropwise, whereupon the temperature rises to the boiling point of the solvent Stirring under reflux is continued for 3-6 h, followed by evaporation of the solvent. To precipitate Et3N HCI, the residue is mixed with diethyl ether or diisopropyl ether (500 mL), then filtered by suction, again evaporated, and the residue distilled with exclusion of humidity (Scheme 2.18) [60]. 

It should be borne in mind that both in the first and last runnings there is some of the main product. The vapour pressure of a distillable substance is so considerable even below the boiling point that its vapours already pass over along with the more volatile constituents (usually residues of solvent) of the original material. On the other hand the boiling point of a substance rises when it is mixed with higher boiling substances. 

The atmospheric bottom, also known as reduced oil, is then sent to the vacuum unit where it is further separated into vacuum gas oil and vacuum residues. Vacuum distillation improves the separation of gas oil distillates from the reduced oil at temperatures less than those at which thermal cracking would normally take place. The basic idea on which vacuum distillation operates is that, at low pressure, the boiling points of any material are reduced, allowing various hydrocarbon components in the reduced crude oil to vaporize or boil at a lower temperature. Vacuum distillation of the heavier product avoids thermal cracking and hence product loss and equipment fouling. 

The reaction mixture is now transferred to a Claisen flask connected with a water-cooled condenser, and the phosphorus oxychloride is removed at ordinary pressure by raising the temperature of the oil bath (Note 2) gradually to 200-2 20°. The water condenser is then replaced by a short air-cooled condenser and the residual liquid is distilled under reduced pressure (Note 3). A small quantity of phosphorus oxychloride first distils over, after which the receiver is changed and the temperature rises rapidly to the boiling point of />-nitrobenzoyl chloride, I97°/73 Pirn. (i55°/20 mm.). During this distillation the oil bath should be kept at a temperature of about 230-250° (or at 210 -2150 if 20 111m. pressure is used). The yield is 500-534 g. (90-96 per cent of the theoretical amount). The distillate... 

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