Temperature reflux

The design of any of the distillation processes discussed requires choosing an operating pressure, bottoms temperature, reflux condenser temperature and number of trays. This is normally done using any one of several commercially available process simulation programs which can perform the iterative calculations discussed in Chapter 6. 

The manufacture of the cyclohexyl analog is as follows. Phenyl magnesium bromide was prepared from 48.5 g (0.308 mol) of bromobenzene, 7 g (0,29 mol) of magnesium, and 125 ml of dry ether. To it was added at 5°C over a period of A hour 40 g (0.18 mol) of cyclohexyl (3-(N-piperidyl)-ethyl ketone (BP 115° to 117°C/1 mm) in 125 ml of dry ether. The mixture was allowed slowly to come to room temperature, refluxed for one hour, and then poured into ice containing 80 ml of concentrated hydrochloric acid. Ammonium chloride (100 g) and 200 ml of concentrated ammonium hydroxide were added and the organic layer was separated. After drying and removing the solvent, the residue was distilled under reduced pressure. The base distilled at 158° to 170°C (1 mm) and solidified. Upon recrystallization from methanol it melted at 112° to 113°C. 

Manganese(III)-promoted radical cyclization of arylthioformanilides and a-benzoylthio-formanilides is a recently described microwave-assisted example for the synthesis of 2-arylbenzothiazoles and 2-benzoylbenzothiazoles. In this study, manganese triacetate is introduced as a new reagent to replace potassium ferricyanide or bromide. The 2-substituted benzothiazoles are generated in 6 min at 110°C imder microwave irradiation (300 W) in a domestic oven with no real control of the temperature (reflux of acetic acid) (Scheme 15). Conventional heating (oil bath) of the reaction at 110 °C for 6 h gave similar yields [16]. 

A wide array of aliphatic and aromatic amines has been converted to amides in very high yields by the particularly reactive tetrazolides. The reaction temperature was 10 °C to 20 °C. Higher temperatures (refluxing THF) should be avoided because of instability of the tetrazolide, which in this case was prepared from benzoyl chloride and phenyltetrazole in 68% yield.[99],[100]... 

In the reaction of 1-alkoxycarbonylimidazoles with 2-aminobenzimidazole at low temperature and short reaction time an acylation at the ring nitrogen was encountered. At higher temperature (refluxing mesitylene) and longer reaction time, however, the 2-amino group is acylated [222]... 

Zhou, F., Zhao, X., Zheng, H., Shen, T. and Tang, C. (2005) Low-temperature refluxing synthesis of nanosized LiMn204 cathode materials. Chemistry Letters, 34, 1270-1271. 

Ti/Zr reaction time Acetic acid amount Acetic acid reaction time Solution Concentration Pb dissolution temperature Refluxing... 

Interesting rearrangements proceed upon refluxing the azido diene 105 in benzene solution and form 61% of the vinylaziridine 106 as a mixture of diastereoisomers and the vinylogous urethane 108 (28%) (equation 37)53. It was shown that the process 106 - 108 occurs entirely at elevated temperature (refluxing xylene, ca 140 °C). However, treatment of the aziridine 106 with p-toluenesulfonic acid in THF at room temperature gives rise to trans,trans-, 3-butadiene carboxylic ester 107 in 98%53. 

The reaction mixture is cooled to 5-10° in an ice-salt bath (Note 3), and, with continued stirring, a solution of 31.7 g. (21.3 ml., 0.250 mole) of oxalyl chloride in 200 ml. of dry carbon disulfide is added through the dropping funnel in the course of 20 minutes. After the addition is complete, the thick black reaction mixture is allowed to warm to room temperature, refluxed for 1 hour, and then cooled to 0-5° in an ice bath. The mixture is stirred throughout these steps. One hundred grams of chipped ice is added with stirring, followed by 400 ml. of cold water. Steam is then passed into the flask until the carbon disulfide and unreacted dimethylaniline are removed, and the green-black... 

Some time ago Conia and Limasset2 reported that hindered, enolizable ketones, which do not undergo Wittig reactions readily, do react, although slowly, at elevated temperatures (refluxing benzene or xylene). 

A flask equipped with a low-temperature reflux condenser was charged with l//-heplafluorobul-2-ene [20 g, 0.11 mol ratio (E/Z) 48 52] and MeCN (30 mL). To the vigorously stirred mixture, NaOCl soln (70 mL) was added at - 10 to 0 C and the reaction was continued under these conditions for 5 h. The lower organic layer was separated, washed with H20, and dried (MgS04). The crude product was bro-minated with dropwise addition of Br2 and external irradiation with UV light to separate any unrcacted starting alkene. The product was obtained by fractional distillation on a packed column (metal spirals) yield 15.2 g (70%) (E/Z) 46 54 bp 22-23 C. 

Regardless of the solvent utilized, the extraction may take place at a high temperature (reflux) or at room temperature. In order to ensure complete extraction, the process is repeated four or five times until a colorimetric test confirms that no sugars remain in the final extract. Table 3 summarizes some of the most important problems encountered in the extraction step. 

Remark 2 The separators are sharp and simple distillation columns (i.e., sharp splits of light and heavy key components without distribution of component in both the distillate and bottoms one feed and two products). The operating conditions of the distillation columns (i.e., pressure, temperature, reflux ratio) are fixed at nominal values. Hence, heat integration options are not considered, and the hot and cold utilities are directly used for heating and cooling requirements, respectively. 

Five equivalents of DMAD were used in refluxing solvent. Best results are obtained in refluxing toluene, starting from secondary arylamides. Alkylamides (R2 = Me) require higher temperature (refluxing xylene) to get yields in the same range.458... 

C. Methyl a-(bromomethyl)acrylate. in a dry, 250-mL three-necked flask, equipped with a mechanical stirrer, reflux condenser, and an addition funnel, 20 g (0.077 mol) of methyl 3, 3 -dibromoisobutyrate (Note 14s 6) in 50 mL of anhydrous benzene (Note 157) is stirred vigorously. Triethylamine (Notes 168 and 17) (7.7 g, 0.076 mol) in 50 mL of benzene is introduced dropwise at a rate of about 3 mL. per min. After the addition is complete the mixture is stirred for an additional 1 hr at room temperature, refluxed for 1 hr, and then cooled to 20°C. The reaction mixture is filtered with suction and the amine salt washed twice with 20 mL of benzene. The filtrate and washings are combined in a round-... 

PRESSURE DROP PER TRAY REFLUX TEMPERATURE Reflux comp<3)... 

Methyl Pentafluoroethyl Tellurium A mixture of 9.0 g (57.1 mmol) dimethyl tellurium and 17.9 g (72.8 mmol) pentafluoroethyl iodide is treated with 2.3 g (22.8 mmol) triethylamine at — 78° in a flask equipped with a low-temperature reflux condenser. The mixture is allowed to warm to 20 and then irradiated for 3 h with the reflux condenser kept at — 35°. The mixture is fractionally distilled to give methyl pentafluoroethyl tellurium as a light-yellow liquid that is stable toward water but easily oxidized yield 63% b.p. 42°. 

Fresh lithium tetrahydridoaluminate(l-), UAIH4 (about 2 g), is placed in a N2-purged tipping tube fitted to one joint of a 250-mL, two-necked, round-bottomed flask containing a magnetic stirring bar. The other joint is connected to the vacuum line by means of a conventional low-temperature reflux condenser. ... 

---