Internal thermometer

A dry 500-ml round-bottomed three-necked flask fitted with a stirrer, internal thermometer, and a pressure-equalized dropping funnel is placed under nitrogen and the flask is charged with 0.148 mole of freshly distilled cyclohexanone and 0.148 mole of freshly distilled ethyl chloroacetate. A solution of 6.0 g of potassium and 125 mL of dry terr-butyl alcohol is introduced into the dropping funnel, and the system is exhausted and... 

Preparation of 2-bromo-3-(p-tolyl)propene (typical procedure) A three-necked, 50 mL flask equipped with an argon inleL a rubber septum and an internal thermometer was charged with bis(p-bromophenyl)ditelluride (1.7 g, 3.0 mmol, 1 equiv) and Ni(acac)2 (77 mg, 0.3 mmol, 10 mol%). The reaction mixture was cooled to -40°C and THF (6 mL) was added. It was further cooled to -78°C and Et2Zn (1.5 mL, 15 mmol, 5 equiv) was slowly added via syringe. The reaction was allowed to warm to room temperature and was stirred for 6 h. Meanwhile, a mixture of copper cyanide (2.68 g, 23 mmol) and lithium chloride (2.54 g, 60 mmol) was dried under vacuum (130°C, 2 h) and dissolved in THF (10 mL). This solution was added to the reaction mixture at -60°C, followed by 2,3-dibro-mopropene (6.0 g, 30 mmol, 10 equiv). The reaction mixture was warmed up to room temperature and worked up as usual. The crude oil obtained after evaporation of the solvents was purified by flash chromatography (hexanes), affording the product (1.45 g, 5.2 mmol, 88% yield) as a colourless oil. 

In a 250 ml three-necked flask fitted with stirrer and internal thermometer 11.04 g (0.078 mol) of 2-chloro-1,4-phenylenediamine are dissolved in 150 ml dry A/,/V-dimeth-ylacetamide (containing 2 wt% LiCi).29.5 ml (0.233 mol) of highly pure trimethylchlo-rosilane (>99%) are dropped into the solution under stirring at 20 °C.Then 15.71 g (0.078 mol) of terephthaloyl dichloiide are added, whereupon the temperature and the... 

A. 1-Butyl-3-methyiimidazolium chioride. A 2-L, three-necked, round-bottomed flask is equipped with a heating oil bath, a nitrogen inlet adapter, an internal thermometer adapter, an overhead mechanical stiner, eind a reflux condenser. The flask is flushed with... 

A 3-L, three-ncck, round-bottom flask, equipped with an internal thermometer, a N2 inlet, a mechanical stirrer, and a 1-L pressure-equalizing addition funnel, was charged with cyclopropyl phenyl sulfide (168 g, 1.12 mol) and anhyd THF (1200 mL). The solution was cooled to 0 °C in an ice bath. To the stirred solution... 

A 1-1., three-necked, round-bottomed flask is equipped with an internal thermometer, mechanical stirrer, dropping funnel, and calcium chloride drying tube. The flask is charged with 500 ml. of dimethyl sulfoxide and 15 g. (0.11 mole) of potassium carbonate (Note 1). The mixture is heated to 100°, and a solution of 10.0 g. (0.038 mole) of 11-bromoundecanoic acid (Note 2) in 200 ml. of dimethyl sulfoxide is added dropwise with vigorous stirring over 1... 

The spatial uniformity of temperature in the cell is difficult to determine, and we are not aware of a careful study of this problem. In most experiments, it is the temperature of the electrode-solution interface or that of the diffusion layer that is relevant. A possible internal thermometer could be created by measuring a temperature-sensitive voltammetric function, for example, the peak separation in the cyclic voltammogram of a reversible reaction, which is 2.22RT/ F. The resolution is not likely to be outstanding, but such a technique would probably allow detection of serious differences between the thermocouple reading and the actual temperature of the electrode-solution interface. 

A 1-1. round-bottomed flask is equipped with an internal thermometer, a sealed stirrer, and a reflux condenser, the upper end of which is protected with a calcium chloride drying tube. In this flask are placed 307 g. (2 moles) of dry, pulverized betaine hydrochloride (Note 1) and 285 g. (174 ml., 2.4 moles) of thionyl chloride. The mixture is stirred and heated slowly. When the internal temperature reaches 68° copious evolution of sulfur dioxide and hydrogen chloride occurs, and the mass becomes pasty. The temperature is maintained with stirring at 68-70° for 1.5 hours (Note 2). 

A total of 59 g of the neat 1 -allyloxy-3,4-dimethoxybenzene was provided with an internal thermometer, and heated with an open flame. The color quickly became purple, then lightened to a red at 70 °C, and finally to a pale pink by 210 °C. At 240 °C an exothermic reaction set in with the temperature going up to almost 290 °C. It was held in the 270-280 °C range for several min, then allowed to return to room temperature. GC analysis showed two peaks, the second and major one being the desired 1,2,4,5-isomer. A small sample was caught by prep-GC, and it successfully seeded the crude Claissen rearrangement product. The isolated 2-allyl-4,5-dimethoxyphenol, pressed on a porous plate, had a mp of 39.5-40.5 °C which was improved to 41.5-42 °C by recrystallization from hexane. 

In a round-bottomed flask containing an internal thermometer, there was... 

The following is the specific procedure for the preparation of levoglucosenone (2) by the pyrolysis of 5 g of cellulose (l).8 To a 50-mL round-bottom flask fitted with a vacuum distillation apparatus was added phosphoric acid (25 mg, 0.5 wt %), cellulose (5 g) and vegetable oil (15 g). The slurry was stirred for about 5 min under reduced pressure (20-30 mm Hg), and then heated by an appropriate heating mantle for 7 min to 270°C, as indicated by the internal thermometer. The reaction mixture began to turn black and water distillate appeared at about 140°C. Yellow distillate containing water and levoglucosenone (2) appeared on the flask wall around 270°C, and the temperature in the distillation head reached around 110-120°C. The reaction... 

One three-necked, round-bottomed flask (50 mL) equipped with an argon inlet, a septum cap, internal thermometer, and a magnetic stirring bar... 

The temperature of the reaction mixture should be monitored by means of an internal thermometer (or a temperature probe), as shown in Figure 1.3, since the internal temperature may differ significantly from that of the cooling bath... 

The checkers used an internal thermometer and maintained the reaction temperature between -78° and -70 °C during the addition. 

The temperature can then be noted and the probe withdrawn. This is often a much easier procedure than the more usual method of setting up the reaction apparatus to include an internal thermometer, and is particularly useful for small-scale set-ups where an internal thermometer cannot be used. 

When using an internal thermometer to measure the temperature of a liquid or solution which is being stirred with a magnetic flea or stirring bar, ensure that the thermometer bulb does not come into contact with it. 

The general procedure for the coupling of styrenes with bromo- and chloroarcnes [16] is exemplified by this preparation (Scheme 3-56). In a 100-mL three-necked flask equipped with a reflux condenser, stirrer, and internal thermometer were placed, under a stream of nitrogen, 4-bromoacetophenone (23a-Br) (5.0 g, 25 mmol) [or 4-chloroacetophenone (23a-Cl) (3.3 mL, 3.9 g, 25 mmol) plus TBABr (1.64 g. 5 mmol)], styrene (4.3 mL, 3.9 g, 37 mol), 2,6-di(tert-butyl)phenol (20 mg, as a radical scavenger), NaOAc (2.5 g, 30 mmol), and A(A-dimethylacetamide (50 mL). To the well-stirred suspension was added 12 mg (0.1 mol%) of the palladacycle la, and the mixture was heated at 130 "C for 24 h (54 h with 4-chloroacetophenone). After the reaction mixture had cooled to rt, it was poured into ice-water (200 mL). The precipitate was collected on a filter, carefully washed with water and recrystallized from acetone/water to yield 4.9 g (89%) of 258a (3.8 g, 69% from 4-chloroacetophenone). 

A. 2-Hydroxy-5-methylpyridine (1) (Note 1). A 500-mL, two-necked, round-bottomed flask (Note 2) equipped with an internal thermometer and egg-shaped, Teflon-coated magnetic stirrer is charged with 150 mL of water (H20) and 40 g of... 

Iodo-2-fluoropyridine (15.52 g, 69.60 mmol) was dissolved in dry THE (150 mL) and cooled to -70 °C. Then n-BuLi (73.08 mmol, typically a solution in hexanes) was added, and the reaction was stirred at -70 °C for 20 min. Subsequently, dry zinc chloride (10.44 g, 76.61 mmol) was added as a solution in dry THE (60 mL) while keeping the temperature below -60 °C. (Use an internal thermometer.) The reaction mixture was then wanned to room temperature whereupon tetrakis (triphenylphosphine)palla-dium (0.40 g, 0.35 mmol) and 2,4-dichloropyrimidine (7.26 g, 48.73 mmol) in THE (100 mL) were added, and the reaction mixture was refluxed until complete conversion. The reaction mixture was poured into a 10% aqueous EDTA solution and extracted with CH2CI2. The crude material was purified by flash chromatography eluting with petro-leuni ether EtOAc (10 1) to deliver 9.17 g (90%) of the pyrimidine as beige crystals. 

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