Pressure bath

In a similar way H2C=C=CH-SC2H5, b.p. 30 c/12 nmHg, n 1.5210, was prepared in 864 yield from CH3C=C-SC2H5. After the greater part of the solvent had been distilled off at normal pressure (bath temperature below 70°C), the remaining liquid was distilled at water-pump pressure and collected in a single receiver... 

Here, At is the size of the time step, Tp is a characteristic relaxation time, and Pg is the pressure of the external constant-pressure bath. The instantaneous pressure can be calculated as follows ... 

The pressure can similarly be held (approximately) constant by coupling to a pressure bath . Instead of changing the velocities of the particles, the volume of the system is changed by scaling all coordinates by a factor closely related to that shown in... 

After 30 minutes the solid sulfinic acid is separated on a fritted-glass filter. The sulfinic acid is dissolved from the filter by a mixture of 750 ml. of ether and 750 ml, of methylene chloride. The solution is dried over calcium chloride and evaporated to dryness under reduced pressure (bath temperature 25°) (Note 5). The residue is suspended in 50 ml. of water, and small portions of dilute ammonia are added to the well-stirred suspension until it has a pH of 9 (Note 6). Insoluble impurities are separated by filtration, and 2-nitrobenzenesulfinic acid is precipitated from the filtrate by adding 5-ml. portions of 6N hydrochloric acid with cooling the sulfinic acid precipitated by each portion of acid is separately collected on a Buchner funnel (Note 7). The acid, a pale yellow solid, is dried on a clay plate in a vacuum desiccator over potassium hydroxide pellets, m.p. 120-125° (dec.), weight 9.4-14.9 g. (50-80%). If the 2-nitrobenzenesulfinic acid is to be used for the hydrogenation of the next step high purity is required, and it is generally advisable to reprecipitate the acid once more in the same way (Note 8). 

Benzothiadiazole 1,1-dioxide slowly decomposes even at 0°, hence it should always be used on the day on which it is made. For most purposes it is not necessary to isolate the dioxide the ether solution can be used, or solutions in other solvents can be prepared by adding the other solvent and distilling off the ether under reduced pressure (bath temperature 0°). In this way larger amounts of the dioxide than are described in this procedure can be handled without danger. 

A solution of 0.54 g. (2 mmoles) of ferric chloride hexahydrate and 0.33 g. (3 mmoles) of diethylammonium chloride (Note 1) in 5 g. of methanol is added to a solution of 11.2 g. (0.1 mole) of 1-octene (Note 2) and 0.42 g. (2 mmoles) of benzoin (Note 3) in 36 g. (0.3 mole) of chloroform (Note 4). The resulting homogeneous mixture is introduced into a Carius tube of about 100-ml. capacity. Air is displaced by dropping a few pieces of dry ice into the tube (Note 5). The tube is sealed (Note 6), heated to 130°, kept at that temperature for 15 hours, cooled to room temperature (Note 7), and opened. The contents of the tube are transferred to a separatory fuimel, and the tube is rinsed with about 10 ml. of chloroform. The reaction mixture is washed with 40 ml. of water. The aqueous solution is extracted with 10 ml. of chloroform, and the extract is added to the original chloroform layer. Solvent is distilled at atmospheric pressure (bath temperature up to 130°). The distillation flask is allowed to cool, and distillation is continued at 25 mm. (bath temperature up to 120°) (Note 8). The flask is cooled again, and distillation is continued to dryness at 0.1 mm. (bath temperature up tc 150°), giving crude l,l,3-trichloro- -nonane (19.4 g.) as a yellow oil, b.p. 60-85° (0.1 mm.), 1.4650. The purity of this... 

Distillation. The crude CMPO (169 g) is distilled through a short, wide, connecting tube into a dry-ice cooled receiver at reduced pressure (bath temperature of 220°C/0.001 torr). A significant degree of decomposition is observed during the distillation. The impurities from the distillate are removed by washing a heptane solution with 5% Na2C03. 

B,155,1 m Z. Shakhashiri, "Determination of the Molecular Mass of a Volatile Liquid," Chemical Demonstrations, A Handbook for Teachers of Chemistry, Vol. 1 (The University of Wisconsin Press, Madison, 1983) pp. 51-54. A boiling-water bath is used to heat a volatile liquid until it is vaporized, completely filling an Erlenmeyer flask covered by aluminum foil with a pinhole orifice. From atmospheric pressure, bath temperature, volume of the flask, and mass of recondensed vapor, the molar mass of the volatile liquid is determined. 

Remove the DMF under reduced pressure (bath temperature c. 75°C at 1 mmHg pressure) and take up the residue in dichloromethane (100 mL) and water (100 mL). Transfer the mixture to a separating funnel, separate the organic layer and wash with more water (100 mL). Dry the organic layer with magnesium sulfate, (c. 2 g), filter and remove the solvent using a rotary evaporator to leave a pale-yellow solid residue. 

Filter the mixture and remove the solvent by distillation under reduced pressure (bath temperature c. 50°C, at 0.5 mmHg using a vacuum pump). 

Slowly add the p-halo thioether solution from the addition funnel over a period of 18 h. Once the addition is complete, continue stirring for a further 2 h. Remove the DMF by distillation under reduced pressure (bath temperature 50°C, 0.2 mmHg) and swirl the residue with dichloromethane (2 x 150 mL) for 15 min. 

MD simulations can also be used for the pmf calculations with umbrella sampling or the perturbation method. An effective procedure for implementing isothermal-isobaric conditions is to couple the system to a constant temperature and pressure bath. A leap-frog algorithm is then preferred for integrating Newton s equations. " In addition, the SHAKE procedure can be applied to constrain intramolecular degrees of freedom, This is often done to eliminate bond vibrations which permits use of a larger time step, about 1-2 fs. 

The solids were then extracted with chloroform (4 x 50 mL), and the chloroform extracts concentrated under reduced pressure (bath temperature <30 °C) to give a viscous red oil. 

---