Mechanism condensation

For a conserved order parameter, the interface dynamics and late-stage domain growth involve the evapomtion-diffusion-condensation mechanism whereby large droplets (small curvature) grow at tlie expense of small droplets (large curvature). This is also the basis for the Lifshitz-Slyozov analysis which is discussed in section A3.3.4. 

Dichlorobutane. Place 22-5g. of redistilled 1 4-butanediol and 3 ml. of dry pyridine in a 500 ml. three necked flask fitted with a reflux condenser, mechanical stirrer and thermometer. Immerse the flask in an ice bath. Add 116 g. (71 ml.) of redistilled thionyl chloride dropwise fix>m a dropping funnel (inserted into the top of the condenser) to the vigorously stirred mixture at such a rate that the temperature remains at 5-10°. When the addition is complete, remove the ice bath, keep the mixture overnight, and then reflux for 3 hours. Cool, add ice water cautiously and extract with ether. Wash the ethereal extract successively with 10 per cent sodium bicarbonate solution and water, dry with anhydrous magnesium sulphate and distil. Collect the 1 4-dichloro-butane at 55-5-56-5°/14 mm. the yield is 35 g. The b.p. under atmospheric pressure is 154 155°. 

The equilibrium of the last step (3), which is not actually part of the condensation mechanism, is far to the right because of the greater basic strength of the ethoxide ion as compared to (IV), and this largely assists the forward reactions in (1) and (2). The reaction mixture contains the sodium derivative of the keto-ester, and the free ester is obtained upon acidification. 

Dinitroaniline from 3 5-dinItrobenzoic acid. Place a solution of 50 g. of 3 5-dinitrobenzoic acid (Section IV, 168) in 90 ml. of 10 per cent, oleum and 20 ml. of concentrated sulphuric acid in a 1-litre three necked flask equipped with a reflux condenser, mechanical stirrer, adropping funnel, and thermometer (FUME CUPBOARD ). Add 100 ml. of clJoroform and raise the temperature to 45°. Stir rapidly and add 17 -5g. of sodium azide in small portions whilst maintaining the temperature at 35-45°. The reaction is accompanied hy foaming, which usually commences after about 3 g. of sodium azide has been introduced. After all the sodium azide has been added raise the temperature so that the chloroform refluxes vigorously and maintain this temperature for 3 hours. Then cool the reaction mixture, pour it cautiously on to 500 g. of crushed ice, and dilute with 3 litres of water. After 1 hour, separate the yellow solid by filtration at the pump, wash well with water and dry at 100°. The yield of 3 5-dinitroaniline, m.p. 162-163°, is 39 g. The m.p. is unaffected by recrystallisation from dilute alcohol. 

Langmuir referred to the possibility that the evaporation-condensation mechanism could also apply to second and higher molecular layers, but the equation he derived for the isotherm was complex and has been little used. By adopting the Langmuir mechanism but introducing a number of simplifying assumptions Brunauer, Emmett and Teller in 1938 were able to arrive at their well known equation for multilayer adsorption, which has enjoyed widespread use ever since. 

Fig. 5. Protein folding. The unfolded polypeptide chain coUapses and assembles to form simple stmctural motifs such as -sheets and a-hehces by nucleation-condensation mechanisms involving the formation of hydrogen bonds and van der Waal s interactions. Small proteins (eg, chymotrypsin inhibitor 2) attain their final (tertiary) stmcture in this way. Larger proteins and multiple protein assembhes aggregate by recognition and docking of multiple domains (eg, -barrels, a-helix bundles), often displaying positive cooperativity. Many noncovalent interactions, including hydrogen bonding, van der Waal s and electrostatic interactions, and the hydrophobic effect are exploited to create the final, compact protein assembly. Further stmctural...

Early patents indicated that because water inhibits the aldol condensation mechanism, it was necessary to dry recycle acetone to less than 1% water (139—142). More recent reports demonstrate DAA production from waste acetone containing 10—50% water (143), and enhanced DAA production over anion-exchange resins using acetone feeds that contain 3—10% water (144,145). 

Condensation Mechanisms Condensation occurs when a saturated vapor comes in contact with a surface whose temperature is below the saturation temperature. Normally a film of condensate is formed on the surface, and the thickness of this film, per unit of breadth, increases with increase in extent of the surface. This is called film-type condensation. 

A dry 1-L, three-necked, round-bottomed flask, fitted with a reflux condenser, mechanical stirrer, and ground-glass stopper, is charged with 111.0 g (0.25 mol) of phosphorus sulfide, P4S10 (Note 1) and 270 g (2.5 mol) of anisole (Note 1). Stirring Is commenced and the mixture is heated at reflux temperature by use of a heating mantle. After 1 hr, the solution Is... 

Cyalohexylideneaaetonit ri-le. A 1-L three-necked, round-bottomed flask equipped with a reflux condenser, mechanical stirrer and addition funnel, is charged with potassium hydroxide (855 pellets, 33.0 g, 0.5 mol. Note 1) and acetonitrile (250 ml. Notes 2 and 3). The mixture is brought to reflux and a solution of cyclohexanone (49 g, 0.5 mol. Note 4) in acetonitrile (100 mL) is added over a period of 0.5-1.0 hr. Heating at reflux is continued for 2 hr (Note 5) after the addition is complete and the hot solution is then poured onto cracked ice (600 gl. The resulting binary mixture is separated... 

Scheme 11. Proposed quinone methide condensation mechanism. Work by Murray (and Lemon unpublished) showed clearly that the quinone methides formed from o-hydroxymethyl and not /7-hydroxymethyl groups in the presenee of ester.

The formation of structure (24) is very difficult to rationalize in terms an acid-catalyzed condensation mechanism, but the formation... 

Steam traps are installed in condensate, mechanical return systems and are a frequently overlooked item for reducing operating costs. Large industrial process plants typically have many hundreds of steam traps installed to recover low-energy condensate and remove (potentially corrosive) air and carbon dioxide. 

Dissolve 71 g. of P-methylnaphthalene in 460 g. (283 ml.) of A.B. carbon tetrachloride and place the solution in a 1 -litre three-necked flask equipped with a mechanical stirrer and reflux condenser. Introduce 89 g. of JV-bromosuccinimide through the third neck, close the latter with a stopper, and reflux the mixture with stirring for 16 hours. Filter ofiT the succinimide and remove the solvent under reduced pressure on a water bath. Dissolve the residual brown oil (largely 2-bromomethyl naphthalene) in 300 ml. of A.R. chloroform, and add it to a rapidly stirred solution of 84 g. of hexamine in 150 ml. of A.R. chloroform contained in a 2-litre three-necked flask, fitted with a reflux condenser, mechanical stirrer and dropping funnel maintain the rate of addition so that the mixture refluxes vigorously. A white solid separates almost immediately. Heat the mixture to reflux for 30 minutes, cool and filter. Wash the crystalline hexaminium bromide with two 100 ml. portions of light petroleum, b.p. 40-60°, and dry the yield of solid, m.p. 175-176°, is 147 g. Reflux the hexaminium salt for 2 hours with 760 ml. of 60 per cent, acetic acid, add 160 ml. of concentrated hydrochloric acid, continue the refluxing for 5 minutes more, and cool. Extract the aldehyde from the solution with ether, evaporate the ether, and recrystallise the residue from hot -hexane. The yield of p-naphthaldehyde, m.p. 69-60°, is 60 g. 

The intramolecular version of ester condensation is called the Dieckmann condensation.217 It is an important method for the formation of five- and six-membered rings and has occasionally been used for formation of larger rings. As ester condensation is reversible, product structure is governed by thermodynamic control, and in situations where more than one product can be formed, the product is derived from the most stable enolate. An example of this effect is the cyclization of the diester 25.218 Only 27 is formed, because 26 cannot be converted to a stable enolate. If 26, synthesized by another method, is subjected to the conditions of the cyclization, it is isomerized to 27 by the reversible condensation mechanism. 

The reaction is carried out in a 500-ml. three-necked flask equipped with a reflux condenser, mechanical stirrer, heating mantle, and nitrogen inlet. The equipment is similar to that pictured in Fig. 11, except that an addition funnel is not required. In the reaction flask 20 g. (0.36 mol, 100% excess) of potassium hydroxide is dissolved in 300 ml. of absolute ethanol. The spare neck is closed with a ground-glass stopper, and the solution is stirred until it reaches room temperature. Addition of the carborane to the warm basic solution may result in an initial vigorous reaction. To this solution is added 30.0 g. (0.175 mol) of solid dimethylcarborane. The solution is stirred for one hour at room temperature and is then heated at the reflux temperature for 14 hours or until hydrogen evolution has stopped. 

Methylthiobutyl glucosinolate derives from L-methionine by a complex elongation process leading to dihomomethionine. Four of the five carbons of methionine are retained, one being lost in a decarboxylation. The two necessary additional carbons each derive from a methyl group of acetyl-S-CoA by a complex, multi-step condensation mechanism (Equation 11) ... 

The mechanisms proposed over the last 50 years for the Fischer-Tropsch synthesis, principally on the basis of studies using heterogeneous catalyst systems, may be divided into three main classes (a) metal-carbide mechanisms (b) hydroxyl carbene, =CH(OH), condensation mechanisms and (c) CO insertion mechanisms. 

In a 2-1. round-bottomed three-necked flask, fitted with an efficient reflux condenser, mechanical stirrer, and dropping funnel (Note 1), are placed 133.3 g. (1 mole) of anhydrous powdered aluminum chloride, 137.4 g. (1 mole) of phosphorus trichloride, and 184.6 g. (1.2 moles) of carbon tetrachloride (Note 2). The reactants are stirred slowly until they are thoroughly mixed, and then heat is applied carefully until the reaction begins. At this point the liquid boils vigorously, and the reaction mixture becomes thicker so that faster stirring is necessary. Finally, the stirrer is stopped when the... 

In a 5-1. three-necked flask fitted with reflux condenser, mechanical stirrer, thermometer, and nitrogen gas inlet is placed a solution of 80.0 g. (43.5 ml., 0.82 mole) of concentrated sulfuric acid in 3 1. of water. The solution is stirred under nitrogen, and 740.0 g. (2.49 moles) of reagent mercuric sulfate is added to form a suspension of deep-yellow, basic mercuric sulfate. The mixture... 

Figure 8.3 Scheme for global acetylene chlorination/condensation mechanism leading to hexachlorobenzene. (From A. Wehrmeier et al., Environ. Sci. Technol, 1998.)... 

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