Continuous hydration-condensation reaction

Following the production of 1,2-enol forms of aldose and ketose amines, a series of degradations and condensations results in the formation of melanoidins. The a-fi-dicarbonyl compounds enter into aldol type condensations, which lead to the formation of polymers, initially of small size, highly hydrated, and in colloidal form. These initial products of condensation are fluorescent, and continuation of the reaction results in the formation of the brown melanoidins. These polymers are of nondistinct composition and contain... 

The detailed structures of alite and belite are known. Both consist of isolated SiO, telrahedra, the so-called Q species. Following hydration to form Si-OH groups, there is a condensation reaction that results in pairs of SiO tetrahedra becoming joined as dimers, the so-called Q species [57]. Condensation reactions continue and these cause short-chain silicate species to form, with Q end groups and mid-chain units (ie, SiO tetrahedra joined at two comers to other SiO tetrahedra [62]). In addition, some of the mid-chain units contain aluminium rather than silicon, and so are CF(1 Al) species. 

Fit a 1500 ml. bolt-head flask with a reflux condenser and a thermometer. Place a solution of 125 g. of chloral hydrate in 225 ml. of warm water (50-60°) in the flask, add successively 77 g. of precipitated calcium carbonate, 1 ml. of amyl alcohol (to decrease the amount of frothing), and a solution of 5 g. of commercial sodium cyanide in 12 ml. of water. An exothermic reaction occurs. Heat the warm reaction mixture with a small flame so that it reaches 75° in about 10 minutes and then remove the flame. The temperature will continue to rise to 80-85° during 5-10 minutes and then falls at this point heat the mixture to boiling and reflux for 20 minutes. Cool the mixture in ice to 0-5°, acidify with 107-5 ml. of concentrated hydrochloric acid. Extract the acid with five 50 ml. portions of ether. Dry the combined ethereal extracts with 10 g. of anhydrous sodium or magnesium sulphate, remove the ether on a water bath, and distil the residue under reduced pressure using a Claiseii flask with fractionating side arm. Collect the dichloroacetic acid at 105-107°/26 mm. The yield is 85 g. 

The carbonyl compound to be reduced (0.1 mole) is placed in a 250-ml round-bottom flask with 13.5 g of potassium hydroxide, 10 ml of 85% hydrazine hydrate, and 1(X) ml of diethylene glycol. A reflux condenser is attached and the mixture is heated to reflux for I hour (mantle). After refluxing 1 hour, the condenser is removed and a thermometer is immersed in the reaction mixture while slow boiling is continued to remove water. When the pot temperature has reached 200°, the condenser is replaced and refluxing is continued for an additional 3 hours. The mixture is then cooled, acidified with concentrated hydrochloric acid, and extracted with benzene. The benzene solution is dried, and the benzene is evaporated to afford the crude product, which is purified by recrystallization or distillation. 

A. Ethyl hydrazinecarboxylate. To 100 g. (97 ml., 2.0 moles) of 100% hydrazine hydrate, contained in a 1-1. round-bottomed Hank, iH added 236 g. (243 ml., 2.0 moles) of diethyl carbonate (Note I). The flask is fitted with a calcium chloride-containing drying tube and is shaken vigorously to mix the two liquids. After about 5 minutes, the milky emulsion becomes warm, and shaking is continued until a clear solution is obtained (approximately 20 minutes). The flask is equipped with a reflux condenser fitted with a calcium chloride-containing drying tube and is heated on a steam bath for 3.5 hours. The reaction mixture is transferred to a 500-ml. round-bottomed flask and is... 

The fact that silanol persistence can be favored by equilibrium conditions rather than control of condensation kinetics by steric or electronic factors is usually not considered. The phase separation which results from highly condensed systems continuously removes material from deposition solutions, depleting soluble silane species. While condensed silanols or siloxanes are typically not regarded as participating in a reversible reaction with water or alcohol, they do indeed participate in an equilibrium reaction. Iler [16] has shown that even hydrated amorphous silicon dioxide has an equilibrium solubility in methanol, which implies the formation of soluble low molecular... 

In a S-1. round-bottomed flask equipped with a reflux condenser and a mechanical stirrer are placed 236 g. (1.5 moles) of / chloronitrobenzene, 960 g. (4 moles) of sodium sulfide nona-hydrate, and 2.5 1. of water. With rapid agitation, the reaction mixture is slowly heated to the reflux temperature (Note 1). Heating is continued over a period of 20 hours. 

A SOLUTION of 250 g. (1.51 moles) of chloral hydrate (Note i) in 450 cc. of warm water (50-60°) is placed in a 3-I. round-bottomed flask bearing a reflux condenser and thermometer (Note 2). The condenser is temporarily removed and 152.5 g. (1.52 moles) of precipitated calcium carbonate added this is followed by 2 cc. of amyl alcohol (Note 3) and a solution of 10 g. of sodium cyanide (Note 4) in 25 cc. of water. Althou the reaction is exothermic, the reaction mixture is heated with a low flame so that it reaches 75° in about ten minutes at this point heating is discontinued. The temperature continues to rise to 80-85° during five to ten minutes and then drops. As soon as the temperature begins to fall the solution is heated to boiling and refluxed for twenty minutes. The mixture is then cooled to 0-5° in an ice bath, acidified with 215 cc. of concentrated hydrochloric acid (sp. gr. 1.18) and extracted with five loo-cc. portions of ether (Note 5). The combined ether extracts are dried with 20 g. of anhydrous sodium sulfate, the ether is removed by distillation from a steam bath, and the residue distilled in vacuum from a Claisen flask with a fractionating side... 

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