Condensation, additional

Acetaldehyde is a highly reactive compound exhibiting the general reactivity of aldehydes (qv). Acetaldehyde undergoes numerous condensation, addition, and polymerisation reactions under suitable conditions, the oxygen or any of the hydrogens can be replaced. 

Apart from the waterside problems discussed earlier, which are due to impurities introduced with either the MU or the returned condensate, additional problems may develop both in the pre-boiler system and further downstream. These problems are associated with the final blended FW and are primarily related to oxygen corrosion of various items of pre-boiler equipment or the deposition of scales and metal oxides on waterside surfaces. 

The reaction is carried out in a 1-1. three-necked flask equipped with a mechanical stirrer, reflux condenser, addition funnel, and nitrogen inlet (Fig. 11). A nitrogen atmosphere is strictly maintained throughout the course of the reaction. Clean magnesium chips, 6.1 g. (0.25 mol, 20% excess), and about... 

The Na2B9C2Hn is prepared simultaneously under nitrogen in a 300-ml. three-necked round-bottomed flask equipped with a condenser, addition funnel, and a magnetic stirring bar. Sodium hydride, 1.51 g. (0.063 mol) (2.70 g. of a 56% dispersion in mineral oil), is washed twice with 30 ml. of THF to remove the mineral oil and then is immediately washed with a total of... 

In step growth polymerization, initially dimer formation takes place due to condensation, addition or ring opening etc., e.g. 

Uses Insulator fluid for electric condensers additive in high pressure lubricants. In fluorescent and high-intensity discharge ballasts manufactured prior to 1979 (U.S. EPA, 1998). 

A. Phenyl vinyl aulfide. In a 1-L, three-necked, round-bottomed flask fitted with magnetic stirrer, condenser, addition funnel, and nitrogen inlet tube is placed 400 mL of ethanol. Sodium metal (23 g, 1 g-atom), cut into small pieces, is added with stirring. When conversion to sodium ethoxide is... 

S. Phenyl vinyl eulfone. In a 250-mL, three-necked, round-bottomed flask fitted with a magnetic stirrer, condenser, addition funnel, and thermometer is placed 19.7 g (0.145 mol) of phenyl vinyl sulfide dissolved in 70 mL of glacial acetic acid. Hydrogen peroxide (30%, 56 mL, 0.5 mol) is added slowly at such a rate to maintain a reaction temperature of 70°C (Note 7). The reaction mixture is heated at reflux for 20 min, cooled, and treated with ether (150 mL) and water (200 mL). The organic phase is separated, washed with water (50 mL) and brine (50 mL), and concentrated at 70°C/0.3 mm for 3 hr, to afford 18-19 g (74-78%) of phenyl vinyl sulfone as a colorless... 

Freshly prepared Zn/Cu couple (4.8 g) was added to a rapidly stirred solution of 2-chloro-3,3-difluoro-l-phenylbulane (1.02 g, 5 mmol) in DMF (19 mL). The resulting slurry was heated to 95 3C under a reflux condenser. Additional Zn/Cu couple (2.4 g) was added every 24 h until the reaction was judged complete (GC. 72 h). The mixture was worked up and the solvent removed under reduced pressure to give a yellow oil. Chromatography (silica gel) gave the product yield 0.45 g (60%) ratio (E/Z) 35 65. 

An assembly for heating a reaction mixture under reflux is illustrated in Fig. 2.54. The precise design of condenser depends upon the volatility of the reaction liquid, low boiling liquids (<60°C) require the use of a double surface condenser. Additionally a calcium chloride tube may be inserted at the end of the condenser if the reaction mixture contains moisture-sensitive components. It is... 

In a formal sense, POMs are produced via Bronsted acid-base condensation-addition processes, e.g. 

Uses Chlorodiphenyls are used in combination with chlorinated naphthalenes, which are stable, thermoplastic, nonflammable, and are used in electric cables and wires in the production of electric condensers, additives for extreme pressure lubricants, and as a coating in foundry. Chlorodiphenyls are widely used in the manufacture of herbicides, lacquers, paper, plasticizers, resins, rubbers, textiles, wood preservatives, and electric equipments. 

B. l,6-Dimethyltricyclo[4.l.0.021]hept-3-ene. A solution of 20.95 g (0.075 mol) of 7,7-dibromo-l,6-dimethylbicyclo[4.1.0]hept-3-ene in 500 mL of anhydrous ether is placed in a 1-L, three-necked flask equipped with a magnetic stirring bar, reflux condenser, addition funnel, and nitrogen inlet tube. With stirring under nitrogen and external cooling in an... 

Assemble the three-necked flask, mechanical stirrer, condenser, addition funnel and drying tubes, and purge the assembly with dry nitrogen. 

B. n-Butyl 2,2-difluorocyclopropanecarboxylate. A 500-mL, round-bottomed, three-necked flask is fitted with a magnetic stirrer, condenser, addition funnel, gas dispersion tube extending to the bottom of the flask, and gas outlet with a paraffin oil bubbler. The flask is charged with 200 mL of toluene, 0.4 g of sodium fluoride (0.06 eq), and 20 g of n-butyl acrylate (0.156 mol) (Notes 7, 8). The solution is heated to reflux and slow N bubbling is initiated with stirring for 1 hr. Trimethylsilyl 2-fluorosulfonyl-2,2-difluoroacetate (62.5 g, 0.31 mol, 1.6 eq) (Note 5) is added dropwise (Note 9). The mixture is heated for 8 hr, then cooled and filtered under vacuum filtration through a Celite pad (Note 10). Toluene is removed by simple distillation at atmospheric pressure, and the residue distilled at reduced pressure to obtain 15.4 g of n-butyl 2,2-difluorocyclopropanecarboxylate (55%) (bp 99-101°C at 58 mm) as a colorless liquid (Note 11). 

Condensation Addition Opening Coupling Reaction Insertion Coupling... 

A powerful sulphury aroma compound, 3-mercapto-2-methylpentan-l-ol (51), has recently been identified [13] in a complex process flavouring. It has a low odour threshold of 0.15 mg/L of water. The formation could be traced back to the onions present in the process flavouring and its formation is explained from propanal present in onions via aldol condensation, addition of hydrogen sulphide and enzymatic reduction (Fig. 3.31). 

There are two fundamental polymerization mechanisms. Classically, they have been differentiated as addition polymerization and condensation polymerization. In the addition process, no by-product is evolved, as in the polymerization of vinyl chloride (see below) whereas in the condensation process, just as in various condensation reactions (e.g., esterification, etherification, amidation, etc.) of organic chemistry, a low-molecular-weight by-product (e.g., H2O, HCl, etc.) is evolved. Polymers formed by addition polymerization do so by the successive addition of unsaturated monomer units in a chain reaction promoted by the active center. Therefore, addition polymerization is called chain polymerization. Similarly, condensation polymerization is referred to as step polymerization since the polymers in this case are formed by stepwise, intermolecular condensation of reactive groups. (The terms condensation and step are commonly used synonymously, as we shall do in this book, and so are the terms addition and chain. However, as it will be shown later in this section, these terms cannot always be used synonymously. In fact, the condensation-addition classification is primarily applicable to the composition or structure of polymers, whereas the step-chain classification applies to the mechanism of polymerization reactions.)... 

Iv) Substitution. The skeleton of an oligomeric or polymeric system is constructed by condensation, addition or ring-opening techniques, but variations in side-group structure must generally be introduced by substitutive methods ... 

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