Alcohol condensation reactions

Nylon was the first commercial polymer to make a substantial impact on the textile industry, but polyesters now comprise the largest segment of the market for synthetic fibers. In fact, polyesters account for 40% of the more than 4 billion kilograms of synthetic fibers produced in the United States each year. The leading polyester, by far, is poly(ethylene terephthalate), or PET. This polymer is made from terephthalic acid and ethylene glycol in an acid -alcohol condensation reaction ... 

Rao et which reported the formation of ether and water molecules through alcohol condensation reaction. As reported above, the stabilization of the HTB metastable phase also takes place through the occurrence of a side reaction. 

Condensa.tlon, A variety of condensation reactions involving the hydroxyl or the carboxyl or both groups occur with lactic acid. The important reactions where products can be obtained ia high yields are esterificatioa (both iatramolecular and with another alcohol or acid), dehydration, and aminolysis. 

These reversible reactions are cataly2ed by bases or acids, such as 2iac chloride and aluminum isopropoxide, or by anion-exchange resias. Ultrasonic vibrations improve the reaction rate and yield. Reaction of aromatic aldehydes or ketones with nitroparaffins yields either the nitro alcohol or the nitro olefin, depending on the catalyst. Conjugated unsaturated aldehydes or ketones and nitroparaffins (Michael addition) yield nitro-substituted carbonyl compounds rather than nitro alcohols. Condensation with keto esters gives the substituted nitro alcohols (37) keto aldehydes react preferentially at the aldehyde function. 

The replacement of the hydrogen of the methylo1 compound with an alkyl group renders the compound much more soluble in organic solvents and more stable. This reaction is also cataly2ed by acids and usually carried out in the presence of considerable excess alcohol to suppress the competing self-condensation reaction. After neutrali2ation of the acid catalyst, the excess alcohol may be stripped or left as a solvent for the amino resin. 

Reactions. Saligenin [90-01-7] undergoes the typical reactions of phenols and benzyl alcohol. When heated above 100°C, it transforms into a pale yellow resinous material. Amorphous condensation products are obtained when saligenin reacts with acetic anhydride, phosphoms pentachloride, or mineral acids. Upon boiling with dilute acids, saligenin is converted into a resinous body, saliretin, a condensed form of saligenin. Condensation reactions of saligenin with itself in the absence of any catalysts and in the presence of bases have also been studied. 

Properties. SUica gel (see Eig. 8) is a coherent, rigid, continuous three-dimensional network of spherical particles of coUoidal sUica. Both sUoxane, —Si—O—Si—, and sUanol, —Si—O—H, bonds are present in the gel stmcture. The pores are intercoimected and fUled with water and/or alcohol from the hydrolysis and condensation reactions (40). A hydrogel is a gel in which the pores are filled with water. A xerogel is a gel from which the hquid medium... 

Many anthraquinone reactive and acid dyes are derived from bromamine acid. The bromine atom is replaced with appropriate amines in the presence of copper catalyst in water or water—alcohol mixtures in the presence of acid binding agents such as alkaU metal carbonate, bicarbonate, hydroxide, or acetate (Ullmaim condensation reaction). 

Polyesters. Polyester is used in embedding resins for electronic components because of its low cost compared to siUcones and epoxides. Polyesters (qv) are condensation products of dicarboxyhc acids and dihydroxy alcohols the reaction provides a wide range of viscosities for polyesters. 

The condensation reaction is promoted by certain polar solvents and of the many which have been tested dimethyl sulphoxide appears to be the most effective. As usual with linear condensation polymers molecular equivalence and near-absence of monofunctional material is necessary to ensure a high molecular weight. Moisture and alcohols can also have a devastating effect on the molecular weight. In the case of water it is believed that 4-chlorophenyl 4-hydroxyphenyl sulphone is formed which functions as an effective chain terminator. Gross contamination with air is also believed to reduce the maximum attainable molecular weight as well as causing intense discolouration. 

The reaction mixture is heated and allowed to reflux, under atmospheric pressure at about 100°C. At this stage valve A is open and valve B is closed. Because the reaction is strongly exothermic initially it may be necessary to use cooling water in the jacket at this stage. The condensation reaction will take a number of hours, e.g. 2-4 hours, since under the acidic conditions the formation of phenol-alcohols is rather slow. When the resin separates from the aqueous phase and the resin reaches the requisite degree of condensation, as indicated by refractive index measurements, the valves are changed over (i.e. valve A is closed and valve B opened) and water present is distilled off. 

The general definition of a condensation reaction is a one that involves product formation by expulsion of water (or other small molecule) as a by-product. By this definition, activation and methylolation are also condensations. In more precise terms the chain-building process should be described as a condensation polymerization, however, in the jargon of the phenolics industry, the term condensation is usually reserved for the chain-building process. This terminology is not necessarily observed in the literature [88]. Many literature reports correctly refer to methylolation as a condensation reaction. The molecular weight development of the phenol alcohol adducts may also be classified as a step-polymerization. 

Reaction of dibenzylamine with ethylene oxide affords the amino alcohol, 82. Treatment of that product with thionyl chloride gives the a-sympathetic blocking agent, dibenamine (83). (Condensation of phenol with propylene chlorohydrin (84) gives the alcohol, 85. Reaction with thionyl chloride affords the chloride (86). Use of the halide to alkylate ethanolamine affords the secondary amine (87). Alkylation of this last with benzyl chloride... 

In 450 cc of methanol is added 47 grams of sodium metal and the mixture allowed to completely react to form a methanol solution of sodium methoxide. The methanol solution of sodium methoxide is then cooled to 60°C and 68 grams of thiourea which has been thoroughly dried is added with stirring until a uniform solution is formed. Thereafter, 157 grams of diethyl allyl-(1-methylbutyl)malonate is added to the solution of the sodio derivative of thiourea at a temperature of 55°C and the condensation reaction mixture maintained at the said temperature for 24 hours. Methyl alcohol is removed under vacuum during the course of the reaction while maintaining a temperature of 55°C. 

Nitriles react with alcohols in the presence of hydrochloric acid to form iminoester hydrochlorides, which are hydrolyzed to the esters (Pinner synthesis). Heitz and coworkers [21-23] published several fine papers on the polyazoester synthesis from the reaction of a series of poly(oxyethylene) glycol or poly(oxypropylene) glycol and AIBN in the presence of dry hydrochloric acid at 0-5°C according to Pinner synthesis. Condensation reactions of ACPC and dihydroxy terminated poly(oxy-ethylene) glycol yield polyazoesters [24,25]. 

Bisphenol A is a solid material in the form of white flakes, insoluble in water but soluble in alcohols. As a phenolic compound, it reacts with strong alkaline solutions. Bisphenol A is an important monomer for producing epoxy resins, polycarbonates, and polysulfones. It is produced by the condensation reaction of acetone and phenol in the presence of HCI. (See Chapter 10, p. 273)... 

Aldehydes and ketones with an a hydrogen atom undergo a base-catalyzed carbonyl condensation reaction called the aldol reaction. For example, treatment of acetaldehyde with a base such as sodium ethoxide or sodium hydroxide in a protic solvent leads to rapid and reversible formation of 3-hydroxybutanal, known commonly as aldol (aidehyde + alcohol), hence the general name of the reaction. 

Tire mechanism of the Claisen condensation is similar to that of the aldol condensation and involves the nucleophilic addition of an ester enolate ion to the carbonyl group of a second ester molecule. The only difference between the aldol condensation of an aldeiwde or ketone and the Claisen condensation of an ester involves the fate of the initially formed tetrahedral intermediate. The tetrahedral intermediate in the aldol reaction is protonated to give an alcohol product—exactly the behavior previously seen for aldehydes and ketones (Section 19.4). The tetrahedral intermediate in the Claisen reaction, however, expels an alkoxide leaving group to yield an acyl substitution product—exactly the behavior previously seen for esters (Section 21.6). The mechanism of the Claisen condensation reaction is shown in Figure 23.5. 

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