Condensation with elimination

Two molecules condense with elimination of water to the so-called methazonic acid, which has the constitution of nitroacetaldoxine (I) (Meister).1... 

These pre-condensates are soluble in water and alcohol they are transformed by further condensation with elimination of water, first into high-molecular-weight, poorly soluble materials and finally into crosslinked insoluble products. The structure of the crosslinked (hardened) urea-formaldehyde resins is not yet entirely understood. 

An example of this class of condensation with elimination of water is the formation of a-phenyl-cinnamic nitrile, from benzaldehyde and benzyl nitrile ... 

Potassium and sodium disulphate bring about condensation with elimination of water. The following examples illustrate the use of this method 45... 

Bis[A -Lrimethylsilyliminodiphenylphosphano]mcthane and tellurium tetrachloride in dry toluene condensed with elimination of chlorotrimethylsilane to form a six-membered heterocycle with a N—Te —N group. The hydrolytically stable heterocycle has a low solubility in organic solvents2. 

Ring Closure by Means of a Condensation Reaction a. Condensation with Elimination of Water. The starting materials are mono- and diacid hydrazides, acylsemicarbazides, and related compounds. The ring closure producing the oxadiazole proceeds as in Eq. (1). The well-known conversion of JV.A -diacid hydrazides to... 

Starting from the aldol condensation product of HFA with acetone (255), a series of nickel and copper di- and triamide complexes have been synthesized, which can undergo intramolecular condensation with elimination of water 181). 

Berthelot found that when two organic molecules condense with elimination of water, the b.p. of the product is 100°-120° lower than the sum of the b.ps. of the two compounds. It is curious that the b.ps of the methyl ketones, methyl esters, and corresponding acid chlorides are very close... 

It was soon discovered that ferrocene condenses with aldehydes under suitable conditions either condensation with elimination of water or carbinol formation may occur 136,166, 202). Further, base-catalyzed aldol and Claisen condensations involving the -hydrogen atom of acetyl-ferrocene can be carried out 100). 

An alternative tandem Michael addition/aldol condensation for the synthesis of 3,5-diaryl-substituted phenols 121 employs, instead of 1-(2-oxopropyl)pyridinium chloride (112), l-(benzotriazol-l-yl)propan-2-one (119) in the presence of excess of NaOH in refluxing ethanol (equation 106) ". Under these conditions, several types of 3,5-diaryl-substituted phenols 121 have been obtained in 52-94% yield. The reaction proceeds by Michael addition of the enolate of 119 to the a,/3-unsaturated ketone 118 to afford intermediate 120, which then undergoes an intramolecular aldol condensation with elimination of benzotriazole. 

IPPP, a nucleophile (by virtue of its terminal vinyl group), and DMAPP, an electrophile, undergo condensation with elimination of pyrophosphate to yield geranyl pyrophosphate (an electrophile), which condenses with a molecule of IPPP to yield a farnesyl pyrophosphate and pyrophosphate. These reactions are probably catalyzed by the same cytosolic enzyme complex. Two molecules of farnesyl pyrophosphate and then condense head-to-head to form squalene by action of microsomal squalene synthase (Figure 19-14). 

Heterometallic alkoxides are generally obtained either by reaction between Lewis acids and bases or by condensation with elimination of volatile or insoluble by-products. 

Both the heat-cured and RTV silicones are formed by condensation polymerization and are sometimes referred to as alkoxy- or acetoxy-cured systems. The basic hydroxysilane starting materials are produced by the hydrolysis of mixtures of mono-, di-, and trichlorosilanes as depicted in Figure 3.7. " Condensation with elimination of water produces hydroxyl-terminated alkylpolysiloxanes. These resins can be further polymerized in the presence of alkoxysilanes such as propylorthosilicates to yield the RTV silicones (Figure 3.8). Catalysts such as organotitanates or dibutyltindilaurate may accelerate the curing process. 

Without additional reagents Condensation with elimination of hydrogen chloride... 

After an aldol-type condensation, or after a condensation with elimination of water, cyclohexanone yields polymers with the monomeric unit... 

This reaction can proceed one step further to produce the acetone trimer. A condensation with elimination reaction for acetone yields mesityl oxide and, via a subsequent step, pherone ... 

Preceding condensation with elimination of hydrogen bromide... 

Figure 4-5. (a) Schematic example of isolated and terminal hydroxyl groups, (b) H-bonded hydroxyl chain example ofsilanol condensation with elimination of water andformation of isolated hydroxyls on the silica film surfaces. (Reprinted from Journal of Non-Crystalline Solids, 316, P. Innocenzi, Infrared spectroscopy of solr-gel derived silica-based films a spectra-microstructure overview , p. 318, Copyright (2003), with permission from Elsevier.)... 

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