Unsaturated compounds, hydration

Aqueous mineral acids react with BF to yield the hydrates of BF or the hydroxyfluoroboric acids, fluoroboric acid, or boric acid. Solution in aqueous alkali gives the soluble salts of the hydroxyfluoroboric acids, fluoroboric acids, or boric acid. Boron trifluoride, slightly soluble in many organic solvents including saturated hydrocarbons (qv), halogenated hydrocarbons, and aromatic compounds, easily polymerizes unsaturated compounds such as butylenes (qv), styrene (qv), or vinyl esters, as well as easily cleaved cycHc molecules such as tetrahydrofuran (see Furan derivatives). Other molecules containing electron-donating atoms such as O, S, N, P, etc, eg, alcohols, acids, amines, phosphines, and ethers, may dissolve BF to produce soluble adducts. 

Hydration, Alcoholation and the Related Reactions of Unsaturated Compounds... 

Catalytic hydration and alcoholation of unsaturated compounds such as alkenes or alkynes would be a high value-adding step in the synthesis of compounds of complicated structure as well as in the large-scale production of industrially useful simple compounds. The activation of the O-H bond of water, alcohol, or carboxylic acid by transihon metals is relevant to a variety of such catalytic processes. 

Hydrogen atoms and hydroxyl radicals react with aliphatic compounds mainly by H-abstraction from the chain, although reactions with certain substituents are also important. With hydrated electrons the functioned group is the only site of reaction and its nature determines the reactivity. The reactions of hydrated electrons are by definition electron transfer reactions. The rate of reaction of a certain substrate will depend on its ability to accommodate an additional electron. For example, in an unsaturated compound the rate may depend on the presence of a site with a partial positive charge. Thus acrylonitrile and benzonitrile are three orders of magnitude more reactive toward e q than are ethylene and benzene. On the other hand, this large difference does not exist in the case of addition of H and OH. 

At high degree of exchange, Li" cations are located in the least hydrated sites (25). Such sites may be Si, S/, Sn (26). Because of their location in the screened positions, they interact weakly with molecules of adsorbed substances but, as under the accepted conditions of thermal activation other cations are surrounded by water molecules, one may assume that just these cations form the main centers responsible for the increase of both retention volumes and heat adsorption of unsaturated compounds and carbon monoxide. 

The oxidation of alkenes by Se02 or its hydrated form SeO(OH)2) results in the formation of allyl alcohols and a,/3-unsaturated compounds, or allylic acetate when the reaction is carried out in acetic acid, (a) The oxidation generally occurs without double bond rearrangement, (b) Oxidation of 2-methyl-2-alkenes occurs at the (E) methyl group, (c) 1-Substituted cyclohexene is oxidized at the 6-position this rules out the formation of allylic free radicals or carbonium ions. The widely accepted mechanism of this reaction has been proposed by Sharpless it... 

From a historical point of view, the earliest work followed some studies on the hydration of unsaturated compounds u> by Lucas et al. 12L They were able to study the following reaction ... 

Two examples of monocyclic 1,3,4-oxadiazepines have been reported. The fully unsaturated compounds have, however, not been isolated, although the photolysis of pyrimidine. iV-oxides is known to involve such oxadiazepines as unisolable intermediates <69TL4899>. 2-Benzoylpropene or 2-benzoylpropanol condensed with hydrazine hydrate and an appropriate carboxylic acid to form the hydrazone esters (133), which were converted into the 6,7-dihydro-l,3,4-oxadiazepines (134) (30 72% yields) by intramolecular attack of the amino group to the ester carbonyl, followed by acid-catalyzed loss of water (Scheme 23) <84S342>. 

Inorganic materials such as titanium dioxide, Ti02, and cadmium sulfide, CdS, can initiate the polymerization of unsaturated compounds upon exposure to light [49-51]. For the photoinitiation of the polymerization of methyl methacrylate by nanosized titanium dioxide [49, 50], the mechanism presented in Scheme 10.8 has been proposed. Accordingly, electrons released upon absorption of light by the Ti02 particles are trapped at the hydrated surface of the particles by groups. formed in this way can react with molecular... 

The COj species in the HT interlayer could be exchanged with OH ions by calcination at 723 K and hydration at room temperature. A spinel phase of Mg-Al mixed oxide obtained after the calcination transforms into the original layered structure during the hydration. This reconstruction is known as the memory effect of HT materials. The reconstructed HT catalyzed the Knoevenagel condensation of various aldehydes with nitriles in the presence of water [119]. The reconstracted HT also showed an aqueous Michael reaction of nitriles with a,p-unsaturated compounds. The layered double-hydroxide-supported diisopropylamine catalyzed the Knoevenagel condensation of aromatic carbonyl compounds with malononitrile or ethyl cyanoacetate [120]. This solid base could be recycled at least four times, and exhibited activity for aldol, Henry, Michael, transesterification, and epoxidation of alkenes. 

Catalytic hydration of unsaturated bonds is to a certain extent a complementary process to Wacker-type oxidation. Hydration catalyzed by transition-metal complexes has been rather little studied [185]. One process involving hydration and having a good industrial perspective is the telomerization of unsaturated compounds. For example, the aqueous telomerization of butadiene can afford octadienols. The process may be performed in a micellar system in the presence of surfactants with remarkable selectivity [186] ... 

This oxidative step is followed by hydration of the unsaturated compound to the corresponding L-)J-hydroxyacyl-CoA derivative ... 

Unsaturated Polyesters. There are two approaches used to provide flame retardancy to unsaturated polyesters. These materials can be made flame resistant by incorporating halogen when made, or by adding some organic halogen compound when cured. In either case a synergist is needed. The second approach involves the addition of a hydrated filler. At least an equal amount of filler is used. 

Fatty acids are degraded by two-carbon units in a reverse manner analogous to their biosynthesis. The acyl-CoAs are first dehydrogenated to a,(3-unsaturated acyl-CoA, and then hydrated to (3-hydroxyacyl-CoA, followed by oxidation to (3-ketoacyl-CoA. The C-C bond between C-2 and C-3 of the latter compound is broken by a free CoA molecule via thiolysis to form an acyl-CoA that is two carbons shorter and acetyl-CoA. Unlike fatty acid biosynthesis, each step of the (3 oxidation of fatty acids is... 

Pyrazoline compounds are partially unsaturated pyrazoles. Jeong et al. [95, 96] and Moustafa and Ahmad [92] described the formation of these compounds from chalcones (e.g., 196) using hydrazine hydrate to form the pyra-zolines (e.g., 197, Scheme 53 [95]). Chimenti et al. also described the synthesis of the pyrazolines from reaction of hydrazine with chalcones but included acetic acid in the reaction mixture [97]. 

There are two degrees of unsaturation since the compound C H lacks four H s from being an alkane. The addition of 2 mol of H, excludes a cyclic compound. It may be either a diene or an alkyne, and the latter functional group is established by hydration to a carbonyl compound. The skeleton must be... 

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