Water alkenes

Montmorillonites containing interlamellar water associated with cations (Cu2+, Fe3+, Al3+) react under mild conditions with terminal alkenes to give the corresponding di-sec-alkyl ethers.26 The alkene-water reaction is a stoichiometric process, while the reaction of the second molecule of alkene with the intermediate 2-alkanol is catalytic. 

Hydrocarboxylation Alkene, water, and CO Carboxylic acid All in Chapter 4... 

The SnCl3 ligand is a good leaving group and can thus provide a site for substrate coordination in catalytic reactions platinum metal systems will catalyze hydrogenation or hydroformylation of alkenes, water-gas shift, and other reactions in solutions or in melts of quaternary salts (R4N+SnClj). 

The literature of biphasic hydrogenations contains plenty of substrates (al-kenes and cycloalkenes, arylaliphatic olefins, carbonyl compounds, etc.), mainly with TPPMS as water-soluble ligand (solubility approx. 200 g/1 [150] as compared with 1100 g/1 with TPPTS [37]). So far, no industrial process has been derived from these smdies. Besides the development of the basics of biphasic operation, the research concentrates on fundamental work concerning the question of where the reaction takes place phase boundary, organic phase, or aqueous phase. Wilkinson [29] concluded from his hydrogenation tests with hexenes or cyclohexenes in the presence of TPPMS that the somewhat lower rate of hydrogenation as compared with monophasic conversion should be due to the necessary diffusion of the hydrogen to the alkene/water interface. In this way the iso-... 

Acid-catalyzed hydration of alkenes (Section 6.10) The elements of water add to the double bond In accordance with Markovnikov s rule. R2C = CR2 + H2O R2CHCR2 OH Alkene Water Alcohol CH3 (CH3)2C=CHCH3 CH3CCH2CH3 M2SU4 OH 2-Methyl-2-butene 2-Methyl-2-butanol (90%)... 

All of the eUminations that we have described so far have involved electrically neutral substrates. However, eliminations are known in which the substrate bears a positive charge. One of the most important of these is the E2-type elimination that takes place when a quaternary ammonium hydroxide is heated. The products are an alkene, water, and a tertiary amine ... 

Not every HX is a strong enough acid to protonate an alkene. Water, HOH (here X = OH), is an example of such a weak acid. Yet it would be very useful to be able to add the elements of water to an alkene, to hydrate an alkene as in Figure 3.80,... 

Other H—X molecules are not strong enough acids to protonate alkenes. Water (HOH) is an excellent example. However, such molecules wiU add if the reaction is acid-catalyzed. Enough acid catalyst is added to give the protonated alkene, which is attacked by water. The catalyst is regenerated in the last step and recycles to carry the reaction further. 

From a synthetic point of view, the participation of water in brominations, leading to bromohydrins, is probably the most important example of nucleophilic participation by solvent. In the case of unsymmetrical alkenes, water reacts at the more substituted carbon, which is the carbon with the greatest cationic character. If it is desired to favor introduction of water, it is necessary to keep the concentration of the bromide ion as low as possible. One method for accomplishing this is to use N-bromosuccinimide (NBS) as the brominating reagent. High yields of bromohydrins are obtained by use of NBS in aqueous DMSO. The reaction is a stereospecific anti addition. As in bromination, a bromonium ion intermediate can explain the anti stereospecificity. It has been shown that the reactions in dimethyl... 

In a process analogous to the hydration of alkenes, water can be added to alkynes in a Markovnikov sense to give alcohols—in this case enols, in which the hydroxy group is attached to a double-bond carbon. As mentioned in Section 12-16, enols spontaneously rearrange to the isomeric carbonyl compounds. This process, called tautomerism, interconverts two isomers by simultaneous proton and double-bond shifts. The enol is said to tautomerize to the carbonyl compound, and the two species are called tautomers (tauto, Greek, the same mews, Greek, part). We shall look at tautomerism more closely in Chapter 18 when we investigate the behavior of carbonyl compounds. Hydration followed by tautomerism converts alkynes into ketones. The reaction is catalyzed by Hg(II) ions. 

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