Hydrates, alcoholates from

Hammett equation, applied to azines, 217 Hetarynes, 121-143 contrasted with arynes, 125 Heteroaromatic compounds, covalent hydration of, 1-41 "pKa generalizations for, 48-61 Heterocyclic acids, pH-rate profile for, 67 Heterocyclic diazonium compounds, 241 Heptaazanaphthalenes, 393 Hexaazanaphthalenes, 393 Hippuroflavin, 80 Hydrated salts, isolation of, 16 Hydrates, alcoholates from, 16 isolation of, 16... 

Direct Hydration. The acid-catalyzed direct hydration of propylene is exothermic and resembles the preparation of ethyl alcohol from ethylene (qv). 

Synthetic pine oil is produced by the acid-catalyzed hydration of a-pinene (Fig. 1). Mineral acids, usually phosphoric acid, are used in concentrations of 20—40 wt % and at temperatures varying from 30—100°C. Depending on the conditions used, alcohols, chiefly a-terpineol (9), are produced along with /)-menthadienes and cineoles, mainly limonene, terpinolene, and 1,4- and 1,8-cineole (46—48). Various grades of pine oil can be produced by fractionation of the cmde products. Formation of terpin hydrate (10) from a-terpineol gives P-terpineol (11) and y-terpineol (12) as a consequence of the reversible... 

Sulfuric acid is about one thousand times more reactive with isobutylene than with the 1- and 2-butenes, and is thereby very useful in separating isobutylene as tert-huty alcohol from the other butenes. The reaction is simply carried out by bubbling or stirring the butylenes into 45—60% H2SO4. This results in the formation of tert-huty hydrogen sulfate. Dilution with water followed by heat hydrolyzes the sulfate to form tert-huty alcohol and sulfuric acid. The Markovnikov addition implies that isobutyl alcohol is not formed. The hydration of butylenes is most important for isobutylene, either directiy or via the butyl hydrogen sulfate. 

There are two main processes for the synthesis of ethyl alcohol from ethylene. The eadiest to be developed (in 1930 by Union Carbide Corp.) was the indirect hydration process, variously called the strong sulfuric acid—ethylene process, the ethyl sulfate process, the esterification—hydrolysis process, or the sulfation—hydrolysis process. This process is stiU in use in Russia. The other synthesis process, designed to eliminate the use of sulfuric acid and which, since the early 1970s, has completely supplanted the old sulfuric acid process in the United States, is the direct hydration process. This process, the catalytic vapor-phase hydration of ethylene, is now practiced by only three U.S. companies Union Carbide Corp. (UCC), Quantum Chemical Corp., and Eastman Chemical Co. (a Division of Eastman Kodak Co.). UCC imports cmde industrial ethanol, CIE, from SADAF (the joint venture of SABIC and Pecten [Shell]) in Saudi Arabia, and refines it to industrial grade. 

Other synthetic methods have been investigated but have not become commercial. These include, for example, the hydration of ethylene in the presence of dilute acids (weak sulfuric acid process) the conversion of acetylene to acetaldehyde, followed by hydrogenation of the aldehyde to ethyl alcohol and the Fischer-Tropsch hydrocarbon synthesis. Synthetic fuels research has resulted in a whole new look at processes to make lower molecular weight alcohols from synthesis gas. 

In these solutions, the hydrated electrons from the radiolysis of water produce CO by their reaction with COj, and the OH radicals attack the alcohol to form (CHjIjCOH radicals (see also footnote on page 117). 

Soulier et al. (35) isolate eight triterpenic alcohols from sal and illipe butters besides other compounds. They separate these compounds after saponification of the fatty matter and fractionation of the unsaponifiable on an aluminium oxide column (hydrated at 5%). Two successive HPLC separations and a TLC-AgN03 permit the isolation of highly purified fractions. Through the use, among others, of the H-NMR and MS techniques, they identify nine... 

Thus, we need to prepare 180-labeled ethyl alcohol from the other designated starting materials, acetaldehyde and 180-enriched water. First, replace the oxygen of acetaldehyde with 180 by the hydration-dehydration equilibrium in the presence of 180-enriched water. 

For these reasons, acid-catalyzed hydration is often not the method of choice for preparing alcohols from alkenes. Another reaction that accomplishes this same transformation, often in higher yield, is described in Section 11.6. 

The mechanism of the formation of the tetrahydropyranyl ether (see Figure 23.1) is an acid-catalyzed addition of the alcohol to the double bond of the dihydropyran and is quite similar to the acid-catalyzed hydration of an alkene described in Section 11.3. Dihydropyran is especially reactive toward such an addition because the oxygen helps stabilize the carbocation that is initially produced in the reaction. The tetrahydropyranyl ether is inert toward bases and nucleophiles and serves to protect the alcohol from reagents with these properties. Although normal ethers are difficult to cleave, a tetrahydropyranyl ether is actually an acetal, and as such, it is readily cleaved under acidic conditions. (The mechanism for this cleavage is the reverse of that for acetal formation, shown in Figure 18.5 on page 776.)... 

The crystals dissolve in alcohol, but not in ether. Alkalies and alkali peroxides precipitate the hydrated sesquioxide from the aqueous solution. 

The cis hydration renders it possible to synthesize diastercomeric alcohols from suitably substituted alkenes or their functionalized derivatives13-17. 

Other functional groups may be present in the molecule containing the double bond. Methallyl alcohol, H2C = C(CHjX HjOH, is hydrated by a mixture of 25% sulfuric acid in the presence of isobutyraldehyde to give the cyclic acetal of isobutylene glycol with the aldehyde. Hydrolysis of the acetal by dilute mineral acid gives isobutylene glycol (94%). Hydration of the double bond by aqueous sulfuric acid has been used to make chloro-i-butyl alcohol from methallyl chloride and /S-hydroxybutyric acid from crotonic acid. ... 

Hultgren A, Rau DC. Exclusion of alcohols from spermidine-DNA assemblies probing the physical basis for preferential hydration. Biochemistry 2004 43 8272-8280. 

Lithium iodide forms a solid complex with ammonia, Li(NH3)4l, but the related hydrate, alcoholate and amine complexes are less stable. These complexes presumably involve ion-dipole bonds (p. 115), the nitrogen lone pairs surrounding the Li+ some covalent character (dative bonding) is also permissible if s and p orbitals on the Li are invoked. The chloride, bromide and iodide of lithium are much more soluble in alcohol and ether than those of the other alkali metals, but this is not always a reliable indication of covalent character. The property is employed in separating lithium from sodium. 

Properties (L(-)-phenylalanine) Plates and leaflets from concentrated aqueous solutions, hydrated needles from dilute aqueous solutions, decomposes at 283C. Soluble in water slightly soluble in methanol and ethanol. (D(+)-phenylalamne ) Leaflets from water, decomposes 285C. Soluble in water slightly soluble in methanol. (DL-phenylalanine) Leaflets or prisms from water or alcohol sweet tasting. Decomposes 318-320C. Soluble in water. 

The hydration reaction (addition of water) is another very important addition reaction of alkenes. It is used commercially for the preparation of a wide variety of alcohols from petroleum by-products. Ethanol, the most important industrial alcohol, is produced industrially by the hydration of ethylene from petroleum, using H2SO4 as a catalyst. 

In lowering the concentration in ethanol ( 9 or 14 mol%), ice Ic starts first to crystallize at -143 K. The hydrate 1 begins to develop at - 163 K, i.e. at higher temperature compared with the 54 mol% EtOH deposit (Figure 3). Apparently, water molecules in excess need first to be excluded as ice Ic in order for the mixture to achieve the appropriate component ratio H20/EtOH for hydrate 1 formation. The hydrate 2 formation is shifted to 188 K (14 mol%), 193 K (31 mol%) or can be absent from the pattern (9 mol%). In this latter case, the (hydrated) alcohol clusters apparently remain disseminated in ice as the ratio water/EtOH required for hydrate 2 formation cannot be reached within the stability field of the phase. Further, its domain of existence seems to narrow as XEton decreases. A more detail account will be given in a forthcoming paper. 

---