Alcohol as solvent

Ethanol is an excellent solvent for many organic compounds, especially those with lone pair electrons that are hydrogen bond acceptors. Polar compounds dissolve readily in the like polar solvent. Nonpolar compounds dissolve in alcohols to some extent, but the solubility is often hmited because the extensive hydrogen-bonding network of the alcohol must be broken to accommodate the solute. 

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Oxidation of acetophenone with selenium dioxide iu the i)reseiice of dioxan or ethyl alcohol as solvent affords j.henylglyoxal ... 

When applied to the preparation of alkenes the reaction is carried out m the presence of a strong base such as sodium ethoxide (NaOCH2CH3) m ethyl alcohol as solvent... 

These reactions are usually performed in water or alcohols as solvents and the alkox ide ion intermediate is rapidly transformed to an alcohol by proton transfer The other involves acid catalysis Here the nucleophile is often... 

In early work, vinyl chloride had been heated with stoichiometric amounts of alkaU alkoxides in excess alcohol as solvent, giving vinyl ethers as products (210). Supposedly this involved a Williamson ether synthesis, where alkaU alkoxide and organic haUde gave an ether and alkaU haUde. However, it was observed that small amounts of acetylene were formed by dehydrohalogenation of vinyl chloride, and that this acetylene was consumed as the reaction proceeded. Hence acetylene was substituted for vinyl chloride and only catalytic amounts of alkaU were used. Vinylation proceeded readily with high yields (211). 

The reaction can be driven to the tetraalkoxide stage by addition of an amine or ammonia to scavenge the Hberated hydrochloric acid. The amine or ammonium hydrochloride that forms can be filtered from the reaction mass and the tetraalkyl titanate purified by distillation. If the reaction is mn in the starting alcohol as solvent, the chloride salts formed are in a finely divided state and difficult to filter. When the reaction is mn in the presence of an inert hydrocarbon solvent such as heptane or toluene, a much more readily filterable salt is obtained. The solution of cmde tetraalkyl titanate can be distilled to remove solvent and give a pure product (1,2). 

Catchpole-Kinp examined binaiy diffusion data of near-critical fluids in the reduced density range of 1 to 2.5 and found that their data correlated with average deviations of 10 percent and a maximum deviation of 60 percent. They observed two classes of behavior. For the first, no correction fac tor was required R = 1). That class was comprised of alcohols as solvents with aromatic or ahphatic solutes, or carbon dioxide as a solvent with ahphatics except ketones as solutes, or... 

The use of benzyl alcohol as solvent produces the dibenzyl acetal at C-21, and this can be reductively removed to produce the 21-hydroxy compound... 

Ri = N3, R.2 = H), and an equilibrium is observed in the case of the deuterated compound (59 Ri = R2 = N 02). Certain secondary amino-substituted compounds (59, 60 Rj =RNH, R2 = H) show solvent dependence of their equilibria solutions in dimethyl sulfoxide contain mainly form 59, whereas alcohols as solvents favor form 60. ... 

Esters can also be synthesized by an acid-catalyzed nucleophilic acyl substitution reaction of a carboxylic acid with an alcohol, a process called the Fischer esterification reaction. Unfortunately, the need to use an excess of a liquid alcohol as solvent effectively limits the method to the synthesis of methyl, ethyl, propyl, and butyl esters. 

As mentioned above, by this technique using a suspended catalyst free fatty acids also can be hydrogenated, provided the reaction is performed in an excess of the corresponding fatty alcohol as solvent [40]. 

In contrast to the asymmetric procedures discussed above, the metal-catalyzed oxidation of alkyl aryl sulphides by t-butylhydroperoxide carried out in a chiral alcohol gives rise to chiral sulphoxides of low optical purity (e.e. 0.6-9.8%). Similarly, a very low asymmetric induction was noted when prochiral sulphides were oxidized by sodium metaperiodate in chiral alcohols as solvents ... 

Unlike the case of the Ni-catalyzed reaction, which afforded the branched thioester (Eq. 7.1), the PdCl2(PPh3)3/SnCl2-catalyzed reaction with 1-alkyne and 1-alkene predominantly provided terminal thioester 6 in up to 61% yield in preference to 7. In 1983, a similar hydrothiocarboxylation of an alkene was also documented by using a Pd(OAc)2/P( -Pr)3 catalyst system with t-BuSH to form 8 in up to 79% yield (Eq. 7.6) [16]. It was mentioned in the patent that the Pt-complex also possessed catalyhc activity for the transformation, although the yield of product was unsatisfactory. In 1984, the hydrothiocarboxylation of a 1,3-diene catalyzed by Co2(CO)g in pyridine was also reported in a patent [17]. In 1986, Alper et al. reported that a similar transformation to the one shown in Eq. (7.3) can be realized under much milder reaction conditions in the presence of a 1,3-diene [18], and the carboxylic ester 10 was produced using an aqueous alcohol as solvent (Eq. 7.7) [19]. 

Entries 4 and 5 involve formation of ethers using alcohols as solvents, whereas the reaction in Entry 6 forms an amide in acetonitrile. Entries 7 and 8 show use of other nucleophiles to capture the mercurinium ion. 

Whereas in alcohols as solvents good yields of esters are obtained a self-condensation of the ester was observed in THF.[123]... 

As discussed before, a,P-unsaturated ketones are usually reduced to saturated ketones in isopropyl alcohol as solvent, the reaction proceeding via the enol after H-abstraction by the carbonyl group. When some selected a,p-enones are irradiated in their n-n absorption band (i.e. excitation... 

M. Jackson and H. H. Mantsch, Halogenated alcohols as solvents for proteins FTIR spectro scopic studies. Biochim. Biophys. Acta 1118, 139 143 (1992). 

The symbols were defined in Section IV.B.) A full discussion of the ortfio-effect as revealed in this work would be inappropriate here. We must restrict ourselves to the more limited task of indicating the role of o-N02. We discuss first the work involving alcohols as solvents. To apply the extended Hammett equation, i.e. to determine the regression coefficients a, fi and

intercept term h, it is first necessary to select a set of substituents which can be expected to be well-behaved . Particular problems for or and v may be caused by conformational effects, and internal hydrogen-bonding may occur... 

The regression equations were established for data in 11 alcohols as solvents and were used to assess the peculiar behaviour of another 15 orf/zo-substituents in respect of conformational effect and intramolecular hydrogen-bonding143,145. Flere we are concerned with assessing the situation for o-N02. We first give as an example the regression for 2-methoxyethanol as solvent ... 

It may be mentioned in passing that Chapman and coworkers148 determined rate coefficients for the reactions at 30 °C of phenylacetic acid and various meta- or /zara-substituted phenylacetic acids with DDM in 10 alcohols as solvents. The nitro acids were included. There were some interesting indications of solvent dependence for the apparent a values of /zara-substituents, including N02, for which values ranging from 0.69 to 0.77 were... 

The solvating properties of protonic solvents such as methanol, ethanol, or acetic acid, are intermediate between those of water and aprotic solvents. This factor accounts for many differences between water and the alcohols as solvents. For example, CoBr2 is ionized in water, while in methanol tetrahedral CoBr2 (CH3OH)2 is found23). 

Very recently, other Japanese workers applied A(-bromocaprolactam and a chiral alcohol as solvent for the same purpose as well as chiral A -chlorocaprolactam and water as oxidant (60,61). In both cases optically active sulfoxides were obtained in low optical and chemical yields. 

Alkylation of enolate is an important synthetic method.27 The alkylation of relatively acidic compounds such as /i-dikctoncs, /i-ketoesters, and esters of malonic acid can be carried out in alcohols as solvents using metal alkoxides as bases. The presence of two electron-withdrawing substituents facilitates formation of the enolate resulting from removal of a proton from the carbon situated between them. Alkylation then occurs by an Sn2 process. Some examples of alkylation reactions involving relatively acidic carbon acids are shown in Scheme 1.5. These reactions are all mechanistically similar in that a... 

There have been efforts to enhance stereoselectivity in radical polymerization by using fluoroalcohols or Lewis acids that complex with monomers such as MMA and vinyl acetate [Isobe et al., 2000, 2001a Okamoto et al., 2002], In almost all instances the effects are nil or very small. For example, the use of perfluoro-t-butyl alcohol as solvent instead of toluene changes (rr) from 0.89 to 0.91 in the polymerization of MMA at —78°C. An exception is in the polymerization of acrylamide in the presence of some rare-earth Lewis acids such as ytterbium triflate. The polymer is atactic at 0°C, (m) = 0.46, in the absence of the Lewis acid, but significantly isotactic, (m) — 0.80, in the presence of the Lewis acid. The reason for this effect is unclear. More highly isoselective polymerization occurs in some radical polymerizations of MMA (Sec. 8-14b). 

The major limitation of the potential value of the Venturello-Ishii systems, however, is related to the use of toxic and industrially undesirable chlorinated solvents , defeating the environmental advantages of H2O2 as primary oxygen source . In this respect, the PCWP catalytic system was modified by using t-butyl alcohol as solvent and by... 

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