Ethanol as solvent

Ionisations 2, 3 and 5 are complete ionisations so that in water HCI and HNO3 are completely ionised and H2SO4 is completely ionised as a monobasic acid. Since this is so, all these acids in water really exist as the solvated proton known as the hydrogen ion, and as far as their acid properties are concerned they are the same conjugate acid species (with different conjugate bases). Such acids are termed strong acids or more correctly strong acids in water. (In ethanol as solvent, equilibria such as 1 would be the result for all the acids quoted above.) Ionisations 4 and 6 do not proceed to completion... 

Diaryloxaziridines are even less stable. With oxaziridines (66 Ar = Ph or 4-Me2NC6H4) acid amide formation at 25 °C proceeded in the course of 66 and 10 h respectively in the latter case there were equal amounts of H and aryl migration. Ethanol as solvent again accelerated the reaction, in the latter case by a factor of lO. ... 

One of the simplest methods for preparation is by reaction of the thiol with KOH and RX in ethanol as solvent. 

The relative effects of methanol and ethanol as solvents in the reaction of 2-chloro-5-nitropyridine with aniline can be deduced from recent data by Chapman et and are reported in Table V. These... 

Both the malonic ester synthesis and the acetoacetic ester synthesis are easy to cany out because they involve unusually acidic dicarbonyi compounds. As a result, relatively mild bases such as sodium ethoxide in ethanol as solvent can be used to prepare the necessary enolate ions. Alternatively, however, it s also possible in many cases to directly alkylate the a position of monocarbonyl compounds. A strong, stericaliy hindered base such as LDA is needed so that complete conversion to the enolate ion takes place rather than a nucleophilic addition, and a nonprotic solvent must be used. 

Santamaria, R.I. et al.. Selective enzyme-mediated extraction of capsacinoids and carotenoids from Chili Guajillo Puja Capsicum annuum L.) using ethanol as solvent, J. Agric. Food Chem., 48, 3063, 2000. 

A key requirement for diimidazole formation appears to be substitution of the 2-position, since 4(5)-aminoimidazole (25 R = H) gave only the monomeric species (70 R = H). The choice of solvent is also important when dioxane replaced ethanol as solvent, diimidazole formation was suppressed [92JCS(P 1)2789]. 

The cellulose derivatives used were obtained by the fractional precipitation method with the use of ethanol as solvent and n-... 

Attention should be paid to the appearance of spurious peaks in the fragmentation patterns of amines determined by GC-MS, when the analytes came into contact with methanol or ethanol as solvents. Thus, for example, Schiff bases may be formed on condensation of a primary amine with traces of formaldehyde or acetaldehyde present in the solvent. Although the peaks of such product may be unresolved in the chromatogram, they may appear as ions with mass increments of +12 or +26 in the mass spectrogram, complicating the identification of the analyte, as was the case with some amphetamine drugs99. 

The homogeneous solvolysis of this substrate in aqueous ethanolic solvents can be monitored by the change in conductance as HCl is produced. Initial studies of the reaction in aqueous ethanol as solvent at 25 °C using a cleaning bath (45 kHz) revealed modest rate enhancements (up to about 2-fold) with the larger values being obtained in the more alcoholic media [37]. Similar results were found for the solvo-lyses in aqueous propan-2-ol and 2-methylpropan-2-ol. More substantial rate enhancements were obtained in the more ethanolic media and at lower temperature [38,39]. Detailed studies of the aqueous ethanol system led to the following main conclusions ... 

Pd- and Pt-nanoparticles protected by PS-b-PMAA were used to perform catalytic hydrogenations of cyclohexene in ethanol as solvent It could be shown that such colloids are catalytically active and thus interesting for the development of catalysts tailored for special reactions. 

The ketoximes 9 were synthesized by refluxing the ketones 8 and hydroxylamine hydrochloride in a mixture of pyridine and ethanol as solvent (Scheme 7). The microwave heating reduced markedly the reaction time (1-3 min versus 45 min in an oil bath). 

The activated Ba(OH)2 was used as a basic catalyst for the Claisen-Schmidt (CS) condensation of a variety of ketones and aromatic aldehydes (288). The reactions were performed in ethanol as solvent at reflux temperature. Excellent yields of the condensation products were obtained (80-100%) within 1 h in a batch reactor. Reaction rates and yields were generally higher than those reported for alkali metal hydroxides as catalysts. Neither the Cannizaro reaction nor self-aldol condensation of the ketone was observed, a result that was attributed to the catalyst s being more nucleophilic than basic. Thus, better selectivity to the condensation product was observed than in homogeneous catalysis under similar conditions. It was found that the reaction takes place on the catalyst surface, and when the reactants were small ketones, the rate-determining step was found to be the surface reaction, whereas with sterically hindered ketones the adsorption process was rate determining. 

The use of methanol or ethanol as solvent (or sometimes the molecule of water resulting from the spontaneous dehydration) often leads to the isolation of a Fischer-type alkoxy- or hydroxy-carbene [M]=C(OR)CH=CR R instead of the desired allenylidene. Addition of nucleophiles to allenylidenes dominates the reactivity of these electrophilic groups (see below). Nevertheless, in some cases, the use of silver (I) salts Ag[X] (X = PFg, TfO, BF4 ) results in a more practical and flexible synthetic method since the use of nucleophilic polar solvents can be avoided. 

In this work we extend our study to the hydrogenation and isomerization of a series of a,p-unsaturated alcohols, such as 2-propen-l-ol (A2), (E -2-buten-l-ol (EB2), (" -2-penten-l-ol (ZP2), (E -2-penten-l-ol (EP2), (" -2-hexen-l-ol (ZH2), (E -2-hexen-l-ol (EH2), carried out in the presence of RhCl(PPh3)3, with and without triethylamine (NEts), at 303 K, using ethanol as solvent. The major targets of our research are to investigate the influence of the unsaturated alcohol structure on the product distribution and to verify the possibility of extending the results, previously obtained with (" -2-butene-1,4-diol, to other analogous substrates. 

Reactions of a,p-unsaturated alcohols with hydrogen were carried out in the presence of RhC PPhsJs, with and without NEts, at 303 K, 0.1 MPa hydrogen pressure and using ethanol as solvent. Under the experimental conditions adopted, the reaction, in... 

This weak transition is due to the promotion of an electron from the non-bonding molecular orbital n to an anti-bonding tt orbital. This transition is usually observed in molecules that contain a heteroatom as part of an unsaturated system. The most common of these bands corresponds to the carbonyl band at around 270 to 295 nm, which can be easily observed. The molar absorption coefficient for this band is weak. The nature of the solvent influences the position of absorption bands because the polarity of the bond is modified during absorption. For example, ethanal Amax = 293 nm (e = 12 in ethanol as solvent). 

Figure 11 UV (Araa in nm (logc), ethanol as solvent) and H NMR data (DMSO-d6, 5 in p.p.m.) for borazarothienopyridines...

Hexakis imidazole and pyrazole complexes of nickel(II) can be easily obtained by the direct reaction of the hydrated nickel(II) salt with the appropriate ligand using ethanol as solvent and stoichiometric amounts of the reactants.898 899 Analogous complexes can be obtained with pyrazoles and imidazoles having substituents in positions not adjacent to the donor site. 

The main reaction product is ethylbenzene (50-80%). c Ethanol as solvent. 

Hydration reactions of alkynes and nitriles were studied over various zeolites in liquid phase, with ethanol as solvent. Alkyne hydration led to expected carbonyl compounds whereas the formation of the amide and of the corresponding ester was observed during nitrile hydration. 

It must be stated that the use of ethanol as solvent in the nitrile reaction makes it difficult to understand the mechanism. At this stage of our present results, it is particularly not possible to determine if the ester is formed from a direct addition of ethanol on the starting nitrile or from the amide as intermediate. As shown in Table 1, the less acidic HY zeolite favours ester formation while in the case of the HMg zeolites the amide is preferably formed. Such results seem to indicate that the ester formation occurs over weak acidic sites whereas the hydration reaction needs stronger acidic sites. 

Exercise 8-23 Would you expect the SN2 reaction of sodium cyarnde with methyl bromide to be faster, slower, or about the same with (CH3)2S=0 or ethanol as solvent Explain. 

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