Formation of alcohols

Resorcinol or hydroquinone production from m- or -diisopropylben2ene [100-18-5] is realized in two steps, air oxidation and cleavage, as shown above. Air oxidation to obtain the dihydroperoxide (DHP) coproduces the corresponding hydroxyhydroperoxide (HHP) and dicarbinol (DC). This formation of alcohols is inherent to the autooxidation process itself and the amounts increase as DIPB conversion increases. Generally, this oxidation is carried out at 90—100°C in aqueous sodium hydroxide with eventually, in addition, organic bases (pyridine, imidazole, citrate, or oxalate) (8) as well as cobalt or copper salts (9). 

The formation of alcohols by acid-catalyzed addition of water to alkenes is a fundamental organic reaction. At the most rudimentary mechanistic level, it can be viewed as involving a carbocation intermediate. The alkene is protonated, and the carbocation is then captured by water. 

The C2-symmetric epoxide 23 (Scheme 7) reacts smoothly with carbon nucleophiles. For example, treatment of 23 with lithium dimethylcuprate proceeds with inversion of configuration, resulting in the formation of alcohol 28. An important consequence of the C2 symmetry of 23 is that the attack of the organometallic reagent upon either one of the two epoxide carbons produces the same product. After simultaneous hydrogenolysis of the two benzyl ethers in 28, protection of the 1,2-diol as an acetonide ring can be easily achieved by the use of 2,2-dimethoxypropane and camphor-sulfonic acid (CSA). It is necessary to briefly expose the crude product from the latter reaction to methanol and CSA so that the mixed acyclic ketal can be cleaved (see 29—>30). Oxidation of alcohol 30 with pyridinium chlorochromate (PCC) provides alde-... 

Faraday, in 1834, was the first to encounter Kolbe-electrolysis, when he studied the electrolysis of an aqueous acetate solution [1], However, it was Kolbe, in 1849, who recognized the reaction and applied it to the synthesis of a number of hydrocarbons [2]. Thereby the name of the reaction originated. Later on Wurtz demonstrated that unsymmetrical coupling products could be prepared by coelectrolysis of two different alkanoates [3]. Difficulties in the coupling of dicarboxylic acids were overcome by Crum-Brown and Walker, when they electrolysed the half esters of the diacids instead [4]. This way a simple route to useful long chain l,n-dicarboxylic acids was developed. In some cases the Kolbe dimerization failed and alkenes, alcohols or esters became the main products. The formation of alcohols by anodic oxidation of carboxylates in water was called the Hofer-Moest reaction [5]. Further applications and limitations were afterwards foimd by Fichter [6]. Weedon extensively applied the Kolbe reaction to the synthesis of rare fatty acids and similar natural products [7]. Later on key features of the mechanism were worked out by Eberson [8] and Utley [9] from the point of view of organic chemists and by Conway [10] from the point of view of a physical chemist. In Germany [11], Russia [12], and Japan [13] Kolbe electrolysis of adipic halfesters has been scaled up to a technical process. 

A mixture of water/pyridine appears to be the solvent of choice to aid carbenium ion formation [246]. In the Hofer-Moest reaction the formation of alcohols is optimized by adding alkali bicarbonates, sulfates [39] or perchlorates. In methanol solution the presence of a small amount of sodium perchlorate shifts the decarboxylation totally to the carbenium ion pathway [31]. The structure of the carboxylate can also support non-Kolbe electrolysis. By comparing the products of the electrolysis of different carboxylates with the ionization potentials of the corresponding radicals one can draw the conclusion that alkyl radicals with gas phase ionization potentials smaller than 8 e V should be oxidized to carbenium ions [8 c] in the course of Kolbe electrolysis. This gives some indication in which cases preferential carbenium ion formation or radical dimerization is to be expected. Thus a-alkyl, cycloalkyl [, ... 

The aim of this review is to demonstrate the potential of surface forces measurement as a novel means for investigating surfaces and complex soft systems by describing our recent studies, which include cluster formation of alcohol, polyion adsorption, and polyelectrolyte brushes. 

Adsorption phenomena from solutions onto sohd surfaces have been one of the important subjects in colloid and surface chemistry. Sophisticated application of adsorption has been demonstrated recently in the formation of self-assembhng monolayers and multilayers on various substrates [4,7], However, only a limited number of researchers have been devoted to the study of adsorption in binary hquid systems. The adsorption isotherm and colloidal stabihty measmement have been the main tools for these studies. The molecular level of characterization is needed to elucidate the phenomenon. We have employed the combination of smface forces measmement and Fomier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR) to study the preferential (selective) adsorption of alcohol (methanol, ethanol, and propanol) onto glass surfaces from their binary mixtures with cyclohexane. Om studies have demonstrated the cluster formation of alcohol adsorbed on the surfaces and the long-range attraction associated with such adsorption. We may call these clusters macroclusters, because the thickness of the adsorbed alcohol layer is about 15 mn, which is quite large compared to the size of the alcohol. The following describes the results for the ethanol-cycohexane mixtures [10],... 

The low allylic alcohols (< 6%) yield suggests that the alcohol is reoxidized to the corresponding ketone, probably by Fe =0 species (M = O) (29). Alcohol oxidation tests (Figure 49.2) confirm that the formation of alcohol is an intermediate step in the synthesis of the corresponding ketone, equations 9-11. 

Scheme 7.4 illustrates some of the important synthetic reactions in which organolithium reagents act as nucleophiles. The range of reactions includes S/v2-(ype alkylation (Entries 1 to 3), epoxide ring opening (Entry 4), and formation of alcohols by additions to aldehydes and ketones (Entries 5 to 10). Note that in Entry 2, alkylation takes place mainly at the 7-carbon of the allylic system. The ratio favoring 7-alkylation... 

Sterically congested ketones have been prepared in good yield in this way without significant formation of alcohols. 

Hydrogenation of amides normally result in the formation of alcohols, whereas lactams give cyclic amines. The work presented in this paper is the first example that we are aware in which a lactam was hydrogenated by a ruthenium catalyst. To verify that acid promoted the lactam carbonyl hydrogenation, two... 

In the cases of oxiranes, the formation of alcohols and oxo compounds (ketones and aldehydes) are the result of primary processes.3,274-286 Hydrogenation of oxo compounds does not occur on surfaces covered with oxirane. The adsorption of oxiranes on metal surfaces is irreversible during adsorption, ring-opening takes place also. As the temperature is raised, the proportions of the oxo compounds increase. 

Reaction 6 representing /1-scission of alkoxyl radicals leading to the reduction of molar mass competes with transfer of a free radical centre to surrounding groups with consequent formation of alcoholic groups (reaction 7), which subsequently loose water and C = C unsaturation appears randomly along the polymer chain. 

Although the sol-gel process is highly convenient for the immobilization of biomolecules, a major limitation is the formation of alcohol as a by-product during the... 

The addition of water and a non-hydrogen-bonding solvent to the reduction medium causes the reactions to shift toward the formation of alcohol products.313 For example, triethylsilane in a mixture of concentrated hydrochloric acid and acetonitrile (5 4) reduces 1-heptanal to 1-heptanol in quantitative yield after 3 hours at room temperature. In a mixture of triethylsilane in sulfuric acid, water, and acetonitrile (2 2 5), //-hep(anal gives a 97% yield of the same alcohol after 1.25 hours (Eq. 156).313... 

Butyl alcohol is not the principal use of butanal obtained by propene hydro formylation. Rather its major market is 2-ethylhexanol that is prepared via aldol condensation followed by hydrogenation. [4] Thus formation of alcohols when aldehydes are desired is not only a direct efficiency loss, but also the alcohol impurity will form hemiacetals and acetals that complicate refining and lead to increased operating costs. 

This view is supported by the formation of alcohols and aldehydes, which is not possible via mechanism 1. For the formation of these oxygenates, insertion of CO is necessary. Therefore, several authors and first of all M. E. Dry26 proposed a combined mechanism where hydrocarbons are mainly formed via CH2 insertion and oxygenates via CO insertion. We extend this proposal by the assumption that hydrocarbons are also formed via CO insertion in the same way as oxygenates. 

However, the detailed description of the FT product distribution together with the reactant conversion is a very important task for the industrial practice, being an essential prerequisite for the industrialization of the process. In this work, a detailed kinetic model developed for the FTS over a cobalt-based catalyst is presented that represents an evolution of the model published previously by some of us.10 Such a model has been obtained on the basis of experimental data collected in a fixed bed microreactor under conditions relevant to industrial operations (temperature, 210-235°C pressure, 8-25 bar H2/CO feed molar ratio, 1.8-2.7 gas hourly space velocity, (GHSV) 2,000-7,000 cm3 (STP)/h/gcatalyst), and it is able to predict at the same time both the CO and H2 conversions and the hydrocarbon distribution up to a carbon number of 49. The model does not presently include the formation of alcohols and C02, whose selectivity is very low in the FTS on cobalt-based catalysts. 

The hydrocarbon with a tertiary C—H bond is oxidized to stable tertiary hydroperoxide. This hydroperoxide is decomposed homolytically with the formation of alcohol [82] ... 

Fig. 1.14. Main processing steps in the formation of alcohols starting from fats and oils.

Consistent with this mechanism is the fact that the reaction takes place with inversion of configuration at the reaction centre (Johnson and Nidy, 1975). For alkyl tosylates similar results have been reported (San Fillippo et al., 1975). The formation of alcohols under these conditions has been ascribed to secondary reactions (Chern et al., 1978 Johnson et al., 1978). Under certain conditions alcohols are even the only isolated products (Corey et al., 1975). 

These findings for Re peroxo complexes are in striking contrast with Ti and V catalyzed reactions [41, 51, 52, 111, 113] in which the metal-alcoholate bond drives the allylic OH directivity. We recall that the formation of alcoholate intermediates was also rejected for epoxidations of allylic alcohols with Mo and W peroxo compounds while H-bonding (between OH and the reacting peroxo fragment) was considered consistent with kinetic data for these complexes [115]. 

How Does Arabidopsis Assemble Homoterpene Volatiles 11.4.1 Formation of Alcohol Precursors... 

The treatment of alkyl chlorides with aqueous KOH leads to the formation of alcohols but In the presence of alcoholic KOH, alkenes are major products. Explain. 

Hydroboration occurred from the less hindered top face of rac-29 and resulted in the formation of alcohol rac-30. After a three-step sequence which included oxidation with tetrapropylammonium perruthenate (TPAP), methyl lithium addition and repeated oxidation with TPAP, ketone rac-31 was isolated. Finally, epimerization of the stereogenic center at C-7 to the correct configuration and methylenation with the Lombardo reagent led to the formation of racemic kelsoene (rac-1). 

The nucleophilic reactions of Grignard rej ents include reactions that create carbon-carbon bonds and the formation of alcohols. 

TABLE 16.4. Standard Enthalpy of Formation of Alcohols" (kcal/mol)... 

The ketone/alcohol ratio is also dependent on the nature of the phthallocyanine complex and of the substrate. Indeed, Fet.BuPc favors the formation of alcohols in the oxidation of cyclohexane with PhIO, as shown in Figure 8 [67], whereas the use of n-alkanes with increasing chain length enhances the formation of ketones on FePcY with t-ButOOH as oxidant, as is seen in Figure 9 [57]. 

The data in Table 7 show that the selectivity for 2-oxygenated products in the oxidation of alkanes on TS-1 is somewhat higher than could be expected on statistical grounds. Only for 3-methylpentane, this selectivity becomes overcompensated by the higher reactivity of tertiary C-H compared to secondary C-H positions. This indicates that the first step of the oxidation, i.e. the formation of alcohols from alkanes is slightly regioselective. Within the ketone fraction, the selectivity for 2-ketones is even more pronounced, indicating that 2-alcohols are selectively oxidized to 2-ketones in the... 

From the mechanistic scheme depicted in Figure 4 it can be deduced that in order to maximize the production of C2 to C- olefins the combination of the following factors are required, a) After adsorption the CO molecule should dissociate to ensure that the dominant active surface species is "CH (the presence of a high level of active undissociated CO molecules would lead to CO insertion (see step 2 (ii) in Figure 4) which could result in the formation of alcohols in preference to hydrocarbons (see step 3 (ii) in Figure 4). 

Class (3) reactions include proton-transfer reactions of solvent holes in cyclohexane and methylcyclohexane [71,74,75]. The corresponding rate constants are 10-30% of the fastest class (1) reactions. Class (4) reactions include proton-transfer reactions in trans-decalin and cis-trans decalin mixtures [77]. Proton transfer from the decalin hole to aliphatic alcohol results in the formation of a C-centered decalyl radical. The proton affinity of this radical is comparable to that of a single alcohol molecule. However, it is less than the proton affinity of an alcohol dimer. Consequently, a complex of the radical cation and alcohol monomer is relatively stable toward proton transfer when such a complex encounters a second alcohol molecule, the radical cation rapidly deprotonates. Metastable complexes with natural lifetimes between 24 nsec (2-propanol) and 90 nsec (tert-butanol) were observed in liquid cis- and tra 5-decalins at 25°C [77]. The rate of the complexation is one-half of that for class (1) reactions the overall decay rate is limited by slow proton transfer in the 1 1 complex. The rate constant of unimolecular decay is (5-10) x 10 sec for primary alcohols, bimolecular decay via proton transfer to the alcohol dimer prevails. Only for secondary and ternary alcohols is the equilibrium reached sufficiently slowly that it can be observed at 25 °C on a time scale of > 10 nsec. There is a striking similarity between the formation of alcohol complexes with the solvent holes (in decalins) and solvent anions (in sc CO2). 

In oxidation studies it has usually been assumed that thermal decomposition of alkyl hydroperoxides leads to the formation of alcohols. However, carbonyl-forming eliminations of hydroperoxides, usually under the influence of base, are well known. Of more interest, nucleophlic rearrangements, generally acid-catalyzed, have been shown to produce a mixture of carbonyl and alcohol products by fission of the molecule (6). For l-butene-3-hydroperoxide it might have been expected that a rearrangement (Reaction 1) similar to that which occurs with cumene hydroperoxide could produce two molecules of acetaldehyde. 

The desired products are hydrocarbons in the C5 to C10 range that can be used in gasoline production. Iron-, cobalt- and nickel-based catalysts plus the proper selection of reaction temperatures and pressures are used to control product output. Increasing residence time in the reactor yields more paraffinic products and reduces the formation of alcohol and acid. 

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