Formate/alcohol ratio

The ratio of formates to alcohols [relation (10)] was observed to remain constant throughout a catalytic reaction, as had earlier been reported in the hydrogenation of an aldehyde by HCo(CO)4 (45). This observation provides further evidence that methyl formate is actually a primary product of the reaction. The formate/alcohol ratio was found to be independent of H2 partial pressure, but to increase substantially with CO pressure (nearly... 

The concept of a (bound) formaldehyde intermediate in CO hydrogenation is supported by the work of Feder and Rathke (36) and Fahey (43). Experiments under H2/CO pressure at 182-220°C showed that paraformaldehyde and trioxane (which depolymerize to formaldehyde at reaction temperatures) are converted by the cobalt catalyst to the same products as those formed from H2/CO alone. The rate of product formation is faster than in comparable H2/CO-only experiments, and product distributions are different, apparently because secondary reactions are now less competitive. However, Rathke and Feder note that the formate/alcohol ratio is similar to that found in H2/CO-only reactions (36). Roth and Orchin have reported that monomeric formaldehyde reacts with HCo(CO)4 under 1 atm of CO at 0°C to form glycolaldehyde, an ethylene glycol precursor (75). The postulated steps in this process are shown in (19)—(21), in which complexes not observed but... 

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]. 

Fig. 24. Dependences of the initial rate of TBA formation and ratio of DIP/TBA on H3PMo,2O40 concentration in the hydration of butenes. TBA, lerl-butyl alcohol DIB, diisobutylene. 357 K, isobutylene/1-butene = 1/1 (molar). (From Ref. 163.)...

Several studies have been made of the effect of added metal ions on the pinacol/alcohol ratio. Addition of antimony(m) chloride in catalytic amounts changes the product of the electrochemical reduction of acetophenone in acidic alcohol at a lead electrode from the pinacol in the absence of added metal salt to the secondary alcohol in its presence53. Antimony metal was suspected to be an intermediate in the reduction. Conversely, addition of Sm(in) chloride to DMF solutions of aromatic aldehydes and ketones54 and manganese(II) chloride to DMF solutions of hindered aromatic ketones55 results in selective formation of pinacols in excellent yields. When considering these results one should keep in mind the fact that aromatic ketones tend to form pinacols in DMF even in the absence of added metal ions1,29,45. 

It is assumed that the optimum hexadecyltrimethylammonium bromide-cetyl alcohol ratio for the formation of perfect crystals also corresponds to the formation of the highest-stability emulsions. The measurement of emulsion stability by ultracentrifugation (8) showed that emulsions prepared with a 1 3 hexadecyltrimethylammonium bromide-cetyl alcohol molar ratio showed the best stability. Therefore, the rodlike particles formed in this system should have the highest crystallinity, which was confirmed by electron diffraction measurements in the transmission electron microscope (2). The ratio P(2)/P(2)b> where the subscript b denotes the system of highest crystallinity, has values of 0.894, 0.419, and 0.189 for hexadecyltrimethylammonium bromide-cetyl alcohol molar ratios of 1 1, 1 0.50, and 1 0.33, respectively, relative to a value of 1.000 for the 1 3 ratio. 

Hilker et al. adapted the successful DKR of secondary alcohols developed at DSM48 to prepare chiral polymers from a,a -dimethyl-l,4-benzenedimethanol (1,4-diol) and dimethyl adipate (DMA) (Figure 11.3a) [51]. The applied catalytic system consisted of a Ru-Noyori type racemization catalyst 1 (Figure 11.3b) and Novozym 435. This catalyst combination tolerates a wide range of acyl donors, and it was anticipated that bifunctional monomers could result in the the formation of enantio-enriched polycondensates. Moreover, Novozym 435 is highly enan-tioselective in the transesterification of secondary benzylic alcohols ( -ratio is ca. 1 x 106) [52],... 

The chemical (Gif system) and the electrochemical conversion (Gif-Orsay system) have been compared in the oxidation of six saturated hydrocarbons (cyclohexane, 3-ethylpentane, methylcyclopentane, cis- and traus-decalin and adamantane). The results obtained for pyridine, acetone and pyridine-acetone were similar for both systems. Total or partial replacement of pyridine for acetone affects the selectivity for the secondary position and lowers the ratio ketone secondary alcohol. The formation of the same ratio of cis- and traws-decal-9-ol from either cis- or trans-deca in indicates that tertiary alcohols result from a mechanism essentially radical in nature. The C /C ratio between 6.5 and 32.7 rules out a radical mechanism for the formation of ketones and secondary alcohols. Ratios of 0.14 and 0.4 were reported for radical-type oxidations of adamantane and cis-decalin. Partial replacement of pyridine by methanol, ethanol or f-propanol results in diminished yields and a lower selectivity. Acetone gives comparable yields however, the C /C ratio drops to 0.2-10.7. 

Equation 6.87 predicts that the time tp until liquid crystal formation begins is proportional to the square of the initial drop radius and inversely proportional to the bulk surfactant concentration. These predictions were in agreement with experiments for systems containing pure nonionic surfactants, n-hexadecane, oleyl alcohol, and water (Lim and Miller, 1991a). Moreover, for a hydrocar-bon alcohol ratio of 3 1 by weight and for solutions of at 30°C, the phase diagram was determined and K calculated as 0.52. When the data were htted to Equation 6.87, D2 was found to be 1.3 x 10" ° m /sec. The Stokes-Einstein equation was then used to estimate micelle radius r. 

The decomposition of cyclohexylhydroperoxide was also studied in the presence of molybdenum and chromium complexes [356]. The decomposition of cyclohexylhydroperoxide in benzene catalyzed by [Mo02(acac)2], has many characteristics of the [VO(acac)2]-catalyzed reaction [355]. The ketone/alcohol ratio in the product was 1 and the kinetic pattern of reaction is similar. When chromium(III) acetylacetonate is used, however, there is a substantial difference. The chromium complex selectively converts cyclohexyl hydroperoxide to cyclohexanone. It is suggested that in this case the extent of release of free radicals to the solution is small [356]. The ketone/alcohol ratio in this case is " 13.7. The predominant formation of cyclohexanone on decomposition of cyclohexyl hydroperoxide in the presence of [Cr(acac)3] is no doubt related to the much higher yield of ketone obtained in cyclohexane oxidation in the presence of chromium complexes than observed when Mo or V compounds are used as catalysts [356]. 

Further evidence for an intermediate hydropero.xide was found in Zn -Fe -superoxide ex periments when PPh3 was added before tlie formation of the superoxide. This did not change the total amount of oxidation (ketone + alcohol), but did dramatically change the ketone to alcohol ratio in favor of alcohol. Hydroperoxides are. of course, rapidly reduced by PPli3 to alcohols. Furthermore when trimethyl phosphite is used instead of PPI13, the products of the reaction are phosphate and ketone. [7] Trimethyl phosphite is a reagent which reduces hydroperoxides at once to alcohols. This new trimethyl phosphite reaction can be understood better when we ask the question how is tlie hydroperoxide fonned ... 

Due to the presence of high amounts of water and alcohols in the sol the epoxy ringopening reactions mainly result in the formation of diols and ether products as can be seen by C-NMR spectroscopy (not illustrated here). Their amounts depend on the wa-ter/alcohol ratio in the sols (Hoffmaim, 1999). It can be concluded that Ihe longer the storage period at ambient temperature the lower is the epoxy-group concentration in the coating sol. 

The nitro alcohols available in commercial quantities are manufactured by the condensation of nitroparaffins with formaldehyde [50-00-0]. These condensations are equiUbrium reactions, and potential exists for the formation of polymeric materials. Therefore, reaction conditions, eg, reaction time, temperature, mole ratio of the reactants, catalyst level, and catalyst removal, must be carefully controlled in order to obtain the desired nitro alcohol in good yield (6). Paraformaldehyde can be used in place of aqueous formaldehyde. A wide variety of basic catalysts, including amines, quaternary ammonium hydroxides, and inorganic hydroxides and carbonates, can be used. After completion of the reaction, the reaction mixture must be made acidic, either by addition of mineral acid or by removal of base by an ion-exchange resin in order to prevent reversal of the reaction during the isolation of the nitro alcohol (see Ion exchange). 

The stringency of the conditions employed in the unmodified cobalt 0x0 process leads to formation of heavy trimer esters and acetals (2). Although largely supplanted by low pressure ligand-modified rhodium-catalyzed processes, the unmodified cobalt 0x0 process is stiU employed in some instances for propylene to give a low, eg, - 3.3-3.5 1 isomer ratio product mix, and for low reactivity mixed and/or branched-olefin feedstocks, eg, propylene trimers from the polygas reaction, to produce isodecanol plasticizer alcohol. 

Equation 20 is the rate-controlling step. The reaction rate of the hydrophobes decreases in the order primary alcohols > phenols > carboxylic acids (84). With alkylphenols and carboxylates, buildup of polyadducts begins after the starting material has been completely converted to the monoadduct, reflecting the increased acid strengths of these hydrophobes over the alcohols. Polymerization continues until all ethylene oxide has reacted. Beyond formation of the monoadduct, reactivity is essentially independent of chain length. The effectiveness of ethoxylation catalysts increases with base strength. In practice, ratios of 0.005—0.05 1 mol of NaOH, KOH, or NaOCH to alcohol are frequendy used. 

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