Alcohols as by-product

The numerous substitution reactions lay in the background of the application of metal alkoxides in inorganic and metal-organic synthesis (preparation of halides, hydrides, sulfides, carboxylates, alkyl derivatives, certain classes of coordination compounds, etc.). One advantage of their application is the formation of only alcohols as by-products ... 

This boast was somewhat premature, because the most difficult step of the four-step process was still unsolved. The dehydration of butylene glycol to the desired butadiene, as Meisenburg had remarked eleven years earlier, presented great difficulties, because apart from butadiene, other products of the dehydration were also formed, which gave rise to heavy contamination. I.G. Hochst had developed an alum catalyst, based on earlier work at Bayer, but Richard Leopold of Hochst ruefully reported in April 1927 that one of the hydroxyl groups resisted dehydration, giving rise to allyl carbinol and crotyl alcohol as by-products. ... 

Since S. cerevisiae is the workhorse in industrial ethanol fermentations and has the natural capacity to secrete fusel alcohols as by-products (reviewed in Hazelwood et ah, 2008), this organism is supposed to be an attractive host for the production of higher alcohols. Furthermore, S. cerevisiae tolerates up to 20% ethanol and also shows a comparatively high tolerance against butanol (Knoshaug and Zhang, 2009 Chen et ah, 2011). 

Comparison of the results of Tsuji-Trost coupling of ethyl cinnamyl carbonate and ethyl acetoacetate (Scheme 60) in biphasic mixtures either with water or with an ionic liquid showed clear advantage of using the IL solvent (292). The organic reactants are much better soluble in [bmim]Cl than in water which leads to faster reactions and in the absence of water formation of cinnamyl alcohol as by-product is avoided. 

Yeast. Yeast are troublesome because they thrive in the white water and form slimy, tenacious deposits on submerged surfaces. Yeast will grow under anaerobic conditions and produce earbon dioxide and alcohol as by-products of yeast fermentation. Yeasts can also lead to problems when they grow in starch slurries and cause fermentation. 

High reactivity of in situ generated aluminum alkoxide can be applied to Oppenauer oxidation of various benzyl alcohols (Scheme 6.62) [79]. In the presence of 10 mol% of Me3 Al, secondary benzyl alcohols were oxidized to the corresponding ketones by 3-nitrobenzaldehyde in quantitative yield. Reaction time is very short, generally 30 minutes. Under these conditions, remaining 3-nitrobenzaldehyde and 3-nitrobenzyl alcohol as by-product can be easily removed by filtration through alumina pad. Additionally, oxidation of primary aliphatic alcohol was proceeded smoothly under these conditions. 

The high sodium ion concentration results in facile crystallisation of the sodium salt. This process of salting out with common salt may be used for recrystallisation, but sodium benzenesulphonate (and salts of other acids of comparable molecular weight) is so very soluble in water that the solution must be almost saturated with sodium chloride and consequently the product is likely to be contaminated with it. In such a case a pure product may be obtained by crystallisation from, or Soxhlet extraction with, absolute alcohol the sul-phonate is slightly soluble but the inorganic salts are almost insoluble. Very small amounts of sulphones are formed as by-products, but since these are insoluble in water, they separate when the reaction mixture is poured into water ... 

Other sulfur compounds such as thiourea, ammonium dithiocarbamate, or hydrogen sulfide also lead to 2-mercaptothiazoles. Thus thiourea has been used in the syntheses of 4,5-dimethyl (369) and 4-aryl-2-mercapto-thiazoles (Table 11-30) (519). The reactions were carried out by condensing the ia -thiocyanatoketones with thiourea in alcohol and water acidified with hydrochloric acid. By this procedure, 4-aryl-2-mercaptothiazoles were obtained in yields of 40 to 80% with bis-(4-aryl-2-thiazolyl) sulfides as by-products (519). These latter products (194) have also been observed as a result of the action of thiourea on 2-chloro-4-arylthiazole under the same experimental conditions. They can be separated from 2-mercaptothiazoles because of their different degrees of solubility in sodium hydroxide solution at 5%. In this medium bis-(4-phenyl-2-thiazolyl)sulfide is... 

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

Miscellaneous Derivatives. Other derivatives of toluene, none of which is estimated to consume more than ca 3000 t (10 gal) of toluene aimuaHy, are mono- and dinitrotoluene hydrogenated to amines ben2otrich1 oride and chlorotoluene, both used as dye intermediates / 7-butylben2oic acid from / 7-butyltoluene, used as a resin modifier dodecyltoluene converted to a ben2yl quaternary ammonium salt for use as a germicide and biphenyl, obtained as by-product during demethylation, used in specialty chemicals. Toluene is also used as a denaturant in specially denatured alcohol (SDA) formulas 2-B and 12-A. 

Acid Anhydrides. Acid anhydrides react with alcohols to form esters (in high yields in many cases) with a carboxyUc acid formed as by-product ... 

Ethyl ether and ethyl alcohol which are formed as by-products are removed by distillation and the ethyl cellulose is precipitated by hot water. The polymer is then carefully washed to remove sodium hydroxide and sodium chloride and dried. 

The dihydroxyacetone side chain is conveniently protected by forming 17a,20 20,21-bismethylenedioxy compounds (BMD) (92). Formation of llf -ethers as by-products from 11 -hydroxycompounds (91) can be limited by using formalin with a low methanol content, or better with paraformaldehyde as a source of alcohol-free formaldehyde. ... 

The reaction between perfluoraarylmagnesium halides and esters of dicar-boxyltc acids gives, besides the expected keto esters, secondary alcohols as reduction products [29, 30, 31] (equation 10) Such a reduction is enhanced by higher temperature The hydrogen necessary for reduction comes from the solvent, diethyl ether, which is dehydrogenated to ethyl vinyl ether, which has been identified as a by-product in a similar reaction of perfluoroalkyllithium compound [52]... 

A problem often encountered in the oxidation of primary alcohols to acids is that esters are sometimes produced as by-products. For example, oxidation of ethanol yields acetic acid and ethyl acetate ... 

Step 3 of Figure 29.3 Alcohol Oxidation The /3-hydroxyacyl CoA from step 2 is oxidized to a /3-ketoacyl CoA in a reaction catalyzed by one of a family of L-3-hydroxyacyl-CoA dehydrogenases, which differ in substrate specificity according to the chain length of the acyl group. As in the oxidation of sn-glycerol 3-phosphate to dihydroxyacetone phosphate mentioned at the end of Section 29.2, this alcohol oxidation requires NAD+ as a coenzyme and yields reduced NADH/H+ as by-product. Deprotonation of the hydroxyl group is carried out by a histidine residue at the active site. 

Another example of dynamic kinetic resolution is the reduction of a sulfur-substituted ketone. Thus, yeast reduction of (R/S)-2-(4-methoxyphenyl)-l, 5-benzothiazepin-3,4(2H, 5H)-dione gave only (2S, 3S)-alcohol as a product out of four possible isomers as shown in Figure 8.39c [29kj. Only (S)-ketone was recognized by the enzyme as a substrate and reduction of the ketone proceeded... 

In current industrial practice, benzaldehyde is added to fermenting baker s yeast Saccharomyces cerevisiae) with resultant PAC production occurring from the yeast-derived pyruvate. Typically PAC concentrations of 12-15 g F are produced at yields of 65-70% theoretical in a 10-12 h biotransformation process. [2], Appreciable concentrations of benzyl alcohol are produced as by-product due to oxidoreductase activity in the fermentative yeast. 

The results of the series of reactions shown in eq. 2 are listed in Table 1 together with our early reported data on the hydrogenation of 2-octanone (Z) [4]. The hydrogenation on all substrates proceeded smoothly and gave the corresponding chiral secondary alcohol. In the case of 3, 4, S, and 6, some amounts of lactone were produced as by-product. From this study, quite interesting stereochemical behavior... 

Oxidation by the Dess-Martin Reagent. Another reagent that has become important for laboratory synthesis is known as the Dess-Martin reagent,28 which is a hypervalent iodine(V) compound.29 The reagent is used in inert solvents such as chloroform or acetonitrile and gives rapid oxidation of primary and secondary alcohols. The by-product, o-iodosobenzoic acid, can be extracted with base and recycled. 

In general, the Henry reaction proceeds in a non-selective way to give a mixture of anti (erythro) and syn (threo) isomers. Ab initio calculations on the Henry reaction suggest that free nitronate anions (not influenced by cations) react with aldehydes via transition states in which the nitro and carbonyl dipoles are antiperiplanar to each other. This kind of reaction yields anti-nitro alcohols. The Henry reaction between lithium nitronates and aldehydes is predicted to occur via cyclic transition states yielding syn-nitro alcohols as major products (Eq. 3.64).108... 

Alternative to m-chloroperbenzoic acid.1 This oxidant has been introduced as a suitable replacement for m-chloroperbenzoic acid, which is no longer available from commercial sources because of hazards in the manufacture. Actually MMPP is a safer reagent than MCPBA, which is shock-sensitive and potentially explosive. MMPP is soluble in water and in low-molecular-weight alcohols. The by-product, magnesium phthalate, is water-soluble and easily removed. It is generally more stable than other percarboxylic acids. It can replace MCPBA for the usual classic oxidations epoxidation, Baeyer-Villiger reactions, and oxidation of amines to N-oxides. 

In the presence of an alcohol and ferf-amines the corresponding triaUcylphosphates are formed in high yields. Elemental tellurium is formed as by-product. ... 

Many hydroxy compounds would not survive such harsh treatment therefore other methods must be used. Some alcohols were hydrogenolyzed with chloroalanes generated in situ from lithium aluminum hydride and aluminum chloride, but the reaction gave alkenes as by-products [605], Tertiary alcohols were converted to hydrocarbon on treatment at room temperature with triethyl- or triphenylsilane and trifluoroacetic acid in methylene chloride (yields 41-92%). Rearrangements due to carbonium ion formation occur [343]. 

Reactions lla-e add up to Reaction 10. Reactions lla-b have been shown above to be catalyzed by Rh/CH3l. Reaction 11c, i.e. acid-catalysed pyrolysis of EDA to acetaldehyde and acetic anhydride, is well documented (9). Both reaction lid, hydrogenation of aldehyde, and Reaction lie, carbonylation of alcohols, are of course well known. The reaction sequence is in agreement with the fact that EDA and AH, especially in short-duration experiments, are detected as by-products. Acetaldehyde is also observed in small quantities, but no ethanol is found. Possibly, Reactions lid and He occur concertedly. We have separately demonstrated that both EDA and AH are suitable feeds to produce propionic acid under homologation reactions conditions. We thus demonstrated... 

Fermentation is the anaerobic decomposition of organic compounds, basically carbohydrate, into alcohols by the action of bacterial enzymes. Ethanol is the desired product of carbohydrate fermentation, but other alcohols, acids, ketones, and aldehydes can form as by-products. One common example of ethanol production from biomass is the fermentation of com. For illustration, this process will be summarized. 

---