Esterification Potassium hydroxide

As with poly(vinyl alcohol), poly(vinyl cinnamate) is prepared by chemical modification of another polymer rather than from monomer . One process is to treat poly(vinyl alcohol) with cinnamoyl chloride and pyridine but this is rather slow. Use of the Schotten Baumann reaction will, however, allow esterification to proceed at a reasonable rate. In one example poly(vinyl alcohol) of degree of polymerisation 1400 and degree of saponification of 95% was dissolved in water. To this was added a concentrated potassium hydroxide solution and then cinnamoyl chloride in methyl ethyl ketone. The product was, in effect a vinyl alcohol-vinyl cinnamate copolymer Figure 14.8)... 

Mildly basic liquiddiquid conditions with a stoichiometric amount of catalyst prevent hydrolysis during alkylation [101] and, more recently, it has been established that solid-liquid or microwave promoted reactions of dry materials are more effective for monoalkylation [102-106] of the esters and also permits dialkylation without hydrolysis. Soliddiquid phase-transfer catalytic conditions using potassium f-butoxide have been used successfully for the C-alkylation of diethyl acetamido-malonate and provides a convenient route to a-amino acids [105, 107] use of potassium hydroxide results in the trans-esterification of the malonate, resulting from hydrolysis followed by O-alkylation. The rate of C-alkylation of malonic esters under soliddiquid phase-transfer catalytic conditions may be enhanced by the addition of 18-crown-6 to the system. The overall rate is greater than the sum of the individual rates observed for the ammonium salt or the crown ether [108]. 

A potential industrial route to potassium dinitromethane (18) involves treatment of methyl malonate (107) with red fuming nitric acid to give methyl Q ,Q -dinitroacetate (108), followed by hydrolysis-decarboxylation with aqueous potassium hydroxide. Dinitromethane is a precursor to 2,2-dinitroethanol and 2,2-dinitro-1,3-propanediol, both of which are useful in addition and esterification reactions for the production of energetic oligomers and plasticizers. 

The process involves reacting the degummed oil with an excess of methyl alcohol in the presence of an alkaline catalyst such as sodium or potassium methoxide, reaction products between sodium or potassium hydroxide and methyl alcohol. The reaction is carried out at approximately 150°F under pressure of 20 psi and continues until trans-esterification is complete. Glycerol, free fatty acids and unreacted methyl alcohol are separated from the methyl ester product. The methyl ester is purified by removal of residual methyl alcohol and any other low-boiling-point compounds before its use as biodiesel fuel. From 7.3 lb of soybean oil, 1 gallon of biodiesel fuel can be produced. See FIGURE 12-5. 

In the event, iodolactonization of the carboxylate salt derived from the ester 458 afforded 459, and subsequent warming of the iodo lactone 459 with aqueous alkali generated an intermediate epoxy acid salt, which suffered sequential nucleophilic opening of the epoxide moiety followed by relactonization on treatment with methanol and boron trifluoride to deliver the methoxy lactone 460. Saponification of the lactone function in 460 followed by esterification of the resulting carboxylate salt with p-bromophenacylbromide in DMF and subsequent mesylation with methanesulfonyl chloride in pyridine provided 461. The diazoketone 462 was prepared from 461 by careful saponification of the ester moiety using powdered potassium hydroxide in THF followed by reaction with thionyl chloride and then excess diazomethane. Completion of the D ring by cyclization of 462 to the keto lactam 463 occurred spontaneously on treatment of 462 with dry hydrogen chloride. 

This mixture was saponified with methanolic potassium hydroxide to give the two epimers of 267 in quantitative yield. By enol acetylation, 267 was converted to 268 which in turn was oxidized by osmium tetroxide and periodate to the noraldehydes 269. The mixture 269 was converted to 270 via oxidation, esterification, and mild alkaline hydrolysis. The hydroxyesters 270 were oxidized by the Jones method to afford the single crystalline diketoester 271. Ketalization of 271 yielded the ketal 272 in quantitative... 

Esterification with higher diazoalkanes [205] has also been suggested. A 2-ml volume of 50% potassium hydroxide solution was added to 5 ml of diethyl ether in a small flask. N-n-Butyl(or propyl)-N-nitrosoguanidine (1 g) was suspended in diethyl ether and added to the flask through a separating funnel. The reaction was carried out in a water-bath at 45°C. The diazo compound have been passed through a cooler, was trapped in diethyl ether. Hydrochlorides of amino acids (about 5 mg) were dissolved in 4 ml of methanol... 

The Michael conjugate addition of an oxygen to an activated double bond has also been exploited in order to obtain 2,5-disubstituted tetrahydrofurans. The diacetoxynonenoate 1 is cyclized with methanolic potassium hydroxide to give the tetrahydrofuranyl derivative 2 in 97 % yield after esterification with diazomethane. The 1,3-asymmetric induction is low as indicated by the cisf trans diastereomeric ratio (67 33) which was determined by a GLC comparison with known material50. 

Migrations of the double bond and carbon-skeleton rearrangements are important in the preparation of several olefinic compounds. A number of alkyl cyclopentenes are available in quantities suitable for synthetic work by the isomerization of cyclohexene and its homologs over alumina at 470- 480°. o-Allylphenol is isomerized by methanolic potassium hydroxide at 110° to o-propenylphenol (75%). Several /5, y-olefinic acids are conveniently obtained from the corresponding a /3-isomers by equilibration in basic media. The two isomeric acids are readily separated by partial esterification of the resulting mixtures since the /3,y-isomers are more easily esterified. "... 

Esterification of hindered carboxylic acids. Hindered carboxylic acids can be estcrified in high yield by alkylation of their potassium salts in ethanol-HMPT. In a typical procedure an acid such as (1) is dissolved in 50% cthanol-HMPT powdered potassium hydroxide is added and the mixture is heated at 50° until solution is complete. 

Fatty acids react with alkaline catalysts to form catalytically inactive soaps (3). The chemical reaction consumes one mole of fatty acid per mole of alkaline catalyst. Although fatty acid composition of the starting material varies, the content determined by titration reflects the amount of catalyst that would be consumed in a chemical reaction. By calculation, it may be determined that one gram of fatty acid (expressed as oleic acid) will react with about 0.2 g of anhydrous potassium hydroxide or 0.14g of anhydrous sodium hydroxide. Often, additional catalyst must be added to esterify a vegetable oil containing higher levels of fatty acids (3). Conversely, acid catalysts are not inactivated by fatty acids (3). In a unique reaction, fatty acids produced during biodiesel manufacture are actually used as a catalyst in their own esterification (see below). 

Alcohol esterification is usually catalysed by homogeneous catalysts such as sulfuric acid (5), para-toluenesulfonic acid (6) or bases such as sodium (potassium,. ..) hydroxide (carbonate,...) (3,7). Unfortunately, it is well known that these bases favour the production of soaps. Moreover, homogeneous catalysts are corrosive, difficult to separate from the products and lead to excessive wastes (salts). 

Removal of the unreacted diene, bp 45 °C/20 torr, followed by distillation, bp 123 °C/0.2 torr, gave /-menthyl chrysanthemate (4.7 g, 76%) whose GC analysis showed the following composition d-trans, 89.9% l-trans, 2.7%, and the cis isomers, 7.4%. The cis/trans ratio was 7/93 and ee of the trans isomer was 94%. Complete hydrolysis of the /-menthyl ester with potassium hydroxide in aqueous ethanol followed by esterification with d-2-octanol in the presence of thionyl chloride and pyridine gave the corresponding d-2-octyl ester. GC analysis revealed the following composition d-trans, 90.4% l-trans, 4.7% d-cis, 3.6%, and... 

Procedure Amines, 10-1000 jug, were acetylated by treatment with 10-20 All of redistilled acetic anhydride and 10-20 /rl of pyridine (distilled over potassium hydroxide). Excess reagents were removed in a vacuum desiccator. Methyl esters of amine acids were prepared by refluxing in methanolic hydrogen chloride. iV-Acetylation of these esters was by treatment with acetic anhydride and pyridine. Esterification of other acids was carried out with diazomethane in ether. The products were dissolved in ethyl acetate, and volumes of 0.1 to 2 ju.1 were injected into the gas chromatograph. Amounts of sample injected were about 0.1 jitg for rapidly eluted compounds and 1 p,g for those with long retention times. In some cases, acetone condensation products of the primary amines were chromatographed. Catecholamines, however, underwent decomposition under these conditions. 

For esterifications it is best to prepare an ethereal solution of diazomethane. Such solutions are not stable, decolorizing gradually with evolution of nitrogen. Diazomethane solutions can be dried with potassium hydroxide, but losses must then be allowed for. Alcoholic solutions of diazomethane are less stable than ethereal ones. 

Two sterically hindered /V-sulfonylated aminobomeols 42 were prepared from camphorquinone 11 and used after esterification for the formation of enolates which are alkylated or oxidized diastereoselectively (Sections D.1.1.1.3.2., D. 1.5.2.1., D. 1.5.2.3. and D.4.I.). The synthesis of these auxiliaries involves the reaction of camphorquinone 11 with 3,5-dimethylaniline to give the mono-imine by reaction with the sterically less hindered carbonyl group, followed by reduction with boranate and reaction with benzenesulfonyl chloride to give the exo.exo-product. or initial reduction with zinc/potassium hydroxide, then sulfonylation, and finally reduction with boranate to give the endo,endo-isomer21. 

Acetyl value n. The number of milligrams of potassium hydroxide (KOH) necessary to neutralize the acetic acid liberated by hydrolysis of 1 g of an acetylated compound. It can also be written as a measure of the degree of esterification or combination of acetyl radicals with cellulose in acetate or triacetate products. 

---