Formate esters, reaction with aqueous hydroxide

Reactions of the Side Chain. Benzyl chloride is hydrolyzed slowly by boiling water and more rapidly at elevated temperature and pressure in the presence of alkaHes (11). Reaction with aqueous sodium cyanide, preferably in the presence of a quaternary ammonium chloride, produces phenylacetonitrile [140-29-4] in high yield (12). The presence of a lower molecular-weight alcohol gives faster rates and higher yields. In the presence of suitable catalysts benzyl chloride reacts with carbon monoxide to produce phenylacetic acid [103-82-2] (13—15). With different catalyst systems in the presence of calcium hydroxide, double carbonylation to phenylpymvic acid [156-06-9] occurs (16). Benzyl esters are formed by heating benzyl chloride with the sodium salts of acids benzyl ethers by reaction with sodium alkoxides. The ease of ether formation is improved by the use of phase-transfer catalysts (17) (see Catalysis, phase-thansfer). 

Figure 22.28 and Figure 22.29 show, respectively, the H and C-NMR spectra of the oligoesters prepared from epoxidized sunflower oil methyl esters (methyl biodiesel from sunflower oil) and di-l,2-cyclohexanedicarboxylic anhydride using triethylamine as initiator. These materials are soluble in common organic solvents such as acetone, ethanol, tetrahydrofurane, and chloroform, but insoluble in water. Oligoesters from epoxidized biodiesel can be used as intermediate materials for the synthesis of polyelectrolytes by saponification reactions with aqueous solution of sodium or potassium hydroxide at room temperature (Fig. 22.27). The products obtained after saponification present solubility in water. Amphiphilic materials, such as the polyelectrolytes prepared from epoxidized biodiesel, have hydrophobic and hydrophilic segments. They can spontaneously self-organize in a wide variety of structures in aqueous solution. Understanding the dynamics of the formation and transition between the various self-organized structures is important for technological applications.

The catalytic conditions (aqueous concentrated sodium hydroxide and tetraalkylammonium catalyst) are very useful in generating dihalo-carbenes from the corresponding haloforms. Dichlorocarbene thus generated reacts with alkenes to give high yields of dichlorocyclopropane derivatives,16 even in cases where other methods have failed,17 and with some hydrocarbons to yield dicholromethyl derivatives.18 Similar conditions are suited for the formation and reactions of dibromocar-benc,19 bromofluoro- and chlorofluorocarbene,20 and chlorothiophenoxy carbene,21 as well as the Michael addition of trichloromethyl carbanion to unsaturated nitriles, esters, and sulfones.22... 

A reaction occurring in a bulk phase will show an increase in the rate with the area as shown in Fig. 5.3 for a reaction occurring in the film or at the interface, the rate will be linearly dependent on the interfacial area. The interfacial area in a dispersed two-phase liquid-liquid system can be estimated by measuring the rate of a suitable test reaction in a reactor with the known interfacial area (a flat interface, Section 5.3.2.1), and comparing it with the reaction rate in a dispersed system [6, 15]. A convenient reactive system for this purpose is a formate ester and 1-2 M aqueous NaOH. Formate esters are very reactive to hydroxide ion (fo typically around 25 M 1 s 1), so the reaction is complete inside the diffusion film, and the reaction rate is proportional to the interfacial area. A plot of the interfacial area per unit volume against the agitator speed obtained in this way in the author s laboratory for the equipment shown in Fig. 5.12 is shown in Fig. 5.14 [8]. 

The hydrolysis of esters is accomplished by refluxing with aqueous or alcoholic alkali hydroxides. Acid-catalyzed hydrolysis is an equilibrium reaction usually favoring ester formation. High-molecular-weight esters with branching in either acid or alcohol portions are sometimes hydrolyzed with difficulty. 

This crude acid (28 g) is heated in water (120 ml) for 2.5 h under reflux. The resulting AT-acetyltryptophan is less soluble that the starting acid and gradually crystallizes from the reaction mixture. Sodium hydroxide (16 g, 0.4 mole) in water (40 ml) is next added and the solution is boiled for 20 h under reflux. It is then treated with charcoal, filtered, and acidified with glacial acetic acid (24 g, 0.4 mole), this causing immediate formation of a white precipitate. The mixture is kept for 12 h in a refrigerator, after which the precipitate is collected and dissolved in aqueous sodium hydroxide (5 g in 200 ml). This solution is treated with charcoal and filtered. 95% ethanol (100 ml) is added to the filtrate which is then warmed to 70°, acidified with glacial acetic acid (7.5 ml), and cooled slowly. Tryptophan, which separates as plate-like crystals, is filtered off, washed successively with water (2 x 40 ml), ethanol (2 x 40 ml), and ether (2 x 30 ml). The yield is 81 % calculated on the ester product (14 g), and the m.p. is 272-280° (dec.) after recrystallization from 33 % ethanol. 

An example is the reaction of 2,3-dimethyl-2-butene with potassium permanganate to make two C-0 bonds. This product (126) is called a manganate ester. The concerted nature of the reaction of the alkene is important because 125 reacts to form 126 in such a way that the rate of bond formation for each C-0 bond is close, so they have a cis relationship. Indeed, cyclic product 126 has a cis relationship of the two atoms that form bonds to carbon. An alkene is normally added to potassium permanganate in an aqueous hydroxide solution. 

A simple test for aliphatic dithiocyanates consists in the development of a red color on the addition of ferric chloride to a solution formed by heating the thiocyanate with aqueous sodium hydroxide followed by acidification. A few instances have been reported in which a monothiocyano compound produces a red color with ferric chloride alone. A more general test involves heating a thiocyanate with alkaline lead tartrate, which results in the formation of a yellow precipitate. The reaction with sodium malonic ester to produce a disulfide has been suggested as a qualitative test. A method for the quantitative determination involves heating the compound under reflux with an ethanolic solution of sodium... 

Polymeric amines can be proton acceptors, acyl transfer agents, or ligands for metal ions. The 2- and 4-isomers of poly(vinylpyridine) (11) and (12) and the weakly basic ion exchange resins, p-dimethylaminomethylated PS (2) and poly(2-dimethylaminoethyl acrylate), are commercial. The ion exchange resins are catalysts for aldol condensations, Knoevenagel condensations, Perkin reactions, cyanohydrin formation and redistributions of chlorosilanes. " The poly(vinylpyridine)s have been used in stoichiometric amounts for preparation of esters from acid chlorides and alcohols, and for preparation of trimethylsilyl ethers and trimethylsilylamines from chlorotrimethylsilane and alcohols or amines. Polymer-suppored DBU (l,8-diazabicyclo[5.4.0]undec-7-ene) (52) in stoichiometric amounts promotes dehydrohalogenation of alkyl bromides and esterification of carboxylic acids with alkyl halides. The protonated tertiary amine resins are converted to free base form by treatment with aqueous sodium hydroxide. 

Although the present procedure illustrates the formation of the diazoacetic ester without isolation of the intermediate ester of glyoxylic acid />-toluenesulfonylhydrazone, the two geometric isomers of this hydrazone can be isolated if only one molar equivalent of triethylamine is used in the reaction of the acid chloride with the alcohol. The extremely mild conditions required for the further conversion of these hydrazones to the diazo esters should be noted. Other methods for decomposing arylsulfonyl-hydrazones to form diazocarbonyl compounds have included aqueous sodium hydroxide, sodium hydride in dimethoxyethane at 60°, and aluminum oxide in methylene chloride or ethyl acetate." Although the latter method competes in mildness and convenience with the procedure described here, it was found not to be applicable to the preparation of aliphatic diazoesters such as ethyl 2-diazopropionate. Hence the conditions used in the present procedure may offer a useful complement to the last-mentioned method when the appropriate arylsulfonylhydrazone is available. 

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