Aqueous oxalic acid

The tetrahydropyranyl ether, prepared from a phenol and dihydropyran (HCl/ EtOAc, 25°, 24 h), is cleaved by aqueous oxalic acid (MeOH, 50-90°, 1-2 h). ... 

The tetrahydropyranyl ether, prepared from a phenol and dihydropyran (HCl/EtOAc, 25°, 24 h) is cleaved by aqueous oxalic acid (MeOH, 50-90°, 1-2 h). Tonsil, Mexican Bentonite earth, HSZ Zeolite, and H3[PW,204o] have also been used for the tetrahydropyranylation of phenols. The use of [Ru(ACN)3(triphos)](OTf)2 in acetone selectively removes the THP group from a phenol in the presence of an alkyl THP group. Ketals of acetophenones are also cleaved. ... 

The first use of chiral oxazolines as activating groups for nucleophilic additions to arenes was described by Meyers in 1984. " Reaction of naphthyloxazoline 3 with phenyllithium followed by alkylation of the resulting anion with iodomethane afforded dihydronaphthalene 10 in 99% yield as an 83 17 mixture of separable diastereomers. Reductive cleavage of 10 by sequential treatment with methyl fluorosulfonate, NaBKi, and aqueous oxalic acid afforded the corresponding enantiopure aldehyde 11 in 88% yield. 

Meyers has demonstrated that chiral oxazolines derived from valine or rert-leucine are also effective auxiliaries for asymmetric additions to naphthalene. These chiral oxazolines (39 and 40) are more readily available than the methoxymethyl substituted compounds (3) described above but provide comparable yields and stereoselectivities in the tandem alkylation reactions. For example, addition of -butyllithium to naphthyl oxazoline 39 followed by treatment of the resulting anion with iodomethane afforded 41 in 99% yield as a 99 1 mixture of diastereomers. The identical transformation of valine derived substrate 40 led to a 97% yield of 42 with 94% de. As described above, sequential treatment of the oxazoline products 41 and 42 with MeOTf, NaBKi and aqueous oxalic acid afforded aldehydes 43 in > 98% ee and 90% ee, respectively. These experiments demonstrate that a chelating (methoxymethyl) group is not necessary for reactions to proceed with high asymmetric induction. 

RP-8 CHCl3-MeOH-5% aqueous EDTA (65 20 5, lower phase) and MeOH-ACN 0.5 M aqueous oxalic acid pH (3 1 1 4) 0.2 M aqueous oxalic acid and 10% TEA observed with UV 366 nm Honey... 

The structure of the levan synthesized by the action of B. subtilis on sucrose was determined by Hibbert and Brauns.89 Levan, in a yield of 60-65% calculated on the D-fructose part of the sucrose, was obtained by precipitation of the concentrated culture into methanol, and purified by reprecipitation and electrodialysis. Hydrolysis of purified levan with 0.5% aqueous oxalic acid for one hour at 100° gave a 99% yield of crystalline D-fructose. Triacetyllevan was prepared by treatment with acetic anhydride in pyridine, and deacetylation with alcoholic alkali yielded material identical with the original levan.940... 

It has been reported that the cleavage of SAMP hydrazones can proceed smoothly with a saturated aqueous oxalic acid, and this allows the efficient recovery of the expensive and acid-sensitive chiral auxiliaries SAMP and RAMP. No racemization of the chiral ketones occurs during the weak acid oxalic acid treatment, so this method is essential for compounds sensitive to oxidative cleavage.393... 

Since the advent of the one step procedure for the preparation of various substituted thenaldehydes (44), the majority of the necessary starting materials were readily available. Consequently, the Reformatsky reaction was studied with these compounds. With the a-bromoesters the reaction was successfully carried out with four of the thenaldehydes and 2-acetothienone. The nature of the product seemed to depend on the degree of branching of the bromoester. In only one case, where ethyl bromoacetate was used, was a hydroxyester obtained. However, when the carbon atom adjacent to the carbethoxy group was substituted, the product usually contained a hydroxyl group. The dehydration by means of aqueous oxalic acid resulted in a nearly quantitative conversion to the unsaturated esters. 

Polymers of D-fructose are important carbohydrate reserves in a number of plants. Inulins and levans are two major types that differ in structure. D-Fructans require only relatively mild conditions for their hydrolysis, for example, levan was qualitatively hydrolyzed by hot, dilute, aqueous oxalic acid. Permethylated fructans could be hydrolyzed with 2 M CF3CO2H for 30 min at 60°. Fructan oligosaccharides were hydrolyzed in dilute sulfuric acid (pH 2) at 70 (see Ref. 53) or 95° (0.1 M). D-Fructans from timothy haplocorm (where they comprise 63% of the water-soluble carbohydrates) could be hydrolyzed with 0.01 M hydrochloric acid at 98°. 

The use of a chiral starting material (140, R = Me) and a prochiral electrophile, such as pivalaldehyde, gave a ca 1 1 mixture of diastereomers. On the other hand, careful hydrolysis of compounds 142 (aqueous oxalic acid, silica gel) afforded the corresponding functionalized a, -unsaturated cyclohexenones 143 in >95% yield. 

Careful hydrolysis of compounds 173 (aqueous oxalic acid, silica gel) yielded the corresponding functionalized a,/3-unsaturated ketones 174 in >95% yield. 

Particulate matter collected on filter wet ashed, fused with K2S2O7, coprecipitate Th with PbS04, dissolve 1n DTPA, clean-up by complexatlon, extract Th In aqueous oxalic acid and electrodeposit Th. 

This is a white crystalline solid obtained by treating polonium(IV) hydroxide or chloride with aqueous oxalic acid solubility studies indicate complex ion formation (11). 

Ammonium Dioxalato - diammino - chromium, [Cr(NH3)2 (C204)2]NH4.2H20, is obtained in red needles by acting upon dibromo-diaquo-diammino-chromic bromide with aqueous oxalic acid at a temperature of 60° C. The colour changes in solution to dark red and the salt separates. From the ammonium salt other salts may be prepared by treating an aqueous solution with metallic halide. The potassium salt crystallises in red needles containing two molecules of water the sodium salt crystallises in dark red prisms the lithium salt in red needles or leaflets and the caesium salt in dark red needles. These salts are very stable and may be reerystallised from water. 

The solubility of Ta205 in aqueous oxalic acid solutions is much lower than that of Nb2Os and the resulting solutions are more complex owing to the presence of polymeric species.452... 

Self-Test 10.17A Use the information in Table 10.9 to calculate the pH of a 0.010 M aqueous oxalic acid solution. 

The first step consists of the formation of lithio salts by treatment of 5,6-dihydrooxazines with phenyl-, n-butyl-, or t-butyllithium in tetra-hydrofuran at -780.1,3,22,223 The lithio salts can readily be alkylated by alkyl halides to 75, and the product can be reduced with aqueous sodium borohydride (or borodeuteride) at pH 7 in tetrahydrofuran-ethanol-water at -35° to -45°C to tetrahydro-l,3-oxazines (76) in quantitative yield. The latter 224-228 23e on hydrolysis with aqueous oxalic acid give aldehydes (77) [Eq. (63)]. 

A very useful three-carbon olefin is acrolein dimethyl acetal (5). Acrolein itself cannot be used because it polymerizes and/or reacts with amines under the normal reaction conditions. With piperidine or morpholine as the base, acrolein acetals react in good yield with a wide variety of vinylic bromides to give dienal acetals and/or ami-noenal acetals. These product mixtures, after being treated with excess aqueous oxalic acid and being steam distilled, yield E,E-conjugated dienals, usually in good yields. Methacrolein acetals and 3-buten-2-one ethylene ketal also react well, but the crotonaldehyde acetals do not. 

COOH)2 (aq.). Thomsen15 and Berthelot10 25 measured the heat of solution of oxalic acid. WTith Thomsen s value S= —2.26200, we have computed, for (COOH)2 (aq.), Qf= 195.3. Thomsen s15 data on the reaction of aqueous hypochlorous acid with aqueous oxalic acid yield, for (C00H)2 (aq.), Qf = 194.5. Berthelot s25 data on the reaction of gaseous chlorine with aqueous oxalic acid yield, for (COOH)2 (aq.), Qf= 194.8. Berthelot s2 data on the reaction of aqueous potassium permanganate with aqueous oxalic acid yield, for (C00H)2 (aq.), Qf=195.5. 

NH4)2C204 (aq.). Berthelot131 measured the heat of neutralization of aqueous ammonia with aqueous oxalic acid. 

Fe2(C204)3 (aq.). The data of Lemoine1 on the heat of mixing aqueous ferric chloride with aqueous oxalic acid, and of aqueous ferric oxalate with aqueous hydrochloric acid, yield, for Fe2(C2O4)3(100), <2/=610.4. Data on the heat of dilution of aqueous ferric oxalate were reported by Lemoine.1... 

BaC204 H20 (c). Berthelot10 measured the heat of reaction of aqueous oxalic acid with aqueous barium hydroxide to form the monohydrate. 

As shown in Scheme 17,180 was available from the common, totally synthetic, intermediate 17. Using reported methodology for the introduction of vinylsilanes,57 17 was reacted smoothly with (methoxy dimethylsilyl) trimethylsilyl methyl-lithium in pentane to afford (EIZ) vinyl silane 220 in 54% yield. The main by-product in this reaction was ketone 17, which could be recycled thus, based on recovered 17, the yield of 220 was 93%. Hydrolysis of ketal 220 occurred without protodesilylation upon exposure to aqueous oxalic acid absorbed onto silica gel to give ketone 221 in 80% yield. Upon low-temperature ozonolysis of 221 in methanol, a remarkably stable dioxetane 223 was produced, as evidenced in the H NMR... 

In another synthesis of this alkaloid the tricyclic lactone 30 was prepared by a series of reactions in which most of the steps gave satisfactory yields. Hydrolysis with aqueous oxalic acid and condensation with anthraniladehyde generated compound 31 which had already been converted into camptothecine (21). It should be added that the early promise of this alkaloid as a therapeutic agent in cancer therapy has not been confirmed in clinical trials (22). 

In 1895 Dull,9 who was studying inulin and its products of hydrolysis, found that when either fructose or sorbose was treated with an aqueous solution of oxalic acid under pressure, a substance was obtained which had the formula CeHeOa and resembled furfural in its properties. This substance was further investigated by Kiermayer4 who found that fructose and sucrose were the best sources when they were heated with 0.3% aqueous oxalic acid at 120°. It was however only the fructose portion of the sucrose molecule which was transformed since the glucose moiety was recovered unchanged. Kiermayer prepared several derivatives of CeH Os and from its reactions concluded that its structure was probably /3-hydroxy-S-methylfurfural (III). Van Ekenstein and... 

Blanksma5 continued the investigation of the formation of hydroxy-methylfurfural and confirmed Kiermayer s results that it was formed from hexoses by elimination of three molecules of water on acidic degradation and showed that ketoses reacted more readily than aldoses, a fact which was observed by Kiermayer when sucrose was treated with aqueous oxalic acid. Kiermayer had observed also that levulinic acid was obtained when hydroxymethylfurfural was treated with aqueous oxalic acid under pressure and this received further confirmation by Van Ekenstein and Blanksma.6 It was these authors who first pointed out that the complete degradation of hexoses to levulinic acid took place through the intermediate formation of hydroxymethylfurfural. 

Ta,Nb in aqueous oxalic acid or HC1 (289) HDEHP in heptane none Eff= 85%c... 

Ferric hydroxide is readily soluble in mineral acids yielding the corresponding ferric salt, and in ferric chloride solution yielding oxy compounds which are acidic in their behaviour, decomposing carbonates, and can therefore hardly be termed basic chlorides.3 It dissolves in aqueous oxalic acid to an extent directly proportional to the concentration of the acid, no definite basic oxalate being formed at 25° C. from solution.4 It does not combine with carbon dioxide when freshly precipitated and suspended in water.5... 

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