Carboxylic acid melting point

N. A. Izmailov and K. P. Partskha-ladze. Ukrain. Khim. Zhur. 22,156-65,167-72 (1956). Melting point carboxylic acids, phenol with acetonitrile. 

The acidity of malonic ester thus permits the preparation of substituted malonic esters containing one or two alkyl groups. How can these substituted malonic esters be used to make carboxylic acids When heated above its melting point, malonic acid readily loses carbon dioxide to form acetic acid in a similar way substituted malonic acids readily lose carbon dioxide to form substituted acetic acids. The monoalkyl- and dialkylmalonic esters we have prepared are readily converted into monocarboxylic acids by hydrolysis, acidification, and heat ... 

The melting points of a few selected primary aromatic amides (together with those of the xanthylamides, where known) are collected in Table IV,191. A more detailed list will be found in the column headed Amides in Table IV,175 (Armnalic Carboxylic Acids). 

The melting points of some typical substituted aromatic amides are collected in Table IV,192. Other examples will be found in the appropriate columns of Tables IV,100A and B Primary and Secondary Aromatic Amines) and of Table IV,175 (Aromatic Carboxylic Acids). 

The melting points and boiling points of carboxylic acids are higher than those of hydro carbons and oxygen containing organic compounds of comparable size and shape and indicate strong mtermolecular attractive forces... 

Hydrogen bonding m carboxylic acids raises their melting points and boiling points above those of comparably constituted alkanes alcohols aldehydes and ketones... 

C, which decomposes when heated above the melting point. Its solubility at 25°C in g/100 g solvent is water. 111 methanol, 5 ethanol, 1.4 acetone, 0.04 and carbon tetrachloride, 0.004. Because its carbon—fluorine bond is unreactive under most conditions, this salt can be converted by standard procedures to typical carboxylic acid derivatives such as fluoroacetyl esters (11,12), fluoroacetyl chloride [359-06-8] (13), fluoroacetamide (14), or fluoroacetonitrile [503-20-8] (14). 

Orotic acid (971) has a chequered history. It was isolated in 1905 from the whey of cows milk in Italy and it was subsequently synthesized in the United States in 1907. However, the workers involved were discouraged by some difference in melting points and no direct comparison of specimens was ever made. To make matters worse, the same laboratories prepared the isomeric 5-hydroxy-2-oxo-l,2-dihydropyrimidine-4-carboxylic acid and announced it as orotic acid, again without any direct comparison. Only in 1930 did a German worker actually compare directly natural and the original synthetic orotic acid, thereby showing them to be identical (30CB1000). 

Isoxazoles, isoxazolines, isoxazolidines and benzisoxazoles are all thermally stable, distilling without decomposition, but the stability of the system depends on the substitution pattern. For example, aminoisoxazoles distill unchanged but the isoxazole carboxylic acids usually decompose at or above their melting points without giving the corresponding isoxazole. 

The melting and boiling points of carboxylic acids are much higher than would be expeeted on the basis of their molecular weights. The usual explanation is that they form weak intramolecular bonds. 

In 1897, Reissert reported the synthesis of a variety of substituted indoles from o-nitrotoluene derivatives. Condensation of o-nitrotoluene (5) with diethyl oxalate (2) in the presense of sodium ethoxide afforded ethyl o-nitrophenylpyruvate (6). After hydrolysis of the ester, the free acid, o-nitrophenylpyruvic acid (7), was reduced with zinc in acetic acid to the intermediate, o-aminophenylpyruvic acid (8), which underwent cyclization with loss of water under the conditions of reduction to furnish the indole-2-carboxylic acid (9). When the indole-2-carboxylic acid (9) was heated above its melting point, carbon dioxide was evolved with concomitant formation of the indole (10). 

The first synthesis of cinnoline was reported by von Richter in 1883. The diazonium chloride 5 which was obtained from o-aminophenylpropiolic acid (4), was heated in water at 70°C to provide the 4-hydroxycinnoline-3-carboxylic acid (6). When this acid 6 was heated above its melting point, carbon dioxide was liberated and 4-hydroxycinnoline (7) was obtained. Distillation of 4-hydroxycinnoline (7) with zinc dust furnished a small amount of oil, which was assumed to be cinnoline (8). The preparation of 4-hydroxycinnoline (7) was repeated by Busch and Klett, although in lower yield when compared to the original report. Busch and Rast later converted the 4-hydroxycinnoline (7) successfully to cinnoline (8) via the 4-chlorocinnoline (9). ... 

The melting point of the ethyl ester of 2-amino-4-methylselena-zole-5-carboxylic acid is given as 180-181 °C and that of the free acid as 181-182°C. In addition, the melting points of the acetyl derivatives are very close to each other. These facts led King and... 

After one day standing in a refrigerator, the product was filtered and washed with water, thus yielding 5 g of 2-phenyl-2-hydroxy-cyclohexane-carboxylic acid, melting point (Kofler) 143°C to 145°C. 

Under a pressure of 4,5 ml the 1 methyl-4-phenyl-piperidine-4-carboxylic acid nitrile passes over at a temperature of about 148°C in the form of a colorless oil under a pressure of 6 ml it passes over at about 158°C. After having been allowed to cool the distillate solidifies completely to form a crystalline mass. Its solidification point is at 53°C the yield amounts to about 135 parts, that is, about % of the theoretical yield. When recrystallized from isopropyl alcohol the hydrochloride of the nitrile forms colorless crystals, readily soluble in water and melting at 221° to 222°C. 

The suspension was heated to 90°C, while stirring. The crystals were separated and recrystallized from 2B0 cm of a mixture of DMF (1 volume) and ethanol (4 volumes). After drying in vacuo ovar phosphorus pentoxide, 29.5 g (yield 70%) of 1-ethyl-6-fluoro-4-oxo-7-pl-perazinyl-1,4-dihydroquinoline-3-carboxylic acid, melting point 222°C, were obtained. 

B.5 parts of 1 -azaphenothiazine carboxylic acid chloride and 14 parts of piperidino-ethoxy-ethanol were introduced into 100 parts of chlorobenzene and the mixture boiled under reflux for 5 minutes. After cooling off the precipitated hydrochloride salt of piperidino-ethoxy-ethanol was filtered off on a suction filter. Water was added to the filtrate and the pH thereof adjusted to 5 to 6 with dilute HCI. The aqueous phase was then removed, a caustic soda solution added thereto and then extracted with ether. The ethyl extract waswashed with water, then dried with potash and the ether distilled off. 9.4 parts of the piperidino-ethoxy-ethyi ester of 1 -azaphenothiazine carboxylic acid were obtained. This product was dissolved in 20 parts of isopropanol and the solution neutralized with isopropanolic HCI. The monohydrochloride which precipitated out after recrystallization from isopropanol had a melting point of 160°Cto 161°C. 

C) 6-(n)-Propyl-2-Pyridone-4-Carboxylic Acid The 64 grams of the product just obtained are treated with 500 cc of concentrated hydrochloric acid at boiling point. 40 grams of a product, having a melting point of 285°C, are obtained. 

The organic layer wasdried with anhydrous magnesium sulfate and then filtered. The solution was concentrated under vacuum at 30°C to 35°C until reduced to half of its original volume and then cooled to 5°C to allow the crystallization of the compound. Thus, the cake was filtered, washed with cool ethyl acetate, and dried under vacuum. Yield 74% (76.7 g) of phthalidyl ester of 2-(3 -trifluoromethylanilino)-pyridin-3-carboxylic acid, melting point 165°C to 167°C. 

Amino acid zwitterions are internal salts and therefore have many of the physical properties associated with salts. They have large dipole moments, are soluble in water but insoluble in hydrocarbons, and are crystalline substances with relatively high melting points. In addition, amino acids are amphiprotic they can react either as acids or as bases, depending on the circumstances. In aqueous acid solution, an amino acid zwitterion is a base that accepts a proton to yield a cation in aqueous base solution, the zwitterion is an add that loses a proton to form an anion. Note that it is the carboxylate, -C02-, that acts as the basic site and accepts a proton in acid solution, and it is the ammonium cation, -NH3+, that acts as the acidic site and donates a proton in base solution. 

Therefore a special N-containing ether carboxylate was developed [36] with a high melting point ( 90°C) with a good foam and low hard water sensibility. This is obtained by condensation of a fatty acid (e.g., lauric acid) with diglycolamine, followed by carboxymethylation with NaOH and SMCA, washing out of the reaction mixture with a aqueous solution of a strong acid, separation of the oil layer, and neutralization with NaOH or KOH. The result is an ether carboxylate with exactly 2 EO units with the structure ... 

Lithium compounds are used in ceramics, lubricants, and medicine. Small daily doses of lithium carbonate are an effective treatment for bipolar (manic-depressive) disorder but scientists still do not fully understand why. Lithium soaps—the lithium salts of long-chain carboxylic acids—are used as thickeners in lubricating greases for high-temperature applications because they have higher melting points than more conventional sodium and potassium soaps. 

---