Carboxylic acid derivatives melting point

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). 

The melting points of the derivatives of a number of selected aromatic carboxylic acids are collected in Table IV, 175. 

The boiling points and melting points of other carboxylic acid derivatives are similar to those of other polar compounds of comparable size and shape. 

Usually decarboxylation is accomplished by heating the acids above their melting points, often in the presence of a copper-chromium catalyst. Imidazole-4,5-dicarboxylic acid can be monodecarboxylated by heating its monoanilide imidazole- and benzimidazole-2-carboxylic acids decarboxylate very readily indeed, so readily that the carboxyl function makes a useful blocking group in metallation procedures (see Scheme 7.2.1) [3-5]. A potentially useful method of preparation of imidazole-4-carboxylic acid derivatives heats the 4,5-dicarboxylic acid (2) with acetic anhydride to form (1), which is essentially an azolide and very prone to nucleophilic attack which cleaves the nitrogen-carbonyl bond (Scheme 8.3.1). With methanol the methyl ester (3) is formed with hydrazines the 4-hydrazides (4) result [6]. 

Alkylselenazoles, for example, 2,4-dimethylselenazole (b.p. 163-4°C/760mm), are generally liquids. Aryl or carboxylic acid derivatives, such as 2-methyl-4-phenylselenazole (m.p. 63 °C) are solids, except for some 2-phenylselenazoles which are liquids. 2-Amino and 2-hydrazino-selenazoles are almost always solids with the melting point increasing as the molecular weight increases... 

From the list of melting points of derivatives of halo acids given in Table 10 it is evident that for the identification of halo acids, amides, anilides and /7-toluides are suitable / -bromophenacyl esters were prepared only in a few cases. If satisfactory results cannot be obtained by the application of procedures given for the preparation of carboxylic acid derivatives (see p. 249), original literature should be consulted. Identification of aromatic, halo acids is easy because they are well-crystallized solids, and, in addition the preparation of derivatives, for example, p-bromophenacyl esters, causes no difficulty. 

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 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... 

Physical properties of carboxylic acids and derivatives include solubility, melting point, boiling point, and a few other characteristics. In this section we examine each class and discuss the most important physical properties. (In the upcoming section Considering the Acidity of Carboxylic Acids, we discuss the most important chemical property of Ccirboxylic acids — acidity.)... 

Caprolactam (melting point 69.3°C, density 1.02, flash point 125°C, fire point 140°C), so named because it is derived from the original name for the C6 carboxylic acid, caproic acid, is the cyclic amide (lactam) of 6-aminocaproic acid. 

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