Carboxylic acid derivatives boiling point

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

A third category of syn eliminations involves pyrolytic decomposition of esters with elimination of a carboxylic acid. The pyrolysis of acetate esters normally requires temperatures above 400° C and is usually a vapor phase reaction. In the laboratory this is done by using a glass tube in the heating zone of a small furnace. The vapors of the reactant are swept through the hot chamber by an inert gas and into a cold trap. Similar reactions occur with esters derived from long-chain acids. If the boiling point of the ester is above the decomposition temperature, the reaction can be carried out in the liquid phase, with distillation of the pyrolysis product. 

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.)... 

Furan is a colorless liquid, boiling point 32°C. insoluble in water, soluble in alcohol or ether. Furan vapor produces a green coloration on pine wood moistened with hydrochloric acid. Furan may he made from mucic acid. COOHtCHOHLCOOH. by dry distillation into pyromneie acid, C4H1O - COOH. and then heating the latter under pressure at 270 C. Furan derivatives arc known, namely, methyl, primary alcohol, aldehyde, carboxylic acid, in which the group attachment is at carbon number 2 ... 

The presence of amino, carboxyl, hydroxyl, carbonyl, etc., groups in organic molecules increases their boiling points very substantially, and thus, the probability of undesirable interactions (namely, irreversible adsorption and catalytical decomposition) in the GC analytical system. Some very polar biomolecules cannot be volatilized, in a conventional way, without a loss of their chemical individuality. However, as shown repeatedly during the last two decades, suitable derivatives can frequently be prepared that are sufficiently volatile and stable for GC investigations. Even as seemingly non-volatile substances as carbohydrates, amino acids or alkaloids can now be chromatographed successfully as derivatives. 

Fatty acid methyl esters (FAMEs), esterified in the carboxylic group, are by far the most widely used derivatives. The boiling points of the methyl esters are markedly lower than those of the free FAs, being also more soluble in organic solvents. Several methods have been proposed for their preparation, based on the presence of free FAs, short-chain FAs, or highly PUFA. 

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