Aliphatic amine groups, determination

The nucleophilic substitution of the reactive chlorine atoms in hexa- and dichloride clathrochelates by a series of aliphatic amines is very sensitive to the effects of the medium (primary, the solvent employed), and the trend of the reaction is determined to a great extent by the donor properties of the amines and the steric accessibility of the nucleophilic centre. The subsequent substitution reaction course and feasible reaction products in the case of hexachloride precursors are presented in Scheme 24. The stepwise-formed clathrochelate complexes are denoted according to the degree of the substitution of chlorine atoms by amine groups ... 

Carboxylic and sulfonic acid groups import acidity to organic compounds. Most carboxylic acids and sulfuric acids are readily dissolved in water, and their titration with a base is straightforward. If solubility in water is not sufficient, the acid can be dissolved in ethanol and titrated with aqueous base. Aliphatic amines and many saturated cyclic amines can be titrated directly with a solution of a strong acid. Esters are determined by saponification with a measured quantity of standard base. The excess base is titrated with standard acid. 

A similar substitution on anilines causes the reverse effect. Nitro groups in ortho position either in the isocyanate or the aniline lower the reactivity by steric hindrance. These authors also reported that the reaction is subject to catalysis by pyridine, tertiary bases, and certain carboxylic acids but is unaffected by water, inorganic acids, bases, or salts. Relative rates for the reactions of some primary aliphatic amines with phenyl isocyanates have been determined by Davis and Ebersole (52). 

The addition of an aliphatic amine did not have a major influence on the starting time of the degradation, but it had an influence on the spreading of the oxidation (Figure 11). As the spreading rate is determined by the oxidation of formed aldehydes, it is reasonable to assume that the aliphatic amines counteract the influence of these aldehydes. It is known that aliphatic amines can react with aldehydes to form more stable imines or enamines [16], which is a reasonable mechanism that explains the activity of aliphatic amines. Thus for oligomeric HAS with aliphatic amines in their backbone not only the piperidinyl groups is important, but also the chemical structure of the backbone. 

An example of analytical application was the determination of LMW aliphatic amines, a group of important compounds widely found in environmental samples, usually in aqueous solution. Detection of these amines at trace level is difficult due to their high basicity and strong adsorption on solid surfaces (Figure 11.19). 

High-molecular-weight aliphatic amines are used extensively in many industries. The total primary- and secondary-amine content of aliphatic amines can be determined easily and rapidly by functional-group analysis in the near infrared [9], using chloroform solvent and 5-cm fused-silica cells. Primary amines have characteristic absorption maxima at 2.02 /um and 1.55 m, whereas secondary amines absorb only at 1.55 fim. Quantitation is achieved by the calibration-curve method using a series of standard solutions of primary and of secondary amines. Most other methods for the determination of total primary, secondary, or tertiary amine in a mixture are lengthy or inaccurate, or are unsuitable for small samples. 

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