Nomenclature and Physical Properties

Amines are alkyl or aryl derivatives of NH,. Replacing one, two, or three H s of NH, gives primary (1°), secondary (2°) and tertiary (3°) amines, respectively. 

Amines are named by adding the suffix-amine to the name of (a) the alkyl group attached to N or b) the longest alkane chain. The terminal e in the name of the parent alkane is dropped when amine follows but not when, for example, diamine follows [see Problem 18.1(d)]. Thus, CH3CH(NH2)CHjCHj is named sec-butylamine or 2-butanamine. Amines, especially with other functional groups, are named by considering amino, N-alkylamino and N,N-dialkylamino as substituents on the parent molecule N indicates substitution on nitrogen. 

Aromatic and cyclic amines often have common names such as aniline (benzenamine), Cf,H5NH2 p-toluidine, p-CH,C(,H4NH2 and piperidine [Problem 18.1(g)]. 

Like the oxa method for naming ethers (Problem 14.61), the aza method is used for amines. Di-n-propylamine, CH3CH2CH2NHCH2CH2CH3, is 4-azaheptane and piperidine is azacyclohexane. The four H s of NH can be replaced to give a quaternary (4°) tetraalkyl (tetraaryl) ammonium 

Problem 18.3 Predict the orders of a) boiling points, and (b) solubilities in water, for 1°, 2°, and 3° amines of identical molecular weights. 

The four Inof NH can be replaced to give a quaternary (4 ) tetraalkyl (tctraaryl) ammonium ion. 

Both physical properties depend on the ability of the amino group to form H-bonds. 

All three kinds of amines exhibit the first type of H-bonding, which is thus a constant factor. The more H s on N, the more extensive is the second kind of H-bond and the more soluble is the amine. Thus the order of water solubility is RNH2 (1°) R2NH (2°) R3N (3°). 

Aromatic flnd cyclic amines often have common names such as aniline (benzenamine), C6H5NH2  

Many carboxylic acids have common names that are derived from Latin or Greek words that indicate one of their natural sources. Methanoic acid is called formic acid (formica, Latin ant). Ethanoic acid is called acetic acid (acetum, Latin vinegar). Butanoic acid is one compound responsible for the odor of rancid butter, so its common name is butyric acid (butyrum, Latin butter). Pentanoic acid, as a result of its occurrence in valerian, a perennial herb, is named valeric acid. Hexanoic acid is one compound associated with the odor of goats, hence its common name, caproic acid (caper, Latin goat). Octadecanoic acid takes its common name, stearic acid, from the Greek word stear, for tallow. 

Most of these common names have been used for a long time and some are likely to remain in common usage, so it is helpful to be familiar with them. In this text we shall refer to methanoic acid and ethanoic acid as formic acid and acetic acid, respectively. However, in almost all other instances we shall use lUPAC systematic or substitutive names. 

Carboxylic acids are polar substances. Their molecules can form strong hydrogen bonds with each other and with water. As a resnlt, carboxylic acids generally have high boiling points, and low-molecular-weight carboxylic acids show appreciable solubility in water. As the length of the carbon chain increases, water solubility declines. 

Salts of carboxylic acids are named as -ates in both common and systematic names, -ate replaces -ic acid. The name of the cation precedes that of the carboxylate anion. Thus, CH3C02Na is sodium acetate or sodium ethanoate. 

Sodium and potassium salts of most carboxylic acids are readily soluble in water. This is true even of the long-chain carboxylic acids. Sodium or potassium salts of long-chain carboxylic acids are the major ingredients of soap (see Section 23.2C). 

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Structure, Nomenclature, and Physical Properties A. Structure and Properties... 

Table 2.1 Nomenclature and Physical Properties of Straight-Chain Alkanes...

Discuss the structure, classification, nomenclature and physical properties of amines. Give examples. 

In this chapter, we study the structure, nomenclature, and physical properties of alkenes. Alkynes are discussed separately in Chapter 7. 

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