Nitrogen basic properties

In 1877, Maly (45) discussing formula 34 applied to thiohydantoine found it unable to explain the basic properties of the compound. He preferred a structure in which the -CH2-CO- group would be bonded to only one nitrogen atom. Meyer (46) prepared a monophenyl thiohydantoin (m.p. 178°C) by condensing diloroacetanilide with thiourea and proposed 42 for its structure. 

Florisil Cleanup of chlorinated hydrocarbons, nitrogen, and aromatic compounds Has basic properties and may not be compatible with acids... 

Many pharmacologically active organic chemicals fonnd in natnre are alkaloids. In general, these componnds contain one or more nitrogen atoms, which in turn impart some basicity to the molecnle. Well-known alkaloid examples are caffeine, cocaine, codeine, ephedrine, morphine, nicotine, qninine, and scopolamine. Heroin is derived from morphine by a chemical modification that increases lipophilicity, making the heroin molecnle inherently more pharmacologically potent than morphine. The exhibition of its basic properties by an alkaloid (Aik) involves (by definition) the acceptance of a proton H+ according to ... 

Alkaloids are found mainly in plants, and are nitrogenous bases, typically primary, secondary, or tertiary amines. The basic properties facilitate their isolation and purification. Water-soluble salts are formed in the presence of mineral acids (see Section 4.11.1), and this allows separation of the alkaloids from any other compounds that are neutral or acidic. It is a simple matter to take a plant extract in a water-immiscible organic solvent, and to extract this solution with aqueous acid. Salts of the alkaloids are formed, and, being water soluble, these transfer to the aqueous acid phase. On basifying the acid phase, the alkaloids revert back to an uncharged form, and may be extracted into fresh organic solvent. 

Note that the side-chains of glutamine and asparagine are not basic these side-chains contain amide functions, which do not have basic properties (see Section 4.5.4). The heterocyclic ring in tryptophan can also be considered as non-basic, since the nitrogen lone pair electrons form part of the aromatic jt electrons and are unavailable for bonding to a proton (see Section 11.8.2). 

Hydrazine exhibits basic properties because of its lone pair of electrons on each nitrogen atom. Many of its reactions are analogous to those of ammonia. 

Amides have very weak basic properties and protonation is possible either on the oxygen (A) or on the nitrogen (B).82 83... 

Alkaloids are extremely difficult to define because they do not represent a homogeneous group of compounds from either the chemical, biochemical or physiological viewpoint. All do occur in plants, but some are found in animals, and practically all have been reproduced in the laboratory by chemical synthesis. Most possess basic properties due to the presence of an amino nitrogen, and many, specially thoses pertinent to pharmacy and medicine, possess marked physiological activity. 

Unlike amines, imides do not have basic properties in water solution the electron pair of nitrogen is partly delocalized over the carbonyl groups,... 

Undoubtedly, pyridine, C5H5N (2), is the best-known heterocyclic nitrogen ligand and its coordination chemistry has been studied in great detail, as have its simple derivatives bearing a non-coordinating substituent. For the physical properties, the reader is referred to the heterocyclic literature.1 3,5,9 The basic properties of pyridine have been mentioned above. Alkyl-substituted derivatives are slightly more basic [pA (base) values of about 5-7]. 

Nitrogenous base. An aromatic nitrogen-containing molecule with basic properties. Such bases include purines and pyrimidines. 

The three carbon atoms and one nitrogen atom of the nucleus contribute four 7r-electrons, and the nitrogen atom in position 1, which is not involved in double bond formation, donates its electron pair, thus creating an aromatic sextet of 77-electrons. At the same time the 1-position nitrogen loses its basic properties, although the nitrogen atom in position 2 remains weakly basic. 

Since amines are organic bases, water solutions show weakly basic properties. If the basicity of aliphatic amines and aromatic amines are compared to ammonia, aliphatic amines are stronger than ammonia, while aromatic amines are weaker. Amines characteristically react with acids to form ammonium salts the nonbonded electron pair on nitrogen bonds the hydrogen ion. 

The nitrogen atom, as in aliphatic amines, pyridine etc., exhibits basic properties, that is to say the nitrogen atom can bind a proton through its free electron pair. In pyrrole the resonance possibilities II and III are, however, lost on the addition of a proton, so that the positive ion is thus not stabilized by resonance, whereby the proton attraction, that is the basicity, is very small for pyrrole. The formation of a negative ion, as in pyrrole-potassium, gives no hindrance so that pyrrole does show acid properties. 

Since the first structure determination of tri(silyl)amine, which has shown the molecule to have a planar configuration at nitrogen [21], the unexpected structural features of silylated amines have attracted considerable interest. The planar structure is associated with a low nitrogen basicity and with poor donor properties of the silylated amines. Pertinent conclusions had to be drawn from rather limited structural... 

Systems in which the nitrogen is attached to carbon bearing only perfluoroalkyl groups, rather than fluorine, are particularly stable but weak bases for example, perfluoro-f-butylamine is practically devoid of basic properties [269] (Figure 8.104). Diazotisation of the amine gives a mixture of the alcohol and the nitroso derivative [270] (Figure 8.105). 

N-Aryl substituents usually depress the basic properties of the imidazole or benzimidazole nucleus. The effects of substituents on the aryl group are evident from the data listed in Table 7 which also lists rate constants for quaternization with iodoethane, a reaction which is dependent upon the nucleophilic character of the pyridine-type nitrogen (70CHE194). A phenyl group withdraws electrons from the imidazole ring, but does so rather weakly. The p value of +0.753 for the protonation process is in accord with weak electron transfer from the phenyl substituent to the basic nitrogen. 

Since nitrogen centres are responsible for the acidic and basic properties of 1,2,4-triazoles, salt formation may be considered to involve reactions at such centres. A number of inorganic salts and complexes have been noted (oocbss) but their exact nature and reactivity are not quite clear. 

---