Ammonium ions quaternary nitrogen compounds

Cationic surfactants produce a positively charged surfactant ion in solution and are mainly quaternary nitrogen compounds such as amines and derivatives and quaternary ammonium salts. Owing to their poor cleaning properties, they are little used as detergents rather their use is a result of their bacteriocidal qualities. Relatively little is known about the mechanisms of biodegradation of these compounds. 

The quaternary ammonium compounds paraquat and diquat are widely used non-selective contact herbicides, which are extremely toxic to humans. Fee et al. [112] established an HPLC-MS-MS procedure for the determination of these herbicides in whole blood and urine using ethyl paraquat as internal standard. After extraction with Sep-Pak C18 cartridges, analytes were separated using ion pair chromatography with heptafluorobutyric acid in 20 mM ammonium acetate and acetonitrile gradient elution. Detection was carried out in ESI MS-MS SRM mode. Using similar separation and detection conditions, paraquat, diquat, difenzoquat, and a number of structurally related quaternary nitrogen muscle relaxants (see Section 20.2.1.3) were determined in whole blood by Ariffin and Anderson [113]. 

Historically, Bernard (1851, 1856) demonstrated that curare (from arrow poisons used by South American Indians) blocked nerve impulse transmission at the junction of the nerve and skeletal muscle. It was later shown that many alkaloids, such as morphine, atropine, nicotine, and even strychnine and brucine (the latter two normally causing convulsions), will become muscle relaxants when quaternized by methylation. It soon became apparent that a great many quaternary ammonium compounds qualitatively share the ability to produce neuromuscular blockade. In fact, the onium ion need not be a nitrogen atom. Thus sulfonium (/ 3S+), phosphonium (/ 3P+), and arsonium (/ 3As+) ions have been shown to be curariform , although of lesser activity than ammonium ions. 

An ion containing a nitrogen atom bonded to any combination of four alkyl or aryl groups is classified as a quaternary (4°) ammonium ion. Compounds contain- Quaternary (4°) ammonium ion ing such ions have properties characteristic of salts. Cetylpyridinium chloride is used An ion in which nitrogen is bonded as a topical antiseptic and disinfectant. 

The compound has two nitrogen atoms. One of the nitrogen atoms (adjacent to the aromatic ring) exhibits a delocalized lone pair, while the other nitrogen atom (of the NH2 group) exhibits a localized lone pair. The localized lone pair is more nucleophilic than the delocalized lone pair, so only the NH2 group is converted into a quaternary ammonium ion, as shown here ... 

Quaternary fluorinated alkyl ammonium compounds The fluorine-containing cationic surfactants of quat type with the general formula C F2 , 1-S02-NH-CH2-CH2-CH2-N (CH3)3 X (n = 8) (Fig. 2.12.1(d)) were examined by FIA—MS using APCI and ESI in the positive and negative modes. The APCI(- -/—) ionisation resulted in a dealkylation at the nitrogen with ions at m/z 585 or 583, respectively. The alkyl chain of this compound contained the moiety C8Fi7. The ions generated under APCI conditions were characterised as dealkylation products—m/z 585 [M — CH2]+ or m/z 583 [M — H— CH3] —as reported in the literature [35,37]. 

The above speculation [21] may be extended to include the related quaternary ammonium compounds such as xylocholine (XXXIX). It is probable that the volumes of the guanidinium ion and the trimethylammonium group are similar. The ionic radius of the guanidinium ion (IX) is about 3A the ionic radius of the tetramethylammonium ion has been estimated [300] to be 3-4A, although rather smaller values have also been proposed [301-303]. Crystallographic analyses of muscarine iodide [304], choline chloride [305] and acetylcholine bromide [306] have revealed that the carbon to nitrogen distance is about l-SA, and that a hydrogen bond (C-H-0 distance 2-87-3 07A) exists in the crystals of these compounds. 

Often, the cationic component of the ion pair is formed by the protonation of a compound of appreciable basicity, most typically a nitrogen-containing base. Alternatively, the cation may be of the quaternary ammonium, phosphonium or arsonium type. 

Finally, it is pertinent, in the present connection, to make a distinction between those displacements in which the transformation of reactants to products does not, at any stage, involve the removal of a proton and those which do, at some stage, require the transfer of a proton to a base. The first type is exemplified by reactions with negatively charged nucleophiles such as alkoxide ion, iodide ion or a mercaptide ion or by reactions with tertiary amines or phosphines, which react to form quaternary ammonium compounds or phos-phonium salts, respectively. When the nucleophile is a primary or secondary amine, the product amine, which will have an additional aromatic ring attached to the amine nitrogen, is almost invariably a weaker base than the reactant amine. Here, as will be shown in later discussion, the question of base catalysis, with its attendant complications, arises. 

---