Quaternary amines characterization

Conventional ionization techniques like El or Cl are less well suited for the characterization of quaternary amines, which are the most common cationic surfactants. Because of their thermal instability and low volatility their corresponding mass spectra only show decomposition products and fragment ions which make it impossible to analyze environmental samples of unknown composition. By the use of EAB-MS and FD-MS, however, ionization of quaternary amines can be achieved without decomposition. FAB spectra are characterized by strong quasimolecular ions as well as structure specific ions. ° FAB in combination with collisionally activated decomposition (CAD) in a tandem mass spectrometer enables a clear differentiation between quasimolecular and fragment ions, which is often difficult using FAB alone. FD spectra of quaternary amines are dominated by quasimolecular ions as already described for other surfactant... 

The effects of various additives on the sensitivity and selectivity ofTSP-LC-MS of thiocyanates and anilines were studied to optimize ionisation conditions. Trialky-lammonium formates were found to increase the selectivity and sensitivity of the TSP process [242]. TSP-LC-MS was also used for the characterization of the quaternary amine pesticides paraquat, difenzoquat, diquat, mepiquat and chlorme-quat from water and soil samples. Base peaks were [M-i-H] and [M-CH3-i-H] [243]. Difenzoquat, a difficult-to-determine quaternary ammonium pesticide was analysed using a post-column ion-pair extraction system [244]. 

The significance of amine value varies with the product. The procedure below, based on simple titration to a visual end point, is useful for quality control of a well-characterized material. For quaternaries, a high amine value may indicate that the compound is not completely neutralized, or it may indicate that primary, secondary, or tertiary amine is present. For new products, it is preferable to conduct the analysis with a recording potentiometric titrator. In the case of a quaternary amine hydroxide, two inflections may be observed. The first is due to the strongly basic quaternary, the second to more weakly basic amines. 

Henrich developed a comprehensive TLC method for identification of surfactants in formulations (4). She specified two reversed-phase and four normal phase systems, with detection by fluorescence quenching, pinacryptol yellow and rhodamine B, and iodine. Prior to visualization, one plate was scanned with a densitometer at 254 nm, and UV reflectance spectra were recorded for each spot detected. Tables were prepared showing the Rf values of 150 standard surfactants in each of the six systems, along with the reflectance spectra and response to the visualizers. This system allows for systematic identification of compounds of a number of surfactant types (LAS, alcohol sulfates and ether sulfates, alkane sulfonates, sufosuccinate esters, phosphate compounds, AE, APE, ethoxylated sorbi-tan esters, mono- and dialkanolamides, EO/PO copolymers, amine oxides, quaternary amines, amphoterics and miscellaneous compounds). Supplementary analysis by normal phase HPLC aided in exactly characterizing ethoxylated compounds. For confirmation, the separated spots may be scraped from one of the silica gel plates and the surfactant extracted from the silica with methanol and identified by IR spectroscopy. 

The only cationic surfactant (Fig. 23) found in any quantity in the environment is ditallow dimethylammonium chloride (DTDMAC), which is mainly the quaternary ammonium salt distearyldimethylammonium chloride (DSDMAC). The organic chemistry and characterization of cationic surfactants has been reported and reviewed [330 - 332 ]. The different types of cationic surfactants are fatty acid amides [333], amidoamine [334], imidazoline [335], petroleum feed stock derived surfactants [336], nitrile-derived surfactants [337], aromatic and cyclic surfactants [338], non-nitrogen containing compounds [339], polymeric cationic surfactants [340], and amine oxides [341]. 

Dicyanoketene ethylene acetal reacts with tertiary amines to give quaternary ammonium inner salts.3 Similarly, it reacts with sulfides to give sulfonium inner salts.3 These products are generally solids that can be used to characterize tertiary amines, and sulfides. Dicyanoketene acetals can be converted to pyrimidines, pyrazoles, or isoxazoles in one step.4... 

Much effort has been devoted to characterizing the interaction of organic molecules with mineral surfaces. Adsorption of organic amines by clay minerals is one such system which has attracted considerable interest. In addition to concern about the subsurface fate and transport of amine-containing organic pollutants, there is fundamental interest in the ability of organic amines to influence the surface chemistry of layer silicates. Boyd et al. (1.2) have demonstrated recently that the presence of quaternary ammonium cations, such as the hexadedyltrimethyl-... 

Amine functions readily react with oxonium sites. This reaction was used for the synthesis of graft copolymers involving reaction of living poly-THF with either poly(p-vinylpyridine) or poly(p-dimethylaminostyrene) S6K Attempts to synthesize macromonomers by a similar route were made57 but their characterization is difficult because they contain quaternary ammonium sites ... 

The dimethyl amine derivative produced was quaternized directly by methyl iodide, added slowly to a chilled solution of the ternary amine in ethyl acetate. When other ring substituents are present, the reductive eunination leads to isomeric configurations, as noted in Table I. Quaternary ammonium halide salts were characterized by melting point, TLC, or microanalytical data and and NMR. 

Recently, we have characterized tertiary amine and quaternary ammonium celluloses made either aqueously or non-aqueously by a variety of instrumental techniques. These techniques have also been used to follow effects of a given anion on the cellulose matrix of a quaternary ammonium cellulose exchanger when the exchanger prepared non-aqueously comes in contact with water. 

Quatemization involves the reaction of a tertiary amine with an alkylating agent. Typically, primary and some secondary alkyl halides are used for this purpose, although alkyl sulfates have also been used. Tertiary hahdes are not useful because they undergo elimination rather than substitution. The reaction, which is an example of an Sn2 process, proceeds readily to give crystalline, stable, and still-aromatic quaternary salts (Scheme 6.6). These have been used for many years to characterize amines. Acyl halides also react in a similar manner with pyridine, but the resulting salts are unstable and generally not isolated. 

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