Quaternary ammonium groups

Ion-exchange separations can also be made by the use of a polymer with exchangeable anions in this case, the lanthanide or actinide elements must be initially present as complex ions (11,12). The anion-exchange resins Dowex-1 (a copolymer of styrene and divinylben2ene with quaternary ammonium groups) and Amherlite IRA-400 (a quaternary ammonium polystyrene) have been used successfully. The order of elution is often the reverse of that from cationic-exchange resins. 

There is a wide variety of dyes unique to the field of hair coloring. Successive N-alkylation of the nitrophenylenediamines has an additive bathochromic effect on the visible absorption to the extent that violet-blue dyes can be formed. Since the simple A/-alkyl derivatives do not have good dyeing properties, patent activity has concentrated on the superior A/-hydroxyalkyl derivatives of nitrophenylenediamines (29,30), some of which have commercial use (31). Other substituents have been used (32). A series of patents also have been issued on substituted water-soluble azo and anthraquinone dyes bearing quaternary ammonium groups (33). 

Strong"Base. Strong base anion-exchange resins have quaternary ammonium groups, - NR OH , where R is usually CH, as the functional exchange sites (see Quaternary ammonium compounds). These resins are used most frequentiy in the hydroxide form for acidity reduction. 

The cationic acrylamide polymers may contain either tertiary amine or quaternary ammonium groups. Because of their positive charge, they are self-retaining on pulp fibers therefore, they can be used effectively in nonalum systems. 

The most common catalysts in order of decreasing reactivity are haUdes of aluminum, boron, zinc, and kon (76). Alkali metals and thek alcoholates, amines, nitriles, and tetraalkylureas have been used (77—80). The largest commercial processes use a resin—catalyst system (81). Trichlorosilane refluxes in a bed of anion-exchange resin containing tertiary amino or quaternary ammonium groups. Contact time can be used to control disproportionation to dichlorosilane, monochlorosilane, or silane. 

Cationic Starches. Commercial cationic starches are starch ethers that contain a tertiary amino or quaternary ammonium group, eg, the diethylaminoethyl ether of starch or the 2-hydroxy-3-(trimethylammonio)propyl ether of starch [9063-45-0], sold as its chloride salt [56780-58-6]. 

In the 1950s acid dyes were successively developed to dye nylon carpet with excellent fastness and uniform leveling. Development of polyacrylonitrile fiber stimulated the invention of anthraquinone basic dyes, modified disperse dyes in which quaternary ammonium groups are introduced. 

The anion-selective (AX) membranes (Eig. 2b) also consist of cross-linked polystyrene but have positively charged quaternary ammonium groups chemically bonded to most of the phenyl groups in the polystyrene instead of the negatively charged sulfonates. In this case the counterions are negatively... 

The cyano, nitro, and quaternary ammonium groups are strongly deactivating and weto-directing. Electrophilic substitutions of compounds with these substituents require especially vigorous conditions and fail completely with all but the most reactive electrophiles. 

At higher pH values the amide groups are unproton-ated [106], while the carboxylate groups [7,11] and quaternary ammonium groups [61] are ionized. Alternatively, the interaction can occur between these cations of the solution and the active groups of the polymer chains for floe formation. 

Cation units usually contain a sulphonic acid resin whilst anion resins fall into the two main categories of strongly basic, with quaternary ammonium groupings and weakly basic, with tertiary amine groups. The final unit is the mixed bed in which, by a mixture of cation and anion resins in the same vessel, the effect is achieved of a multiplicity of separate cation and anion units. Resin separation is necessary for regeneration purposes. Considerable improvements in water quality are obtainable by these means. 

Strongly basic anion exchange resins, e.g. a cross-linked polystyrene containing quaternary ammonium groups, are largely ionised in both the hydroxide and the salt forms. Some of their typical reactions may be represented as ... 

B (12.10) Under various reaction conditions, the isomer ratio of A was consistently higher than B. Isomer A is the expected regioisomer if the diene and dienophile react in their preferred orientation within a mixed micelle in which the quaternary ammonium groups are at the aggregate-water interface and the rest of the molecule is extended into the micelle interior (Figure 12.2). Isomer B comes about from the misalignment of the diene and dienophile within the mixed micelles. 

Anion-exchangers comprise strong-base types incorporating quaternary ammonium groups (—N+R3) and weak-base types incorporating primary, secondary or tertiary amines. They are prepared by chloromethylating the resin followed by treatment with the appropriate amine. 

Most of these products are azo or anthraquinone types, often with a localised quaternary ammonium group isolated from the chromogen by a saturated alkyl chain, as in Cl Basic Red 18 (1.52). Such products often exhibit higher light fastness than the traditional delocalised types. Improved azomethine, methine and polymethine basic dyes of good light fastness are also available. In contrast to the more specialised traditional classes, the azo and methine dyes have contributed to the basic dye range across the entire spectrum of hues (see Table 1.6) and now account for a clear majority of all basic dyes listed in the Colour Index. 

The two main classes of basic dyes vary in the way in which the basic centre is built into the molecule. The use of pendant quaternary ammonium groups, where the charge is insulated from the chromogen, allows disperse dyes to be given a cationic character. Alternatively, the cationic charge is delocalised within the chromogen. 

Typically, Cl Basic Red 24 (4-97) has a structure reminiscent of a disperse dye, except that a quaternary ammonium group is carried on the pendant alkyl chain in the coupling component. This coupling component is prepared by reaction of N-ethylaniline with ethylene oxide followed by conversion of the resulting P-hydroxyethyl derivative into the p-... 

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