Quaternization group

There has been much interest in diquaternary salts of 4,4 -bipyridine, the electrochemistry of which has recently been reviewed. l.l -Dialkyl diquaternary salts of 4,4 -bipyridines are prepared by treating 4,4 -bipyri-dines with excess of an alkyl halide or a dialkyl sulfate or other alkylating agent. This method has been used extensively and provides diquaternary salts of type 92 where both alkyl quaternizing groups are the same (i.e., 92 R = 211,467,689,962,967,968 Qf particular interest is the diquater-... 

Following quaternizing group are used (Me=methyl, Bz=benzyl, Et=ethyl, Bu=butyl, Oc=octyl, FI=hydrogen). Q is the degree of quaternization and Br, Cl and I stand for the elemental code of the counterion. Hydrogenated PVP were prepared by dissolving PVP in aqueous HBr solution at PH=3 which yields Q=30%... 

Contribution of Quaternizing Groups to AG . As discussed above, the apparent binding constant increases with increasing extent of binding (r) caused by positive cooperativity, hence AG , ah , and AS for the various polymers are compared at a given r value (Table I). 

In contrast to the original amino group, which is protonated only at low pH values, the quaternized group is positively charged in a wide pH range and a distinct increase of... 

It has been pointed out (p. 265) that nucleophilic attack upon a quaternary salt may have various consequences the nucleophile may replace substituents from the pyridine nucleus, it may attack and open the ring and it may displace the pyridine ring from the quaternizing group. Numerous examples of the first two kinds of reaction (pp. 200-51, 265), and of the third the important case of the formation of 4-substituted pyridines from 4-pyridyl-pyridinium chloride (pp. 210, 239,251) have been quoted. This last kind is a particular case of arylation of nucleophiles by arylpyridinium salts, and the general case of this reaction and analogous alkylations will now be considered. These are presumably Sjn2 reactions (but see p. 269). 

These dyes possess two independent chromophoric chains of even methine (neutro) and uneven methine (cyanine) fixed on a central ketometbylene nucleus. The methylene reactive group is first used for the neutrocyanine synthesis in position 5. the, quaternization of which can ensure a subsequent polymethine synthesis in position 2 of a cationic dye by ordinary means (Scheme 58). As indicated, this quaternized neutrocyanine (37) may as well give another neutrocyanine. 

Strauss and Williamst have studied coil dimensions of derivatives of poly(4-vinylpyridine) by light-scattering and viscosity measurements. The derivatives studied were poly(pyridinium) ions quaternized y% with n-dodecyl groups and (1 - y)% with ethyl groups. Experimental coil dimensions extrapolated to 0 conditions and expressed relative to the length of a freely rotating repeat unit are presented here for the molecules in two different environments ... 

Quaternized esteramines are usually derived from fat or fatty acid that reacts with an alcoholamine to give an intermediate esteramine. The esteramines are then quaternized. A typical reaction scheme for the preparation of a diester quaternary is shown in equation 9 (210), where R is a fatty alkyl group. Reaction occurs at 75—115°C in the presence of sodium methoxide catalyst. Free fatty acids (230) and glycerides (231) can be used in place of the fatty acid methylester. 

QuaterniZation. Choline chloride [67-48-1] was prepared ia nearly quantitative yield by the reaction of trimethylamine [121-44-8] with ethylene chlorohydrin at 90—105°C and 981—1471 kPa (10—15 kg/cm ) pressure (44). Precursors to quaternary ammonium amphoteric surfactants have been made by reaction of ethylene chlorohydrin with tertiary amines containing a long chain fatty acid group (45). 

Alkyl groups and halogen atoms in tetrazoles are not highly activated unless the ring is quaternized. 

In pyrazoles the two most important effects are produced by nitro groups and by quaternization (Section 4.02.3.1.7). Both enhance considerably the reactivity of a second substituent, for example, that of a methyl group towards aldehydes or of a chloro substituent towards amines. 

The Dppe group was developed for carboxyl protection in peptide synthesis. It is formed from an A -protected amino acid and the alcohol (DCC, DMAP, 3-12 h, 0°, It). It is most efficiently cleaved by quaternization with Mel, followed by treatment with fluoride ion or K2CO3. The ester is stable to HBr/AcOH, BF3-Et20, and CF3CO2H. ... 

It would therefore be deduced that the availability of the electron pair, as influenced by the ring containing the nitrogen atom, the substituents present in that ring, and the steric environment, should affect the rate of quaternization. Furthermore, the solvent for the reactants and the nature of the group R in Eq. (1) would be expected to be important factors in determining the course of the reaction. In the following sections the importance of each of these factors is considered. 

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