DIMETHYLAMMONIUM GROUP

In another estimate (Kirby and Percy, 1989), the carboxyl group in l-methoxymethoxy-8-naphthoic acid and the dimethylammonium group in the l-methoxymethoxy-8-A, A -dimethylnaphthylammonium ion are estimated to lead to rate increases by intramolecular catalysis of < ca. 900 and 1.9 X 10 compared to the value of ca. 1 x 10 calculated for the intramolecular catalytic effect of the carboxyl group in 2-methoxymethoxybenzoic acid. The salicylate ion remains the most efficient leaving group thus far discovered that can take part in hydrogen-bond catalysis of the hydrolysis of acetals. 

The complexation studies described in the previous section clearly indicate that a-CD is threaded by the aliphatic chain of compounds 2" and 3". Since the (ferrocenylmethyl)dimethylammonium group is very bulky, the dissociation of these a-CD complexes takes place by unthreading at the other end of the alkyl chain. We thought that, if we could attach a reactive functional group at this end, it would be possible to trap the chain-threaded CD by reaction of this end with an appropriately bulky capping group. Therefore, we synthesized compounds 4+ and S" " in which the aliphatic chain is terminated in a carboxylic acid group. 

Cl quadrupole relaxation studies of Cl binding to synthetic polycations and polyampholytes have recently been started [525] and, furthermore, observations of Cl NMR in polyanion (poly(phosphate) and poly(methacrylic acid)) solutions have been reported [526 527]. In Fig. 10.1 are shown the Cl transverse relaxation rates (from line widths of Fourier transform spectra) for solutions of poly(N,N-dimethyl-aminoethylmethacrylate) and poly(methacrylic acid) as a function of the degree of ionization, a, of the polyelectrolyte [525]. (a = 0 corresponds to equivalent concentrations of acid and polymer and a = 1 to equivalent concentrations of base and polymer.) The Cl interaction with the polycation can be seen to have a considerable effect on the relaxation rate the linear decrease for intermediate a-values reflects the gradual titration of the dimethylammonium groups. Quadrupole relaxation studies seem to be well suited for elucidating halide ion -... 

Azidochloromethylene)dimethylammonium chloride (2.62) is another reagent which can be used to introduce a diazonio group directly into a phenol (Kokel and Viehe, 1980). 

Cationic surfactants are surface-active agents that have one or more functional groups in their molecule that ionise in aqueous solution to produce positively charged organic ions. The most representative cationic surfactants are quaternary ammonium derivatives in which the N atom is bonded to four alkyl groups. For many years, ditallow dimethylammonium chloride (DTDMAC) has been the most widely used product of this family. Its recalcitrance to biodegradation, however, has... 

Gold nanoparticles can also be stabilized using polymers that do not have specific functional groups through physisorption. Among the possible stabilizers, the polymers used most often to stabilize Au NPs are the water soluble polymers poly(N-vinylpyrrolidone) (PVP), polyethylene glycol) (PEG), poly(vinyl pyridine), poly(vinyl alcohol) (PVA), poly(vinyl methyl ether) (PVME), and polyelectrolytes such as PAA, chitosan, polyethyleneimine (PEI) or poly(diallyl dimethylammonium) chloride (PDDA) [99]. 

Later, similar experiments were made for cationic networks of polyfdiallyl-dimethylammonium bromide) in the presence of sodium dodecyl sulfate or potassium salts of carboxylic acids with different lengths of hydrocarbon groups [66-68]. 

Natural lipids used for fusion experiments were mainly phospholipids with different chain lengths and their mixtures with cholesterol. As polymerizable lipids, butadienic derivatives with a phosphatidylcholine (19) and a dimethylammonium head group (26) were used in the fusion experiments. 

The parallelism in reactions with HMPT and mixtures of phosphorus pentoxide and amines can best be realized by looking at the mechanism of HMPT reactions [1 5 ]. In the reaction of p-methoxy-benzylalcohol with HMPT which produce the corresponding N,N-dimethylbenzyl amine--p-methoxybenzyl phosphate was identified in the XP NMR spectrum of the reaction mixture. Since pyrophosphate was also observed during the reaction of the benzyl alcohol with HMPT, the intermediate formation of the metaphosphate anion can be assumed. Addition of the benzyl alcohol to that anion then produce the benzyl phosphate. Phosphate ions are known to be good leaving groups so that a benzylamine can easily be produced from the phosphate by reaction with di-methylamine released from the dimethylammonium ion. The phosphoric acid produced during the reaction is believed to react with HMPT, so that more dihydro-gen-bis(dimethylammonium) pyrophosphate is formed. 

As an example let us compare the system of electron configurations of triphenylmethylchloride (abs. band 4250 A) with those of triphenylmethane (abs. 2690 A, similar to benzene) and with those of fuchsone dimethylammonium chloride, (abs. 4810 A) where a dimethylamino group has been introduced. 

Cationic surfactants with an electron rich phenyl substituent on the hydrophilic ammonium head group (phenyl, 2,4-dimethoxyphenyl, and 2,4-dimethoxybenzyl dimethylammonium bromides) were found to be more efficient catalysts than CTAB for the hydrolysis of 2,4- and 2,6-dinitrophenyl phosphates (Bunton et al., 1970). The pseudo-first order rate constants increased appreciably at low concentrations of these... 

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