77-Alkyltrimethylammonium

The least sterically hindered p hydrogen is removed by the base in Hofmann elimination reactions. Methyl groups are deprotonated in preference to methylene groups, and methylene groups are deprotonated in preference to methines. The regioselectivity of Hofmann elimination is opposite to that predicted by the Zaitsev rule (Section 5.10). Elimination reactions of alkyltrimethylammonium hydroxides are said to obey the Hofmann rule they yield the less substituted alkene. 

The fact that f.a.b.-m.s. can be used to observe cluster ions has been exploited in a study of metal binding to cyclodextrins, and in an investigation of the complexes formed between a 3-O-methylmannose dodecasac-charide and alkyltrimethylammonium ions having decyl and hexadecyl as alkyl chains. In the latter study, the larger organic cation was shown to form the stronger complex. 

As an example, take the manufacture of mesoporous silica (amorphous Si02) with uniformly sized pores. Rod-like micelles of alkyltrimethylammonium ions form in an aqueous solution of an alkyltrimethylammonium halide. The micelles have a positive electric... 

Alkyltrimethylammonium surfactants, such as hexadecyltrimethylammonium chloride (HTAC) [6, 9, 38-41], hexadecyltrimethylammonium hydroxide (HTAH) [38, 42], hexadecyltrimethylammonium bromide (HTAB) [43-46], te-tradecyltrimethylammonium bromide (TTAB) [47], pentadecyltriethylammon-... 

Fig. 6 General structures of the most important surfactants and metabolites alkylphenol polyethoxylate (APE) alkylphenol (AP) alkyl ether (AE) alkylphenol ethoxy carboxylate (APEC) linear alkylbenzenesulfonates (LAS) alkyltrimethylammonium compounds (ATMAC) dialkyldimethylammonium compounds (DADMAC) alkyldimethylbenzylammonium compounds (ADMBAC) esterquat (EQ) diesterquats (DEQ). X is usually a chlorine or bromine atom. DDAC (didecyldimethylammonium chloride) and BDD12AC (benzyldimethyldode-cylammonium) are the two target analytes with a reported immunochemical technique developed for their analysis [153,154]...

Smaller, hard cations, such as alkyltrimethylammonium salts and crown ether-cation complexes, will promote the elimination of dichlorocarbene to form a hard ion pair of type Q+C1 . 

OH -C Cl < MeS04 < Br < NO3. The shape and thickness of the monolayer of cetrimide (197c) formed at the air-water interface was determined by neutron reflection. The total thickness of the monolayer was estimated to be 2.1 0.2 nm, of which 1.0 nm is immersed in water six water molecules are associated with each molecule of surfactant436. Similar studies were performed for various C10 to (jx alkyltrimethylammonium surfactants. Interpretation of the neutron reflection results included an estimate... 

R Hansson and M. Akngren Interaction of Alkyltrimethylammonium Surfactants with Polyacrylate and Poly(Styrenesulfonate) in Aqueous Solution Phase Behavior and Surfactant Aggregation Numbers. Langmuir 10, 2115 (1994). 

M. Ahngren, P. Hansson, E. Mukhtar, and S. van Stam Aggregation of Alkyltrimethylammonium Surfactants in Aqueous Poly(Styrenesulfonate) Solutions. Langmuir 8, 2405 (1992). 

V. Bergeron Disjoining Pressures and Eihn Stabflity of Alkyltrimethylammonium Bromide Foam Films. Langmuir 13, 3474 (1997). 

Candau SJ, Hirsch E, Zana R. New aspects of the behavior of alkyltrimethylammonium bromide micelles—hght-scattering and viscosimetric studies. J Phys Paris 1984 45 1263-1270. 

The physical chemical behavior of betaine esters of long-chain alcohols shows strong similarities to the common, closely related alkyltrimethylam-monium surfactants both in dilute and concentrated aqueous systems, hi consistence with the findings about CMC s of surfactants containing normal ester bonds (see above) it has been found that the CMC for a betaine ester with a hydrocarbon chain of n carbons is very close to the value for an alkyltrimethylammonium chloride surfactant with a hydrocarbon chain of n + 2 carbons [32], The binary phase diagram of dodecyl betainate-water has an appearance very similar to that of an alkyltrimethylammonium surfactant with a hydrophobic tail of a similar size [30]. 

If short-chain alkyltrimethylammonium ions, R(CH3)3N", are used as the surfactant, the alkyl chain length determines whether micro- or mesoporous materials are formed. For alkyl chain lengths of Ce or shorter, microporous zeolites such as ZSM-5 are formed but for longer chains, mesoporous materials are isolated. 

The Effects of Complexing Agents. Cai et al.66 replaced the sodium counterion of MX-DNA with various aliphatic amine cations, e.g. spermine cation, and alkyltrimethylammonium cation as well as polymeric amine cations, such as poly-L-lysine and polyethylenimine to vary the separation between DNA duplexes. The radiation-produced electrons from the complexing agents readily transfer to the more electron affinic DNA. 

A novel aspect of the Hofmann elimination is its regioselectivity. Elimination in alkyltrimethylammonium hydroxides proceeds in the direction that gives the less substituted alkene. 

Formation of the Sic Phase in Binary Aqueous Alkyltrimethylam-monium Halide Solutions. These considerations are well illustrated by the formation of the Slc phase in aqueous alkyltrimethylammonium halide solutions (17) (Figure 7). This phase is apparently composed of Si micelles—probably on balance prolate—arranged in a primitive, cubic lattice and rotating fairly freely at the lattice points. The lattice is formed by dodecyl- and tetradecyltrimethylammonium chlorides but not by the hexadecyl or octadecyl chlorides nor by any of the corresponding bromides. This may be expressed as follows. 

Alkyl (Me, Et, n-Pr, n-Bu), alkyldimethyl, and alkyltrimethylammonium bromides retard the neutral hydrolysis of 1-benzoyl-1,2,4-triazole (190) to benzoic acid and the triazole (191).162 This effect is attributed to a dominant stabilization of the initial state through hydrophobic interactions with the co-solute. The effects of cetylpyridinium bromide on the hydrolysis of 2,4-dinitrochlorobenzene by hydroxide ion in water have been reported.163... 

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