2-Alkyl-2,4,4-trimethyl-1,3-dioxanes

Acetoxy-2,4-dimethyl-m-dioxane Alkyl dimethyl ethylbenzyl ammonium chloride Alkyl trimethyl ammonium bromide Betaine hydrochloride Bishydroxyethyl dihydroxypropyl stearaminium chloride Calcium hypochlorite N-Chlorosuccinimide Cocamine acetate Cocoalkonium chloride Cocopropylenediamine Cocotrimonium chloride Copper acetoarsenite Copper gluconate (ic) Dehydroacetic acid Dialkyl dimethyl ammonium chloride... 

C-alkylated Meldrum s acid derivatives are cleaved asymmetrically by alkoxide anions in the presence of quininium salts to yield chiral half esters (9.2.2) [11]. Thus, benzylquininium and cinchonidinium salts produce fl-hemi-esters and the cincho-nium and quinidinium salts produce the S-hemi-esters from, for example, 2,2,5-trimethyl-5-pheny 1-1,3-dioxane-4,6-dione. 

CMCs of these polyfluorinated surfactants are of the order of 10 5 m.47 Plots of the observed H chemical shifts versus surfactant concentration of cetyl trimethyl ammonium chloride, cetyl pyridinium chloride, cetyl dimethyl phenyl ammonium chloride, cetyl dimethyl benzyl ammonium chloride, cetyl dimethy 1-2-phenyl ethyl ammonium chloride, and cetyl dimethyl-3-phenyl propyl ammonium chloride, are sigmoidal and were fitted to a model based on the mass action. The H chemical shift-based CMC values are in excellent agreement with those determined by the surface tension method.48 The micellization processes of dodecyl trimethyl ammonium halides (chloride and bromide) studied by calorimetric titration show different behaviors at 298 K. However, these disappear at 313 K, while the results measured by the chemical shift versus surfactant concentration do not show this difference.49 The CMC of 3-aminopropyl triethoxy silane in toluene is ca. 0.47m, measured by H and l3C chemical shifts.50 The CMC of optically active potassium A -n-dodecanoyl alaminate measured by H and l3C chemical shifts is lower (11-15 him) in D20 than that in a mixed solvent of 1,4-dioxane and D20 (19mM).-51 The H chemical shift shows that the CMC of resorcinol-type calix[4] phosphoric esters having four alkyl side-chains, [4]Ar 5P-R-n, is insensitive to the length of the side-chains, n.52 The CMC values of a family of surfactants, the sodium cyclohexyl alkanoates, with different lengths of the alkanoate side-chains, were obtained from 13C chemical-shift measurements. The results show that these amphiphiles have high CMCs (0.12-1.02 m).-53... 

Treatment of the phosphine resin 33 with alkyl bromides, e.g. 34, gave the corresponding phosphonium bromide 35 in excellent yields. The formation of the phosphorane was described as a cmdal step, for which the transport of the base to the phosphonium site within the polymer was essential. Various bases, such as sodium hydride, potassium tert-butoxide in THF, and n-butyllithium in dioxane, have been employed. Good results for the formation of the ylide were obtained with a mixture of sodium methoxide, methanol, and THF, and more recently with sodium bis(trimethyl)silylamide in THF [34, 35]. After the addition of aldehyde 36... 

A report has appeared of the H n.m.r. spectra of some 4-methyl-6-alkyl-and 4,5,5-trimethyl-6-alkyl-l, 3-dioxans with and without methylation at C-2. The authors suggested that 2,2-r-4-trimethyl-/-6-t-butyl-l,3-dioxan (12) is in a twist conformation. 

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