Binding of secondary dialkylammonium salts by pyrido-21-crown-7

Pyrido-21-crown-7 (P21C7) has been synthesized and shown to form [2]pseudorotaxanes spontaneously with secondary dialkylammonium ions. These complexes are stronger than their benzo-21-crown-7 counterparts and much stronger than their dibenzo-24-crown-8 counterparts. Based on this new P21C7/secondary dialkylammonium salt recognition motif, a [2]rotaxane terminated by phenyl groups as stoppers has been successfully constructed using the threading-followed-by-stoppering technique.     

Kinetics of decomposition of alkylammonium salts

The thermogravimetric curves of di-n-propylammonium, di-iso-propylammonium, di-n-butylammonium and di-iso-butylammonium chlorides showed similar profiles, characterized by mass loss in only one stage, corresponding to decomposition of compounds. The following thermal stability order was obtained: [Bu₂ ⁿNH₂]Cl>[Pr₂ ⁿNH₂]Cl>[Pr₂ ⁱNH₂]Cl>[Bu₂ ⁱNH₂]Cl. The values of activation energy for non-isothermal data obtained by Ozawa and Coats-Redfern integral methods were in agreement and stability order obtained by thermogravimetry were reproduced in both methods. The decomposition reactions of [Pr₂ ⁿNH₂]Cl, [Pr₂ ⁱNH₂]Cl and [Bu₂ ⁱNH₂]Cl were better described by A3 model and [Bu₂ ⁿNH₂]Cl by A2 model. This revised version was published online in August 2006 with corrections to the Cover Date.     

Metal directed assembly of ditopic containers and their complexes with alkylammonium salts

A new self-folding cavitand has been assembled through metal coordination to give a thermodynamically stable ditopic receptor of nanosize dimensions which has been used in the reversible binding of di-alkylammonium and n-alkylammonium salts.     

Factors influencing enantiomeric recognition of primary alkylammonium salts by pyridino-18-crown-6 type ligands

Equilibrium constant (K), enthalpy change (H), and entropy change (S) values were determined for the interactions of a series of chiral pyridino-18-crown-6 type ligands with enantiomers of several primary alkylammonium salts in various solvents. Good enantiomeric recognition in terms of logK was observed in many systems with logK values greater than 0.4. The extent of enantiomeric recognition and the stabilities of the chiral crown ether-ammonium salt complexes were found to depend on the rigidity of the macrocyclic frame of the ligand, the type and arrangement of the donor atoms on the ligand, the bulkiness of the substituents on the ligand's chiral centers, the location of the chiral centers on the ligand, and the solvent. The effects of these factors on the extent of enantiomeric recognition and on the stabilities of the complexes were examined for the systems studied.     

Reaction of ethoxyvinyl derivatives of pyrylium and pyridinium salts with primary and secondary amines

The reaction of -ethoxyvinylpyrylium salts with primary aromatic amines gives -R-aminovinylpyrylium salts, the alkaline hydrolysis of which gives azomethines and, subsequently, pyranylideneacetaldehydes; reaction with methylamine gives N-methylpyridinium salts, which, under the influence of alkali, give pyridinylideneacetaldehydes, while reaction with secondary amines gives -R,R-dialkylaminovinylpyrylium salts or acetalacylals; reaction with acetate gives hydroxyvinylpyridines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1338–1343, October, 1974.     

Fast atom bombardment mass spectra of some alkylammonium 4-toluenesulfonate salts

The fast atom bombardment positive ion mass spectra of low molecular weight alkylammonium 4-toluenesulfonate salts are dominated by cluster ions of the type [(AB)_nA]⁺ or [(AB)_nH]⁺, where A is a cation, B an anion, n an integer from 0 to 4. With one exception the base peak is the cation A⁺.     

Nonideal behavior of alkylammonium salts in organic solvents at elevated temperatures

Osmometric vapor-pressure-lowering measurements on toluene, butylbenzene, chlorobenzene, and chloronaphthalene solutions of several secondary, tertiary, and quaternary long-chain (at least five carbon atoms per chain) alkylammonium chlorides, bromides, thiocyanates, nitrates, and perrhenates in the temperature range between 50–130°C show an appreciable amount of molecular association. The extent (number of aggregated units) and/or the degree (size of aggregated units) of aggregation decreases with the number of carbon atoms per chain, the polarity of the solvent, and the temperature, but increases with the size of the anions and the solute concentration. The data were treated quantitatively in terms of activity coefficients via the Gibbs-Duhem relation and also in terms of specific oligomer formation. The latter treatment shows the salts to form a dimer and one (exceptionally two) higher oligomer, for which the association constants have been calculated.     

Mechanism for the inhibition of the autooxidation of cyclohexanone by alkylammonium salts

Conclusions Tetraalkylammonium salts may efficiently hinder the oxidation of ketones by catalyzing the decomposition of -ketohydroperoxides, mainly through a pathway not involving the formation of free radicals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2100–2102, September, 1987.     

Structural and dynamical aspects of alkylammonium salts of a silicodecatungstate as heterogeneous epoxidation catalysts

The structural and dynamical aspects of alkylammonium salts of a silicodecatungstate [(CH(3))(4)N](4)[γ-SiW(10)O(34)(H(2)O)(2)] [C1], [(n-C(3)H(7))(4)N](4)[γ-SiW(10)O(34)(H(2)O)(2)] [C3], [(n-C(4)H(9))(4)N](4)[γ-SiW(10)O(34)(H(2)O)(2)] [C4], and [(n-C(5)H(11))(4)N](4)[γ-SiW(10)O(34)(H(2)O)(2)] [C5] were investigated. The results of sorption isotherms, XRD analyses, and solid-state NMR spectroscopy show that facile sorption of solvent molecules, flexibility of structures, and high mobility of alkylammonium cations are crucial to the uniform distribution of reactant and oxidant molecules throughout the bulk solid, which are related to the high catalytic activities for epoxidation of alkenes.     

Reactions of 4-methoxypyrylium salts with secondary amines

4-Aminopyrylium derivatives were prepared from secondary amines and 4-methoxy-2,6-dimethylpyrylium perchlorate ( 1a ) and the corresponding 2,6-diphenyl derivative. Excess amine or elevated temperature resulted in the addition of two equivalents of amine to 1a . The reactions of the aminopyrylium salts with hydroxide, ammonia, primary amines, hydrazines, cyanoacetamides, ethyl cyanoacetate, malononitrile, nitromethane, sodium sulfide, and a Grignard reagent are described.