NMR spectroscopic investigation of multi-walled carbon nanotubes modified by amino groups

The results of the functionalization of multi-walled carbon nanotube surface by amines containing different substituents at the nitrogen atom, namely, primary n-hexylamine, secondary izadrine, and tertiary N-benzylmorpholine and dithiline, are presented. It was shown by NMR spectroscopy, thermal analysis, mass spectrometry, X-ray photoelectron spectroscopy, and elemental analysis that the interaction of primary and secondary amines with modified nanotubes results in the formation of a covalent bond with the nitrogen atom of amines, while the reactions with tertiary amines afford quaternary ammonium salts; diamine is attached covalently through both amine groups.     

Complexation Between (O‐Methyl)6‐2,6‐Helic[6]arene and Tertiary Ammonium Salts: Acid/Base‐ or Chloride‐Ion‐Responsive Host–Guest Systems and Synthesis of [2]Rotaxane

Complexation between (O ‐methyl)₆‐2,6‐helic[6]arene and a series of tertiary ammonium salts was described. It was found that the macrocycle could form stable complexes with the tested aromatic and aliphatic tertiary ammonium salts, which were evidenced by ¹H NMR spectra, ESI mass spectra, and DFT calculations. In particular, the binding and release process of the guests in the complexes could be efficiently controlled by acid/base or chloride ions, which represents the first acid/base‐ and chloride‐ion‐responsive host–guest systems based on macrocyclic arenes and protonated tertiary ammonium salts. Moreover, the first 2,6‐helic[6]arene‐based [2]rotaxane was also synthesized from the condensation between the host–guest complex and isocyanate.     

Reactivity of polyhydroxyalkyl-heterocycles towards Lewis acids

We report the reactivity of different polyhydroxyalkyl-heterocycles towards ceric ammonium nitrate (CAN) and ferric chloride. The behaviour of 2-methyl-5-(tetritol-1-yl)-pyrroles and -furans is different towards CAN oxidation. Pyrroles afford 2,5-diformylheterocycles, while furans give access to 1,4-dicarbonyl compounds containing three stereogenic centres. Ferric chloride promotes an intramolecular C-arylation reaction on O-benzylated-polyhydroxyalkyl furans, yielding an isochroman moiety, which is the basic skeleton of a variety of natural products.     

Selective reduction of tertiary alkyl,benzyl, and allyl halides to hydrocarbons using lithium 9,9-di-n-butyl-9-borabicyclo[3.3.1]nonanate

The title 9-borabicyclo[3.3.1]nonane(9-BBN) ate complex (1) brings about selective removal of tertiary alkyl, benzyl and allyl halides to give the corresponding hydrocarbons in excellent yields without concomitant attack on secondary, primary and aryl derivatives. The reduction of cis- and trans - 4 - t - butyl - 1 - methylcyclohexyl chlorides (2) with 1 gives 4 - t - butyl - 1 - methylcyclohexanes (3) with partial inversion of configuration in cyclohexane, while that in benzene gives thermodynamically stable trans-3 predominantly. The reactions of 1,1 - dimethyl - 5 - hexenyl chloride (4) and 1,7,7 - trimethylbicyclo[2.2.1]hept - 2 - yl chloride (8) with 1 proceed with the rearrangements characteristic to a carbonium ion intermediate. The reduction of 1 - ethyl - 1 - methylpentyl chloride with 1 follows a second-order rate equation.     

Response and selectivity characteristics of alkylammonium ion-selective electrodes

A series of poly(vinyl chloride) matrix coated-wire electrodes based on dinonylnaph-thalene sulfonic acid (DNNS) selective to various alkylammonium ions was prepared and selectivity characteristics were evaluated. A set of tributylammonium electrodes was used to study the interference by a homologous series of alkylammonium ions. Selectivity coefficient (k^pot_i,j) values for alkylammonium ions at a given carbon number decreased in the order primary, secondary, tertiary, quaternary. A linear increase in log k^pot_i,j with carbon number was observed in each series. Two additional sets of electrodes selective to dodecylammonium ion and to di-n-hexylammonium ion were evaluated for response to other C-12 amines. Electrodes for primary amines showed little or no response to secondary and tertiary amines, while electrodes for tertiary amines responded strongly to primary amines and less strongly to secondary amines. The effect of structural modifications was evaluated in a study of N-substituted cydohexylamines. The dependence of the magnitude of k^pot_i,j on the concentration of the interference was determined for both strongly and weakly interfering species. For strong interferences, k^pot_i,j was observed to increase to a maximum value of characteristic concentration. For weak interferences, the k^pot_i,j variation with concentration was markedly less. Guides for estimating the response to an interfering species based on its structure and molecular weight were obtained. The results are compared to analogous solvent-extraction systems. The significance of these results is discussed in terms of quantifying different components in binary mixtures using several electrodes simultaneously.     

Detection of Quaternary Ammonium Drugs in Equine Urine by Liquid Chromatography-Mass Spectrometry

Quaternary ammonium drugs are anticholinergic agents and some of which have been known to be abused in equine sports. A general screening method for this class of drugs in equine urine by liquid chromatography-mass spectrometry (LC-MS) has not been reported. The paper describes an efficient LC-MS-MS method for the simultaneous detection and confirmation of twenty quaternary ammonium drugs at low ng mL^?1 in equine urine after solid-phase extraction. Quaternary ammonium drugs were extracted from equine urine by solid-phase extraction using ISOLUTE^® CBA SPE Columns and analysed by LC-MS-MS in the positive electrospray ionisation mode. Separation of twenty quaternary ammonium drugs (the quaternary ammonium ions of edrophonium chloride, pyridostigmine bromide, neostigmine bromide, bretylium tosylate, ipratropium bromide, tubocurarine chloride, N-butylscopolammonium bromide, mepenzolate bromide, rocuronium bromide, clidinium bromide, pipenzolate bromide, isopropamide iodide, glycopyrronium bromide, alcuronium chloride, oxyphenonium bromide, propantheline bromide, tridihexethyl chloride, vecuronium bromide, mivacurium chloride and pancuronium bromide) was achieved in a reversed phase column with a mixture of aqueous ammonium formate (pH 3.0, 10 mM) and acetonitrile as the mobile phase. Detection and confirmation of the twenty quaternary ammonium drugs at about 5 ng mL^?1 in equine urine could be achieved within 22 min using product-ion scan MS-MS. The target analytes were detected by examination of extracted-ion chromatograms of their product ions. Drugs spiked in different equine urine (n = 15) were consistently detected. Negative samples (n = 30) of normal post-race equine urine have also been analysed, no matrix interference at the targeted masses and retention times was observed. The method was successfully applied to the analyses of drug-administration samples. Other method validation data including reproducibility and recovery will also be presented. An LC-MS-MS method for the simultaneous detection and confirmation of twenty quaternary ammonium drugs in equine urine was developed. The methodology should be applicable to other biological matrices such as human urine.     

Free radical and isomerisation processes during the electrochemical fluorination of n-butyryl chloride, i-butyryl chloride and pivaloyl chloride in anhydrous hydrogen fluoride

Electrochemical perfluorination (ECPF) of the title compounds containing primary, secondary and tertiary carbon atoms was carried out in anhydrous hydrofluoric acid (AHF). Detailed analysis of major and minor products suggest that carbon chain isomerisation involving cyclo-propane intermediate is more prevalent during ECPF of i-butyryl chloride when compared to n-butyryl chloride. Simple statistical probability involving free radical intermediates also support this observation. ECPF involving cyclo-propane intermediate is even more prevalent in pivaloyl chloride containing three methyl substituents. In this case, perfluorinated cyclo-propane intermediates were also observed in the product sample. Distribution of minor perfluorinated and partially fluorinated products also suggest the predominant role of normal free radical pathway involving single-electron transfer.     

Effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid solution

In this study, the effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid (HCl) solution was investigated by using dodecyl trimethyl ammonium chloride (DTAC), tetradecyl trimethyl ammonium chloride (TTAC), cetyl trimethyl ammonium chloride (CTAC), and octadecyl trimethyl ammonium chloride (OTAC) as corrosion inhibitors to uncover their structure–efficiency relationships. The effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in HCl solution was studied under different conditions, such as corrosion inhibitor concentration, temperature, and acidity, and this was done using the weightlessness method. The results obtained show that these inhibitors have high corrosion inhibition effect on A₃ steel, and the corrosion inhibition efficiency is dependent on the length of the alkyl chain. At the same concentration, the longer the alkyl chain, the weaker the corrosion inhibition effect. When the temperature was 50 °C and the concentration of corrosion inhibitor was 70 mg/L, the corrosion inhibition efficiency order of the four cationic surfactants was DTAC > TTAC > CTAC > OTAC. Besides, the experimental results obtained show that the adsorption of the inhibitor on the A₃ steel surface conforms to the Langmuir type isotherm, and then the corresponding adsorption thermodynamic parameters were obtained according to these parameters. It was observed that ΔH, ΔS, and E_a increased with increase in the length of the alkyl chain. The adsorption of the inhibitor on the steel surface is an exothermic, spontaneous, entropy process.     

Enantiomer assays of amino acid derivatives using tertiary amine appended trans-4-hydroxyproline derivatives as chiral selectors in the gas phase

A pair of pseudo-enantiomers, tertiary amine appended trans-4-hydroxyproline derivatives were designed, synthesized, and evaluated as chiral selectors for enantiomer analysis of DNB-amino acid and their amides, in single-stage electrospray ionization/mass spectrometric experiments. The chiral selectors were designed to remove the interaction of the hydroxyl group of trans-4-hydroxyproline as well as separate the ionization site from the sites required for effective chiral recognition. Addition of a chiral analyte to a solution containing two pseudo-enantiomeric chiral selectors, affords selector-analyte complexes in the electrospray ionization mass spectrum where the ratio of these complexes is dependent on the enantiomeric composition of the analyte. The relationship between the ratio of the selector-analyte complexes in the electrospray ionization mass spectrum and the enantiomeric composition of the analyte can be used to relate the extent of the measured enantioselectivity and for quantitative enantiomeric composition determinations. Effects of acid modifiers (ammonium chloride, acetic acid, formic acid and hydrochloric acid) and instrument conditions on the selector-analyte ion intensity and the enantioselectivity (α_MS) were investigated. The largest α_MS was observed using ammonium chloride at a concentration around 0.5-1 mM at desolvation temperature of 150 °C. Capillary voltage has little effects on α_MS values. The sense of chiral recognition by MS is consistent with what is observed chromatographically. Quantitative enantiomeric composition determinations for N-(3,5-dinitrobenzoyl) leucinyl butylamide were performed. A comparison to the enantioselectivities towards a scope of analytes observed by chiral HPLC using a 3,5-dimethylanilide-proline-derived chiral stationary phase, is presented.     

An ion-exchange scheme for the determination of the major cations in sea water

A cation-exchange scheme is described for the determination of the principal cations in sea water. The cations are adsorbed onto a column of Amberlite CG 120. Sodium and potassium are eluted together using 0.15 M ammonium chloride and determined gravimetrically as sulphates; potassium is then determined gravimetrically as potassium tetraphenylboron and sodium is determined by difference. Magnesium and calcium are eluted by means of 0.35 M ammonium chloride and 1 M ammonium acetylacetonate (pH 9.6) respectively, and titrated with EDTA. Finally, strontium is eluted with 2 M nitric acid and determined by flame photometry. Tests made using an artificial sea water showed that the method had coefficients of variation of 0.02, o.22, 0.04, 0.08 and 0.8% for sodium, potassium, magnesium, calcium and strontium respectively.     

Lewis acid-catalyzed oxidative rearrangement of tertiary allylic alcohols mediated by TEMPO

Two methods for the oxidative rearrangement of tertiary allylic alcohols have been developed. Most of tertiary allylic alcohols studied were oxidized to their corresponding transposed carbonyl derivatives in excellent to fair yields by reaction with TEMPO in combination with PhIO and Bi(OTf)₃ or copper (II) chloride in the presence or not of oxygen. Other primary oxidants of TEMPO such as PhI(OAc)₂, mCPBA, and Oxone^® were unsatisfactory giving the enone in modest to low yields.     

Preparation of sulfonamides from N-silylamines

Sulfonamides have been prepared in high yields by the reactions of N-silylamines with sulfonyl chlorides and fluorides. In a competition experiment, the sulfonyl chlorides were found to be far more reactive than sulfonyl fluorides. The chemistry may be used to prepare aliphatic, aromatic, tertiary, secondary, and primary sulfonamides. It may also be done in the absence of solvent and the byproduct trimethylsilyl chloride recovered in good yield. Primary sulfonamides were synthesized from the sulfonyl chloride with aminotriphenyl silane (Ph₃SiNH₂), a conversion demonstrated with the synthesis of the carbonic anhydrase inhibitor, acetazolamide.     

Acyl iodides in organic synthesis: XI. Unusual N-C bond cleavage in tertiary amines

Acyl iodides reacted with excess primary and secondary amines in a way similar to acyl chlorides, yielding the corresponding carboxylic acid amide and initial amine hydroiodide. Reactions of tertiary amines with acyl iodides were accompanied by cleavage of the N-C bond with formation of the corresponding N,N-di(hydrocarbyl)carboxamide and alkyl iodide. In the presence of excess tertiary amine the latter was converted into quaternary tetra(hydrocarbyl)ammonium iodide.     

Interaction of the low-molecular weight salts with cationic polyelectrolytes

The interaction of several mono-, di-, and trivalent anions with cationic polyelectrolytes having different contents in N,N-dimethyl-2-hydroxypropylen ammonium chloride units (polymer A) or tertiary amine N-atoms and PEG (polymer PEGA) in the main chain was studied by viscosimetric and conductometric measurements. Both methods have shown a stronger interaction for tri- and bi- than for univalent counterions. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2571–2581, 1997     

Photometric determination of quaternary ammonium compounds with hexanitrodiphenylamine. II

In strongly alkaline medium (more than 0.1 N NaOH) hexanitrodiphenylamine anion reacts with base. The reaction is rather slow and is partly reversible.Quaternary ammonium ions can be determined by extraction of their hexanitrodiphenylamine complexes with chloroform or methylene chloride at pH 11 or with methylene chloride from 3N NaOH. Only the latter method is applicable to compounds containing several quaternary ammonium groups. The compounds extracted have high molar extinction and good stability. Quaternary ammonium ions can be determined in the presence of amines, and in some cases determination of quaternary ammonium ions in admixture is possible.     

Investigation of the catalytic activity of an electron-deficient vanadium(IV) tetraphenylporphyrin: A new, highly efficient and reusable catalyst for ring-opening of epoxides

In this work, the catalytic activity of high-valent tetraphenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [V^IV(TPP)(OTf)₂], in the nucleophilic ring-opening of epoxides is reported. This new V(IV) catalyst was used as an efficient catalyst for alcoholysis with primary (methanol, ethanol and n-propanol), secondary (iso-propanol) and tertiary alcohols (tert-butanol), hydrolysis and acetolysis of epoxides with acetic acid and also for the conversion of epoxides to 1,2-diacetates with acetic anhydride, conversion of epoxides to thiiranes with ammonium thiocyanate and thiourea, and for conversion of epoxides to acetonides with acetone. The catalyst was reused several times without loss of its activity.     

Spektrofotometrische bestimmung von calciumspuren nach ihrer abtrennung aus konzentrierten Lithiumchlorid-Lösungen mittels kationenaustausch

Calcium was separated from 1–2 M solutions of lithium chloride by means of Wofatit CP cation exchanger. Calcium was quantitatively separated from lithium by elution with 1 M ammonium chloride. Calcium, was eluted with hydrochloric acid and, eventually, measured spectrophotometrically at 567 mμ after addition of buffer and cresolphthalexone. The sensitivity was found to be 0.002 μg Ca/cm2 and Beer's law was obeved up to 15 μg Ca. With l g of lithium, the limit of determination was 10^-4% Ca.     

Miniemulsion polymerization of styrene using well-defined cationic amphiphilic comblike copolymers as the sole stabilizer

Well-defined, positively charged, amphiphilic copolymers containing long alkyl side chains were used as stabilizers in the miniemulsion polymerization of styrene. The copolymers were prepared by controlled free-radical copolymerization of styrene and vinyl benzyl chloride using either the reversible addition-fragmentation chain transfer method or TEMPO-mediated polymerization. The benzyl chloride moities were modified by two different long alkyl chain tertiary amines (N,N-dimethyldodecyl amine and N,N-dimethylhexadecyl amine) to yield the amphiphilic copolymers with vinylbenzyl dimethyl alkyl ammonium chloride units. Owing to their high structural quality, only a small amount of these copolymers was required to stabilize the latex particles (0.5–2 wt% vs styrene). Moreover, in the absence of any hydrophobic agent, the amphiphilic comblike copolymer preserved the colloidal stability of both the initial liquid miniemulsion and the final latex. Ill-defined, analogous copolymers were synthesized by conventional free-radical polymerization and in comparison, exhibited poor stabilization properties.     

Synthesis, characterization and X-ray structural determination of a stable dication derived from symmetrical ortho-aminophenyl diamine and 2-pyridinecarboxaldehyde

N,N′-Bis(2-aminophenyl)-1,2-ethanediamine is synthesized from 1,2-diaminoethane and 1-chloro-2-nitrobenzene in the presence of sodium carbonate and the product reduced by zinc dust and ammonium chloride. A novel stable dication is synthesized by reaction of N,N′-bis(2-aminophenyl)-1,2-ethanediamine and 2-pyridinecarboxaldehyde in the presence of manganese chloride in methanol. The X-ray structural analysis shows formation of the dication.