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The series of gemini amine-oxide surfactants with the formula CnH2n+1CONH(CH2)2N+O−(CH3)–(CH2)3–(CH3)N+O−(CH2)2NHCOCnH2n+1 (n = 11, 13, 15, and 17) has been synthesized successfully. Their isoelectric point and acid dissociation constant were measured to determine the ionization form of the surfactant molecules in aqueous solution within different pH values. The studies showed that the length of the hydrophobic alkyl chains had a great influence on the pH-stimuli responsive behavior of these surfactants. When n ≤ 13 (n-3-n-OA), the regularity of the pH-stimuli responsive behavior of the surfactant solutions was relatively consistent, while the surfactants with longer hydrophobic alkyl chain lengths lost this regularity (n ≥ 15). In addition, vesicles were observed in most of these surfactant aqueous solutions, with the exception of 11-3-11-OA. Moreover, the obvious flocculation phenomenon was observed within the range of pH 4–5, and they flocculated rapidly when they approached their isoelectric points. This process was reversible, which brought more possibilities for their application in drug delivery and release.

“Worm”-containing viscoelastic fluids formed by single C22-tailed surfactants have attracted special interests over the past decade due to their unique rheological response. Here, a viscoelastic wormlike micellar solution of erucyldimethyl amidopropyl amine oxide (EMAO) was first reported and investigated. Upon increasing concentration, EMAO can self-assembly into micelles at a very low concentration, and then these micelles grow into long threadlike worms, which further entangle with each other in the semi-dilute region (>0.55 mM), enhancing the viscosity by several orders of magnitude. EMAO worms exhibit a smaller sensitivity to pH at room temperature than those of short-chain counterparts, but show evident pH responsiveness at high temperature due to the presence of multiple hydrogen bonds and cloud point, which is barely observed for short-chain amine oxide surfactants. The hydrogen bonds and cloud point also result in an uncommon thermo-thickening behaviour in a certain temperature range. Compared with short-chain amine oxide worms, EMAO worm possesses stronger thickening ability, better biodegradable and lower toxicity, giving it a rich prospective for use in gel cleaners, clear fracturing fluids, etc.

The amphiphilic osmolyte trimethylamine-N-oxide (TMAO) is commonly found in natural organisms, where it counteracts biochemical stress associated with urea in aqueous environments. Despite the important role of TMAO as osmoprotectant, the mechanism behind TMAO's action has remained elusive. Here, we study the interaction between urea, TMAO, and water in solution using broadband (100 MHz-1.6 THz) dielectric spectroscopy. We find that the previously reported tight hydrogen bonds between 3 water molecules and the hydrophilic amine oxide group of TMAO, remain intact at all investigated concentrations of urea, showing that no significant hydrogen bonding occurs between the two co-solutes. Despite the absence of direct TMAO-urea interactions, the solute reorientation times of urea and TMAO show an anomalous nonlinear increase with concentration, for ternary mixtures containing equal amounts of TMAO and urea. The nonlinear increase of the reorientation correlates with changes in the viscosity, showing that the combination of TMAO and urea cooperatively enhances the hydrogen-bond structure of the ternary solutions. This nonlinear increase is indicative of water mediated interaction between the two solutes and is not observed if urea is combined with other amphiphilic solutes.

The amine oxide species, which plays an important role in cellulose chemistry, has been studied using molecular orbital techniques. The results of these calculations have been used to generate and evaluate a new force-field for the amine oxide molecule which has been tested against high quality ab initio calculations. Long time scale molecular dynamics simulations on the cellulose water amine oxide system correctly predict many aspects of the behaviour of this complex tertiary system, especially with respect to the concentration dependence of its physical and transport properties and reveal new structural information.

Kinetic and product analyses have been made of the oxidation of an activated azo dye, 4-(4-sulfophenylazo)-N,N-dimethylaniline (Methyl Orange, 1) and a series of tautomeric arylazonaphthol dyes by peracids at 40 °C in alkaline media, particularly peroxosulfate. The arylazonaphthol dyes are readily degraded into fragments (k2E = 102–103M–1 s–1) whereas the azo link in Methyl Orange is relatively inert (k2E 10–1M–1 s–1) consistent with the view that dyes that contain the azo or hydrazo link are more resistant to oxidation than the common anion form of arylazonaphthol dyes. Methyl Orange is decolourised by peroxosulfate (k2E = 7.6 M–1 s–1) simply via oxidation of the tertiary amine to amine oxide, resulting in a shift of the spectrum into the UV region. The reaction site in arylazonaphthol dyes has been pinpointed by investigating k2E for substituted dyes with the 1-arylazo-2-naphthol and 2-arylazo-1-naphthol structural motifs. In direct contrast to results for oxidation by hydrogen peroxide, the presence of an ortho-sulfonate in the aryl ring retards oxidation but an ortho-sulfonate in the naphthol ring does not. This suggests oxidation is initiated by electrophilic reaction by the negatively charged peroxosulfate at the nitrogen atom of the common dye anion that is in close proximity to the aryl ring. In contrast to oxidation by hypochlorite, the introduction of an amino group into the 8-position of 2-arylazo-1-naphthol dyes protects the dye against oxidation, via its influence upon the dye pKA.

Complex formation, and proton transfer processes in the polarizable hydrogen bonds formed, have been studied with 1,8-bis(dimethylaminomethyl)naphthalene N,N′-dioxide (1)+ R-phenol and with 1,2-bis(dimethylaminomethyl)benzene N,N′-dioxide (2)+ R-phenol systems in acetonitrile solutions as a function of the pKa of the substituted phenols. In the first family of systems the complex formation is not complete but increases with decreasing pKa of the phenols, whereas in the second one it is always complete.In both complexes an OH ⋯ ON ⇌ O–⋯ H+ON equilibrium is observed. With decreasing pKa of the phenols the left hand well of the double minimum proton potential is first raised. After formation of a strong shorter hydrogen bond with almost no barrier within the proton potential, which is on average largely symmetrical, the right hand well is lowered and finally the proton is localized at the N-oxide group. The proton polarizability of the hydrogen bond first increases and then decreases again. With compound 2, besides the heteroconjugated hydrogen bonds increasingly shorter homoconjugated intramolecular NO ⋯ H+⋯ ON hydrogen bonds are formed with decreasing pKa of the phenols. In the systems with more acidic phenols only this species is present.

Organic–inorganic hybrid materials based on porous silica materials functionalized with amine-containing organic species are emerging as an important class of materials for the adsorptive separation of acid gases from dilute gas streams. In particular, these materials are being extensively studied for the adsorption of CO2 from simulated flue gas streams, with an eye towards utilizing these materials as part of a post-combustion carbon capture process at large flue gas producing installations, such as coal-fired electricity-generating power plants. In this Application Article, the utilization of amine-modified organic–inorganic hybrid materials is discussed, focusing on important attributes of the materials, such as (i) CO2 adsorption capacities, (ii) adsorption and desorption kinetics, and (iii) material stability, that will determine if these materials may one day be useful adsorbents in practical CO2 capture applications. Specific research needs and limitations associated with the current body of work are identified.

A number of derivatives of the hitherto unreportedpyrrolo[3,2-f ]quinolin-7-one tricyclic system have beensynthesised from 6-nitroquinolone by successive reduction,tosylation, methylation, detosylation, prop-2-ynylation andtreatment with m -chloroperoxybenzoic acid.

In this work we have investigated hydration properties of aqueous solutions up to a solute molar fraction X2 = 0.125 of two isosteric molecules – the bioprotectant trimethylamine-N-oxide (TMAO) and the denaturant tert-butyl alcohol (TBA) – using molecular dynamics simulation at 298 K. Statistical analyses of the trajectories show in particular that as the solute concentration increases the number of the water molecules in the first hydration shell decreases uniformly for TMAO, while for TBA it decreases more rapidly in a concentration range where experiments indicate that TBA starts to self-aggregate. No appreciable solute segregation occurs for TMAO even in the most concentrated solution, where on the average each water molecule is shared by two solutes. This result parallels what has been recently found for glycine betaine, an organic osmolyte closely related to TMAO.

Treatment of a dilute solution of 4-[N-methylanilino]but-2-yn-1-ol 1 with MCPBA in chloroform/dichloromethane/benzene gives a symmetrical ten-membered cyclic bisether 5 containing two indole moieties in 56% yield.

Two separate potentiometric titrations are used to quantify mixtures of long chain tertiary amine oxide and tertiary amine as their cations. A direct titration of the mixture in water at pH 2 against a standard sodium lauryl sulfate solution, using a poly(vinyl chloride) membrane sensing electrode, determines the total surfactant content, reported as % m/m tertiary amine oxide. A simple extraction is used to separate the tertiary amine, which is subsequently titrated under the same conditions. This titration is quantitative for dimethylalkylamine oxides and their corresponding amines (where alkyl = C10–C16). Seven analyses are performed on an aqueous mixture and give the following results: tertiary amine oxide, 23.8 ± 0.1% m/m and tertiary amine, 1.0 ± 0.1% m/m, at a 95% confidence level. This method is capable of determining tertiary amine at 0.1% m/m in the presence of 25% m/m tertiary amine oxide with no interference. The same aqueous mixture is spiked with tertiary amine to test the quantitative recovery of the amine. The recovery is 3.1% m/m compared with an expected value of 3.2% m/m amine.

A number of hitherto unreported pyrrolocoumarin derivatives 7a–h, a new tricyclic system, have been synthesised from 6-aminocoumarin 1 by successive tosylation, methylation, detosylation, prop-2-ynylation and treatment with m-chloroperoxybenzoic acid. Compounds 7a–h have been converted into methoxy derivatives 8a–h by simple treatment with methanol.

Pyrolysis of protopine N-oxide (6) leads to the dibenzoxazacycloundecine (7) whose reduction with palladium catalyst affords (±)-corydalisol (2). Alternatively, zinc in acetic acid treatment of (7) leads to (±)-hypecorine (3) and (±)-corydalisol (2).

The infrared spectra have been recorded, in the region 1200–200 cm.–1, for trimethylamine oxide and trimethylphosphine oxide complexes of the types (i) ML2X2, where X = Cl, Br, or l, and M = Co or Zn, and (ii) SnL2X4, where X = F, Cl, Br, or l. Assignments have been made for ν(N–O), ν(P–O), ν(M–O), and ν(M–X) stretching frequencies. These data are discussed in relation to the stereochemistry of the complexes and the relative bonding properties of the amine oxide and phosphine oxide and other oxo-ligands. The relatively high ν(M–O) values of 575–520 cm.–1 which have been assigned for the amine oxide complexes indicate that this ligand is a stronger donor than both trimethylphosphine oxide [with ν(M–O) at 470–400 cm.–1] and pyridine N-oxide [with ν(M–O) at 450–300 cm.–1].

A variety of organoheteroatom oxides such as sulphoxides, sulphones, N-oxides, a phosphine oxide, and an organo tin oxide were rapidly deoxygenated at room temperature by using a stoicheiometric amount of SmI2 in tetrahydrofuran–hexamethylphosphoric triamide.

Chlorine has been substituted at the 2- and 4-positions in the pyridine and quinoline rings of the corresponding N-oxides and 35Cl n.q.r. spectra have been studied in the temperature range 77–300 K. The change in the n.q.r. frequencies in N-oxides as compared to their parent compounds are interpreted in terms of the conjugative effect and the inductive effect of the N+—O– group. The negative temperature coefficients of the resonance frequencies in chloropyridine-N-oxides have been analysed using the Bayer, Kushida and Brown equations. The calculated torsional frequencies, which are in the range 52–78 cm–1, are found to be only slightly temperature dependent.

The rate of rearrangement of N-arylamine oxides (4) to O-arylhydroxylamines (5) was measured in different solvents. The rate of isomerisation of p-nitrophenyl N-oxides correlates with the dielectric constants of aprotic solvents and with the hydrogen-bonding ability of protic solvents. The rearrangement of o-nitrophenyl N-oxides shows much less variation in rate with solvent polarity. All kinetic results are explained in terms of an intramolecular cyclic mechanism (SNi).

The temperature dependence of the primary deuterium kinetic isotope effect has been applied as a criterion of transition state (TS‡) structure in the syn-elimination reaction of bicyclo [2.2.1]heptan-2-exo-yl toluene-p-sulphonate, caused by two different hindered bases in a low dielectric, aprotic solvent. The isotope effect (kH/kD= 3.43 ± 0.02) was temperature independent, and identical for the two bases used (t-butoxide and cyclohexylcyclohexyl oxide). These results are interpreted to indicate a non-planar, cyclic TS‡ involving non-linear hydrogen transfer. A comparison with the analogous Hofmann and amine oxide elimination reactions affords some understanding of the factors controlling TS‡ structure in cyclic syn-elimination processes.

Siloxyammonium salts prepared from tertiary amine N-oxides and trialkylsilyl trifluoromethanesulphonate undergo rearrangement in the presence of strong bases to give α-siloxyamines, which can be converted into secondary amine derivatives.

Bases with four N or NO acceptor groups have been studied by infrared spectroscopy as free bases and H+ or Li+ monosalts in solution. The following compounds were investigated: 1,2-bis[2,2-bis(2-pyridyl)ethyl]benzene (compound 1) as HAuCl4 and LiClO4 monosalts, 1,2-bis[2,2-bis(dimethylamino)ethyl]benzene (compound 2) as LiClO4 monosalt and 1,2-bis[2,2-bis(2-pyridyl)ethyl]benzene tetra-N-oxide (compound 3) as LiClO4 monosalt.The proton fluctuates between the four N acceptors of the HAuCl4 monosalts of compound 1 and this motion causes large proton polarizability. All the N acceptors are influenced by the proton to the same extent. In the case of the LiClO4 monosalts of compounds 2 and 3, the Li+ ion fluctuates between the four NO acceptors causing large Li+ polarizability. In the case of the LiClO4 monosalt of compound 1 the Li+ ion fluctuates only between two N acceptors.

The N-oxides of N-(2,4-dinitrophenyl)-piperidines and -morpholine undergo thermal rearrangement to the substituted hydroxylamines. The kinetics of the rearrangement were studied in aprotic solvents at four or five temperatures. Steric and polar factors have great influence on the rate of rearrangement. The kinetic results together with cross-over experiments are in full agreement with an intramolecular cyclic mechanism (SNi).

Tertiary amines are catalytically oxidized with molecular oxygen in homogeneous solutions containing RuCl3·xH2O to afford as a major product the corresponding N-oxide, the first example of such an oxidation.

meta-Chloroperbenzoic acid rapidly oxidizes ethylenediaminetetra-acetic acid to the N,N′-dioxide which suppresses the CuII catalysed m-chloroperbenzoic acid oxidation of amaranth [trisodium 1-(4-sulpho-1-naphthylazo)-2-naphthol-3,6-disulphonate] by scavenging free radical chain propagating species.

1-Phenoxy-4-tetrahydroquinolybut-2-yne on treatment with m-chloroperbenzoic acid rearranges to give 5,5′,6,6′-tetrahydro-2,2′-diphenoxymethyl-1,1′-methylenebis(4H-pyrrolo[3,2,1-ij]quinoline).

Transfer of chirality of tetraco-ordinate nitrogen to carbon atom occurred in the thermal sigmatropic rearrangement of (+)-N-trans-but-2-enyl-N-ethyl-p-toluidine oxide to (+)-O-1-methylprop-2-enyl-N-ethyl-p-tolylhydroxylamine, whose absolute configuration was correlated with (S)-(+)-butan-2-ol.

3,4-Dimethoxy-NN-dimethylphenethylamine N-oxide reacts with iron(II) ion to give the corresponding tertiary amine, the demethylated secondary amine, and 1,2,3,4-tetrahydro-6,7-dimethoxy-2-methylisoquinoline in relative amounts which depend, in a way which has been rationalised, upon the reaction temperature and time, the presence of a base, and the concentration of iron(II).

The [2,3]-sigmatropic rearrangement of (R)-NN-dimethyl-3-(1-phenyl-phenyl-trans-but-1-enyl)amine oxide to give (S)-O-trans-1-phenyl-but-2-enyl-NN-dimethylhydroxyl-amine was effected thermally with nearly complete transfer of chirality from tetramally carbon to trigonal carbon via a cyclic half-chair transition state conformation.

Pyridine, γ-picoline, pyridine, N-oxide, and γ-picoline N-oxide complexes of manganese(II), cobalt(II), nickel(II), copper(II), and zinc(II) halogenoacetates have been prepared and characterised by vibrational and electronic spectroscopy and magnetic susceptibility measurements. The complexes prepared were of the type M(amine)4-(halogenoacetate)2, M(amine)2(halogenoacetate)2, M(amine oxide)2(halogenoacetate)2, and M(amine oxide)-(halogenoacetate)2.