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Ion Pairing (ion + pairing)

Distribution by Scientific Domains

Chemistry	95%

Selected Abstracts

Diffusion and NOE NMR Studies on Multicationic DAB-Organoruthenium Dendrimers: Size-Dependent Noncovalent Self-Assembly to Megamers and Ion Pairing,

CHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2009
Stefania Pettirossi Dr.
Abstract Supra-mega ion pairing: Multicationic organoruthenium dendrimers show a notable tendency to self-aggregate when the concentration is increased, leading to megamers. This tendency increases with the generation. The self-aggregation of dendrimers to megamers is coupled with a decrease in the extent of ion pairing, as illustrated. New multicationic organoruthenium dendrimers (RuPF6 -Dabn, n=2, 4, 8, 16) have been synthesized by coupling of [Ru(,6 - p -cymene)(,3 -dpk-OCH2CH2OH)]X (1PF6, dpk=2,2,-dipyridyl ketone, X=PF6) with 1,4-diaminobutane (DAB) and polypropylenimine dendrimer DAB- dendr -(NH2)n {n=4, 8, 16} mediated by 1,1,-carbonyldiimidazole (CDI). The intermediate in the synthesis, [Ru(,6 - p -cymene)(,3 -dpk-OCH2CH2OC(O)Im]X (2PF6, Im=imidazole, X=PF6) has been isolated and characterized by single-crystal XRD. The intra- and supramolecular structures in a solution of RuPF6 -Dabn dendrimer have been investigated by multidimensional and multinuclear NMR techniques. Diffusion NMR experiments on dilute solutions indicated that the linear distance between two metal centers (14.9,22.1,Å depending on the dendrimer generation) is much greater than the diameter of 1PF6 (9.9,Å). 19F,1H-HOESY NMR experiments (HOESY= heteronuclear Overhauser effect spectroscopy) showed that the counterion is positioned on the surface of the dendrimers and assumes the same relative anion,cation orientation as in 2PF6. Diffusion NMR experiments on RuPF6 -Dabn dendrimers in CD2Cl2 at different concentrations revealed a process of supramolecular assembly of dendrimers to megamers that is strongly favored for the highest generations. Megamer formation is coupled with an increased fraction of free ions (,) and a consequent reduction in ion-paired ruthenium centers. Graphs of , versus CRu (the concentration of ruthenium centers) showed a minimum for RuPF6 -Dab4, RuPF6 -Dab8, and RuPF6 -Dab16 at a position coinciding with the significant presence of supramolecular dendritic dimers. The tendency to ion pairing decreases as the dendrimer generation increases. [source]

Four Generations of Water-Soluble Dendrimers with 9 to 243 Benzoate Tethers: Synthesis and Dendritic Effects on Their Ion Pairing with Acetylcholine, Benzyltriethylammonium, and Dopamine in Water

CHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2008
Elodie Boisselier
Abstract Water-soluble benzoate-terminated dendrimers of four generations (from G0 with 9 branches to G3 with 243 branches) were synthesized and fully characterized. They form water-soluble assemblies by ion-pairing interactions with three cations of medicinal interest (acetylcoline, benzyltriethylammonium, and dopamine), which were characterized and investigated by 1H,NMR spectroscopy, whereas such interactions do not provoke any significant shift of 1H,NMR signals with the monomeric benzoate anion. The calculated association constants confirm that the dendritic carboxylate termini reversibly form ion pairs and aggregates. Diffusion coefficients and hydrodynamic diameters of the dendrimers, as well as changes thereof on interaction with the cations, were evaluated by DOSY experiments. The lack of increase of dendrimer size on addition of the cations and the upfield shifts of the 1H,NMR signals of the cation indicate encapsulation within the hydrophobic dendrimer interiors together with probable backfolding of the benzoate termini. [source]

7Li, 31P, and 1H Pulsed Gradient Spin-Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh3), Fluorenyllithium, and Li[N(SiMe3)2] amongst Other Salts

CHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2005
Ignacio Fernández
Abstract 7Li, 31P, and 1H variable-temperature pulsed gradient spin-echo (PGSE) diffusion methods have been used to study ion pairing and aggregation states for a range of lithium salts such as lithium halides, lithium carbanions, and a lithium amide in THF solutions. For trityllithium (2) and fluorenyllithium (9), it is shown that ion pairing is favored at 299 K but the ions are well separated at 155 K. For 2-lithio-1,3-dithiane (13) and lithium hexamethyldisilazane (LiHMDS 16), low-temperature data show that the ions remain together. For the dithio anion 13, a mononuclear species has been established, whereas for the lithium amide 16, the PGSE results allow two different aggregation states to be readily recognized. For the lithium halides LiX (X = Br, Cl, I) in THF, the 7Li PGSE data show that all three salts can be described as well-separated ions at ambient temperature. The solid state structure of trityllithium (2) is described and reveals a solvent-separated ion pair formed by a [Li(thf)4]+ ion and a bare triphenylmethide anion. [source]

The Role of Ion Pairs in the Second-Order NLO Response of 4-X-1-Methylpiridinium Salts,

CHEMPHYSCHEM, Issue 2 2010
Francesca Tessore Dr.
Abstract A series of 4-X-1-methylpyridinium cationic nonlinear optical (NLO) chromophores (X=(E)-CHCHC6H5; (E)-CHCHC6H4 -4,-C(CH3)3; (E)-CHCHC6H4 -4,-N(CH3)2; (E)-CHCHC6H4 -4,-N(C4H9)2; (E,E)-(CHCH)2C6H4 -4,-N(CH3)2) with various organic (CF3SO3,, p -CH3C6H4SO3,), inorganic (I,, ClO4,, SCN,, [Hg2I6]2,) and organometallic (cis -[Ir(CO)2I2],) counter anions are studied with the aim of investigating the role of ion pairing and of ionic dissociation or aggregation of ion pairs in controlling their second-order NLO response in anhydrous chloroform solution. The combined use of electronic absorption spectra, conductimetric measurements and pulsed field gradient spin echo (PGSE) NMR experiments show that the second-order NLO response, investigated by the electric-field-induced second harmonic generation (EFISH) technique, of the salts of the cationic NLO chromophores strongly depends upon the nature of the counter anion and concentration. The ion pairs are the major species at concentration around 10,3,M, and their dipole moments were determined. Generally, below 5×10,4,M, ion pairs start to dissociate into ions with parallel increase of the second-order NLO response, due to the increased concentration of purely cationic NLO chromophores with improved NLO response. At concentration higher than 10,3,M, some multipolar aggregates, probably of H type, are formed, with parallel slight decrease of the second-order NLO response. Ion pairing is dependent upon the nature of the counter anion and on the electronic structure of the cationic NLO chromophore. It is very strong for the thiocyanate anion in particular and, albeit to a lesser extent, for the sulfonated anions. The latter show increased tendency to self-aggregate. [source]

Comparison of methanol and acetonitrile as solvents for the separation of sertindole and its major metabolites by capillary zone electrophoresis

ELECTROPHORESIS, Issue 17 2005
Xavier Subirats
Abstract Sertindole (1-[2-[4-[5-chloro-1-(4-fluorophenyl)-1H -indol-3-yl]-1-piperidinyl]ethyl]-2-imidazolidinone), an atypical antipsychotic drug, was separated by capillary electrophoresis from its two main metabolites norsertindole and dehydrosertindole. The low solubility of the analytes in water (octanol-water partition coefficient is about 105) is overcome by the use of methanol (MeOH) and acetonitrile (ACN) as solvents for the background electrolyte (BGE). Mobilities were measured in BGEs with defined pH in a broad range. It was found that in MeOH the mobility of the analytes is mainly governed by acid,base equilibria, whereas in ACN other reactions like ion pairing and homoconjugation play a pronounced role and lead to a complex pattern of the mobility as function of the pH. However, separation can be obtained in less than 10,min in both solvent systems. [source]

Roles of adenine anchoring and ion pairing at the coenzyme B12 -binding site in diol dehydratase catalysis

FEBS JOURNAL, Issue 24 2008
Ken-ichi Ogura
The X-ray structure of the diol dehydratase,adeninylpentylcobalamin complex revealed that the adenine moiety of adenosylcobalamin is anchored in the adenine-binding pocket of the enzyme by hydrogen bonding of N3 with the side chain OH group of Ser,224, and of 6-NH2, N1 and N7 with main chain amide groups of other residues. A salt bridge is formed between the ,-NH2 group of Lys,135 and the phosphate group of cobalamin. To assess the importance of adenine anchoring and ion pairing, Ser,224 and Lys,135 mutants of diol dehydratase were prepared, and their catalytic properties investigated. The S,224A, S,224N and K,135E mutants were 19,2% as active as the wild-type enzyme, whereas the K,135A, K,135Q and K,135R mutants retained 58,76% of the wild-type activity. The presence of a positive charge at the ,135 residue increased the affinity for cobalamins but was not essential for catalysis, and the introduction of a negative charge there prevented the enzyme,cobalamin interaction. The S,224A and S,224N mutants showed a kcat/kinact value that was less than 2% that of the wild-type, whereas for Lys,135 mutants this value was in the range 25,75%, except for the K,135E mutant (7%). Unlike the wild-type holoenzyme, the S,224N and S,224A holoenzymes showed very low susceptibility to oxygen in the absence of substrate. These findings suggest that Ser,224 is important for cobalt,carbon bond activation and for preventing the enzyme from being inactivated. Upon inactivation of the S,224A holoenzyme during catalysis, cob(II)alamin accumulated, and a trace of doublet signal due to an organic radical disappeared in EPR. 5,-Deoxyadenosine was formed from the adenosyl group, and the apoenzyme itself was not damaged. This inactivation was thus considered to be a mechanism-based one. [source]

Refined electrolyte-NRTL model: Activity coefficient expressions for application to multi-electrolyte systems,

AICHE JOURNAL, Issue 6 2008
G. M. Bollas
Abstract The influence of simplifying assumptions of the electrolyte-nonrandom two-liquid (NRTL) model in the derivation of activity coefficient expressions as applied to multi-electrolyte systems is critically examined. A rigorous and thermodynamically consistent formulation for the activity coefficients is developed, in which the simplifying assumption of holding ionic-charge fraction quantities constant in the derivation of activity coefficient expressions is removed. The refined activity coefficient formulation possesses stronger theoretical properties and practical superiority that is demonstrated through a case study representing the thermodynamic properties and speciation of dilute to concentrated aqueous sulfuric acid solutions at ambient conditions. In this case study phenomena, such as hydration, ion pairing, and partial dissociation are all taken into account. The overall result of this study is a consistent, analytically derived, short-range interaction contribution formulation for the electrolyte-NRTL activity coefficients and a very accurate representation of aqueous sulfuric acid solutions at ambient conditions at concentrations up to 50 molal. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source]

Hydrophobic ion pairing of isoniazid using a prodrug approach

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2002
Huiyu Zhou
Abstract Inhalation therapy for infectious lung diseases, such as tuberculosis, is currently being explored, with microspheres being used to target alveolar macrophages. One method of drug encapsulation into polymeric microspheres to form hydrophobic ion-paired (HIP) complexes, and then coprecipitate the complex and polymer using supercritical fluid methodology. For the potent antituberculosis drug, isoniazid (isonicotinic acid hydrazide, INH), to be used in this fashion, it was modified into an ionizable form suitable for HIP. The charged prodrug, sodium isoniazid methanesulfonate (Na,INHMS), was then ion paired with hydrophobic cations, such as alkyltrimethylammonium or tetraalkylammonium. The logarithms of the apparent partition coefficients (log P,) of various HIP complexes of INHMS display a roughly linear relationship with the numbers of carbon atoms in the organic counterions. The water solubility of the tetraheptylammonium,INHMS complex is about 220-fold lower than that of Na,INHMS, while the solubility in dichloromethane exceeds 10 mg/mL, which is sufficient for microencapsulation of the drug into poly(lactide) microspheres. The actual logarithm of the dichloromethane/water partition coefficient (log P) for tetraheptylammonium,INHMS is 1.55, compared to a value of ,,1.8 for the sodium salt of INHMS. The dissolution kinetics of the tetraheptylammonium,INHMS complex in 0.9% aqueous solutions of NaCl was also investigated. Dissolution of tetraheptylammonium,INHMS exhibited a first-order time constant of about 0.28 min,1, followed by a slower reverse ion exchange process to form Na,INHMS. The half-life of this HIP complex is on the order of 30 min, making the enhanced transport of the drug across biological barriers possible. This work represents the first use of a prodrug approach to introduce functionality that would allow HIP complex formation for a neutral molecule. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:1502,1511, 2002 [source]

Recognition of protonated aliphatic ,,,-diamines by coproporphyrin I tetraanion in water

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2002
Alejandro Flores-Villalobos
Abstract Interactions of aliphatic ,,,-diamines [H2N(CH2)nNH2, 2,,,n,,,8] with coproporphyrin I tetraanion (CP) were studied by spectrophotometry, fluorimetry and 1H NMR spectroscopy in the pH range 7,10 and ionic strengths 0.01,0.1,M. Diprotonated diammonium cations induce dimerization of CP by forming 1:1 complexes with CP which undergo much stronger self-aggregation than free CP tetraanions. On increasing the number of methylene units n connecting the ammonium groups, the binding constants for the complex formation with monomeric CP (KL) increase but the dimerization constants of the resulting complexes decrease. A hydrophobic contribution to the binding free energy of ,1.6,±,0.2,kJ,mol,1 per methylene unit was obtained from the linear correlation of logKL values extrapolated to zero ionic strength vs the number of methylene units (n,=,2,6). A model for diammonium-induced porphyrin dimerization is proposed, which involves complexation of diammonium cations with CP monomer via a combination of electrostatic and hydrophobic interactions and subsequent formation of porphyrin face-to-face dimers in which diammonium cations serve as the stabilizing bridges via ion pairing to carboxylate groups of two CP monomeric units. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Evaluation of mobile phase, ion pairing, and temperature influence on an HILIC-MS/MS method for L -arginine and its dimethylated derivatives detection

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2008
Giuseppe Paglia
Abstract Asymmetric NG,,NG -dimethylarginine (ADMA) increases in diseases such as renal failure, diabetes mellitus, and hypercholesterolemia. The feasibility and utility of a hydrophilic interaction chromatography (HILIC) method for the separation of free L -arginine (Arg), ADMA, and symmetric NG,,NG, -dimethylarginine (SDMA) on a typical silica column were explored and the impact of some experimental parameters on the chromatographic behavior of these analytes was investigated. The effect of water and TFA content in mobile phase and of column temperature was investigated during the development of a fast and simple HILIC-MS/MS method that might be suitable for the quantification of free Arg, ADMA, and SDMA in plasma for routine analysis. Our results show that a good compromise between efficiency and peak shape with acceptable retention and total chromatographic run time is achieved using an ACN/water (90:10) mobile phase with TFA% as additive ranging from 0.015 to 0.025% and column temperature ranging from 25 to 30°C. [source]

Direct determination of phosphorylated intracellular anabolites of stavudine (d4T) by liquid chromatography/tandem mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2001
Alain Pruvost
The objective was to develop and validate a routine assay for active intracellular anabolites of stavudine (d4T), a nucleoside reverse transcriptase inhibitor in human PBMC, applicable to pharmacokinetic studies and treatment monitoring. This was achieved using liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS), which theoretically allies optimum sensitivity, specificity and high sample throughput. After cellular lysis in a Tris/methanol buffer, the extract spiked with 2[H8]-ATP (internal standard) is directly injected into the LC/MS/MS system. Phosphorylated metabolites of d4T as well as deoxythymidine-triphosphate, the competitor on the reverse transcriptase, are separated from d4T on a reverse-phase microbore column with ion pairing. The detection is performed in the multiple reaction monitoring (MRM) mode after drug ionisation in negative mode electrospray. The limit of quantitation for d4T-TP was 138 fmol per 7,mL blood (9.8 fmol per 106 cells) and CV% for repeatability and intermediate precision were lower than 15%. Stability of compounds was checked before and during the process of isolation of PBMC. Cellular samples from several d4T-treated patients were successfully analysed using this method and d4T-triphosphate and deoxythymidine triphosphate were recovered. In conclusion, we have developed and validated a routine LC/MS/MS method that allows the simultaneous determination of mono-, di- and triphosphorylated anabolites of d4T in PBMC as well as the natural corresponding triphosphate in one analysis. For the first time, the chain terminator ratio (d4T-TP/dT-TP) could be directly measured. This method can be used simply and routinely on more than 35 samples per day. Extension to other nucleoside analogues is under development. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Separation of amino acids, their derivatives and enantiomers by impregnated TLC

BIOMEDICAL CHROMATOGRAPHY, Issue 3 2001
R. Bhushan
The present state of TLC with respect to separation of amino acids, their different derivatives and their enantiomers by the technique of impregnation is discussed. The main approaches to impregnation viz. mixing of a suitable reagent with the adsorbent prior to plate-making, immersion of the untreated plate in the solution of impregnating reagent prior to development, and modification of the adsorbent, have been identified and discussed for each class of these compounds. The role of impregnation in resolving enantiomers or in improving the separation of mixtures of amino acids or their derivatives in terms of ion pairing, complex formation, ligand exchange or other steric interactions has been elaborated in each category. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Cyclometalated IrIII Complexes with Substituted 1,10-Phenanthrolines: A New Class of Efficient Cationic Organometallic Second-Order NLO Chromophores

CHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2010
Adriana Valore Dr.
Abstract Cyclometalated cationic IrIII complexes with substituted 1,10-phenanthrolines (1,10-phen), such as [Ir(ppy)2(5-R-1,10-phen)]Y (ppy=cyclometalated 2-phenylpyridine; R=NO2, H, Me, NMe2; Y,=PF6,, C12H25SO3,, I,) and [Ir(ppy)2(4-R,7-R-1,10-phen)]Y (R=Me, Ph) are characterized by a significant second-order optical non linearity (measured by the electrical field induced second harmonic generation (EFISH) technique). This nonlinearity is controlled by MLCT processes from the cyclometalated IrIII, acting as a donor push system, to ,* orbitals of the phenanthroline, acting as an acceptor pull system. Substitution of cyclometalated 2-phenylpyridine by the more , delocalized 2-phenylquinoline (pq) or benzo[h]quinoline (bzq) or by the sulfur-containing 4,5-diphenyl-2-methyl-thiazole (dpmf) does not significantly affect the ,, absolute value, which instead is affected by the nature of the R substituents on the phenanthroline, the higher value being associated with the electron-withdrawing NO2 group. By using a combined experimental (the EFISH technique and 1H and 19F PGSE NMR spectroscopy) and theoretical (DFT, time-dependent-DFT (TDDFT), sum over states (SOS) approach) investigation, evidence is obtained that ion pairing, which is controlled by the nature of the counterion and by the concentration, may significantly affect the ,, values of these cationic NLO chromophores. In CH2Cl2, concentration-dependent high absolute values of ,, are obtained for [Ir(ppy)2(5-NO2 -1,10-phen)]Y if Y is a weakly interacting anion, such as PF6,, whereas with a counterion, such as C12H25SO3, or I,, which form tight ion-pairs, the absolute value of ,, is lower and quite independent of the concentration. This ,, trend is partially due to the perturbation of the counterion on the LUMO ,* levels of the phenanthroline. The correlation between the ,, value and dilution shows that the effect of concentration is a factor that must be taken into careful consideration. [source]

The Role of Solvent on the Mechanism of Proton Transfer to Hydride Complexes: The Case of the [W3PdS4H3(dmpe)3(CO)]+ Cubane Cluster

CHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2010
Andrés
Abstract The kinetics of reaction of the [W3PdS4H3(dmpe)3(CO)]+ hydride cluster (1+) with HCl has been measured in dichloromethane, and a second-order dependence with respect to the acid is found for the initial step. In the presence of added BF4, the second-order dependence is maintained, but there is a deceleration that becomes more evident as the acid concentration increases. DFT calculations indicate that these results can be rationalized on the basis of the mechanism previously proposed for the same reaction of the closely related [W3S4H3(dmpe)3]+ cluster, which involves parallel first- and second-order pathways in which the coordinated hydride interacts with one and two acid molecules, and ion pairing to BF4, hinders formation of dihydrogen bonded adducts able to evolve to the products of proton transfer. Additional DFT calculations are reported to understand the behavior of the cluster in neat acetonitrile and acetonitrile,water mixtures. The interaction of the HCl molecule with CH3CN is stronger than the WH,,,HCl dihydrogen bond and so the reaction pathways operating in dichloromethane become inefficient, in agreement with the lack of reaction between 1+ and HCl in neat acetonitrile. However, the attacking species in acetonitrile,water mixtures is the solvated proton, and DFT calculations indicate that the reaction can then go through pathways involving solvent attack to the W centers, while still maintaining the coordinated hydride, which is made possible by the capability of the cluster to undergo structural changes in its core. [source]

Diffusion and NOE NMR Studies on Multicationic DAB-Organoruthenium Dendrimers: Size-Dependent Noncovalent Self-Assembly to Megamers and Ion Pairing,

Anion,, Slides for Transmembrane Transport

CHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2009
Jiri Mareda Dr.
Abstract The recognition and transport of anions is usually accomplished by hydrogen bonding, ion pairing, metal coordination, and anion,dipole interactions. Here, we elaborate on the concept to use anion,, interactions for this purpose. Different to the popular cation,, interactions, applications of the complementary ,-acidic surfaces do not exist. This is understandable because the inversion of the aromatic quadrupole moment to produce ,-acidity is a rare phenomenon. Here, we suggest that ,-acidic aromatics can be linked together to produce an unbendable scaffold with multiple binding sites for anions to move along across a lipid bilayer membrane. The alignment of multiple anion,, sites is needed to introduce a cooperative multi-ion hopping mechanism. Experimental support for the validity of the concept comes from preliminary results with oligonaphthalenediimide (O-NDI) rods. Predicted by strongly positive facial quadrupole moments, the cooperativity and chloride selectivity found for anion transport by O-NDI rods were consistent with the existence of anion,, slides. The proposed mechanism for anion transport is supported by DFT results for model systems, as well as MD simulations of rigid O-NDI rods. Applicability of anion,, slides to achieve electroneutral photosynthesis is elaborated with the readily colorizable oligoperylenediimide (O-PDI) rods. To clarify validity, scope and limitations of these concepts, a collaborative research effort will be needed to address by computer modeling and experimental observations the basic questions in simple model systems and to design advanced multifunctional anion,, architectures. [source]

7Li, 31P, and 1H Pulsed Gradient Spin-Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh3), Fluorenyllithium, and Li[N(SiMe3)2] amongst Other Salts

The Role of Ion Pairs in the Second-Order NLO Response of 4-X-1-Methylpiridinium Salts,

Chiral NMR discrimination of amines: Analysis of secondary, tertiary, and prochiral amines using (18-crown-6)-2,3,11,12-tetracarboxylic acid,

CHIRALITY, Issue 3-4 2008
Ann E. Lovely
Abstract Enantiomeric discrimination is observed in the 1H and 13C NMR spectra of secondary and tertiary amines in the presence of (,)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (1). Nonequivalence of the resonances of prochiral nuclei in primary and secondary amines is also observed when they associate with 1. The amines are added in their neutral form and are protonated by the carboxylic acid groups of 1 to produce the corresponding ammonium and carboxylate ions. Secondary amines associate with 1 through two hydrogen bonds and an ion pair interaction. Tertiary amines can only form one hydrogen bond to accompany the ion pairing. Chiral discrimination in the 1H and 13C NMR spectra of a series of aryl-containing secondary amines is of sufficient magnitude to determine enantiomeric purities. The discrimination in the spectra of tertiary amines with 1 is smaller, but 13C NMR spectra provided enough distinction for the determination of enantiomeric purity. Chirality, 2008. © 2007 Wiley-Liss, Inc. [source]