56-93-9Relevant articles and documents
Shape-Selective Recognition of Quaternary Ammonium Chloride Ion Pairs
Li, Dong-Hao,Smith, Bradley D.
, p. 2808 - 2816 (2019/03/26)
Synthetic receptors that recognize ion pairs are potentially useful for many technical applications, but to date there has been little work on selective recognition of quaternary ammonium (Q+) ion pairs. This study measured the affinity of a tetralactam macrocycle for 11 different Q+·Cl- salts in chloroform solution. In each case, NMR spectroscopy was used to determine the association constant (Ka) and the structure of the associated complex. Ka was found to depend strongly on the molecular shape of Q+ and was enhanced when Q+ could penetrate the macrocycle cavity and engage in attractive noncovalent interactions with the macrocycle's NH residues and aromatic sidewalls. The highest measured Ka of 7.9 × 103 M-1 was obtained when Q+ was a p-CN-substituted benzylic trimethylammonium. This high-affinity Q+·Cl- ion pair was used as a template to enhance the synthetic yield of macrocyclization reactions that produce the tetralactam receptor or structurally related derivatives. In addition, a permanently interlocked rotaxane was prepared by capping the end of a noncovalent complex composed of the tetralactam macrocycle threaded by a reactive benzylic cation. The synthetic method provides access to a new family of rotaxanated ion pairs that can likely act as anion sensors, molecular shuttles, or transport molecules.
A comparative study of side-chain-type poly(ether ether ketone) anion exchange membrane functionalized with different hetero-cycloaliphatic quaternary ammonium groups
Yao, Dan,Wei, Tonghui,Shang, Lichao,Na, Hui,Zhao, Chengji
, p. 7975 - 7983 (2019/03/19)
Anion exchange membranes based on side-chain-type quarternized poly(ether ether ketone)s (QPEEKs), containing different hetero-cycloaliphatic quaternary ammonium groups, were prepared via a multi-step procedure, including polycondensation with a monomer containing pendant methylphenyl groups, bromomethylation, and followed by quaternization with 1-methylpyrrolidine (MPY), 1-methylpiperidine (MPRD), 1-methylimidazole (MIDZ) and N-methyl morpholine (MMPH), respectively. The properties of these membranes were then compared with the properties of conventional quarternized poly(ether ether ketone)s containing benzyltrimethylammonium (QPEEK-TMA). Model compounds, QMPY, QMPRD, QMIDZ and QMMPH, were synthesized and used to quantitatively compare the alkaline stability of hetero-cycloaliphatic quaternary ammonium groups using 1H NMR. The results of this study indicated that the alkaline stability of all these model compounds is in the order of QMPY > QMPRD > QTMA > QMIDZ > QMMPH. These QPEEKs membranes display superior thermal, dimensional and mechanical stability. QPEEK-TMA, QPEEK-MPY and QPEEK-MPRD exhibit higher hydroxide conductivities and lower activation energies than QPEEK-MIDZ and QPEEK-MMPH. Furthermore, after exposure to 1 M NaOH at 60 °C for 24 days, QPEEK-MPY and QPEEK-MPRD demonstrated a loss in hydroxide conductivity of 28.5% and 33.4%, respectively. Both values were lower than that of QPEEK-TMA (37.7%). Therefore, among these side-chain-type QPEEKs membranes, QPEEK-MPY and QPEEK-MPRD, containing benzylmethylpyrrolidinium and benzylmethylpiperidinium as cation head-groups, are promising AEM materials for fuel cell construction.
Selective monomethylation of primary amines with simple electrophiles
Lebleu, Thomas,Ma, Xiaolu,Maddaluno, Jacques,Legros, Julien
supporting information, p. 1836 - 1838 (2014/02/14)
Direct monomethylation of primary amines with methyl triflate was achieved with high selectivity (up to 96%). The key point of this single methyl transfer stems from the use of HFIP as the solvent that interferes with amines and avoids overmethylation.
Alkylation of ammonium salts catalyzed by imidazolium-based ionic liquid catalysts
Zheng, Zhuo Qun,Wang, Jie,Wu, Ting Hua,Zhou, Xiao Ping
, p. 1095 - 1101 (2008/03/27)
Quaternary ammonium salts were synthesized from ammonium salts and dialkyl carbonates over imidazolium ionic liquid catalysts. The reaction gave almost stoichiometric amounts of the quaternary ammonium salts for halides and nitrates. It was found that the electron-donating property of the alkyl moieties of ammonium cations, the electrophilic nature of the alkyl group of the carbonate, the acidity of the acid that the anion of the ammonium salt corresponds to, and the steric hindrance of the ammonium salts and the dialkyl carbonates are the key factors that influence the yields of quaternary ammonium salts. Strong electron-donating alkyl groups on the nitrogen atom of the ammonium salt, electron-withdrawing groups on the methylene carbon of dialkyl carbonate, and weaker steric hindrance of the starting ammonium salts and dialkyl carbonates favor the alkylation reaction of ammonium salts.
Structure and Stability of Quaternary Ammonium Interhalides: Experimental and Quantum-Chemical Study
Simonyan,Kletskii,Chernov'yants,Gol'eva
, p. 575 - 582 (2007/10/03)
The electronic structure of a series of ammonium interhalides [R 1R2R3R4N]XI2, where R1 = CH3, C2H5, C3H 7, F, H; R2 = R3 = R4 = CH 3, H; X = Cl, Br, I, was studied by ab initio calculations (RHF/3-21G, RHF/HW, MP2/HW). The thermodynamic stability of these compounds correlates with the strength of the hydrogen bond N-H...X and three-center interhalide bond X-I-I. Calculations confirmed that, in polar solvents, these compounds preferably decompose to [R1R2R3R 4N]+ and XI2- (with subsequent decomposition of the anion), and in nonpolar solvents, to the neutral species [R1R2R3R4N]X and I2. The calculation results were compared to the experimental data obtained by single crystal X-ray diffraction, 1H NMR spectroscopy, and spectrophotometry.
Recognition of quaternary ammonium salts with tetrapeptides containing α-aminoisobutyric acid as a conformational constraint
Yanagihara, Ryoji,Katoh, Masaki,Hanyuu, Masayuki,Miyazawa, Toshifumi,Yamada, Takashi
, p. 551 - 556 (2007/10/03)
Tetrapeptides Trp-Aib-Gly-Leu-NH-Ar (Aib:α-aminoisobutyric acid, 2-amino-2-methylpropanoic acid, Ar = phenyl or 3,5-dimethylphenyl) were synthesized. The peptides bound quaternary ammonium salts as guests in CDCl3. For every guest, the binding constant K of the peptide host which has a 3,5-dimethylphenyl group was larger than that of the host which has a phenyl group. ROESY analysis of the complex revealed that the N+-CH3 groups of the guests were close to the aromatic moieties of the host in the complex. The charge in cation guests, the φ-basicity of the host, and the turn conformation of the peptides were important factors for the complexation.
Guest - Host Interactions in As-Made Al-ZSM-12: Implications for the Synthesis of Zeolite Catalysts
Shantz, Daniel F.,Fild, Christian,Koller, Hubert,Lobo, Raul F.
, p. 10858 - 10865 (2007/10/03)
Al-ZSM-12 samples have been prepared with selectively deuterated benzyltrimethylammonium cations as structure-directing agents (SDAs) to study the motion of the SDA and the spatial relationships between the SDA and the zeolite framework. 2H NMR shows the methyl groups of the structure-directing agent undergo at least two rapid rotations while the benzyl segment is essentially immobile, undergoing only small angle wobbling motions. Cross-polarization and rotational echo double resonance NMR experiments were performed to study the spatial relationships between the SDA and the framework silicon and aluminum. The results from the CPMAS and REDOR experiments show the methylene protons of the structure-directing agent are preferentially located near the silicon atoms adjacent to the framework aluminum. As a consequence there is relative charge ordering between the SDA and the framework aluminum, suggesting that the framework aluminum is directly associated with the charge center of the SDA. Given the reduced number of configurations accessible to the SDAs in the as-made material, we believe the results suggest a possible route to tailoring the spatial arrangement of trivalent framework atoms through selection of SDAs with appropriate charge distributions.
Competing Pathways in the Azomethine Ylide Route to Indoloquinones: An Improved Procedure for the Generation of a Transient 4-Oxazoline from the Oxazolium Salt
Vedejs, Edwin,Monahan, Sean D.
, p. 4763 - 4769 (2007/10/03)
Azomethine ylide generation from the oxazolium salt 22 and PhSiH3/CsF affords complex products derived from the initial cycloadduct 23 via three competing pathways. Colorless intermediates 24-27 have been detected, and their oxidation products 10, 28, and 29 have been identified. Nucleophilic activation of the oxazolium salt 22 is reported using the organic-soluble benzyltrimethylammonium cyanide. This variation affords the unstable cycloadduct 32, which undergoes aromatization via a single pathway involving 24 and 27, and DDQ oxidation gives the indoloquinone 10 in an improved 63% yield. Lower yields using PhSiH3/CsF or NaCN activation methods are attributed to the heterogeneous conditions and interception of the azomethine ylide by unreacted oxazolium salt.
Dealkylation of Quaternary Ammonium Salts by Thiolate Anions: A Model of the Cobalamin-independent Methionine Synthase Reaction.
Hilhorst, Ellen,Chen, Tjoe B. R. A.,Iskander, Atef S.,Pandit, Upendra K.
, p. 7837 - 7848 (2007/10/02)
The reactions of thiolate ions derived from thiophenol and homocysteine with substituted quaternary ammonium salts result in alkyl transfer from nitrogen to sulfur.A radical mechanism for this transalkylation, accounts for the reactivity pattern of the substrate salts.In a model study of the cobalamin-independent methionine synthase reaction, 5,5,6,7-tetramethyl-5,6,7,8-tetrahydropteridinium salt (25), which can be considered as a model for the natural coenzyme 5-CH3H4-folate (1), was allowed to react with the thiolate of homocysteine, whereupon the formation of methionine was observed in good yield.These results suggest that in the enzymatic process the N(5)-CH3 bond may be activated for the methyl transfer step, by coordination of the N(5) with an electrophile or a proton at the active site.
Preparation of organic isocyanates
-
, (2008/06/13)
A process for the manufacture of organic isocyanates which comprises reacting a substituted urea having at least one unsubstituted NH2 group with nitrous acid in the presence of a water-immiscible solvent and a phase transfer agent.
