- Mechanism Involving Hydrogen Sulfite Ions, Chlorite Ions, and Hypochlorous Acid as Key Intermediates of the Autocatalytic Chlorine Dioxide-Thiourea Dioxide Reaction
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The kinetics of the chlorine dioxide-thiourea dioxide reaction was investigated by monitoring absorbance-time profiles at λ = 360 nm. Under acidic conditions, the primary carbon-containing product is cyanamide, not urea as considered previously for many oxidation reactions of thiourea dioxide. Increase of the rate of the reaction by an increase of pH can be readily explained by the slow pH-dependent formation of a more reactive form of thiourea dioxide (TDO) that is produced steadily and unavoidably as the stock TDO solution ages. We have also found that the absorbance-time profiles of the chlorine dioxide-TDO reaction are sigmoidal with excess TDO. The addition of methionine as a hypochlorous acid scavenging agent inhibits the reaction significantly, whereas the addition of chlorite ions and trace amounts of hydrogen sulfite ions accelerates the decay of chlorine dioxide. On the basis of these experiments, a sixteen-step kinetic model involving hypochlorous acid, chlorite ions, and hydrogen sulfite ions as key intermediates that provide an autocatalytic cycle is proposed to account for the overall kinetic behavior observed, including the slow rearrangement of TDO.
- Hu, Ying,Horváth, Attila K.,Duan, Sasa,Csek?, Gy?rgy,Makarov, Sergei V.,Gao, Qingyu
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- Electrooxidation of Formamidine Disulfide Simultaneously Investigated by On-Line High Performance Liquid Chromatography and Cyclic Voltammetry
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The electro-oxidation of formamidine disulfide, an important sulfur-containing compound, was simultaneously investigated with on-line high-performance liquid chromatography and cyclic voltammetry. Using a home-made microporous sampler located at the electrode interface, the solution on the electrode surface was in situ sampled and analyzed. The electrochemical scanning was synchronously performed, which allowed the electro-oxidation products to be detected at a given potential. The main products on the surface of platinum electrode were found to be thiourea, formamidine sulfinic acid, cyanamide, and elemental sulfur. Forced convection arising from the sampling played an important role in the electrochemical oxidation. The extraction of electrode surface solution promoted the renewal of reactant and its intermediates, which induced the change of cyclic voltammetry curve. The forced convection also contributed to the redox peak current of the species on the cyclic voltammetry curves through the change of concentration of reactant and its intermediates. This technique can help to explore the reaction mechanism of complex electrochemical reactions.
- Feng, Na,Li, Fengli,Liu, Yang,Luo, Hainan,Zhang, Baoying,Zhang, Wei,Zhao, Yuyan
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p. 1074 - 1080
(2021/11/03)
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- Photoredox chemistry in the synthesis of 2-aminoazoles implicated in prebiotic nucleic acid synthesis
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Prebiotically plausible ferrocyanide-ferricyanide photoredox cycling oxidatively converts thiourea to cyanamide, whilst HCN is reductively homologated to intermediates which either react directly with the cyanamide giving 2-aminoazoles, or have the potential to do so upon loss of HCN from the system. Thiourea itself is produced by heating ammonium thiocyanate, a product of the reaction of HCN and hydrogen sulfide under UV irradiation. This journal is
- Liu, Ziwei,Wu, Long-Fei,Bond, Andrew D.,Sutherland, John D.
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supporting information
p. 13563 - 13566
(2020/11/17)
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- MOF-Derived Cu-Nanoparticle Embedded in Porous Carbon for the Efficient Hydrogenation of Nitroaromatic Compounds
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Abstract: Novel Cu-nanoparticles (NPs) embedded in porous carbon materials (Cu@C-x) were prepared by one-pot pyrolysis of metal–organic frameworks (MOF) HKUST-1 at different temperatures. The obtained material Cu@C-x was used as a cost-effective catalyst for the hydrogenation of nitrobenzene using NaBH4 as the reducing agent under mild reaction conditions. By considering the catalyst preparation and the catalytic activity, a pyrolysis temperature of 400?°C was finally chosen to synthesize the optimal catalyst. When the aromatic nitro compounds with reducible groups, such as cyano, halogen, and alkyl groups, were tested in this catalytic hydrogenation, an excellent selectivity approaching 100% was achieved. In the recycling experiment, a significant decrease in nitrobenzene conversion was observed in the third cycle, mainly due to the very small amount of catalyst employed in the reaction. Hence, the easily prepared and cost-effective Cu@C-400 catalyst fabricated in this study demonstrates potential for the applications in selective reduction of aromatic nitro compounds. Graphic Abstract: The catalyst Cu@C-400 exhibited 100?% conversion and high selectivity for the hydrogenation of industrially relevant nitroarenes.[Figure not available: see fulltext.].
- Qiao, Chenxia,Jia, Wenlan,Zhong, Qiming,Liu, Bingyu,Zhang, Yifu,Meng, Changgong,Tian, Fuping
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p. 3394 - 3401
(2020/05/19)
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- A Facile Synthesis of Pd–C3N4@Titanate Nanotube Catalyst: Highly Efficient in Mizoroki–Heck, Suzuki–Miyaura C–C Couplings
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Abstract: A Pd–C3N4@titanate nanotube (Pd–C3N4@TNT) catalyst workable in water medium, robust against leaching and agglomeration was prepared in a facile synthetic procedure using quite common chemicals such as TiO2 powder, urea and palladium acetate. The Pd–C3N4@TNT catalyst has been characterized by BET surface area and pore size distribution, X-ray diffraction, solid-state 13C NMR spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy. The Pd–C3N4@TNT is a green catalyst for the Miziroki–Heck and Suzuki–Miyaura C–C coupling reactions in water medium with high efficiency (??99% product yields) due to atomic level immobilization of Pd in C3N4 networked titanate nanotubes. Pd–C3N4@TNT is robust against leaching and agglomeration due to stable and furthermore it is recyclable and usable at least for five repeated cycles. The use of water as solvent, absence of leaching and agglomeration, recyclability and reusability ascertains the greenness of Pd–C3N4@TNT) catalyst and process. Graphic Abstract: Novel Pd–C3N4@titanate nanotube catalyst prepared from bulk TiO2 and urea by simple hydrothermal and thermal pyrolysis followed by immobilization of Pd is active and selective for Mizoroki–Heck, Suzuki–Miyaura C–C couplings in water medium.[Figure not available: see fulltext.].
- Velpula, Venkata Ramana Kumar,Ketike, Thirupathaiah,Paleti, Gidyonu,Kamaraju, Seetha Rama Rao,Burri, David Raju
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- Synthesis of 5 - amino tetrazole method
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Synthesis of 5 - amino tetrazole method, in order to hydrazine hydrate, lime nitrogen, sodium nitrite, inorganic acid and inorganic base as the obtained 5 - amino tetrazole. The method through the metathesis reaction, addition reaction and diazo isomerization reaction of the cyano lead lime nitrogen into the aminoguanidine, then generating aminoguandine isomerization reaction to synthesize 5 - amino tetrazole. The invention compared with the traditional method, has the following advantages: (1) price cheap raw materials as the starting raw material, synthetic product is obtained; (2) simplified 5 - amino tetrazole operation process, reduce the reaction solvent types and process the complexity of the operation, reduces the cost of material and production cost, reduces the 5 - amino tetrazole synthesis cost of, improve the market competitiveness of the product. It has high efficiency, high yield, low cost, easy operation and the like.
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Paragraph 0028; 0029; 0030
(2019/06/13)
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- The synthesis of arylcyanamides: A copper-catalyzed consecutive desulfurization and C-N cross-coupling strategy
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A one pot highly efficient and simple protocol for the construction of aromatic cyanamides from thiourea via desulphurization/C-N cross coupling using a cheap, readily available and air stable copper source as a catalyst has been described. Various iodobenzenes could give their respective C-N cross-coupled products in good to excellent yields under optimized reaction conditions. Further, the substrate scope has been explored.
- Boddapati, S. N. Murthy,Polam, Naresh,Mutchu, Baby Ramana,Bollikolla, Hari Babu
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supporting information
p. 918 - 922
(2018/02/03)
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- The synthesis of aryl cyanamides through C-N cross-coupling
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The methodology for the preparation of aromatic cyanamides has been demonstrated. The present method involves consecutive desulphurization/C-N cross-coupling reaction. Cheap, readily available and air stable cobalt catalyst has been used for this methodology. In addition, the substrate scope has been explored.
- Kondraganti, Lakshmi,Manabolu, Surendra Babu,Dittakavi, Rama Chandran
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p. 629 - 634
(2020/06/26)
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- Photochemistry of 1- and 2-Methyl-5-aminotetrazoles: Structural Effects on Reaction Pathways
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The influence of the position of the methyl substituent in 1- and 2-methyl-substituted 5-aminotetrazoles on the photochemistry of these molecules is evaluated. The two compounds were isolated in an argon matrix (15 K) and the matrix was subjected to in situ narrowband UV excitation at different wavelengths, which induce selectively photochemical transformations of different species (reactants and initially formed photoproducts). The progress of the reactions was followed by infrared spectroscopy, supported by quantum chemical calculations. It is shown that the photochemistries of the two isomers, 1-methyl-(1H)-tetrazole-5-amine (1a) and 2-methyl-(2H)-tetrazole-5-amine (1b), although resulting in a common intermediate diazirine 3, which undergoes subsequent photoconversion into 1-amino-3-methylcarbodiimide (H2N-N=C=N-CH3), show marked differences: formation of the amino cyanamide 4 (H2N-N(CH3)-C=N) is only observed from the photocleavage of the isomer 1a, whereas formation of the nitrile imine 2 (H2N-C-=N+=N-CH3) is only obtained from photolysis of 1b. The exclusive formation of nitrile imine from the isomer 1b points to the possibility that only the 2H-tetrazoles forms can give a direct access to nitrile imines, while observation of the amino cyanamide 4 represents a novel reaction pathway in the photochemistry of tetrazoles and seems to be characteristic of 1H-tetrazoles. The structural and vibrational characterization of both reactants and photoproducts has been undertaken.
- Ismael,Fausto,Cristiano
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p. 11656 - 11663
(2016/12/09)
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- Flow-Tube Investigations of Hypergolic Reactions of a Dicyanamide Ionic Liquid Via Tunable Vacuum Ultraviolet Aerosol Mass Spectrometry
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The unusually high heats of vaporization of room-temperature ionic liquids (RTILs) complicate the utilization of thermal evaporation to study ionic liquid reactivity. Although effusion of RTILs into a reaction flow-tube or mass spectrometer is possible, competition between vaporization and thermal decomposition of the RTIL can greatly increase the complexity of the observed reaction products. In order to investigate the reaction kinetics of a hypergolic RTIL, 1-butyl-3-methylimidazolium dicyanamide (BMIM+DCA-) was aerosolized and reacted with gaseous nitric acid, and the products were monitored via tunable vacuum ultraviolet photoionization time-of-flight mass spectrometry at the Chemical Dynamics Beamline 9.0.2 at the Advanced Light Source. Reaction product formation at m/z 42, 43, 44, 67, 85, 126, and higher masses was observed as a function of HNO3 exposure. The identities of the product species were assigned to the masses on the basis of their ionization energies. The observed exposure profile of the m/z 67 signal suggests that the excess gaseous HNO3 initiates rapid reactions near the surface of the RTIL aerosol. Nonreactive molecular dynamics simulations support this observation, suggesting that diffusion within the particle may be a limiting step. The mechanism is consistent with previous reports that nitric acid forms protonated dicyanamide species in the first step of the reaction.
- Chambreau, Steven D.,Koh, Christine J.,Popolan-Vaida, Denisia M.,Gallegos, Christopher J.,Hooper, Justin B.,Bedrov, Dmitry,Vaghjiani, Ghanshyam L.,Leone, Stephen R.
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p. 8011 - 8023
(2016/10/31)
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- Hydrolysis study of fluoroorganic and cyano-based ionic liquid anions - Consequences for operational safety and environmental stability
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The hydrolytic stability of ionic liquid anions is a key property with regard to their technical applicability and environmental stability. From a technical point of view hydrolytic processes may lead to reduced durability, diminished technical performance and reduced operational safety in that corrosive and/or toxic hydrolysis products are formed. On the other hand, susceptibility to hydrolytic processes is advantageous where environmental stability and persistency are concerned, since hydrolysis is the most important abiotic degradation pathway in the environment. We investigated the hydrolytic stability of the most common ionic liquid anions, dicyanimide [N(CN) 2]-, tricyanmethanide [C(CN)3]-, tetracyanidoboranate [B(CN)4]-, bis(trifluoromethylsulphonyl)imide [(CF3SO2) 2N]-, trifluorotris(pentafluoroethyl)phosphate [(C 2F5)3PF3]- and 1,1,2,2-tetrafluoroethanesulphonic acid [H(C2F4)SO 3]-, as a function of pH (1, 7, 9 and 13) and temperature. The results show that there was no difference in hydrolytic stability as recorded for 1-ethyl-3-methylimidazolium (IM12) or for the alkali cations. All the anions were stable under neutral and slightly basic conditions (half-lives at 25 °C ?1 year). In strongly acidic and basic solutions, however, B(CN)4-, (CF3SO2)2N -, (C2F5)3PF3- and H(C2F4)SO3- were hydrolytically stable, whereas N(CN)2- and C(CN)3- were not. The kinetics of hydrolysis were recorded and Arrhenius plots were generated for the latter two anions. In addition, their hydrolysis pathways and the resulting products were identified via mass spectrometry. The cytotoxicity of hydrolysed IL solutions towards the mammalian cell line IPC-81 and the identified hydrolysis products (pure compounds) was investigated for a first estimate of their toxicological properties.
- Steudte, Stephanie,Neumann, Jennifer,Bottin-Weber, Ulrike,Diedenhofen, Michael,Arning, Juergen,Stepnowski, Piotr,Stolte, Stefan
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p. 2474 - 2483
(2013/02/23)
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- PRODRUGS OF EXCITATORY AMINO ACIDS
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This invention relates to a synthetic excitatory amino acid prodrug and processes for its preparation. The invention further relates to methods of using, and pharmaceutical compositions comprising, the compounds for the treatment of neurological disorders and psychiatric disorders.
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- PROCESS FOR THE SYNTHESIS OF GUANIDINE DERIVATIVES
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The invention pertains to a process for the synthesis of guanidine derivatives of Formula (I) wherein X is selected from OH, OM wherein M is an alkali or earth alkali metal ion, and NR1R2 wherein R1 and R2 are independently H, C1-C6 alkyl, C2-C6 alkenyl, C3-C6 cycloalkyl, or C6-C10 aryl; which comprises a first step of reacting cyanogen chloride (N≡CCI) with NH3 in an organic solvent followed by a second step of reacting with an amine of Formula (II) wherein X has the previously given meaning, optionally followed by a step of converting a compound of Formula (I) into another compound of Formula (I).
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- Silver(I) fluoride and related compounds in chemical synthesis
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Silver(I) fluoride is a versatile tool in desulfuration-fluorination reactions with thiuram disulfides and thioureas. Reactions of AgF and trimethyl(perfluoroorgano)- and trimethyl(alkynyl)-silanes offer a convenient approach to the corresponding organosilver derivatives, which are excellent reagents for oxidative organylations of group 12-16 elements. Reactions of AgF and elements of groups 13-16 open a convenient access to the corresponding fluorides.
- Tyrra, Wieland
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p. 561 - 566
(2007/10/03)
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- Thermal decomposition of cadmium thiourea coordination compounds
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Thermal decomposition of cadmium thiourea coordination compounds was considered. Cadmium sulfide is the final product for all the compounds, whereas the composition of other products of the thermolysis substantially depends on the nature of the acido ligand or the outer-sphere anion. Thermal stability parameters of the coordination compounds under study and effective activation energies of their thermolysis were determined, and a mechanism of the thermolysis was proposed.
- Semenov,Naumov
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p. 495 - 499
(2007/10/03)
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- Photochemistry of 2-azido-1-methylimidazole in aqueous solutions. Observation of the 1-methyl-2-imidazolylnitrenium ion
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Irradiation of 2-azido-1-methylimidazole (12) in aqueous solution gives products from two reaction channels. One pathway involves a ring opening typical of azidoheterocycles. The observed products are glyoxal bis-hydrate, the methylammonium ion, and cyanamide; a glyoxal bis-oxime is presumed to be the intermediate initially formed in the ring opening. The other pathway leads to products that retain the five-membered ring, the 2-amino-4,5-dihydro-4,5-dihydroxy-1-methylimidazolium ion 3, its monophosphate ester 6 when the irradiation is carried out in phosphate buffer, and glutathione adducts 7 and 8 when glutathione (GSH) is present. These products have been previously observed in the reactions of 2-hydroxylamino-1-methylimidazole in aqueous solution, and arise from reaction of the 1-methyl-2-imidazolylnitrenium ion (2+) with water, phosphate, and GSH. This pathway is therefore proposed to involve formation of the cation 2+ via protonation of the singlet 1-methyl-2-imidazolylnitrene 13 formed upon irradiation of the azide. A single transient species undergoing exponential decay with λmax at 230-235 nm is observed with flash photolysis. This transient is assigned to 2+ on the basis of the pH dependence of the yields of products, and especially because of the correspondence of k2(GS-):ks ratios measured directly with flash photolysis and by competition kinetics starting from the hydroxylaminoimidazole. The cation 2+ has a lifetime in water of 100 ms, and shows a high selectivity for GSH with k2(GS-) = 3 × 107 M-1 s-1. There is evidence that this class of nitrenium ion is formed upon reductive metabolism of 2-nitroimidazoles. Thus this class of drugs is capable of producing a relatively long-lived electrophile in biological systems.
- Gadosy, Timothy A.,McClelland, Robert A.
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p. 1459 - 1465
(2007/10/03)
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- General acid catalysis of the reversible addition of thiolate anions to cyanamide
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The addition of aromatic thiols (pKa = 2.6-6.5) to cyanamide to give the isothiourea is subject to general-acid catalysis of the addition of thiolate anions by tertiary ammonium ions, with α = 0.26 and 0.31 (±0.07) for the addition of thiophenol and 4-nitrothiophenol, respectively. The Bronsted coefficients and a small solvent isotope effect of kH2O/kD2O = 1.6 for catalysis by 4-morpholinoethanesulfonic acid (MES) buffer and for the uncatalysed addition of thiophenol are consistent with significant movement of a hydron in the transition state. The conclusion that the reaction proceeds through a basic asymmetric intermediate in the absence of catalysis is supported by the similar rate constants for the addition of thiophenolate anion to cyanamide and to N,N-dimethylcyanamide, which cannot tautomerize to the carbodiimide. The reaction has a central transition state in which S-C bond formation takes place with βnuc = 0.55. It is concluded that the mechanism of catalysis involves partial transfer of a hydron to the cyano nitrogen atom in the transition state.
- Dalby, Kevin N.,Jencks, William P.
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p. 1555 - 1563
(2007/10/03)
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- Photochemical fragmentation of unsubstituted tetrazole, 1,2,3-Triazole, and 1,2,4-triazole: First matrix-spectroscopic identification of nitrilimine HCNNH
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Equilibria between the tautomers of heterocyclic azoles like 1, 2, and 4 have been studied many times. We here show that the application of density functional methods in combination with matrix IR spectroscopy is a useful tool for determining which protomer is preferred in rare gas matrices and thus also can be assumed to dominate in the gas phase. Photolysis of tetrazole (4) in cryogenic matrices allows the IR-spectroscopic identification of a new CH2N2 isomer, the long sought-after nitrilimine HCNNH (6). Flash pyrolysis of 4 also yielded nitrilimine. Upon irradiation this species is converted to a second, previously unknown "isomer", an HCN/NH complex 13. Nitrilimine (6) can also be generated by photolyzing 1,2,3- (1) and 1,2,4-triazole (2) in Ar matrices. The complex photochemistry of all three heterocyclic precursor compounds was unveiled. Our findings were supported by isotopic substitution experiments and by high-level ab initio calculations. Moreover, the IR bands of iminocyanide HNCN were tentatively assigned. This radical has up to now not been observed in a matrix. VCH Verlagsgesellschaft mbH, 1996.
- Maier, Guenther,Eckwert, Juergen,Bothur, Axel,Reisenauer, Hans Peter,Schmidt, Christiane
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p. 1041 - 1053
(2007/10/03)
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- Cyanamide substituted phosphorus compounds
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Referring to the field of phosphorus chemistry the fragment N(CN) is discussed as pseudochalcogen.
- Jaeger, Lothar
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p. 157 - 160
(2007/10/03)
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- Kinetic study of the stability of (NH2)2CSSC(NH2)22+
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The kinetics of the decomposition of formamidine disulfide dihydrochloride, (NH2)2CSSC(NH2)22+ 2Cl-, in aqueous solution at 25 degC are general base catalysed, and rate constants have been measured over the pH range 1.91-9.03.Analysis of the data yields ionisation constants pK1 = 5.49, pK2 = 7.66 and rate constants for deprotonation of the substrate by OH- and H2O.For the doubly charged cation, reaction occurs through a small concentration of a reactive tautomer, (HN=)(NH3+)CSSC+(NH2)2, which is attacked by H2O.The singly charged cation reacts by parallel pathways involving OH- and H2O as attacking bases.
- Rio, L. Garcia,Munkley, Carl G.,Stedman, Geoffrey
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p. 159 - 162
(2007/10/03)
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- Infrared Spectrum of Matrix-Isolated Hexamethylenetetramine in Ar and H2O at Cryogenic Temperatures
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The infrared spectra of hexamethylenetetramine (HMT) isolated in an argon matrix at 12 K, frozen in H2O at temperatures from 12 to 200 K, and as a pure solid, are reported.The results of ultraviolet photolysis of matrix-isolated HMT and HMT frozen in H2O ice are also presented, and implications for infrared astronomy and astrochemistry are discussed.Furthermore, a simple technique for incorporating large nonvolatile organic molecules into a matrix is described.
- Bernstein, Max P.,Sanford, Scott A.,Allamandola, Louis J.,Chang, Sherwood
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p. 12206 - 12210
(2007/10/02)
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- Methoxy- and Aminoisocyanate
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Methoxyisocyanate (1) can be prepared by photolysis of methyl azidoformate (3) or pyrolysis of N-methoxycarbonyl-O-methylhydroxylamine (4).Aminoisocyanate (2) is similarly formed on photolysis of carbamoyl azide (12) and pyrolysis of either methyl carbazate (13) or 3,4-diaminofurazan (14).The infrared spectra of 1 and 2 in an argon matrix at 10 K have been measured, and some of their properties are discussed. - Keywords: Flash pyrolysis/ Matrix IR spectroscopy/ Photolysis
- Teles, Joaquim Henrique,Maier, Guenther
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p. 745 - 748
(2007/10/02)
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- SYNTHESIS, STRUCTURE, AND PROPERTIES OF COMPOUNDS WITH A CHALCOGEN-NITROGEN BOND. XI. REACTION OF SELENIMIDES WITH THIOLS AND THIOAMIDES
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The oxidizing power of chalcogen imides in reactions with thiols and thioamides increases in the order S +-N- bond during the substitution of the phenyl radicals attached to the selenium atom by the electron-donating benzyl groups.
- Naddaka, V. I.,Avanesyan, K. V.,Cherkinskaya, M. L.,Minkin, V. I.
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p. 2245 - 2250
(2007/10/02)
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