F:Flammable;
124-40-3Relevant articles and documents
Combustion and sublimation calorimetric studies on acetylurea and trimethyl isocyanurate
Imamura, Akira,Murata, Shigeo,Sakiyama, Minoru
, p. 389 - 396 (1988)
Standard enthalpies of formation in the crystalline and gaseous states have been determined for acetylurea and trimethyl isocyanurate by oxygen bomb-combustion calorimetry and sublimation calorimetry.Derived values are as follows: .Stabilization energies related to intramolecular interaction between ?-electrons of carbonyl groups and lone-pair electrons of adjacent nitrogen atoms have been evaluated for acetamide and urea as well as for these compounds as enthalpy changes of "isodesmic" reactions using ethane as a reagent for the cleavage of CO-N bonds and are discussed.
Thermal decomposition of trimethylamine borane as a precursor to nanocrystalline CVD BC x N y films
Korobeinichev,Shmakov,Chernov,Kosinova,Sulyaeva,Kuznetsov
, p. 1199 - 1204 (2011)
We have studied the kinetics of BC x N y chemical vapor deposition through trimethylamine borane decomposition at atmospheric pressure. The rate constant of the heterogeneous interaction between trimethylamine borane and an adsorption center has been determined to be k s 0 = 2.7 × 107exp(-10560/T) cm/s. The obtained kinetic parameters of the reaction fully determine the growth rate of nanocrystalline carbonitride films under kinetic control. The film thickness has been determined as a function of time, temperature, reactant concentration, and reactor dimensions.
Poly(iminoborane)s: An Elusive Class of Main-Group Polymers?
Ayhan, Ozan,Eckert, Thomas,Plamper, Felix A.,Helten, Holger
, p. 13321 - 13325 (2016)
The significance of inorganic main-group polymers is demonstrated most clearly by the commercial relevance of polysiloxanes (silicones). Organoboron-based materials such as π-conjugated organoborane polymers and BN-doped polycyclic aromatic hydrocarbons are currently attracting considerable attention. Surprisingly, poly(iminoborane)s (PIBs; [BRNR′]n), that is, the parent unsaturated BN polymers, which are formally isoelectronic to polyacetylene, have not been convincingly characterized thus far. Herein, we present the synthesis and comprehensive characterization of a linear oligo(iminoborane), which comprises a chain of 12–14 BN units on average. With our synthetic approach, unwanted side reactions that result in borazine formation are effectively suppressed. Supporting DFT and TD-DFT calculations provide deeper insight into the microstructure and the electronic structure of the oligomer.
Silicoaluminophosphate molecular sieve DNL-6: Synthesis with a novel template, N,N″-dimethylethylenediamine, and its catalytic application
Wu, Pengfei,Yang, Miao,Zhang, Wenna,Zeng, Shu,Gao, Mingbin,Xu, Shutao,Tian, Peng,Liu, Zhongmin
, p. 1511 - 1519 (2018)
DNL-6, a silicoaluminophosphate (SAPO) molecular sieve with RHO topology, was hydrothermally synthesized using a new structure-directing agent (SDA), N,N′-dimethylethylenediamine. The obtained samples were characterized by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption, which indicated that the synthesized DNL-6s have high crystallinity and relatively high Si content ranging from 20% to 35%. Solid-state magic-angle-spinning (MAS) nuclear magnetic resonance (13C, 29Si, 27Al, 31P, and 27Al multiple-quantum (MQ)) was conducted to investigate the status of the SDA and local atomic environment in the as-synthesized DNL-6. Thermal analysis revealed the presence of a large amount of amines in the DNL-6 crystals (about 4.4 SDAs per α-cage), which was the reason for the formation of DNL-6 with an ultrahigh Si content (36.4% Si per mole). Interestingly, DNL-6 exhibited excellent catalytic performance for methanol amination. More than 88% methanol conversion and 85% methylamine plus dimethylamine selectivity could be achieved due to the combined contribution of strong acid sites, suitable acid distribution, and narrow pore dimensions of DNL-6.
Selective Synthesis of Trimethylamine by Catalytic N-Methylation of Ammonia and Ammonium Chloride by utilizing Carbon Dioxide and Molecular Hydrogen
Beydoun, Kassem,Thenert, Katharina,Streng, Emilia S.,Brosinski, Sandra,Leitner, Walter,Klankermayer, Jürgen
, p. 135 - 138 (2016)
The synthesis of trimethylamine (TMA) through a multicomponent combination of ammonia with carbon dioxide and molecular hydrogen by using a homogeneous ruthenium catalyst was explored. The use of [Ru(triphos)(tmm)] [triphos: 1,1,1-tris(diphenylphosphinomethyl)ethane, tmm: trimethylene methane] together with aluminum trifluoromethanesulfonate as a co-catalyst resulted in high ammonia conversion and excellent selectivity for TMA in organic solvents. Aqueous solutions of ammonium chloride were methylated almost quantitatively to the corresponding hydrochloride salt (i.e., TMA·HCl) in a biphasic solvent system by using the same Ru complex without the need for any co-catalyst.
Enhanced catalytic reduction of N-nitrosodimethylamine over bimetallic Pd-Ni catalysts
Chen, Huan,Li, Ting,Jiang, Fang,Wang, Zhe
, p. 167 - 177 (2016)
Catalytic reduction of N-nitrosodimethylamine (NDMA) was investigated over γ-Al2O3 supported bimetallic Pd-Ni catalysts (3%(PdxNi1-x)). NDMA could be reduced to dimethylamine over 3%(Pd0.8Ni0.2) with a metal-loading-normalized pseudo-first-order rate constant of 836 ± 21 L gme-1 h-1. Characterization results showed that the reducibility of PdO (or NiO) was improved by addition of Ni (or Pd) in 3%(PdxNi1-x); Pd-Ni ensembles were formed in 3%(PdxNi1-x) and there was an electronic transfer from Pd to Ni; metal dispersion was affected by the formation of Pd-Ni ensembles and a volcano curve of metal dispersion via Pd/Ni ratio was observed. The activity profiles demonstrated that TOF had a significant positive relationship with metal dispersion of 3%(PdxNi1-x), indicating high metal dispersion favor NDMA reduction. NDMA reduction over 3%(Pd0.8Ni0.2) catalyst could be described by Langmuir-Hinshelwood model, reflecting an adsorption controlled reduction mechanism. The reduction mechanism of NDMA over 3%(Pd0.8Ni0.2) catalyst was proposed to be that H2 was activated by Pd, and H spillover from Pd to Ni/NiO reduced NDMA though N-N cleavage.
The nonenzymatic decomposition of guanidines and amidines
Lewis, Charles A.,Wolfenden, Richard
, p. 130 - 136 (2014)
To establish the rates and mechanisms of decomposition of guanidine and amidine derivatives in aqueous solution and the rate enhancements produced by the corresponding enzymes, we examined their rates of reaction at elevated temperatures and used the Arrhenius equation to extrapolate the results to room temperature. The similar reactivities of methylguanidine and 1,1,3,3-tetramethylguanidine and their negative entropies of activation imply that their decomposition proceeds by hydrolysis rather than elimination. The influence of changing pH on the rate of decomposition is consistent with attack by hydroxide ion on the methylguanidinium ion (k2 = 5 × 10 -6 M-1 s-1 at 25 C) or with the kinetically equivalent attack by water on uncharged methylguanidine. At 25 C and pH 7, N-methylguanidine is several orders of magnitude more stable than acetamidine, urea, or acetamide. Under the same conditions, the enzymes arginase and agmatinase accelerate substrate hydrolysis 4 × 1014-fold and 6 × 1012-fold, respectively, by mechanisms that appear to involve metal-mediated water attack. Arginine deiminase accelerates substrate hydrolysis 6 × 1012-fold by a mechanism that (in contrast to the mechanisms employed by arginase and agmatinase) is believed to involve attack by an active-site cysteine residue.
Investigating the Underappreciated Hydrolytic Instability of 1,8-Diazabicyclo[5.4.0]undec-7-ene and Related Unsaturated Nitrogenous Bases
Hyde, Alan M.,Calabria, Ralph,Arvary, Rebecca,Wang, Xiao,Klapars, Artis
, p. 1860 - 1871 (2019)
The widespread use of amidine and guanidine bases in synthetic chemistry merits a thorough understanding of their chemical properties. The propensity of these reagents to hydrolyze under mild conditions and generate aminolactams and aminoureas, respectively, has not been adequately described previously. During the synthesis of uprifosbuvir (MK-3682), we became aware of this liability for 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) by observing the formation of an unexpected reaction impurity and traced the root cause to low levels of N-(3-aminopropyl)-?-caprolactam present in the commercial bottle. A controlled stability study over a period of two months at 25 °C demonstrated that, above a threshold water content, DBU steadily hydrolyzed over time. Rates of hydrolysis for DBU, 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), and N,N,N′,N′-tetramethylguanidine (TMG) in organic, aqueous, and mixed solvent systems were then measured to gain a more general appreciation of what conditions to avoid in order to maintain their integrity. Our findings indicate that these bases are hydrolytically unstable in unbuffered and very basic solutions but become significantly more stable in buffered solutions at pH values below 11.6.
Application of the WATR technique for water suppression in 1H NMR spectroscopy in determination of the kinetics of hydrolysis of neostigmine bromide in aqueous solution
Ferdous,Waigh
, p. 559 - 562 (1993)
Both ammonium chloride and guanidinium chloride were used to secure water suppression in 1H NMR spectra using the 'Water Attenuation by T2 Relaxation' (WATR) technique. The effect of phosphate buffer in the suppression was investigated over a range of pH values at 80 MHz. The spin-spin relaxation time of water protons at 80 MHz was found to reach a minimum at pH 7.3 in the presence of 0.1 M phosphate buffer and 1 M guanidinium chloride; these conditions were therefore chosen for subsequent use of the WATR technique in a study of the kinetics of hydrolysis of neostigmine bromide. The method was found to be very convenient for studies of the hydrolysis of this representative amide.
Standard enthalpies of formation of crystalline dimethylammoniumdimethyldithiocarbamate and of dimethyldithiocarbamate complexes of copper(II) and nickel(II). The mean Cu-S and Ni-S bond-dissociation enthalpies
Silva, Manuel A. V. Ribeiro da,Reis, Ana M. M. V.,Faria, Rita I. M. C. P.
, p. 1365 - 1372 (1995)
The standard (p0 = 0.1 MPa) enthalpies of formation of crystalline dimethylammoniumdimethyldithiocarbamate and of the dimethyldithiocarbamate complexes of Ni(II) and Cu(II) were determined, at the temperature 298.15 K, by solution-reaction calorimetry.The enthalpy of "decomposition" of the dimethylammoniumdimethyldithiocarbamate salt and the enthalpies of sublimation of the metal complexes were measured by high-temperature microcalorimetry.From these values, the mean molar bond-dissociation enthalpies m>(M-S) were derived. .
