- Catalytic Synthesis Of Aziridine From 1,2-Diaminoethane
-
The contact conversion of 1,2-diaminoethane over a tungsten trioxide catalyst at 240-580 deg C has been studied by an impulse chromatographic method.The basic reaction path under these conditions is unimolecular deaminocyclization to give aziridine (31-35percent).Piperazine and triethylenediamine, products of bi- and trimolecular deaminocyclization, are present as products.The deamination process is accompanied by coupled dehydrogenation and hydrogenolysis reactions.Addition of the acid anhydrides SiO2, P2O5 and B2O3 to the catalyst increases its activity but has onlyanegligible affect on the activation energy of the process.
- Anderson, A. A.,Simonyan, S. P.,Shimanskaya, M. V.
-
-
Read Online
- Effective utilization of glycerol for the synthesis of 2-methylpyrazine over ZnO-ZnCr2O4 catalyst
-
Bioglycerol an inevitable by-product in the production of biodiesel was effectively utilized for the synthesis of 2-methylpyrazine (2-MP) by vapour phase dehydrocyclization with ethylenediamine over ZnO-ZnCr2O 4(Zn-Cr-O) mixed oxides
- Venugopal,Sarkari,Naveen Kumar,Kotesh Kumar,Syed John,Krishna Reddy,Hari Padmasri
-
-
Read Online
- Influence of Free Amino Acids, Oligopeptides, and Polypeptides on the Formation of Pyrazines in Maillard Model Systems
-
Pyrazines are specific Maillard reaction compounds known to contribute to the unique aroma of many products. Most studies concerning the generation of pyrazines in the Maillard reaction have focused on amino acids, while little information is available on the impact of peptides and proteins. The present study investigated the generation of pyrazines in model systems containing whey protein, hydrolyzed whey protein, amino acids, and glucose. The impact of thermal conditions, ratio of reagents, and water activity (aw) on pyrazine formation was measured by headspace solid-phase microextraction with gas chromatography/mass spectrometry (HS-SPME-GC/MS. The presence of oligopeptides from hydrolyzed whey protein contributed significantly to an increased amount of pyrazines, while in contrast free amino acids generated during protein hydrolysis contributed to a lesser extent. The generation of pyrazines was enhanced at low aw (0.33) and high temperatures (>120 °C). This study showed that the role of peptides in the generation of pyrazines in Maillard reaction systems has been dramatically underestimated.
- Scalone, Gustavo Luis Leonardo,Cucu, Tatiana,De Kimpe, Norbert,De Meulenaer, Bruno
-
-
Read Online
- Volatile Compounds Generated from Thermal Reaction of Methionine and Methionine Sulfoxide with or without Glucose
-
Methionine and methionine sulfoxide were mixed with or without glucose in distilled water, individually.These solutions were heated in closed sample cylinders at 180 deg C for 1 h.The volatile compounds generated were extracted using methylene chloride and analyzed by GC and GC-MS.Pyrazine compounds, especially 2,5-dimethyl-, 2-ethyl-5-methyl-, trimethyl-, and methylpyrazines were the predominant compounds among those generated from thermal interactions of glucose and methionine or methionine sulfoxide.The formation of methional or those compounds derived for methional was found to be more favorable from the thermal degradation of methionine, whereas the formation of dimethyl polysulfides, especially dimethyl disulfide and dimethyl trisulfide, was found to be more favorable from the thermal degradation of methionine sulfoxide.Glucose was found to have a catalytic effect on the formation of volatile compounds from the thermal degradation of methionine or methionine sulfoxide.Keywords: Methionine; methionine sulfoxide; methional; methyl sulfides; volatiles
- Yu, Tung-Hsi,Ho, Chi-Tang
-
-
Read Online
- Binary oxide systems in catalytic synthesis of 2-methylpyrazine from 1,2-propylene glycol and ethylenediamine
-
A series of binary catalysts based on oxides of zinc and variable-valence metals were tested in synthesis of 2-methylpyrazine by catalytic dehydrocyclization of 1,2-propylene glycol with ethylenediamine.
- Balpanov,Krichevskii,Kagarlitskii
-
-
Read Online
- Catalytic synthesis of 2-methylpyrazine over Cr-promoted copper based catalyst via a cyclo-dehydrogenation reaction route
-
The cyclo-dehydrogenation of ethylene diamine and propylene glycol to 2-methylpyrazine was performed under the atmospheric conditions at 380°C. The Cr-promoted Cu-Zn/Al 2O 3 catalysts were prepared by impregnation method and characterized by ICP-AES, N 2 adsorption/desorption, XRD, XPS, N 2O chemisorption, TPR and NH3-TPD techniques. The amorphous chromium species existing in Cu-Zn-Cr/Al 2O 3 catalyst enhanced the dispersion of active component Cu, promoted the reduction of catalyst. Furthermore, the catalytic performance was significantly improved. The acidity of the catalyst played an important role in increasing the 2-MP selectivity. To optimize the reaction parameters, influences of different chromium content, reaction temperature, liquid hourly space velocity (LHSV), reactants molar ratio and time on stream on the product pattern were studied. The results demonstrated that addition of chromium promoter revealed satisfying catalytic activity, stability and selectivity of 2-methylpyrazine. Indian Academy of Sciences.
- Jing, Fangli,Zhang, Yuanyuan,Luo, Shizhong,Chu, Wei,Zhang, Hui,Shi, Xinyu
-
-
Read Online
- A comparative study on the catalytic activity of ZnAl, NiAl, and CoAl mixed oxides derived from LDH obtained by mechanochemical method in the synthesis of 2-methylpyrazine
-
Mixed oxides (mo)-ZnAl; NiAl; CoAl (M2+/Al = 3 M ratio) were obtained from layered double hydroxides (LDH) precursors synthesized by mechanochemical method. The solids were characterized by XRD, DRIFT, H2-TPR, NH3/CO2-TPD and determination of textural properties by N2 adsorption-desorption isotherms. The catalytic activity was tested in the dehydration-cyclization of ethylenediamine with propylene glycol, followed by the dehydrogenation of the obtained piperazine, yielding the 2-methylpyrazine (2-MP) as the main reaction product. At 400 °C, the conversion of both reactants was quasi-total, but the yield to 2-MP was close to 90% on the solids with more active sites favoring dehydration-cyclization (mo-ZnAl and mo-CoAl).
- Teodorescu,Slabu,Pavel,Z?voianu
-
-
Read Online
- Degradation Products Fromed from Glucosamine in Water
-
An aqueous solution of glucosamine hydrochloride was heated to 150 °C for 5 min under different pH conditions. The reaction product mixture obtained was analyzed by GC/MS. It was found that the major products formed were furfurals, especially at pH = 4 and 7. At pH = 8.5, additional flavor components were generated, including pyrazines, 3-hydroxypyridines, pyrrole-2-carboxaldehyde, furans, acetol, and several other compounds. Of the components identified, it is worthwhile to note the formation of pyrazine and methylpyrazine as major components at pH = 8.5. It is proposed that a retro-aldol condensation plays an important role in the formation of the intermediates, α-aminoacetaldehyde (I) and α-amino propanal (II). As a result, self-condensation of I generates pyrazine and combination of I and II generates methylpyrazine. In addition, it is also interesting to note the formation of 3-hydroxypyridines and pyrrole-2-carboxaldehyde. It is suggested that both groups of compounds are derived from furfurals. As the ammonia is liberated from glucosamine, it initiates the ring-opening of furfurals to form 5-amino-2-keto-3-pentenals. Intramolecular condensations of these intermediates between the amino group and the carbonyl groups lead to the formation of 3-hydroxypyridines and pyrrole-2-carboxalhyde.
- Shu, Chi-Kuen
-
-
Read Online
- Kinetics and thermal degradation of the fructose-methionine Amadori intermediates. GC-MS/SPECMA data bank identification of volatile aroma compounds
-
Fructose-methionine Amadori intermediates, prepared from D-glucose and L-methionine, were purified by semi-preparative HPLC.Structural elucidation was achieved by 13C-NMR and mass spectrometry in the FAB+ and FAB- modes.Constant rates of formation of glucosylamine and the Amadori intermediate, and their thermal degradation into reductones and methionine as well as into diglucosylamine, were observed.Thermal degradation of the Amadori intermediate gives not only the well-known degradation products of the sugar moiety and methional (from the Strecker degradation of methionine), but also several heterocyclic compounds (pyridines, pyrazines, pyrroles, and furans).Some of them contain a methylthiopropyl group in their side chain.These new compounds were identified by the fragmentation rules and Kovats additive properties.Out of the 80 compounds isolated, ca. 70 were identified.
- Vernin, Gaston,Metzger, Jacques,Boniface, Christian,Murello, Marie-Helene,Siouffi, Antoine,et al.
-
-
Read Online
- Vapor phase synthesis of methylpyrazine using aqueous glycerol and ethylenediamine over ZnCr2O4 catalyst: Elucidation of reaction mechanism
-
A novel method has been developed for the synthesis of methylpyrazine (MP) by using aqueous glycerol and ethylenediamine (EDA) over Zn-Cr catalyst derived from hydrotalcite precursors. The X-ray diffraction analysis of the oven-dried Zn-Cr samples synthesized at various pH ranging from 7 to 11 showed hydrotalcite phase whereas the calcined catalysts displayed ZnO and ZnCr2O 4 phases. The cyclisation activity of Zn-Cr catalyst prepared at pH ～ 9 demonstrated 99.4% conversion of EDA and 94% of glycerol with ～ 72% selectivity to MP at a reaction temperature of 400 °C. This process demonstrates direct utilization of bio-glycerol for the synthesis of MP.
- Sarkari, Reema,Anjaneyulu, Chatla,Krishna, Vankudoth,Kishore, Ramineni,Sudhakar, Medak,Venugopal, Akula
-
-
Read Online
- Facile synthesis of CuMAl (M = Cr, Mn, Zn, and Co) with highly dispersed Cu and tailorable surface acidity for efficient 2-methylpyrazine synthesis
-
Synthesis of 2-methylpyrazine (2-MP) from 1,2-propylene glycol (PG) and ethylenediamine (ED) was investigated in the presence of multifunctional catalytic systems (CuMAl) possessing acidic and metallic functional sites. Catalytic systems were prepared from mixed CuMAl-layered double hydroxides (CuMAl-LDHs, M = Cr, Mn, Zn, and Co) via their thermal decomposition. CuMAl-LDH were prepared from Cu(NO3)2, M(NO3)x and Al(NO3)3 and NaOH/Na2CO3 as a precipitating agent. X-ray diffraction (XRD), N2 adsorption-desorption, temperature-programmed desorption with ammonia (NH3-TPD), N2O chemisorption, transmission electron microscopy (TEM), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) were used to characterize the physical and chemical properties of the catalysts. The results showed that the nature of the secondary metal M inserted into the LDH structure significantly affected the crystalline structure, the dispersion of copper nanoparticles, and the density of surface acidic sites of the catalysts. The as-prepared CuMAl catalysts displayed promising catalytic performances towards the synthesis of 2-MP. Among them, CuCoAl showed the highest PG conversion (97%) and 2-MP selectivity (55%). These high catalytic activities were found to be associated with the ultra-small Cu nanoparticles (～2 nm) and high surface acidity (2433 μmol g-1).
- Hou, Jindou,Luo, Wen.,Luo, Shizhong,Lin, Chao,Liu, Ping,Liao, Xuemei,Jing, Fangli,Li, Xiaopeng
-
-
Read Online
- SYNTHESIS OF NITROGEN CONTAINING HETEROCYCLES OVER COPPER CHROMITE
-
The reactions of 1,2-diaminopropane, 1-amino-2-propanol, 1-amino-2-ethanol, and N-(β-aminoethyl)-1,2-diaminoethane in the gas phase over copper chromite have been investigated with the objective of synthesising nitrogen containing heterocycles.At 240-360
- Meksh, P.A.,Anderson, A.A.,Shimanska, M.
-
-
Read Online
- DEHYDROGENATION OF PIPERAZINE INTO PYRAZINE ON ALUMINA-PLATINUM CATALYSTS
-
Dehydrogenation of piperazine on alumina-platinum catalysts at 360-400 deg C was investigated.It was found that the alumina-platinum catalyst has low selectivity in the formation of pyrazine (yield /= 43percent), and dehydrogenation is accompanied by decomposition and coke formation and products of decomposition in the formation of alkylpyrazines.The alumina-platinum catalyst in In2O3 and Re2O7 additives permits obtaining pyrazine with a yield of up to 80percent.Dehydrogenation of piperazine is accompanied by reactions of decomposition, dehydroisomerization, and alkylation to a small degree, resulting in the formation of pyrrole, methylimidazole, and alkylpyrazines.
- Isagulyants, G. V.,Gitis, K. M.,Myasnikov, V. A.,Neumoeva, G. E.
-
-
Read Online
- Synthesis of 2-methylpyrazine on ternary oxide catalysts
-
Synthesis of 2-methylpyrazine by cyclocondensation of ethylenediamine with 1,2-propylene glycol in the presence of zinc-molybdenum-chromium catalysts was studied.
- Kagarlitskii,Krichevskii,Balpanov
-
-
Read Online
- Influence of acid-base sites on ZnO-ZnCr2O4 catalyst during dehydrocyclization of aqueous glycerol and ethylenediamine for the synthesis of 2-methylpyrazine: Kinetic and mechanism studies
-
The physicochemical characteristics of ZnO-ZnCr2O4 (Zn-Cr-O) mixed oxides were determined by adsorption and spectroscopic methods. The catalytic activities of Zn-Cr-O was investigated for dehydrocyclization of ethylenediamine and aqu
- Venugopal, Akula,Sarkari, Reema,Anjaneyulu, Chatla,Krishna, Vankudoth,Kumar, Mandari Kotesh,Narender, Nama,Padmasri, Aytam Hari
-
-
Read Online
- Pt/Al2O3 CATALYSTS IN THE SYNTHESIS OF NITROGEN HETEROCYCLES. CATALYTIC SYNTHESIS OF PYRAZINES
-
A study was carried out on the use of Pt/Al2O3 catalysts in the synthesis of pyrazines via the dehydrogenation of piperazines, dehydrodeamination of diamines, and dehydrocyclocondensation of N-hydroxyalkyldiamines.In contrast to the current hypothesis of the intermediate formation of piperazine in the latter two reactions, evidence was found that these reactions proceed through initial dehydrogenation and the dehydrogenated intermediate then undergoes cyclization.Polyalkylpyrazines, formed by the alkylation of the pyrazine ring by hydrogenolysis products, are the major side-products in all the reactions studied.Pyrazines may be obtained in high yield and satisfactory selectivity by selecting suitable modifiers, which enhance the dehydrogenation activity of the catalyst and suppress the hydrogenolysis of the C-N bond.
- Gitis, K. M.,Neumoeva, G. E.,Isagulyants, G. V.
-
-
Read Online
- Glycerol catalytic cyclocondensation with ethanediamine to pyrazinyl compounds over the modified SiO2-Al2O3
-
The Fe, Zn, and Mn-modified SiO2-Al2O3 catalysts for the glycerol vapor-phase cyclocondensation with ethanediamine (ED) to 2-pyrazinemethanol (2-PMol) and 2-methylpyrazine (2-MP) in a fixed-bed system were prepared by coprecipitation and characterized by N2 adsorption-desorption, X-ray powder diffraction, and NH3 temperature-programmed desorption (NH3-TPD) in the present work. The results showed that the Mn-modified SiO2-Al2O3 catalyst with a SiO2/Al2O3 molar ratio 15.84 and 6% Mn gave the highest catalytic activity for formation of 2-PMol (53.1%) and 2-MP (42.9%). Mn species could cause the modulation of the acidic species of catalysts, improving the glycerol cyclocondensation with ED to 2-PMol, and also acted as the catalytic centers for the hydrodehydration of 2-PMol to 2-MP. However, too many strong acidic sites could lead to ED self-cyclocondensation to form a by-product pyrazine. The optimum temperature was tested to be 380°C for the cyclocondensation over a 6%Mn-SiO2-Al2O 3 catalyst.
- Liu, Chuanqi,Xu, Chenghua,Xia, Tongwei,Guo, Yan,Liu, Jianying
-
-
Read Online
- Pyrazine formation from serine and threonine
-
The formation of pyrazines from L-serine and L-threonine has been studied. L-Serine and L-threonine, either alone or combined, were heated at 120 °C as low temperature for 4 h or at 300 °C as high temperature for 7 min. The pyrazines formed from each reaction were identified by GC/MS, and the yields (to the amino acid used, as parts per million) were determined by GC/FID. It was found that pyrazine, methylpyrazine, ethylpyrazine, 2-ethyl-6- methylpyrazine, and 2,6-diethylpyrazine were formed from serine, whereas 2,5- dimethylpyrazine, 2,6-dimethylpyrazine, trimethylpyrazine, 2-ethyl-3,6- dimethylpyrazine, and 2-ethyl-3,5-dimethylpyrazine were formed from threonine. Mechanistically, it is proposed that the thermal degradation of serine or threonine is composed of various complex reactions. Among these reactions, decarbonylation followed by dehydration is the main pathway to generate the α-aminocarbonyl intermediates leading to the formation of the main product, such as pyrazine from serine or 2,5-dimethylpyrazine from threonine. Also, deamination after decarbonylation generates more reactive intermediates, α-hydroxycarbonyls. Furthermore, aldol condensation of these reactive intermediates provides α-dicarbonyls. Subsequently, these α- dicarbonyls react with the remaining serine or threonine by Strecker degradation to form additional α-aminocarbonyl intermediates, which then form additional pyrazines. In addition, decarboxylation and retroaldol reaction may also involve the generation of the intermediates.
- Shu, Chi-Kuen
-
-
Read Online
- Comparison of pyrazines formation in methionine/glucose and corresponding Amadori rearrangement product model
-
The generation of pyrazines in a binary methionine/glucose (Met/Glc) mixture and corresponding methionine/glucose-derived Amadori rearrangement product (MG-ARP) was studied. Quantitative analyses of pyrazines and methional revealed that MG-ARP generated more methional compared to Met/Glc, whereas lower content and fewer species of pyrazines were observed in the MG-ARP model. Comparing the availability of α-dicarbonyl compounds generated from the Met/Glc model, methylglyoxal (MGO) was a considerably effective α-dicarbonyl compound for the formation of pyrazines during MG-ARP degradation, but glyoxal (GO) produced from MG-ARP did not effectively participate in the corresponding formation of pyrazines due to the asynchrony on the formation of GO and recovered Met. Diacetyl (DA) content was not high enough to form corresponding pyrazines in the MG-ARP model. The insufficient interaction of precursors and rapid drops in pH limited the formation of pyrazines during MG-ARP degradation. Increasing reaction temperature could reduce the negative inhibitory effect by promoting the content of precursors.
- Cui, Heping,Deng, Shibin,Hayat, Khizar,Ho, Chi-Tang,Zhai, Yun,Zhang, Qiang,Zhang, Xiaoming
-
-
- Characteristic flavor formation of thermally processed N-(1-deoxy-α-D-ribulos-1-yl)-glycine: Decisive role of additional amino acids and promotional effect of glyoxal
-
The role of amino acids and α-dicarbonyls in the flavor formation of Amadori rearrangement product (ARP) during thermal processing was investigated. Comparisons of the volatile compounds and their concentrations when N-(1-deoxy-α-D-ribulos-1-yl)-glycine r
- Zhan, Huan,Cui, Heping,Yu, Junhe,Hayat, Khizar,Wu, Xian,Zhang, Xiaoming,Ho, Chi-Tang
-
-
- Application of a reusable Co-based nanocatalyst in alcohol dehydrogenative coupling strategy: Synthesis of quinoxaline and imine scaffolds
-
A nitrogen doped carbon supported cobalt catalyzed efficient synthesis of imines and quinoxaline motifs is reported. Co(OAc)2-Phen/Carbon-800 (Co-phen/C-800) showed the superior reactivity compared to other materials prepared at different temperature, in the synthesis of quinoxalines by the coupling between diamines and diols. Moreover, applying the transfer hydrogenation and acceptorless dehydrogenative coupling strategy, imines and quinoxaline derivatives were synthesized from the nitro compounds. The practical applicability of this protocol was demonstrated by the gram-scale synthesis and the reusability of the catalyst upto 8th cycle. Furthermore, several kinetic experiments were carried out to realize the probable mechanism.
- Panja, Dibyajyoti,Paul, Bhaskar,Balasubramaniam, Bhuvaneshwari,Gupta, Raju K.,Kundu, Sabuj
-
-
- Preparation process of pyrazinamide
-
A preparation process of pyrazinamide comprises the following steps: (1) synthesis of 2-methylpyrazine: putting a catalyst I into a reactor I, and performing reducing for 4 hours; adding 2-methylpyrazine into the reactor I, then adding ethylenediamine and 1, 2-propylene glycol, carrying out gas-solid phase contact catalytic reaction in the reactor I, cooling a mixture generated by the reaction through a condenser, feeding the mixture into a receiver, taking tail gas, and performing absorbing, emptying and separating to obtain 2-methylpyrazine, (2) chemical base catalysis; putting the catalystII into a reactor II, introducing an aqueous solution of 2-methylpyrazine in a mass ratio of (1:10)-(1:20) into the reactor II through a metering pump, introducing ammonia gas and air, controlling thetemperature of the reaction system to be 3-6 DEG C, maintaining the pH value to be 9-10, performing reacting for 1-2 hours, and performing heating to 20-30 DEG C to obtain 2-cyanopyrazine; and (3) synthesis of pyrazinamide. The preparation process of pyrazinamide has the advantages of the simple process, the high conversion rate, no generation of by-product pyrazinic acid, the good economic benefits and the wide application prospect.
- -
-
Paragraph 0023-0024; 0028-0029; 0032-0033; 0037-0038; 0042
(2020/07/24)
-
- Reversible Interconversion between 2,5-Dimethylpyrazine and 2,5-Dimethylpiperazine by Iridium-Catalyzed Hydrogenation/Dehydrogenation for Efficient Hydrogen Storage
-
A new hydrogen storage system based on the hydrogenation and dehydrogenation of nitrogen heterocyclic compounds, employing a single iridium catalyst, has been developed. Efficient hydrogen storage using relatively small amounts of solvent compared with previous systems was achieved by this new system. Reversible transformations between 2,5-dimethylpyrazine and 2,5-dimethylpiperazine, accompanied by the uptake and release of three equivalents of hydrogen, could be repeated almost quantitatively at least four times without any loss of efficiency. Furthermore, hydrogen storage under solvent-free conditions was also accomplished.
- Fujita, Ken-Ichi,Wada, Tomokatsu,Shiraishi, Takumi
-
supporting information
p. 10886 - 10889
(2017/08/30)
-
- A highly efficient gas-dominated and water-resistant flame retardant for non-charring polypropylene
-
Traditional phosphorus-nitrogen (P-N) flame-retardant systems for polypropylene (PP) always act through joint action of the gaseous phase and condensed phase, and are accompanied with a decrease of the thermal stability and water resistance. In this work, a novel mono-component and gas-dominated flame retardant, named DPPIP, was prepared through an amidation reaction of diphenylphosphinyl chloride and piperazine, and used to flame retard PP. Experimental results confirmed that both the thermal stability and water resistance of PP/DPPIP were improved. The initial thermal decomposition temperature of PP/25 wt% DPPIP at 5 wt% weight loss was 287.5 °C under air atmosphere, which is higher than that of neat PP (266.1 °C). Besides, a water-resistance test verified that PP/25 wt% DPPIP had a weight loss of only about 0.52 wt%. More importantly, the flame retardant ability of PP/25 wt% DPPIP had been greatly improved, passing the V-0 rating (UL-94). Furthermore, after the water-resistance test, the LOI value of PP/25 wt% DPPIP exhibited nearly no difference and still passed the UL-94 V-0 rating. A cone calorimeter (CC) result indicated that DPPIP had a positive effect on inhibiting heat release of PP during combustion. All of these combustion tests displayed that there was no char left. The flame retardant mechanism of DPPIP was investigated with py-GC/MS and TG-FTIR. The results illustrated that the gaseous phase resulting from the thermal decomposition of DPPIP played the leading role in the self-extinguishing behavior of PP/DPPIP, which consisted of a large amount of inflammable gaseous products such as piperazine and its derivatives, and phosphorus-containing structures.
- Shao, Zhu-Bao,Zhang, Ming-Xin,Han, Ye,Yang, Xu-Dong,Jin, Jing,Jian, Rong-Kun
-
p. 51919 - 51927
(2017/11/22)
-
- The effects of thermal treatment of ZnO–ZnCr2O4 catalyst on the particle size and product selectivity in dehydrocyclization of crude glycerol and ethylenediamine
-
The ZnO–ZnCr2O4 (Zn–Cr–O) sample obtained by decomposition of Zn-Cr hydrotalcite precursor was subjected to the thermal treatment at different temperatures and the physico-chemical properties of the Zn–Cr–O system were compared with
- Sarkari, Reema,Krishna, Vankudoth,Sudhakar, Medak,Rao, Tumula Venkateshwar,Padmasri, Aytam Hari,Srinivas, Darbha,Venugopal, Akula
-
p. 602 - 609
(2016/10/18)
-
- 1H-pyrrole-2,4-dicarbonyl-derivatives and their use as flavoring agents
-
The present invention primarily relates to 1H-pyrrole-2,4-dicarbonyl-derivatives of Formula (I) wherein R1, R2, R3, Z. Z' and J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) or of a mixture of compounds of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
- -
-
-
- Imidazo[1,2-a]pyridine-ylmethyl-derivatives and their use as flavoring agents
-
The present invention primarily relates to imidazo[1,2-a]pyridine-ylmethyl-derivatives of Formula (I) wherein R1, R2, X, W e J are as defined in the description, to mixtures thereof and to the use thereof as flavoring agents. The compounds in accordance with the present invention are suitable for producing, imparting, or intensifying an umami flavor. The invention further relates to flavoring mixtures, compositions for oral consumption as well as ready-to-eat, ready-to-use and semifinished products, comprising an effective amount of the compound of Formula (I) and to specific methods for producing, imparting, modifying and/or intensifying specific flavor impressions.
- -
-
-
- Volatile compounds formed from the pyrolysis of chitosan
-
Chitosan is a renewable resource for the production of nitrogen-containing aromatic heterocyclics. It was found that chitosan started to decompose and produce some volatile compounds at around 525 K in a nitrogen atmosphere, the volatiles were characterized by Fourier transform infrared spectrometer. The apparent activation energy for the thermal degradation of chitosan was determined. To further investigate the degradation, chitosan was pyrolyzed under vacuum at 553 K for 1 h, and the volatile compounds were analyzed by gas chromatography/mass spectrometry. The volatile compounds included aromatic heterocyclics such as pyrazines, pyridines, pyrroles and furans, and the pyrazines were the major products. The pyrolysis mechanism of chitosan was also proposed.
- Zeng, Lintao,Qin, Caiqin,Wang, Liansheng,Li, Wei
-
experimental part
p. 1553 - 1557
(2011/09/14)
-
- Formation of pyrazines in maillard model systems of lysine-containing dipeptides
-
Whereas most studies concerning the Maillard reaction have focused on free amino acids, little information is available on the impact of peptides and proteins on this important reaction in food chemistry. Therefore, the formation of flavor compounds from the model reactions of glucose, methylglyoxal, or glyoxal with eight dipeptides with lysine at the N-terminus was studied in comparison with the corresponding free amino acids by means of stir bar sorptive extraction (SBSE) followed by GC-MS analysis. The reaction mixtures of the dipeptides containing glucose, methylglyoxal, and glyoxal produced 27, 18, and 2 different pyrazines, respectively. Generally, the pyrazines were produced more in the case of dipeptides as compared to free amino acids. For reactions with glucose and methylglyoxal, this difference was mainly caused by the large amounts of 2,5(6)-dimethylpyrazine and trimethylpyrazine produced from the reactions with dipeptides. For reactions with glyoxal, the difference in pyrazine production was rather small and mostly unsubstituted pyrazine was formed. A reaction mechanism for pyrazine formation from dipeptides was proposed and evaluated. This study clearly illustrates the capability of peptides to produce flavor compounds that can differ from those obtained from the corresponding reactions with free amino acids.
- Van Lancker, Fien,Adams,De Kimpe, Norbert
-
scheme or table
p. 2470 - 2478
(2010/09/04)
-
- The effect of pH on the formation of aroma compounds produced by heating a model system containing l-ascorbic acid with l-threonine/l-serine
-
The identification of aroma compounds, formed from the reactions of l-ascorbic acid with l-threonine/l-serine at five different pH values (5.00, 6.00, 7.00, 8.00, or 9.55) and 143 ± 2 °C for 2 h, was performed using a SPME-GC-MS technique, and further use
- Yu, Ai-Nong,Zhang, Ai-Dong
-
experimental part
p. 214 - 219
(2011/12/14)
-
- Investigation of the aroma-active compounds formed in the maillard reaction between glutathione and reducing sugars
-
Aroma-active compounds formed during the thermal reaction between glutathione (GSH) and reducing sugars were analyzed by gas chromatography-mass spectrometry (GC-MS) and GC-olfactometry (GC-O) with aroma extract dilution analysis (AEDA). Application of AEDA to glutathione Maillard reaction products (GSH MRPs) led to the identification of 19 aroma-active compounds in the thermal reaction of glutathione with glucose or fructose. In addition, the carbohydrate module labeling (CAMOLA) approach was also employed to elucidate the formation pathways for selected target sulfur aroma compounds, such as 5-methylthiophene-2-carbaldehyde and 3-methylthiophene-2-carbaldehyde, which have not been reported previously. The intact carbon skeleton of glucose via 3-deoxyhexosone is incorporated into 5-methylthiophene-2-carbaldehyde with the hydrogen sulfide of GSH. On the other hand, the formation of 3-methylthiophene2-carbaldehyde may occur via the recombination of a C-4 sugar fragment and mercaptoacetaldehyde.
- Lee, Sang Mi,Jo, Ye-Jin,Kim, Young-Suk
-
experimental part
p. 3116 - 3124
(2011/08/05)
-
- Synthesis of pyridines and pyrazines using an intramolecular hydroamination-based reaction sequence
-
A management issue! Various pyridines and pyrazines can be efficiently accessed from simple acyclic precursors using an intramolecular hydroamination/isomerization/aromatization sequence (see scheme). ρ-Toluenesulfonic acid (2 mol%) is used to catalyze this novel alkyne annulation, in which the oxime group allows for a subsequent redoxneutral aromatization step to occur.
- Rizk, Toni,Bilodeau, Eric J.-F.,Beauchemin, Andre M.
-
supporting information; experimental part
p. 8325 - 8327
(2010/01/16)
-
- Efficient and chemoselective deoxygenation of amine N-oxides using polymethylhydrosiloxane
-
Deoxygenation of aromatic and aliphatic amine N-oxides to the corresponding amines is achieved under mild conditions. The reagent combination employed for this transformation is polymethylhydrosiloxane (PMHS) in the presence of either tetrakis (triphenylphosphine) palladium (0) [Pd(PPh3)4], titanium (IV) isopropoxide [Ti(i-PrO)4] or palladium on carbon (Pd/C).
- Chandrasekhar,Reddy, Ch. Raji,Rao, R. Jagadeeshwar,Rao, J. Madhusudana
-
p. 349 - 351
(2007/10/03)
-
- Chiral copper(I) iodide based porous coordination frameworks with asymmetrically substituted bridging N-donor ligands
-
The 2-dimensional coordination polymers 2∞[{(CuI)2(Mepyz)2} · Mepyz] (1a), 2∞[CuX(Mepyz)] (2a, X = Br; 2b, X = Cl) and 2∞[(CuX)2(Mepyz)] (3a, X = I;3b, X = Br) may be prepared by reaction of the appropriate copper(I) halide with 2-methylpyrazine (Mepyz) either in acetonitrile solution at 130 °C (2a/2b, 3a/3b) or without solvent at 20 °C (1a). Mepyz ligands bridge (CuI)2 rhomboid dimers in the chiral network of 1a, whose resulting 24-membered rings are large enough to accomodate an Mepyz guest molecule. 1a rapidly loses these guests to afford a crystalline powder (1b), that can reversibly imbibe benzonitrile molecules into its open channels. In contrast to 1a, the sheets of 2a/2b contain zigzag infinite CuX chains, those of 3a/3b staircase 1∞[CuX] double chains as their characteristic substructures. Helical 1∞[CuI] single chains in the 3-dimensional network of 3∞[CuI(Mepip)]4 are bridged by R-2-methylpiperazine (Mepip) ligands in a second example of a chiral coordination polymer.
- Rossenbeck,Sheldrick
-
p. 467 - 472
(2007/10/03)
-
- The effect of high pressure on the formation of volatile products in a model Maillard reaction
-
Reaction progress in the formation and subsequent decay of several of the volatile products from a model Maillard reaction between lysine and xylose has been followed at pH 7 and 10 and at elevated pressures. At low pH, the buildup and decay of 5-methyl-4-hydroxy-3(2H)-furanone and several minor products were observed. The application of high pressure results in a much diminished maximum concentration of each although the time to the maximum is unaffected. At pH 10, products contain nitrogen heterocycles with 2-methylpyrazine being the principal one which builds up and only slowly decays with time. Again, the yield is greatly reduced by pressure. The results are interpreted in terms of the inhibition by pressure of the formation of the precursor the Amadori rearrangement product which affects subsequent products. In some instances rates of formation are also found to be slightly inhibited while degradation of these products is accelerated. The corresponding mechanisms are examined in the light of these results.
- Bristow, Mark,Isaacs, Neil S.
-
p. 2213 - 2218
(2007/10/03)
-
- Process for producing pyrazine compounds
-
A process for producing a pyrazine compound of the general formula (3): STR1 wherein R1, R2, R3 and R4 represent a hydrogen atom or a lower alkyl group, which comprises catalytically reacting in a gaseous phase a diamine compound of the general formula: STR2 with a diol compound of the general formula: STR3 in the presence of a catalyst containing hydrogen-treated silver or a catalyst containing silver and at least one element selected from the group consisting of alkali metals, alkaline earth metals, zinc and lanthanoid elements.
- -
-
-
- Mechanisms of Formation of Alkylpyrazines in the Maillard Reaction
-
The formation of alkylpyrazines was investigated in the reaction of glucose and fructose with -alanine and glycine.The reaction systems were heated for 7 min at 180 deg C.GC-MS and GC-MS/MS data were used to determine the rate of incorporati
- Amrani-Hemaimi, Miriam,Cerny, Christoph,Fay, Laurent B.
-
p. 2818 - 2822
(2007/10/03)
-
- Intermolecular and intramolecular cyclization over modified ZSM-5 and chromite catalysts to synthesize 2-methyl pyrazine and piperazine
-
The synthesis of methyl pyrazine and piperazine has been carried out over HZSM-5 and modified copper-chromite catalysts.The reaction occurs through the dehydrocyclization route at acidic centres.The Bronsted acidic centres at interstitial are particularly responsible for the conversion of propylene glycol, propylene oxide with ethylenediamine and β-hydroxy-propylethylenediamine to the N-containing heterocycles through intermolecular and intramolecular cyclization.In the formation of N-containing heterocycles, the steps involved are dehydration and cyclization.The important difference between these reactions and the methano-to-gasoline (MTG) process is the formation of olefinic compounds as intermediates in the latter.
- Kulkarni, S. J.,Subrahmanyam, M.,Rao, A. V. Rama
-
-
- EFFECT OF TIME AND TEMPERATURE ON THE PREPARATION OF PYRAZINES IN MODEL REACTIONS OF THE SYNTHESIS OF AROMA-FORMING SUBSTANCES
-
The qualitative and quantitative compositions of pyrazines that form in model glucose-ammonia and glucose-ammonia-leucine reactions in a glycerol medium were studied.Reaction conditions were found that ensure the synthesis of 23 alkylpyrazines in total concentration ca. 6 g/kg.The obtained mixture of pyrazines is promising for use in the development of food aroma-forming substances.Keywords: pyrazines, Maillard reaction, capillary gas chromatography.
- Misharina, T. A.,Golovnya, R. V.,Yakovleva, V. N.
-
p. 1258 - 1263
(2007/10/02)
-
- Process for manufacturing pyrazines
-
Pyrazines having the formula (I) STR1 wherein R is H, methyl, or ethyl are prepared by passing a hydrogen stream containing corresponding diamines having the formula (II) STR2 wherein R is same as previously defined, over a copper-chromite catalyst which has been once reduced at 300°-450° C. in a hydrogen-containing stream.
- -
-
-
- CATALYTIC SYNTHESIS OF DIAZINES FROM 1,3-DIAMINOPROPANE AND 3-AMINO-1-PROPANOL
-
The transformation of 1,3-diaminopropane and 3-amino-1-propanol under pulse conditions over tungsten trioxide in an inert atmosphere at 300-500 deg C were investigated.The transformation of 1,3-diaminopropane leads to the formation of saturated pyrimidine
- Oshis, Ya. F.,Anderson, A. A.,Shimanskaya, M. V.
-
p. 740 - 745
(2007/10/02)
-
- Ueber die Synthese von 2,3-Dialkylpyrazinen
-
2,3-Dialkylquinoxalines (4), which are available from the reaction of benzofuroxan (1) with ketones and subsequent reduction of the 2,3-dialkylquinoxaline N,N'-dioxides (3), are converted to 2,3-dialkylpyrazines (6) by oxidation-decarboxylation steps.
- Heyns, Kurt,Behse, Ernst,Francke, Wittko
-
p. 240 - 245
(2007/10/02)
-
- Studies on the Thermolysis of 2-(2-Hydroxy-2-arylethyl)pyrazines. An Example of a Retro-Ene-Type Reaction
-
Several substituted 2-(2-hydroxy-2-arylethyl)pyrazines (1-10) have been prepared and their thermolysis in diglyme and DMF studied.Each of these substrates decomposes to give the parent methylpyrazine and the corresponding aryl aldehyde.Kinetic, isotope effect, and solvent effect studies suggest a mechanism involving a nonpolar concerted six-membered-ring transition state.The degree of proton transfer in the transition state is discussed in detail.Methyl substituents on the pyrazine ring were found to strongly affect the reaction rate.This phenomenon is analyzed interms of the steric and electronic effects induced by the methyl substituents.
- Houminer, Yoram
-
p. 999 - 1003
(2007/10/02)
-
- Pharmaceutical compositions and methods of inhibiting gastric acid secretion
-
Pharmaceutical compositions and methods of inhibiting gastric acid secretion by administering N-alkenyl and N-alkynyl thioamides.
- -
-
-
