Initial Condensation Research Articles

One-Pot Synthesis of 5-Hydroxy-4H-1,3-thiazin-4-ones: Structure Revision, Synthesis, and NMR Shift Dependence of Thiasporine A.

An annulation of arylthioamides with 3-bromopyruvic acid chloride to 5-hydroxy-4H-1,3-thiazin-4-ones has been developed. The initial condensation affords two regioisomeric thiazolinone intermediates in a temperature-dependent manner. The synthesis of the 2-aminophenylthiazinone derivative led to the revision of the previously proposed structure of thiasporine A. Synthesis of the revised structure and NMR analysis revealed that thiasporine A had been isolated as a carboxylate.

Zinc‐Catalyzed Multicomponent Reactions: Easy Access to Furyl‐Substituted Cyclopropane and 1,2‐Dioxolane Derivatives

AbstractA convenient synthesis of cyclopropyl‐substituted furan derivatives by a zinc‐catalyzed three‐component coupling of 1,3‐dicarbonylic compounds, 2‐alkynals and alkenes is reported. A sequence consisting of an initial Knoevenagel condensation, cyclization, and a final cyclopropanation reaction would account for the formation of the final products. In most cases, this multicomponent process proceeds in good yield under mild reaction conditions and in the presence of a low catalyst loading. The efficient formation of 1,2‐dioxolane derivatives by the zinc‐promoted aerobic oxidation of some cyclopropane derivatives is also reported. The 1,2‐dioxolane derivatives are also available by a four‐component reaction.

Effect of temperature and velocity of superheated steam on initial condensation of distillers’ spent grain pellets during drying

ABSTRACTInitial condensation on the sample surface during superheated steam (SS) drying leads to increased sample moisture affecting its mechanical and thermal properties. A study was conducted to understand the effect of temperature and velocity of SS on the amount of initial condensation on distillers’ spent grain pellets with an initial moisture content of 25% (wet basis). These pellets were dried using SS at 120, 150, and 180°C with velocities 0.5, 1.0, 1.2, and 1.4 m/s. Separate experiments were conducted for recording mass and surface temperature of the pellets during SS drying. Mass recorded over the drying period was then compared with the predicted mass obtained by solving the standard heat balance and film condensation equations. The predicted values of mass flux due to initial condensation were in close agreement with directly measured values with a maximum mean square error of 0.20. There was a 60–64% decrease in the amount of initial condensation as the temperature of SS was increased from 120 to 180°C. The results indicate that the initial condensation can be minimal when the temperature of SS is equal or above 180°C with SS velocity equal or above 1 m/s using a preheated drying chamber.

Condensation Corrosion: A Theoretical Approach

O speleogenetskem pomenu vode, ki iz toplega vlažnega zraka kondenzira na hladne jamske stene je napisanega veliko. Kondenzirana voda se hitro uravnoteži z ogljikovem dioksidom v jamski atmosferi, zato raztaplja apnenec in pri tem tvori različne skalne oblike. V članku predstavimo fizikalne osnove in podamo enačbe, ki omogočajo približno oceno hitrosti kondenzacije v različnih pogojih. Zaradi kondenzacijske toplote in prenosa toplote iz zraka na steno, se temperatura stene viša, pri čemer se zmanjšuje razlika temperature med zrakom in steno. To predstavlja robni pogoj za prevajanje toplote iz jame. Pri konstantni temperaturi zraka, hitrost kondenzacije v nekaj dneh pade za več velikostnih redov, dokler ne doseže končne vrednosti, pri kateri se ves toplotni tok prenese na površje. Slednjo za primer krogelnih in valjastih prostorov opišemo kot funkcijo globine rova Z. Pri dnevnih in sezonskih spemembah temperature, značilnih v bližini jamskih vhodov, je hitrost kondenzacije in posledično korozije do 1μm na leto. Teoretične rezultate uporabimo tudi za izračun korozije kapnikov in tipa škrapelj (röhrenkarren), ki jih opisuje Simms (2003). Za pretvorbo hitrosti kondenzacije v hitrost korozije, potrebujemo podatek o stopnji nasičenja vode. V dodatku predstavimo poskus, ki dokazuje, da se voda, ki kondenzira na jamske stene, hitro nasiti tako v primeru apnenca kot v primeru sadre. Condensation of water from warm, humid air to cold rock walls in caves is regarded to play a significant role in speleogenesis. The water condensing to the cave walls quickly attains equilibrium with the carbon dioxide in the surrounding air, and consequently dissolves limestone or gypsum forming various types of macro- ,meso-, and micromorphologies. In this paper we present the basic physical principles of condensation and give equations, which allow a satisfactory estimation of condensation rates. Water condensing to a cooler wall releases heat of condensation, which raises the temperature of the wall thus reducing the temperature difference (T between the warm air and the cave wall. Furthermore one has to take into account the heat flux from the air to the cave wall. This defines the boundary conditions for the equation of heat conduction. For a constant temperature of the air initial condensation rates are high but then drop down rapidly by orders of magnitude during the first few days. Finally constant condensation rates are attained, when the heat flux into the rock is fully transmitted to the surface of the karst plateau. For spherical and cylindrical conduits these can be obtained as a function of the depth Z below the surface. When diurnal or seasonal variations of the air temperature are active as is the case close to cave entrances, condensation rates can become quite significant, up to about 10-6 m/year. The theoretical results are applied also to corrosion of speleothems and the formation of "röhrenkarren" as described by Simms (2003). To convert condensation rates into retreat of bedrock the saturation state of the solution must be known. In the appendix we present experiments, which prove that in any case the solution flowing off the rock is saturated with respect to limestone or gypsum, respectively.

Microbial production of bi-functional molecules by diversification of the fatty acid pathway

Fatty acids that are chemically functionalized at their ω-ends are rare in nature yet offer unique chemical and physical properties with wide ranging industrial applications as feedstocks for bio-based polymers, lubricants and surfactants. Two enzymatic determinants control this ω-group functionality, the availability of an appropriate acyl-CoA substrate for initiating fatty acid biosynthesis, and a fatty acid synthase (FAS) variant that can accommodate that substrate in the initial condensation reaction of the process. In Type II FAS, 3-ketoacyl-ACP synthase III (KASIII) catalyses this initial condensation reaction. We characterized KASIIIs from diverse bacterial sources, and identified variants with novel substrate specificities towards atypical acyl-CoA substrates, including 3-hydroxybutyryl-CoA. Using Alicyclobacillus acidocaldarius KASIII, we demonstrate the in vivo diversion of FAS to produce novel ω-1 hydroxy-branched fatty acids from glucose in two bioengineered microbial hosts. This study unveils the biocatalytic potential of KASIII for synthesizing diverse ω-functionalized fatty acids.

Skeletally Diverse Synthesis of Indole-Fused Diazocine and Diazepine Frameworks by One-Pot, Two-Component Cascade Reaction.

An expeditious and novel strategy has been explored for the synthesis of structurally diverse indole-fused diazocine and diazepine derivatives. A substrate-based diversification approach of methyl-3-aminoindole/indoline benzoates coupled with the Pictet-Spengler reaction and three different reaction cascades furnished indolodiazepine and indoloquinoxalines. The formation of indolodiazocines proceeds through an initial condensation followed by intramolecular alkylation.

ChemInform Abstract: Enantio‐ and Diastereoselective Formal Hetero‐Diels—Alder Reactions of Trifluoromethylated Enones Catalyzed by Chiral Primary Amines.

AbstractA set of enantiopure primary amine catalyzes the formal hetero‐Diels—Alder reaction of the carbonyl group in electron‐deficient trifluoromethylated enones (I) and enolizable acyclic aliphatic enones (II).

Cascade oxime formation, cyclization to a nitrone, and intermolecular dipolar cycloaddition.

Simple haloaldehydes, including enolisable aldehydes, were found to be suitable for the formation of cyclic products by cascade (domino) condensation, cyclisation, dipolar cycloaddition chemistry. This multi-component reaction approach to heterocyclic compounds was explored by using hydroxylamine, a selection of aldehydes, and a selection of activated dipolarophiles. Initial condensation gives intermediate oximes that undergo cyclisation with displacement of halide to give intermediate nitrones; these nitrones undergo in situ intermolecular dipolar cycloaddition reactions to give isoxazolidines. The cycloadducts from using dimethyl fumarate were treated with zinc/acetic acid to give lactam products and this provides an easy way to prepare pyrrolizinones, indolizinones, and pyrrolo[2,1-a]isoquinolinones. The chemistry is illustrated with a very short synthesis of the pyrrolizidine alkaloid macronecine and a formal synthesis of petasinecine.

“Maillard products” and “Maillard reactions” are much discussed in food science and technology, but do such products and reactions deserve their name?

Whereas the number of scientific and technical publications dealing with “Maillard reactions” is increasing in food science and technology, in particular due to the importance of non-enzymatic browning during food production, the expressions “Maillard reaction” and “Maillard products” remain vague, and different authors have different definitions. A historical study of the scientific researches on the reactions between sugars, on the one hand, and compounds containing an amino group on the other hand, shows that only the initial condensation of reducing sugars and peptides or proteins should be called Maillard reaction. The complex reaction pattern that follows this initial condensation should be explored more quantitatively, in order to assess the comparative kinetics of the various reaction pathways leading to the numerous compounds which are finally produced.

ChemInform Abstract: Synthesis of Pyrazolo[5,1‐a]isoindoles and Pyrazolo[5,1‐a]isoindole‐3‐carboxamides Through One‐Pot Cascade Reactions of 1‐(2‐Bromophenyl)buta‐2,3‐dien‐1‐ones with Isocyanide and Hydrazine or Acetohydrazide.

A novel and efficient method for the construction of the pyrazolo[5,1-a]isoindole scaffold via a one-pot three-component cascade reaction of 1-(2-bromophenyl)buta-2,3-dien-1-one with hydrazine and isocyanide promoted by a Pd catalyst is described. This cascade process proceeds through initial condensation of the allenic ketone with hydrazine followed by Pd-catalyzed isocyanide insertion into the C–Br bond and intramolecular C–N bond formation. Interestingly, when acetohydrazide was used in place of hydrazine, a more sophisticated procedure involving condensation, isocyanide insertion into C–H and C–Br bonds, deacetylation, and formation of C–C, C–O, and C–N bonds occurred to afford pyrazolo[5,1-a]isoindole-3-carboxamides with good efficiency.

EVOLUTION OF THE DUST IN V4332 SAGITTARII

An eruptive nova-like event took place in 1994 in the stellar-merger candidate V4332 Sgr. Following the eruption, dust consisting of refractory silicate-rich dust grains containing a significant component of AlO bonding was formed sometime between 1998 and 2003. Observations using Spitzer between 2005 and 2009 show significant changes in the 10 μm silicate stretch feature. There is a deepening of the 10 μm silicate stretch as well as the development of a feature between about 13 and 20 μm consistent with a blend of the MgO and FeO stretching features and the O–Si–O bending mode of increasingly ordered silicate dust. Near-infrared observations show the presence of AlO and water vapor in the outflow in 2003, 2004, and 2005: the AlO has significantly decreased in spectra obtained in 2014 while the water vapor remains largely unchanged. An attempt is made to correlate these observations and understand the significance of these changes using DUSTY modeling. The observations appear consistent with the kinetically controlled condensation of highly underoxidized SiO/AlO/Fe/Mg dust grains in the outflow followed by the continuous evolution of the initial condensate due to thermal annealing and oxidation of the dust via reaction with ambient O, OH, and H2O in the expanding, cooling shell. Periodic monitoring of this dust shell over the mid-infrared spectral range could yield useful information on the evolution of underoxidized silicate condensates exposed to hot water vapor in more conventional circumstellar environments.

Persistent Water-Nitric Acid Condensate with Saturation Water Vapor Pressure Greater than That of Hexagonal Ice.

A laboratory chilled mirror hygrometer (CMH), exposed to an airstream containing water vapor (H2O) and nitric acid (HNO3), has been used to demonstrate the existence of a persistent water-nitric acid condensate that has a saturation H2O vapor pressure greater than that of hexagonal ice (Ih). The condensate was routinely formed on the mirror by removing HNO3 from the airstream following the formation of an initial condensate on the mirror that resembled nitric acid trihydrate (NAT). Typical conditions for the formation of the persistent condensate were a H2O mixing ratio greater than 18 ppm, pressure of 128 hPa, and mirror temperature between 202 and 216 K. In steady-state operation, a CMH maintains a condensate of constant optical diffusivity on a mirror through control of only the mirror temperature. Maintaining the persistent condensate on the mirror required that the mirror temperature be below the H2O saturation temperature with respect to Ih by as much as 3 K, corresponding to up to 63% H2O supersaturation with respect to Ih. The condensate was observed to persist in steady state for up to 16 h. Compositional analysis of the condensate confirmed the co-condensation of H2O and HNO3 and thereby strongly supports the conclusion that the Ih supersaturation is due to residual HNO3 in the condensate. Although the exact structure or stoichiometry of the condensate could not be determined, other known stable phases of HNO3 and H2O are excluded as possible condensates. This persistent condensate, if it also forms in the upper tropical troposphere, might explain some of the high Ih supersaturations in cirrus and contrails that have been reported in the tropical tropopause region.

Imidazolium Sulfonates as Environmental-Friendly Catalytic Systems for the Synthesis of Biologically Active 2-Amino-4H-chromenes: Mechanistic Insights.

Ionic Liquids (ILs) are valuable reaction media extremely useful in industrial sustainable organic synthesis. We describe here the study on the multicomponent reaction (MCR) between salicylaldehyde (2) and ethyl cyanoacetate (3), catalyzed by imidazolium sulfonates, to form chromenes 1, a class of heterocyclic scaffolds exhibiting relevant biological activity. We have clarified the reaction mechanism by combining the experimental results with computational studies. The results reported herein suggest that both the imidazolium core and the sulfonate anions in the selected ILs are involved in the reaction course acting as hydrogen bond donors and acceptors, respectively. Contrarily to the most widely accepted mechanism through initial Knoevenagel condensation, the most favorable reaction pathway consists of an aldolic reaction between reagents followed by heterocyclization, subsequent dehydration, and, finally, the Michael addition of the second molecule of ethyl cyanoacetate (3) to yield the chromenes 1.

Synthesis of Pyrazolo[5,1-a]isoindoles and Pyrazolo[5,1-a]isoindole-3-carboxamides through One-Pot Cascade Reactions of 1-(2-Bromophenyl)buta-2,3-dien-1-ones with Isocyanide and Hydrazine or Acetohydrazide

A novel and efficient method for the construction of the pyrazolo[5,1-a]isoindole scaffold via a one-pot three-component cascade reaction of 1-(2-bromophenyl)buta-2,3-dien-1-one with hydrazine and isocyanide promoted by a Pd catalyst is described. This cascade process proceeds through initial condensation of the allenic ketone with hydrazine followed by Pd-catalyzed isocyanide insertion into the C-Br bond and intramolecular C-N bond formation. Interestingly, when acetohydrazide was used in place of hydrazine, a more sophisticated procedure involving condensation, isocyanide insertion into C-H and C-Br bonds, deacetylation, and formation of C-C, C-O, and C-N bonds occurred to afford pyrazolo[5,1-a]isoindole-3-carboxamides with good efficiency.

Enantio- and Diastereoselective Formal Hetero-Diels-Alder Reactions of Trifluoromethylated Enones Catalyzed by Chiral Primary Amines.

Enantioselective formal hetero-Diels-Alder reactions of trifluoromethylated enones and 2-amino-1,3-butadienes generated in situ from aliphatic acyclic enones and chiral primary amines are reported. The corresponding tetrahydropyran-4-ones are formed in up to 94 % yield and with up to 94 % ee. The reaction was carried out through a stepwise mechanism, including initial aminocatalytic aldol condensation of 2-amino-1,3-butadiene to the trifluoromethylated carbonyl group followed by an intramolecular oxa-Michael addition. Both NMR investigation and theoretical calculations on the transition state indicate that the protonated tertiary amine could effectively activate the carbonyl group of the trifluoromethyl ketone to promote the addition process through hydrogen-bonding interaction of N-H⋅⋅⋅F and N-H⋅⋅⋅O simultaneously, and thus provide a chiral environment for the approach of amino-1,3-butadienes to the activated trifluoromethyl ketone, resulting in high enantioselectivity.

Enhanced production of branched-chain fatty acids by replacing β-ketoacyl-(acyl-carrier-protein) synthase III (FabH).

Branched-chain fatty acids (BCFAs) are important precursors for the production of advanced biofuels with improved cold-flow properties. Previous efforts in engineering type II fatty acid synthase (FAS) for BCFA production suffered from low titers and/or the co-production of a large amount of straight-chain fatty acids (SCFAs), making it nearly impossible for further conversion of BCFAs to branched biofuels. Synthesis of both SCFAs and BCFAs requires FabH, the only β-ketoacyl-(acyl-carrier-protein) synthase in Escherichia coli that catalyzes the initial condensation reaction between malonyl-ACP and a short-chain acyl-CoA. In this study, we demonstrated that replacement of the acetyl-CoA-specific E. coli FabH with a branched-chain-acyl-CoA-specific FabH directed the flux to the synthesis of BCFAs, resulting in a significant enhancement in BCFA titer compared to a strain containing both acetyl-CoA- and branched-chain-acyl-CoA-specific FabHs. We further demonstrated that the composition of BCFAs can be tuned by engineering the upstream pathway to control the supply of different branched-chain acyl-CoAs, leading to the production either even-chain-iso-, odd-chain-iso-, or odd-chain-anteiso-BCFAs separately. Overall, the top-performing strain from this study produced BCFAs at 126 mg/L, comprising 52% of the total free fatty acids.

Chromo-Weibel instabilities in classical Yang-Mills evolution

The standard model of relativistic heavy-ion collisions describes the hadronic collision in four distinct stages: the initial Color glass condensate, the glasma, the quark gluon plasma and finally the hot hadron gas. Exploring the transition from at first Lorentz contracted sheets of hadrons, the color glass condensate, to thermal QCD matter is the core of this work. The study of anisotropically expanding plasmas shows that non-Abelian plasmas isotropize fast enough thanks to the chromo-Weibel instability. In recent work we find filamentation instabilities in SU(3) Yang-Mills plasma. Real time simulations are a highly promising approach to shed light on the fast thermalization of non-equilibrium matter. This involves to further develop both the theoretical foundations of the description of initial-state fluctuations and the computational framework for the turbulent dynamics of nuclear matter at extreme energy densities.

Corrosion Fatigue Crack Propagation Rates for Steam Turbine Blade 13% Cr Steels

Studies of stress corrosion in X12Cr13 and X20Cr13 steels used for rotor blades of steam turbines have been conducted for determining the average rate of corrosion cracking development da / dt. Specimens were exposed to the salt mist environment of 1,2 ppm NaCl concentration in temperature of 60° C. The research environment represents the initial condensate of humidity from 3÷4%. Average rate of corrosion cracking development for specimens of the X12Cr13 is by 0,005 µm/h higher from specimens of the X20Cr13 steel. Course of the corrosion cracking initiation depends to a high degree on metal structure, and probably the close value of cracking propagation rate depends on the similar structure of those steels – high-tempered martensite with carbides at grain boundaries.

Crystallization of silicon nanoclusters with inert gas temperature control

We analyze the fundamental process of crystallization of silicon nanoclusters by means of molecular dynamics simulations, complemented by magnetron-sputter inert gas condensation, which was used to synthesize polycrystalline silicon nanoclusters with good size control. We utilize two well-established Si interatomic potentials: the Stillinger-Weber and the Tersoff III. Both the simulations and experiments show that upon cooling down by an Ar gas thermal bath, initially liquid, free-standing Si nanocluster can grow multiple crystal nuclei, which drive their transition into polycrystalline solid nanoclusters. The simulations allow detailed analysis of the mechanism, and show that the crystallization temperature is size-dependent and that the probability of crystalline phase nucleation depends on the highest temperature the cluster reaches during the initial condensation and the cooling rate after it.

J0540205 反射衝撃波によって誘起される非凝縮性気体を伴う蒸気の凝縮現象に関する分子気体力学に基づく数値計算

On the basis of the molecular gas dynamics analysis, we investigated the influence of non-condensable gas on non-equilibrium vapor condensation induced by reflected shock wave. In the present study, the governing parameters of this problem are initial number density ratio (ratio of the number density of non-condensable gas to that of vapor) and condensation coefficient including in the boundary condition for vapor molecules at vapor-liquid interface. From the present results, it is clarified that the condensation mass flux of vapor is affected by the non-condensable gas near the interface just after the instance when the shock wave reflects at the interface. Furthermore, as the initial number density ratio become larger, the condensation mass flux of vapor is suppressed more strongly, and also the condensation mass flux is not affected by the value of condensation coefficient.