Transform of a thermogram into a thermogenesis curve by the use of the frequency transfer function of a calorimeter

In calorimeter experiments, we obtain the thermogram y = y(t), temperature variation y(t) as a function of time t, when thermal reaction occurs in the calorimeter reaction cell. For thermokinetic studies, we need to know the calorific power generated in the cell, due to the thermal reaction, as a function of time. By use of the frequency transfer function of the calorimeter, we can calculate numerically the calorific power at any time from numerical analysis of the thermogram without any assumption of analytical form of the transfer function.The method is composed of three steps. (1) Experimental determination of the frequency transfer function G of the calorimeter from numerical analysis of the thermogram which is obtained by applying a constant calorific power in the calorimeter cell. (2) Numerical Laplace transform L[y] = Y of the thermogram which is recorded when the thermal reaction under investigation occurs in the cell. (3) Numerical determination of the calorific power, evolved by the thermal reaction in the cell, by numerical inverse Laplace transform of Y/G.This method is examined in two ways. First, simulation by numerical calculation on a mathematical model calorimeter is done and the accuracy of the method is assured. Second, experiments and numerical analysis on the heat-flow (conduction) type of calorimeter are performed to test the availability of the method.     

Thermodynamic study of the liquid Fe-S system by use of a drop calorimeter

Heat contents of the Fe-S system were measured with a drop calorimeter in the sulfur composition range X_s = 0.380–0.500 (FeS) and in the temperature range 942–1506 K to construct an (H_T - H_298.15)-temperature-composition ternary diagram. By use of a thermodynamic analysis method, the mixing free energy, enthalpy and entropy of the liquid Fe-S mixtures were determined at 1473 and 1523 K, based on the measured heat contents. The partial molar free energies (activity of iron and partial pressure of diatomic sulfur) agreed well with the literature values, suggesting the applicability of the thermodynamic analysis method for liquid mixtures with semi-metals or chalcogen.     

Structure of salvigenolide,a novel diterpenoid with a rearranged neo-clerodane skeleton from salviafulgens

From the aerial parts of Salvia fulgens Cav. (Labiatae) a new diterpenoid with a rearranged neo-clerodane skeleton was isolated. This novel compound named salvigenolide, showed a six-seven A/B ring system with a trans fussion. A probable biogenetic route is proposed. Its structure and relative stereochemistry as in $\text{1}$, were established by spectroscopic means and X-ray diffraction analysis.     

Hydrothermal synthesis and characterization of a new layered gallophosphate JGP-L1 with a Ga/P ratio of non-unity

A new compound, Ga₆(OH)₄(HPO₄)₂(PO₄)₅·C₈H₂₈N₅·3H₂O (denoted JGP-L1), with a gallophosphate layer and a Ga/P ratio of 6/7 has been synthesized hydrothermally by using tetraethylenepentamine as template. It is characterized by powder X-ray diffraction (XRD), elemental analysis, inductively coupled plasma, and TGA analysis and structurally determined by single-crystal XRD analysis. JGP-L1 crystallizes in the orthorhombic, space group Pna2₁ (no. 33), with a=16.422(3), b=11.898(2), c=18.730(4) Å, V=3659.6(13) Å³ and Z=4. The structure of JGP-L1 is built up by alternating of Ga(OH)₂O₄ octahedra, Ga(OH)O₄ trigonal bipyramids and PO₄ (or HPO₄) tetrahedra to form inorganic sheets. It is noteworthy that JGP-L1 was synthesized with extremely low reactant concentration, where the reaction mixture exhibits a H₂O:Ga₂O₃ molar ratio of 2220:1.     

Synthesis and reaction with metal ions of a new thionocarbamate

The synthesis and research of a novel thionocarbamate N,N??-diethoxycarbonyl-O,O??-(1,4-butylidene) dithionocarbamate which contains two ester and two thioamide groups are reported. This compound was characterized by elemental analysis, UV spectrum, infrared spectrum, mass spectrum, and ¹H NMR and ¹³C NMR spectroscopy. Additionally, the metal ion?Ccollector interaction in organic solution was put into practice. The results of UV spectroscopic analysis showed that this dithionocarbamate with a new structure exhibited a stronger complex ability with Cu²⁺ than with Ni²⁺ or Fe³⁺. Furthermore, infrared spectroscopic analysis implicated that this dithionocarbamate binds to Cu²⁺ through both the C=O and C=S groups. Bench-scale flotation tests were also carried out, verifying that it has a higher copper flotation recovery and better selectivity to sulfide ores containing Cu compared with universal collectors.     

Preparation and crystal structure of a triple parallel interpenetrated copper coordination polymer based on a flexible bis(imidazole) ligand

A Cu(II) coordination polymer, [Cu(L)(bdc)] _n (L = 1,4-bis(imidazole)butane, bdc = 1,3-benzenedicarboxylate) has been hydrothermally synthesized and characterized by elemental analysis, IR spectrum, thermogravimetric analysis, and single-crystal X-ray diffraction. The complex is a rare example of a threefold parallel interpenetrated coordination bonding network based on undulant [Cu₄(μ ₂-L)₂(μ ₂-bdc)₂] parallelograms with 4⁴-sql layer. The heterogeneous catalytic activity of the complex was tested for the degradation of Congo red azo dye in a Fenton-like process in which the degradation efficiency reached 94 % after 100 min. Kinetic analysis indicates that the degradation rate of the dye can be approximated by pseudo-first-order kinetics.     

Synthesis and isolation of a monoamine having a thermodynamically stabilized pseudo-chirotopic nitrogen

We have synthesized a tricyclic monoamine, (1S,4R)-(E)-7,3′-heptenylene-2,3:5,6-dibenzo-7-azabicyclo[2.2.1]heptane (1), by applying a ring-closing metathesis reaction in the key step of the synthetic route and by using preparative chiral HPLC for the separation. The X-ray crystallographic analysis of its salt with (1R)-camphor-10-sulfonic acid showed that the geometry and absolute configuration are (E) and (1S,4R), respectively. The theoretical calculations revealed that the inversion of the nitrogen atom at the 7-position of (1S,4R)-(E)-1 thus isolated takes place through a very slow process and that the configuration of the N(7) is highly biased to (R), indicating that (1S,4R)-(E)-1 is a thermodynamically controlled N-pseudo-chirotopic compound ((1S,4R,7R): (1S,4R,7S) = 99.68:0.32 at 120 °C).     

Halichonic acid,a new rearranged bisabolene-type sesquiterpene from a marine sponge Halichondria sp.

A new compound, halichonic acid (1), was isolated from a marine sponge Halichondria sp., together with (6R,7S)-7-amino-7,8-dihydro-α-bisabolene (2). The structure of 1 was elucidated by spectroscopic analysis and ECD spectrum calculation to be a rearranged bisabolene-type sesquiterpene having a 3-azabicyclo[3.3.1]nonene moiety. Compound 2 was cytotoxic against HeLa cells with an IC₅₀ value of 50?μM, whereas 1 did not show cytotoxicity even at 50?μM. It is possible that 1 is biosynthesized from farnesyl pyrophosphate and glycine, with rearrangement.     

Synthesis and structure of a chiral dinuclear palladium(0) complex with a 30-membered hexaolefinic macrocyclic ligand

Selective and efficient preparation of a new chiral dipalladium(0) complex with an olefinic macrocyclic ligand named (E,E,E,E,E,E)-1,6,11,16,21,26-hexakis[(4-methylphenyl)sulfonyl]-1,6,11,16,21,26-hexaazacyclotriaconta-3,8,13,18,23,28-hexaenedipalladium(0) (5) is reported. Dinuclear palladium(0) complex 5 has been fully characterized by means of NMR spectroscopy and X-ray diffraction analysis.     

Zoanthoxanthin,a natural 1,3,5,7-tetrazacyclopent-azulene from Parazoanthus axinellae

Zoanthoxanthin, the principal fluorescent pigment of the mediterranean zoanthid Parazoanthus axinellae, has been isolated in crystalline form and identified as 2-amino-3,4-dimethyl-6-dimethylamino-3H-1,3,5,7-tetrazacyclopen 1 from its chemical and spectral properties and by X-ray crystallographic analysis of its 2-chloro-derivative 3.Crystals of 3 are monoclinic, space group P2₁c, with Z = 4, in a unit cell of dimensions a = 7·282, b = 8·408, c = 25·422 A°, β = 94·31°. The structural analysis, carried out by direct methods and refined to an R value of 0·040, has shown that the molecule is nearly planar, the 7-membered carbocyclic ring assuming a shallow boat conformation while the two imidazole rings are slightly bent in the opposite direction with respect to the folding of the central ring.     

Hybridization and correlation in a model calculation of a two-electron bond

The paper presents a quantitative examination of some aspects of the molecular two-electron problem, using a calculation for a two-electron homonuclear bond based on a restricted set of one 2s and one 2p orbital per nucleus. The single-determinant approximations with pure 2s STO's and with hybrid AO's are considered, as well as “partial” configuration mixing (CI) over MO's involving one hybrid per atom and “complete” CI over the whole four-orbital basis. The calculations simulate an exact calculation as regards hybridization and (left-right) correlation effects. These are studied, for the lowest state, at various distances, introducing the axial electron density as a means for interpreting quantitatively the various effects. The importance of orthogonalizing the 2s AO's to the corresponding 1s AO's and the MO's used to the MO formed by 1s AO's is reviewed, pending further numerical analysis.     

Binary 1,4-asymmetric induction from a single allyltin reagent with a chiral nitrogen functional group toward aldehydes

Using a single allyltin reagent with a chiral nitrogen functionality, binary and remote asymmetric induction was realized toward various aldehydes. Either syn- or anti-1,4-amino-alcohols were selectively obtained with the use of Yb(OTf)₃ or SnCl₄, respectively. The structures of both diastereomers were identified by means of X-ray analysis.     

Synthesis of both RP and SP enantiomers of unsymmetrical methylphosphonates based on a new approach utilizing a P-ester bond with α-hydroxyacids

Condensation of methyl methylphosphonochloridate with the dilithium salt of 2-methyllactic acid gave P-racemic methylphosphonates which unexpectedly contained two units of α-hydroxyacid linked via carboxylic ester bond. The racemic mixture was chromatographically separated via diastereomeric salts with quinine or cinchonine to give, based on the X-ray analysis, pure (R_P)-(+) and (S_P)-(−) enantiomers. Both enantiomers were immobilized on the ArgoGel^®–OH solid support. Condensation of methyl methylphosphonochloridate with α-hydroxyacid methyl esters [2-methyllactate, (S_C)-(−)-lactate, methyl (S_C)-(+) and (R_C)-(−)-mandelates] gave chromatographically inseparable 1:1 mixtures of diastereomers in 63–69% yields. A basic hydrolysis of the latter resulted in a selective and unexpected cleavage of the P–OMe group in a quantitative yield [(S_C)-(+) and (R_C)-(−)-mandelates, (S_C)-(−)-lactate] or simultaneous cleavages of P–OMe and C(O)OMe groups (2-methyllactate).     

The fluorine-NHC gauche effect: a structural and computational study

Herein, we report the synthesis and X-ray structural analysis of a collection of fluorinated metal N-heterocyclic carbenes (Ag, Au, Pd, Rh, Ir) and their precursor salts. The common structural feature of these species is a flanking fluoroethyl group, which is either freely rotating or embedded within a bicyclic framework. Solid state analysis confirmed a gauche conformational preference in all cases with the fluorine adopting a syn clinal arrangement (?_[NCCF]～60°) with respect to the triazolium nitrogen at the vicinal position of the NHC. A density functional theory analysis was employed to quantify these effects and evaluate the influence of electronic modulation of the carbenic carbon [(CN⁺); neutral carbene (C:); metal-bound carbene (CM)], on the relative gauche/anti preference, thus highlighting the potential of this conformational phenomenon as a useful molecular design strategy for controlling the topology of organometallic complexes.     

Highly diastereoselective boron and titanium mediated aldol reactions of a mannitol derived 2,3-butanediacetal ethyl ketone

A mannitol derived 2,3-butanediacetal ethyl ketone displays high levels of diastereoselectivity in boron and titanium mediated aldol reactions with a range of aliphatic and aromatic aldehydes to afford syn aldol products in high yield. The stereochemical outcome of the reaction was determined using J-value analysis, NMR analysis of O-acetylmandelate derivatives and X-ray crystallography.     

Uniform linear chains of group 11 atoms: do they have a bias towards a Peierls distortion?

The possible occurrence of a Peierls distortion in metallic uniform linear chains of group 11 atoms is examined on the basis of first-principles DFT calculations and orbital interaction analysis. It is found that, contrary to expectations based on the fact that these systems must possess a half-filled one-dimensional band, none of the three chains of atoms is susceptible to a Peierls dimerization. It is shown that both strong s–z ² mixing and d ¹⁰–d ¹⁰ repulsions are at the heart of this unexpected result. The relationship of these results with the presence of uniform silver chains in the recently reported (Ca₇N₄)[Ag_~1.33] phase is discussed.     

Novel Antifungal Dimers from the Roots of Taiwania cryptomerioides

Five new dimer compounds, namely Taiwaniacryptodimers A–E (1–5), were isolated from the methanol extract of the roots of Taiwania cryptomerioides. Their structures were established by mean of spectroscopic analysis and comparison of NMR data with those of known analogues. Their antifungal activities were also evaluated. Our results indicated that metabolites 1, 2, 4, and 5 displayed moderate antifungal activities against Aspergillus niger, Penicillium italicum, Candida albicans, and Saccharomyces cerevisiae.     

Purification and Characterization of a Urethanase from Penicillium variabile

Urethanase produced by Penicillium variabile was purified through ultrasonication, concentration by polyethylene glycol 20,000, and Superdex G-200 gel filtration chromatography. The molecular weight of urethanase was determined to be around 96 kDa by gel filtration. The purified enzyme showed a single band in SDS-PAGE with the molecular weight of ~13.7 kDa, which suggests that the enzyme has a multimeric structure composed of the same subunits. Peptide map fingerprinting analysis was then carried out by MALDI/TOF-TOF MS. Within the known sequences in NCBI, glucosamine-6-phosphate deaminase and 6-phosphogluconate dehydrogenase get high score as compared with urethanase. Sequence analysis informs that N-terminal sequence of urethanase is GTNTADNDAA. The Minchaelis constant (K _m) and maximum reaction rate (V _m) of urethanase are 27.2 mmol/L and 156.25 μmol/L min, respectively.     

Simultaneous chromatographic identification of a few components in mixtures based on a correlation between their absolute or relative retention times under different conditions

A correlation was established between the absolute and relative retention parameters of various compounds under different conditions of chromatographic analysis (isothermal and temperature programming conditions in gas chromatography or isocratic and gradient elution in high-performance liquid chromatography). This correlation is described by the linear regression equations t _R (II) = = at _R (I) + b with a high degree of accuracy. This property of chromatographic retention parameters allowed us not only to recalculate the values of these parameters determined under different conditions, but also to propose an algorithm for the simultaneous identification of a few components in complex mixtures with the use of published data on retention parameters found under other conditions (even presented as the drawings of chromatograms).     

Synthesis and characterization of a Zn(II) complex of a pyrazole-based ligand bearing a chiral l-alaninemethylester

Reaction of ZnCl₂ with a new ligand N,N-bis(3,5-dimethylpyrazolylmethyl)-l-alaninemethylester (bdmpame) in methanol gives [ZnCl₂(bdmpame)]. The structure of [ZnCl₂(bdmpame)]·CH₂Cl₂ has been resolved by X-ray crystallographic analysis. The Zn atom has a distorted tetrahedral geometry involving a nitrogen atom from each pyrazole in bdmpame and two chloro ligands with bond lengths in the range 2.037(4)–2.237(2) Å. The nitrogen atom of the l-alaninemethylester group in the compound was not coordinated to the metal center, giving an eight-membered ring in which the nitrogen atoms of each pyrazole in bdmpame are coordinated to the metal center. The results of the catalytic enantioselective reduction of acetophenone promoted by ligand/Zn(OTf)₂=1:1 mole ratio in the presence of catecholborane for 48 h at 0°C gives (S)-(−)-1-phenylethanol in 21% ee with 68% yield.