Birthday of Tat’yana Anatol’evna Maryutina

Chronicle

Birthday of Tat’yana Anatol’evna Maryutina     

Synthesis of Some Novel Phenyl Substituted Oxothiazolidin- 1’’,3’’,4’’-thiadiazolo-[3’,4’-b]thiazoline of 3β-Substituted Cholestane

Three title compounds 4a—4c have been synthesized by the cyclodehydration of 1’-benzylidine-4’-(3β-substituted-5α-cholestane-6-yl)thiosemicarbazones 2a—2c with thioglycolic acid followed by the treatment with cold conc. H2SO4 in dioxane. The compounds 2a—2c were prepared by condensation of 3β-substituted-5α-cholestan- 6-one-thiosemicarbazones 1a—1c with benzaldehyde. These thiosemicarbazones 1a—1c were obtained by the reaction of corresponding 3β-substituted-5α-cholestan-6-ones with thiosemicarbazide in the presence of few drops of conc. HCl in methanol. The structures of the products have been established on the basis of their elemental, analytical and spectral data.     

The meaning of ‘concentration’

Terminology within a small laboratory community can be informal without danger of misunderstanding, but communication with a wider audience and not least in publications, needs unequivocal terms for defined concepts. As an example, the many meanings of “concentration” are explored to present a systematic nomenclature, including a concept diagram.

Enthalpy of formation of ye’elimite and ternesite

Journal of Thermal Analysis and Calorimetry - Calcium sulfoaluminate clinkers containing ye’elimite (Ca4Al6O12(SO4)) and ternesite (Ca5(SiO4)2SO4) are being widely investigated as components...     

The estimation of ether’s enthalpies of formation

Taking hydrocarbon as gerneratrix, the differences of enthalpies of formation of ether and their corresponding generatrixes were compared and concluded and the equation to estimate ether’s enthalpy of formation, which was Δ_f H _e^°/(kJ/mol) = K(Δ_f H _m^ℴ − 90 + A) was obtained. The results can be elucidated with bond dissociation energies data, bond-enthalpy of formation method, induction effect and conjugative effect. The more essential account to explain the results can be got by using quantum chemistry theories, etc. Using replacement and comparison method, the way of estimation of organic compounds’ thermodynamic properties including enthalpy of formation can be obtained either. The article is published in the original.     

Paneth’s epistemology of chemical elements in light of Kant’s Opus postumum

Friedrich Paneth’s conception of “chemical element” has functioned as the official definition adopted by the International Union of Pure and Applied Chemistry since 1923. Paneth maintains a distinction between empirical and “transcendental” concepts of element; furthermore, chemical science requires fluctuation between the two. The origin of the empirical-transcendental split is found in Immanuel Kant’s classic Critique of Pure Reason (1781/1787). The present paper examines Paneth’s foundational concept of element in light of Kant’s attempt, late in life, to revoke key distinctions made in his Critique, including that of regulative and constitutive functions of reason. In a section of his Opus postumum devoted to the “Transition from the Metaphysical Foundations of Natural Science to Physics,” Kant bends his philosophical system to address the newly emerging sciences of matter of his time. Specifically, he tried, without success, to develop the transcendental ground for microscale motions of bodies encountered in physical, electrical and chemical processes. Paneth’s discussion of chemical element does not take the Opus postumum into account, which is why it begins with a rejection of Kant’s rejection (in his earlier writings) of chemistry’s status as science. I make the case that Paneth’s definition of element effectively maintains something very like Kant’s critical separation of regulative and constitutive principles, while a advancing the concept of chemical science.     

Birthday of Igor’ Georgievich Zenkevich

Chronicle

Birthday of Igor’ Georgievich Zenkevich     

Improvement of Weyl’s Inequality

Consider the construction of an operator from the sum of two component operators. Weyl’s inequality gives a lower bound to an eigenvalue of the constructed operator using a single eigenvalue from each of the component operators. Using such minimal information gives a poor bound, however, and when the eigenvectors that correspond to the said eigenvalues of the component operators are known, Weyl’s inequality can be significantly improved by considering the overlap of the two eigenvectors. This improvement can sometimes be further improved when several eigenvectors of each component operator are known so that the overlap of sub-eigenspaces are considered instead. The improvement is best when there is minimal overlap and Weyl’s inequality returns when the overlap is complete. An example with the hydrogen molecular ion is presented which illustrates the superiority over Weyl’s inequality when eigenvector or sub-eigenspace information is utilized.     

Stereoselective Synthesis of 1,1’,2,2’-Tetrasubstituted Ferrocenes by Double Lithiation of a 1,1’-Disubstituted Ferrocenyl Pyrroloimidazolone

A 1,1’-disubstituted ferrocenyl pyrroloimidazolone with syn stereochemistry undergoes double lithiation–electrophile quench in a one-pot procedure to give C₂-symmetric 1,1’,2,2’-tetrasubstituted products in >95 : 5 diastereomeric ratio (dr). These results represent an extension of double lithiation to access tetrasubstituted planar chiral ferrocenes for the first time to a nitrogen-linked (pyrroloimidazolone) chiral directing group. The stereochemistry of the products was determined by X-ray crystallography of distannane and dibromide adducts in combination with deuteration, elimination, and transmetalation experiments. Results support that products arise from selective deprotonation of the pro-S_p position of each cyclopentadienyl (Cp) ring.     

Molecular interpretation of Trouton’s and Hildebrand’s rules for the entropy of vaporization of a liquid

The entropy of vaporization at a liquid’s boiling point is well approximated by Trouton’s rule and even more accurately by Hildebrand’s rule. A cell method is used here to calculate the entropy of vaporization for a range of liquids by subtracting the entropy of the gas from that of the liquid. The liquid’s entropy is calculated from the force magnitudes measured in a molecular dynamics simulation based on the harmonic approximation. The change in rotational entropy is not accounted for except in the case of liquid water. The predicted entropies of vaporization agree well with experiment and Trouton’s and Hildebrand’s rules for most liquids and for water except other liquids with hydrogen bonds. This supports the idea that molecular rotation is close to ideal at a liquid’s boiling point if hydrogen bonds are absent; if they are present, then the rotational entropy gain must be included. The method provides a molecular interpretation of those rules by providing an equation in terms of a molecule’s free volume in a liquid which depends on the force magnitudes. Free volumes at each liquid’s boiling point are calculated to be ～1 Å³ for liquids lacking hydrogen bonds, lower at ～0.3 Å³ for those with hydrogen bonds, and they decrease weakly with increasing molecular size.     

Quantum-chemical studies of the protonation of beryllium β’diketonates

Possible routes of the protonation of the free beryllium malonate Be(Mal)₂ and beryllium acetylacetonate Be(Acac)₂ complexes were determined by the quantum-chemical method in the DFT approximation. The influence of the protonation on the electronic and molecular structures (geometry of the metallocycles, energies and compositions of the molecular orbitals, effective charges on the atoms, and site occupancies of atomic orbital overlapping) was studied. The change in the energy of the molecular orbitals was considered as a function of their localization on the protonated and nonprotonated ligands of the complexes. The addition of a proton to one of the oxygen atoms was shown to be most probable.     

The features of nitric acid ‘mercerization’ of cellulose

Transformation of native cellulose species into cellulose-II polymorph through the additive Knecht compound formed under the action of 68.5% nitric acid has been studied. Probable causes of peculiar temperature effects in the course of phase transformations taking place in cellulose of various origin, crystallite dispersity, or morphologic structure are discussed. The processes of hydrolytic destruction and esterification of starting materials during their mercerization by this non-traditional agent at 20 °C and 0 °C are quantitatively characterized. In the case of mercerization of wood microcrystalline cellulose at 20 °C a decrystallizing effect due to side reactions of partial nitration is noted.     

Thermal investigation of ‘molten starch’

Detailed thermal analysis studies have shown that a ‘molten starch’ phase is obtained during controlled heating of starch. Before the ‘molten’ stage, depolymerisation of starch produces lower molecular weight compounds like dextrins, oligo, di- and monosaccharides, as well as other types of compounds. These compounds should have ideal properties for plasticizing starches because of the similarities of the molecules, helping lower phase changes in collaboration with molecular weight decrease. Interestingly, it was found previously that these materials only act as adhesives in a narrow temperature range around 523 K (250 °C) (Shuttleworth et al. J Mater Chem 19(45):8589–8593, 2009). Materials were investigated using thermal and mechanical analyses of single lap joints.     

A 1,1’-ferrocenylene-bridged analogue of BIPNOR

At 170 °C, 1,1’-bis(3,4-dimethylphospholyl)ferrocene (7) isomerises through the corresponding 2H-phospholes that are trapped by diphenylacetylene to give the 1,1’-ferrocenylene-bridged bis–1-phosphanorbornadiene (6). After resolution with an optically pure palladium complex, (R,R)- and (S,S)-(6) are tested in the asymmetric hydrogenation of a dehydroaminoacid, hydroformylation of styrene, and allylation of sodium malonate.     

The Biochemistry of Life’s Energy

On December 10, 1997, the 101st anniversary of Alfred Nobels death, in Stockholms Concert Hall Swedish King Carl XVI Gustav awarded one half of the 1997 Nobel Prize in Chemistry (3.75 million kronor, about $500,000) to Professor Emeritus Paul Delos Boyer, age 79, of the University of California, Los Angeles and Dr. John Ernest Walker, age 56, of the Medical Research Council Laboratory of Molecular Biology, Cambridge, England for their elucidation of the enzymatic mechanism underlying the synthesis of adenosine triphosphate (ATP) and one half (3.75 million kronor, about $500,000) to Professor Emeritus Jens Christian Skou, age 79, of Århus University, Århus, Denmark for the first discovery of an ion-transporting enzyme, Na⁺, K⁺-ATPase.     

Birthday of Victor Grigor’evich Berezkin

Chronicle

Birthday of Victor Grigor’evich Berezkin     

Radiolytic stability of N,N-didodecyl-N’,N’-diethylhexyl diglycolamide

The radiolytic degradation of N,N-di-dodecyl-N′,N′-di-2-ethylhexyl-3-oxapentane-1,5-diamide (D³DEHDGA) was studied at various absorbed doses of γ-radiation. The degradation was assessed by measuring the variation in the extraction behavior of Am(III) in irradiated solvent systems composed of neat D³DEHDGA or 0.1 M D³DEHDGA/n-dodecane in the presence and absence of nitric acid. The distribution ratio of americium (D _Am(III)) decreased with increase of absorbed dose. The presence of n-dodecane and nitric acid enhanced the radiolytic degradation of the solvent. The third phase formation behavior of Nd(III) decreased with increase of absorbed dose and the third phase was not observed at absorbed doses above 100 kGy. The recovery of Am(III) from the irradiated system was near quantitative in five contacts. The study revealed that the extraction and stripping behavior of the irradiated solvent was quite satisfactory for partitioning of minor actinides from real wastes.     

Total Syntheses of 16a’-Homoleurosidine and 16a’-Homovinblastine

Vinblastine has been used in clinic as an anti-cancer agent. Due to its high cytotoxity, generation of vinblastine congeners as safe anti-cancer agents is always the interesting topic in medicinal chemistry. In the previous synthesis of vinblastine, it has been found that a higher energy conformation of vinblastine lacking cytotoxity and inhibition against tubulin polymerization, can be converted to its lower energy natural conformation on heating to 110 oC. The high temperature (110 oC) othe…