On the Neglect of the Philosophy of Chemistry

In this paper I present a historiography of the recent emergence of philosophy of chemistry. Special attention is given to the interest in this domain in Eastern Europe before the collapse of the USSR. It is shown that the initial neglect of the philosophy of chemistry is due to the unanimous view in philosophy and philosophy of science that only physics is a proper science (to put in Kant's words). More recently, due to the common though incorrect assumption that chemistry can in principle be reduced to physics, the neglect continued, even when interest in sciences such as biology and psychology entered more strongly in philosophy of science. It is concluded that chemistry is an autonomous science and is perhaps a more typical science than physics.     

Investigation of the products of the ozonolysis of neoabienols

The ozonolysis of a mixture of 13Z- and 13E-neoabienols (I and III) leads, depending on the conditions, either to 8-hydroxy-14,15-bis-norlabd-11-en-13-one (IV) or to 8-hydroxdriman-11-oic acid (VI) or to driman-8,11-diol (VII). Compound (IV) undergoes hydrogenation smoothly with the formation of a mixture of 8-hydroxy-14,15-bisnorlabdan-13-one (X) and sclareol oxide (XI).Institute of Chemistry, Academy of Sciences of the Moldavian SSR, Kishenev. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 43–50, January–February, 1990.     

Synthesis of tetracarbocyanines by the scission of the pyrylium ring of benzopyrylocyanines

It has been shown that the reaction of monomethinecyanines containing 4-benzopyrylium residues with quaternary salts of derivatives of 2-[(1, 5, 5-trimethylcyclohex-1-en-3-ylidene)-methyl]benzothiazole leads to the scission of the pyrylium ring and the addition of the quaternary salt to the position of scission. The reaction gives tetracarbocyanines containing an o-hydroxyphenyl or an o-acetoxyphenyl substituent in the polymethine chain in addition to a hydrocarbon ring.     

To the Theory of the Aggregation of Polydisperse Colloids

Particle aggregation in polydisperse colloids is studied theoretically. It is assumed that the aggregation follows phase transition scenario with the formation of dense uniform colloidal phases. Bidisperse model corresponding to the system of relatively large and small particles is considered. Van der Waals attraction between large particles and the action of relevant entropy forces due to the presence of depleted layers of small particles are taken into account. The diagrams of equilibrium phase transitions of gas–liquid and gas–solid types occurring in the ensemble of large particles are constructed. The influence of size and concentration of small particles on the pattern and structure of phase diagrams is studied. It is shown that an increase in the concentration of small particles leads, on the one hand, to a rise of phase transition temperature and, on the other hand, to an increase in the threshold concentration of large particles.     

Influence of the spectral bandwith of the spectrometer on the sensitivity using continuum source AAS

The influence of the spectral bandwidth of the spectrometer on the performance of the spectrometer is of great importance in atomic absorption spectrometry using continuum source (CS-AAS). For a theoretical analysis of the detection of small absorbances two cases have to be taken into account: as long as the limiting noise of the signal is given by the detector noise an increase in spectral bandwidth of the spectrometer implies an improvement in the limit of detection. In contrast, if the noise of the signal is dominated by the photon shot noise the detection limit should become independent of the spectral bandwidth. In this case the spectral bandwidth of the spectrometer should be chosen equal to the bandwidth of the absorption line to avoid spectral interferences. Theoretical calculations are presented for the dependence of the characteristic mass on the spectral bandwidth in case of CS-AAS measurements. The results are compared with experimental measurements for six different elements using continuum source as well as line sources. The investigations were done using a double echelle monochromator (DEMON) which offers a high spectral resolution / of about 140,000.     

Integral intensities of the absorption bands of the skeletal vibrations of the heteroaromatic ring in the IR spectra of the furanoquinoline alkaloids

Summary 1. The integral intensities of the bands of the skeletal vibrations of the heteroaromatic ring in the 1480–1630-cm^–1 region of eight furanoquinoline alkaloids have been measured.2. A connection has been found between the values of A and the structures of the furanoquinoline alkaloids and their derivatives which enables such a series of heteroaromatic compounds to be identified: It has been shown that the introduction of an -OCH₃ group into the position of the pyridine nucleus leads to a marked rise (almost twofold) in the value of A;In derivatives of dictamnine (VII-XII), the value of A depends on the position of the methoxy group and on the nature of the substituent in position 7 of the benzene ring;With an increase in the delocalization of the unshared pair of electrons of the oxygen atom of the furan ring, the value of A of the series of alkaloids investigated (VI-XIV) decreases; andCompounds (V-XIV) have the very high values of A of 5.0–7.0 practical units and they exceed the value of the intensities of the carbonyl bandsv(C=0).Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 223–227, March–April, 1976.     

On the form of the single coulostatic decay curve

A plot of E/t ^1/2 versusE as obtained from a single coulostatic decay curve resembles a classical voltammogram. Calculations by digital simulation show that for a reversible electrode reaction the coulostatic voltammogram is shifted to potentials slightly negative of the reversible half-wave potential. Analysis of published data for the reduction of aqueous Pb(II) at a mercury electrode shows that the results were affected by heterogeneous electron transfer kinetics.     

Theoretical study of the cycloaddition of nitrones to cinnamonitrile: effect of Lewis acid coordination on the selectivity of the reaction

A number of quantum chemical and density functional methods have been used to study the chemo- and regioselectivity of the uncatalysed and Lewis acid mediated cycloaddition of the nitrone PhCHN(Me)O with the CC or the CN bond of (E)-cinnamonitrile. In agreement with experimental evidence, Lewis acid coordination to the nitrile strongly promotes reaction at the CN bond over reaction at the alkene moiety. The main factors responsible for this inversion of the chemoselectivity were identified as the following: (i) the Lewis acid strongly stabilises the product of CN addition and the transition state leading to it, thus favouring this reaction both kinetically and thermodynamically. Addition across the CC bond, in contrast, only receives weak kinetic activation; (ii) the cycloaddition to the CC or CN bonds involves different molecular orbitals at the cinnamonitrile, and the Lewis acid influences the orbital involved in CN addition to a larger extent; (iii) the Lewis acid has a stronger effect on the electron distribution of the CN bond. As an overall result, the Lewis acid not only promotes the cycloaddition, but also alters the order of functional group reactivity and brings about a complete change in chemoselectivity.     

Changes in the band structure of a simple polymer on lowering the translational symmetry

By combining the one-dimensional crystal orbitals of a simple polymer under the action of a perturbation which extends the repeating segment from one site to n sites a perturbation method allows the band structure of the new chain to be calculated. As well as estimating the band gaps to a fairly good agreement with the results of the direct method the present technique shows how specific gaps created by the symmetry-lowering will respond to the characteristics of the perturbations imposed.     

Structural aspects of the radiation modification of the dielectric properties of polyolefins

The effects of crystallization conditions and supermolecular structure on the processes of radical formation and changes in the dielectric (tan; ) and strength (E _st) properties of LDPE, HDPE, and PP under exposure to -radiation were studied. It was found that polyolefin specimens with a high crystallinity exhibited an enhanced electric strength, radiation stability, and a high yield of quasi-stable radicals at 293 K. It was assumed that a possible mechanism of the electric strengthening of PE and PP by their radiation modification (at radiation doses of 30–50 and to 5–6 Mrad, respectively) consists in a reaction of the type R^· + e^– R^–, the capture of trapped electrons by quasi-stable radicals.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 3, 2005, pp. 176–182.Original Russian Text Copyright © 2005 by Magerramov, Dashdamirov.     

Synthetic studies in the field of the curare alkaloids

By oxidation and the identification of the oxidation products, it has been shown that the -[4-(2-alkoxy-5-alkoxycarbonylmethylphenoxy)-3-methoxyphenyl] ethylamides of 4-benzyloxyphenylacetic acid obtained previously and differing in their physicochemical properties are based on the same skeleton and differ only in their spatial configuration, since on Bischler-Napieralski cyclization they give isomeric dihydroisoquinoline compounds. The structure of the latter was established by oxidation to the isomeric acids 2,2-dimethoxy-3,4,5-tricarboxy(diphenyl ether) and 2,2-dimethoxy-4,5,5-tricarboxy-(diphenyl ether); the latter is identical with the compound obtained by the degradation of the methyl ester of natural tubocurarine. 1-(4Benzyloxybenzyl)-6-methoxy-7-(2-methoxy-5-methoxycarbonyl methylphenoxy)-N-methyl-1,2,3,4-tetrahydroisoquinoline and a compound isomeric with it have also been synthesized, and the former has been shown to be identical with a substance obtained by independent synthesis from the 4-benzyl ether of N-methylcoclaurine. During the synthesis of the latter it was shown that cyclization takes place unambiguously without the formation of isomeric compounds.For part XIII, see [2].     

Vitamins of the oil of the fruit ofHippophaë rhamnoides

Summary A comparative study of the chemical composition of the oil of the juice and the seed oil of the fruit ofHippophaë rhamnoides has shown that vitamins of the A group are concentrated mainly in the oil of the juice (more than 1000 mg-%) and are represented mainly by -carotene and zeaxanthin in a ratio close to 3:1.The E-group vitamins are uniformly distributed in the oil of the juice and the seed oil (more than 200 mg-%). Of the vitamins of this group, the main representatives detected were - and -tocopherols in a ratio of 2:1.The vitamins of the F group are concentrated only in the seed oil (60% of a mixture of linoleic and linolenic acids on the total fatty acids isolated from the oil, in a ratio of 1.5:1).The position of the ethylenic bond in a C_16:1 acid isolated from products of the hydrolysis of the oil of the juice in a monoenic fraction has been shown by chemical analysis. Its cis configuration was determined by IR spectroscopy, which confirms the structure of this acid as cis-hexadec-9-enoic (palmitoleic) acid. An unusually high content of the C_16:1 acid is characteristic only for the oil of the juice.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 313–317, May–June, 1978.     

Out of the textbook and into the world: Student projects in the radiochemistry laboratory

A major objective of any laboratory course should be to stimulate students to extend their knowledge of the subject to specific problems. In the radiochemistry laboratory course at the University of Kentucky, we encourage students to make the transition from the textbook or laboratory manual to the real world through the use of a special project. This project, which typically replaces two normal laboratory exercises, is a short research problem that the student independently develops and executes. An overview of the incorporation of special projects into our radiochemistry laboratory course is presented.     

Crossing of the Cystic Barriers of Toxoplasma gondii by the Fluorescent Coumarin Tetra-Cyclopeptide

{"type":"entrez-nucleotide","attrs":{"text":"FR235222","term_id":"258291874","term_text":"FR235222"}}FR235222 is a natural tetra-cyclopeptide with a strong inhibition effect on histone deacetylases, effective on mammalian cells as well as on intracellular apicomplexan parasites, such as Toxoplasma gondii, in the tachyzoite and bradyzoite stages. This molecule is characterized by two parts: the zinc-binding group, responsible for the binding to the histone deacetylase, and the cyclic tetrapeptide moiety, which plays a crucial role in cell permeability. Recently, we have shown that the cyclic tetrapeptide coupled with a fluorescent diethyl-amino-coumarin was able to maintain properties of cellular penetration on human cells. Here, we show that this property can be extended to the crossing of the Toxoplasma gondii cystic cell wall and the cell membrane of the parasite in its bradyzoite form, while maintaining a high efficacy as a histone deacetylase inhibitor. The investigation by molecular modeling allows a better understanding of the penetration mechanism.     

Influence of the modifiers on the nature of the stationary phase and the separation of carotenes in sub-critical fluid chromatography

Summary Sixteen solvents were tested as modifiers in the separation of - and -trans/cis carotenes by sub-critical fluid chromatography. The results obtained indicate that the retention behaviour is related to solubility parameters and the dielectric constant of the solvents. The study of the selectivity of thetrans/cis isomers of -carotene leads to a better understanding of the role of the solvents in determining the nature of the stationary phase at the mobile phase interface. The results obtained point out the difference in the conformation of the alkyl chains with three classes of solvents: methanol, acetonitrile, and THF or methylene chloride. The analogy between non aqueous reversed-phase chromatography (NARP) and sub-critical fluid chromatography has also been discussed.     

Effect of Differences in the Orientation of Adsorbed Molecules and in the Magnitudes of Limiting Capacitances of the Inner Part on the Regularities of Coadsorption of Two Organic Substances

The Alekseev–Popov–Kolotyrkin model, complemented with a set of mixed Frumkin isotherms, is used to perform an analysis of joint adsorption of two neutral organic substances when there are substantial differences in (1) limiting potential drops _N1 and _N2 and (2) capacitances of the inner part at ₁ = 1 and ₂ = 1. It is shown that in the absence of a lateral interaction between coadsorbed species and at a certain ratio between their concentrations, in either case there exists a region of potentials where the set of isotherms has three solutions. The stability of these solutions is characterized and the curves of the differential capacitance (equilibrium and nonequilibrium) and the interfacial tension are calculated. A general analysis of the set of isotherms in the region of physically reasonable values of adsorption parameters is conducted.     

A new theoretical approach to the empirical resonance energies of the aromatic hydrocarbons

In the framework of the Hückel MO approximation, the differences in total binding energy between a given molecule and the corresponding distorted Kekulé-type structure are calculated for a variety of benzenoid hydrocarbons. The total binding energy is assumed to be given by the sum of the -electron and -electron binding energies. It is shown that there is a good linear relationship between the calculated differences in total binding energy and the -electron delocalization energies (DE) as obtained by using the simple Hückel MO method. This provides a physical basis for the use of the -electron DE as a theoretical index to the empirical resonance energy (RE). Further, by examining the changes in -electron binding energy between a given molecule and the corresponding distorted Kekulé-type structure, it is concluded that in benzenoid hydrocarbons the main contributor to the RE is not the -electron DE but the compressional energy of bonds.     

Tautomerism of azine derivatives. 5. Effect of the heteroatom on the keto-enol tautomerism of β-keto esters of the azine series

The effect of a nitrogen atom in various positions of the heteroaromatic ring on the ketol-enol equilibrium of 2-, 3-, and 4-pyridoyl-, 2- and 4-pyrimidoyl-, pyrazinoyl-, and 3- and 4-pyrazinoylacetic esters is examined. The anomalous effect of a nitrogen atom on the position relative to the tautomeric fragment is noted and is explained by interaction of the unshared pair of the nitrogen atom with the orbitals of the carbonyl group, which may lead to a decrease in the acceptor character of the azine substituent.See [1] for Communication 4. In Communication 4 [Khim. Geterotsikl. Soedin., No. 6, p. 823 (1980)] there is a misprint in the scheme that illustrates the tautomeric equilibrium -keto esters with the participation of protonated forms. See [16] for the corrected scheme.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 530–535, April, 1981.     

On the derivative of the associated Legendre function of the first kind of integer order with respect to its degree (with applications to the construction of the associated Legendre function of the second kind of integer degree and order)

In our recent works (R. Szmytkowski, J. Phys. A 39:15147, 2006; corrigendum: 40:7819, 2007; addendum: 40:14887, 2007), we have investigated the derivative of the Legendre function of the first kind, P _ν(z), with respect to its degree ν. In the present work, we extend these studies and construct several representations of the derivative of the associated Legendre function of the first kind, \({P_{\nu}^{\pm m}(z)}\), with respect to the degree ν, for \({m \in \mathbb{N}}\). At first, we establish several contour-integral representations of \({\partial P_{\nu}^{\pm m}(z)/\partial\nu}\). They are then used to derive Rodrigues-type formulas for \({[\partial P_{\nu}^{\pm m}(z)/\partial\nu]_{\nu=n}}\) with \({n \in \mathbb{N}}\). Next, some closed-form expressions for \({[\partial P_{\nu}^{\pm m}(z)/\partial\nu]_{\nu=n}}\) are obtained. These results are applied to find several representations, both explicit and of the Rodrigues type, for the associated Legendre function of the second kind of integer degree and order, \({Q_{n}^{\pm m}(z)}\); the explicit representations are suitable for use for numerical purposes in various regions of the complex z-plane. Finally, the derivatives \({[\partial^{2}P_{\nu}^{m}(z)/\partial\nu^{2}]_{\nu=n}, [\partial Q_{\nu}^{m}(z)/\partial\nu]_{\nu=n}}\) and \({[\partial Q_{\nu}^{m}(z)/\partial\nu]_{\nu=-n-1}}\), all with m > n, are evaluated in terms of \({[\partial P_{\nu}^{-m}(\pm z)/\partial\nu]_{\nu=n}}\). The present paper is a complementary to a recent one (R. Szmytkowski, J. Math. Chem 46:231, 2009), in which the derivative \({\partial P_{n}^{\mu}(z)/\partial\mu}\) has been investigated.     

Structure of the product of the sensitized photodimerization of peucedanin

Summary On the basis of the NMR spectrum, a most probable structure has been proposed for the product of the sensitized photodimerization of the natural furocoumarin peucedanin. It has been shown that the latter is formed at the expense of the double bonds of the -pyrone ring of one and of the furan ring of the second molecule in the head to tail manner.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodynkh Soedinenii, No. 6, pp. 680–683, November–December, 1970.