NMR study of some mono- and di-tert-butylnaphthalenes

The proton decoupled ¹³C FT—NMR spectra and ¹H FT—NMR spectra of some mono- and di-tert-butylnaphthalenes have been studied. Some interesting features observed in these spectra have been found to be of diagnostic value in distinguishing the closely related isomers of these compounds. On the basis of the assignment done by earlier workers in case of mono-substituted naphthalenes following the additivity approach, it has been shown that all the ¹³C—NMR signals observed for the present di-substituted naphthalenes can also be assigned; and this procedure thus obviates the use of tedious and some times experimentally inaccessible techniques.     

Synthesis,structure and magnetism of homologous series of polycrystalline cobalt alkane mono- and dicarboxylate soaps

Carboxylate-bridged chain complexes of Co(II) (the diaquacobalt(II) mono- and ,-dialkanoates) form two homologous series of layered compounds which have been fully characterised both structurally and magnetically. The crystal structures of two selected members, [Co[CH3(CH2)10COO]2(H2O)2] and [Co[CH3(CH2)18COO]2(H2O)2], have been solved by X-ray powder diffraction and selected-area electron diffraction methods, and refined by the Rietveld technique. Crystal data: monoclinic, P 2(1)/a; a=9.688(1), b=7.5495(9), c=37.281(5) A, =96.70(3) primary, Z=4; and monoclinic, P 2(1)/a; a=9.7260(7), b=7.5477(7), c=57.53(1) A, =94.66(4) primary, Z=4, respectively. Their isomorphous structures contain layers of octahedral diaquacobalt(II) ions bonded to two chemically inequivalent alkanoates, one chelating and one bridging two Co atoms about 6.3 A apart, thus confirming the rare anti-anti conformation mode of the -RCOO groups recently proposed for diaquacobalt(II) ,-dodecanedioate. Extensive magnetic characterisation allowed estimation of the feeble antiferromagnetic coupling, which is weaker in the mono- than in the dialkanoate series.     

Reversible light-driven structural changes between the mono- and bilayer stacking alignments in 4-octadecyloxystilbazolium arylcarboxylate films

The present investigation deals with the light-driven morphological changes in multilamella films of N-methyl-4-octadecyloxystilbazolium arylcarboxylates (C18OStz+X-) cast on glass slides. The results of XRD analysis show a photostimulated layer expansion and shrinkage of the stacked thin films along the c-axis under alternative illumination at >350 and 254 nm, respectively. It was revealed that such lamellar changes could be switched either way by a reversible transformation between the mono- and bilayer units in these stacked multilamella films. Moreover, such controlled structural adjustments in the alignment could be initiated by the photocyclodimerization of the stilbazolium moieties of the arylcarboxylate salts; i.e., a monolayer-to-bilayer transformation could be induced at a stage of only 10% cyclodimer formation. The photoinduced patterning on the surface of the films was also analyzed by SEM and fluorescence microscopic investigations.     

Theoretical study of mono- and dithiocarbazic acid derivatives

The patterns of charge distribution in a series of derivatives of thiocarbazic acid are studied by means of several theoretical LCAO-MO methods: ab initio minimal basis-set, CNDO/2, INDO and EHT. Correlations are made between the electronic structures obtained from the calculations, the nature of the different substituents and some experimental IR, X-ray and XPS results.     

Far infrared study of some mono- and disaccharides

Some mono- and disaccharides were studied using the far infrared (FIR) spectroscopic method. Results show that every saccharide has a characteristic spectrum pattern. It is useful to distinguish between different saccharides based on the sequence of their relative intensities. Therefore, an encoding method was suggested to label each substance. In this investigation, the FIR spectra of the saccharides were demonstrated using the encoding method and prove the feasibility of the method.     

A computational study of O-O bond formation catalyzed by mono- and bis-MnIV-corrole complexes

A detailed computational study of O-O bond formation, catalyzed by monomeric and dimeric Mn-corrole complexes, is reported. The model explicitly takes into account the solvent, with respect to the first and second coordination spheres, while the bulk solvent is described by the polarizable continuum model. Two reaction mechanisms are proposed and computationally characterized: the concerted and the two-step mechanisms. The concerted mechanism is based on a OH--MnIVO interaction via the outer-sphere pathway involving the bridging solvent molecules in the first coordinating sphere. The two-step mechanism is proposed to operate via the coordination of a hydroxide to the MnIV ion, forming a MnO(OH)--corrole complex with a strongly nonplanar corrole ligand. Comparison of the proposed mechanisms with available experimental data is performed.     

19F NMR study of fluorinated mono- and diacylhydrazines

Conclusions It has been demonstrated by means of¹⁹F NMR that l-acyl-2-alkyl (phenyl) hydrazines are the main products of the monoacylation of alkyl- and phenylhydrazine with derivatives of perfluorocarboxylic acids. The preferred conformations with respect to the amide bond have been determined in mono- and di (perfluoroacyl) hydrazines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2735–2739, December, 1980.     

A synthetic alternative to natural lecithins with antimicrobial properties

Two soft biocompatible cationic surfactants from the amino acid arginine, 1,2-dilauroyl-3-acetylarginyl-rac-glycerol (1212RAc) and 1,2-dimirystoyl-3-acetylarginyl-rac-glycerol (1414RAc), were prepared. Their physicochemical properties show that they can be classified as multifunctional surfactants with self-aggregation behaviour comparable to that of short-chain lecithins. The two surfactants can simultaneously stabilise water-in-oil (W/O) droplets and oil-in-water (O/W) droplets, forming multiple emulsions. They have antimicrobial activity similar to that of conventional cationic surfactants and are as harmless as amphoteric betaines. These surfactants constitute an interesting alternative to the diglycerides and lecithins in formulations that require antimicrobial properties.     

NMR study of mono- and dilithium derivatives of alkyl and arylstannanes

Element-centered mono- and dianions of alkyl- and arylstannanes were studied by NMR spectroscopy. The ¹³C and ¹¹⁹Sn NMR chemical shifts for the dianions R₂SnLi₂ (R = Ph, Et) were measured for the first time.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2229–2231, October, 2004.     

A quantum chemical study of lead(II) thiocomplexes with mono- and bidentate ligands

Model Pb(II) thiocomplexes with mono- and bidentate ligands of the composition [Pb(L^1,2) _n ]²⁻ⁿ (L¹ is (SC₆H₅)⁻ (thiophenolate ion), L² is (S₂CN(CH₃)₂)⁻ (dithiocarbamate ion), n is the number of ligands of 2–6), which simulate fragments of the crystal structures of Pb(II) complex compounds with organic ligands, are studied within density functional theory. Geometric and energy parameters of model complexes with different coordination geometries of the Pb atom are determined and the stereochemical activity of the lone electron pair (LEP, E) of the Pb²⁺ ion is estimated in them. In the studied complexes, the highest Pb-S binding energy is found for the Pb atom surrounded by 2–4 ligands. The geometry of the Pb atom coordinated by S donor atoms can be described in terms of the valence shell electron pair repulsion (VSEPR) model with stereochemically active LEP. The coordination number (cn) of the Pb atom in the most energetically favorable complexes [Pb(SC₆H₅) _n ]²⁻ⁿ is (3+E) − (4+E), and in [Pb(S₂CN(CH₃)₂) _n ]²⁻ⁿ complexes, it is (4+E) and (6+E). Configurations with the mentioned cns are most often observed in the crystal structures of Pb(II) thiocomplex compounds.     

Sulfide and sulfoxide oxidations by mono- and diperoxo complexes of molybdenum. A density functional study

The molecular mechanism for the oxidation of sulfides to sulfoxides and subsequent oxidation to sulfones by diperoxo, MoO(O(2))(2)(OPH(3)) (I), and monoperoxo, MoO(2)(O(2))(OPH(3)) (II), complexes of molybdenum was studied using density functional calculations at the b3lyp level and the transition state theory. Complexes I and II were both found to be active species. Sulfide oxidation by I or II shows similar activation free energy values of 18.5 and 20.9 kcal/mol, respectively, whereas sulfoxides are oxidized by I (deltaG = 20.6 kcal/mol) rather than by II (deltaG = 30.3 kcal/mol). Calculated kinetic and thermodynamic parameters account for the spontaneous overoxidation of sulfides to sulfones as has been experimentally observed. The charge decomposition analysis (CDA) of the calculated transition structures of sulfide and sulfoxide oxidations revealed that I and II are stronger electrophilic oxidants toward sulfides than they are toward sulfoxides.     

Kinetic thermal analytical study of saturated mono-, di- and tri-glycerides

A thermal degradation study using TG–DTG thermogravimetry was performed on three saturated fatty acids esterified with glycerol (i.e. glyceryl-tristearate (C₁₈), -tripalmitate (C₁₆) and -trimyristate (C₁₄)) at different heating rates. In addition, thermogravimetry (TG) and derivative thermogravimetry (DTG) of glyceryl di-stearate and glyceryl mono-stearate were also carried out at different heating rates. A deconvolution procedure applied to the first process and overlapping at least two steps between about 200 and 350 °C, enabled the activation energy of decomposition to be determined both by the Kissinger and the Ozawa–Flynn–Wall isoconversional methods for the deconvoluted steps of the above-mentioned fatty acids.     

A molecular dynamics study on heat conduction characteristics in DPPC lipid bilayer

In this paper, nonequilibrium molecular dynamics simulations were performed on a single component 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine lipid bilayer in order to investigate the thermal conductivity and its anisotropy. To evaluate the thermal conductivity, we applied a constant heat flux to the lipid bilayer along and across the membrane with ambient water. The contribution of molecular interaction to the heat conduction was also evaluated. Along the bilayer plane, there is little transfer of thermal energy by the interaction between lipid molecules as compared with the interaction between water molecules. Across the bilayer plane, the local thermal conductivity depends on the constituents (i.e., water, head group, and tail group of lipid molecule) that occupy the domain. Although the intramolecular transfer of thermal energy in the tail groups of lipid molecules works efficiently to promote high local thermal conductivity in this region, the highest thermal resistance appears at the center of lipid bilayer where acyl chains of lipid molecules face each other due to a loss of covalent-bond and low number density. The overall thermal conductivities of the lipid bilayer in the directions parallel and perpendicular to the lipid membrane have been compared, and it was found that the thermal conductivity normal to the membrane is higher than that along the membrane, but it is still smaller than that of bulk water.     

Structural study of smectic A phases in homologous series of N-alkylpyridinium alkylsulphates

The mesomorphic properties of 27 homologues of the N-alkylpyridinium alkylsulphate series were studied by X-ray diffraction and dilatometry. All of these compounds exhibit single smectic A phases whose layer spacings are between 0.64 and 0.8 times the molecular length. Polarizing optical microscopy observation shows that these peculiar layer spacings are not due to the tilting of the molecules; a new packing model is proposed to explain the particular structure of these thermotropic ionic liquid crystal phases.     

Structural study of smectic A phases in homologous series of N-alkylpyridinium alkylsulphates

The mesomorphic properties of 27 homologues of the N-alkylpyridinium alkylsulphate series were studied by X-ray diffraction and dilatometry. All of these compounds exhibit single smectic A phases whose layer spacings are between 0.64 and 0.8 times the molecular length. Polarizing optical microscopy observation shows that these peculiar layer spacings are not due to the tilting of the molecules; a new packing model is proposed to explain the particular structure of these thermotropic ionic liquid crystal phases.     

Vibrational spectra of mono-, di- and trichloroacetamide and mono- and trifluoroacetamide

The Raman and infrared spectra of five α-halogenoacetamides; mono-, di- and trichloroacetamide (MCA, DCA and TCA) and mono- and trifluoroacetamide (MFA and TFA), in solid phase (KBr pellets and Nujol dispersion) and in solution in several solvents (ClCH₃, Cl₂CH₂, Br₂CH₂, CH₃CN and benzene), have been recorded in order to assign the fundamental bands. The vibrational assignments, the intermolecular hydrogen bonds and the equilibrium mixture of cis and trans isomers have been discussed.