Chemical structure and surface activity

Surface tension measurements on aqueous solutions of 2-alkyl-2-methyl-1,3-dioxolanes, 2-alkyl-4-methyl-1,3-dioxolanes, and 2-alkyl-1,3-dioxanes at a temperature of 293.2 K are presented. The surface tension isotherms obtained were used to calculate some adsorption parameters, i. e. the efficiency of surface tension reduction, pC₂₅, surface excess concentration, , and surface area,A, per molecule in the adsorption layer. The Temkin adsorption isotherm equation was used to calculate standard free energy of adsorption, G ⁰ _=0.5 . The increments for a methylene group in the alkyl chain, G ^o [–CH₂–], and for the residual part of the molecule, G ^o [W], were also determined.The results obtained show that: (i) an increase in alkyl chain length at the C-2 carbon atom of the ring by one methylene unit brings about a marked increase in surface activity; (ii) the introduction of a methyl group into the 1,3-dioxolane ring (i. e., at C-2 or C-4 atom) has a weaker effect on surface activity of alkyl-substituted 1,3-dioxolanes, and (iii) the contribution of the 5- and 6-membered 1,3-dioxacyclane rings to a total surface activity of, respectively, 2-alkyl-1,3-dioxolanes and 2-alkyl-1,3-dioxanes is similar.     

Ringdeformationen und rotameres Verhalten des Phenylrestes in 2,2-disubstituierten 1,3-Dioxanen

Introduction of substituents in position 2 of 1,3-dioxanes decreases the torsional angles of the OCH₂CH₂CH₂O moiety (_{4, 5}, _{5, 6}) indicating an enhanced flattening in this part of the molecule. In geminally substituted 2-alkyl-2-phenyl-1,3-dioxanes the phenyl group isaxial, andgonal with respect to the rotameric state, while in ortho substituted derivatives, e.g. 2-methyl-2-(o-methylphenyl)-1,3-dioxane theaxial phenyl ligand assumes an intermediate rotameric position. Theaxial preference is not influenced by intramolecular dipole—dipole interaction generated by a p-substituent in the phenyl group as is shown for various 2-methyl-2-(p-substitutedphenyl)-1,3-dioxanes.

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Mit 5 Abbildungen

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Herrn Prof. Dr.K. Kratzl zum 60. Geburtstag gewidmet.

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Auszugsweise vorgetragen bei der Tagung des Vereins Österreichischer Chemiker in Wien am 20. März 1975.     

Investigation of furan acetal compounds

New 1,3-dioxanes, which are derivatives of 2-nitro-2-ethylpropane-1,3-diol and aldehydes of the furan series, were synthesized. The nitrodioxanes were reduced by means of sodium amalgam to the corresponding amines. The kinetics of the formation of the nitrodioxanes was studied. The accelerating action of the electron-acceptor diol substituent on the reaction rate was established. The rate constants in the aldehyde series increase on passing from-methylfurfural to-nitrofurfural, and they correlate satisfactorily with Brown's _p ⁺ constants.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1159–1162, September, 1972     

Alkoxy compounds

Twenty-six previously unreported 5-alkoxymethyl-2,5-dialkyl-1,3-dioxanes have been synthesized by the condensation of 2-alkoxymethyl-2-alkylpropane-1,3-diols with aldehydes. It has been shown by an analysis of the PMR spectra of these dioxanes that the 1,3-dioxanes considered are mixtures of two stereoisomers. In some cases these mixtures have been resolved into the individual isomers by vacuum fractionation in efficient columns. The configurations and conformations of the stereoisomeric 5-alkoxymethyl-2,5-dialkyl-1,3-dioxanes have been established by the NMR method; it has been shown that the lower-boiling isomers have the trans configuration and predominantly the chair conformation and the higherboiling isomers the cis configuration and predominantly an unsymmetrical boat conformation.For part XX, see [7].     

The matching of structural elements in reactions for evaluating stabilization energies for benzene and monosilabenzene

Using the 6-31G^* basis set the stabilization energy for monosilabenzene has been calculated as E _T for the homodesmotic reactions in which (i) ethylene is the other reactant with trans 1,3-butadiene and trans 2-sila-1,3-butadiene as the products, and (ii) trans 1,3-butadiene is the other reactant with trans 1,3,5-hexatriene and trans 3-sila-1,3,5-hexatriene as the products. The values are 17.2 and 17.6 kcal mol^–1 respectively, compared to 24.8 and 23.5 kcal mol^–1 respectively for the corresponding reactions of benzene. The difference is E _T for the interchange of =SiH- and =CH- groups between the aromatic and aliphatic structural environments, and is thus more informative than the quotient. The extent of the matching of structural elements in these reactions, and in the benzene reactions using longer chain polyenes, is assessed in terms of the structural environment about each heavy atom in its entirety — namely the nearest neighbor atoms (NN), the next nearest neighbor atoms (NNN), and the more distant atoms (NNNN and NNNNN). Matching by number alone is designated isoplesiotic, and if by both number and kind, homoplesiotic.     

The Mills—Nixon and anomeric effects in 2,3-dihydro-1H-1,3,2-benzodiazaphospholes: a gas-phase electron diffraction study of C6H4(NMe)2PCl using quantum-chemical data and “a priori” force field

Geometric parameters and the force fields of the molecule of 2-chloro-1,3-dimethyl-2,3-dihydro-1H-1,3,2-benzodiazaphosphole, C₆H₄(NMe)₂PCl (1), and the 1,3-dimethyl-2,3-dihydro-1H-1,3,2-benzodiazaphospholium cation, C₆H₄(NMe)₂P⁺ (2), containing a dicoordinated P atom were calculated by the restricted Hartree—Fock (RHF) method using the 6-31G* and 6-311G** basis sets. Vibrational characteristics of the internuclear distances in molecule 1 were calculated using the a priori scaled force field. Structural analysis of the gas-phase electron diffraction data for this molecule was performed with inclusion of nonlinear kinematic effects at the first-order level of perturbation theory. Substantial lengthening of the P—Cl bond and conformational peculiarities of the phosphole fragment of molecule 1 are consistent with the expected manifestations of the anomeric effect. The type of partial localization of the -bonds in the benzene fragment (relative weights of two resonance Kekule structures, or the Mills—Nixon effect) changes on going from covalent to ionized state of the P atom in the annelated five-membered ring.     

Conformational analysis of six-membered cyclic carbonates

The conformational isomerization of 2-oxo-1,3-dioxane and its methyl analogs was investigated by means of ab initio RHF//6-31G(d,p) and MP2//6-31G(d,p) quantum-chemical methods. It is shown that in comparison with 1,3-dioxanes the potential energy surface of the mentioned compounds has a fewer number of stationary points and includes two minima corresponding to conformers of sofa or distorted sofa configuration and one maximum corresponding to 2,5-twist form. The value of potential barrier of interconversion of cyclic carbonates is significantly lower than that of the analogously substituted 1,3-dioxanes.     

Copper(II) halide reactions with the - NH · CS - group in heterocyclic pentaatomic rings

Summary White crystalline complexes of general formula Cu₂L₄X₂ (where X = Cl, Br and L = 1, 3-oxazolidine-2-thione, pyrrolidine-2-thione,N-methyl-1,3-imidazolidine-2-thione andN-ethyl-1,3-imidazolidine-2-thione) and CuLX (where L = 1,3-imidazolidine-2-thione) were prepared by reduction of copper(II) halides and studied by i.r. spectroscopy in the 4000–200 cm^– range. Evidence for ligand coordination to the metal through sulphur was found in each case. The(CuCI) vibration in all the chloro derivatives falls atca. 240 cm^–.     

Furan acetal compounds

A method was developed for the preparation of amino derivatives of 1,3-dioxanes of the furan series by amalgam reduction of the corresponding nitro compounds. This method makes it possible to obtain amino compounds without destruction of the furan and dioxane rings. 2--Aminofuryl-5-alkyl-5-methylol- and 5--aminofuryl-5,5-bis(chloromethyl)-1,3-dioxanes and their azomethines were synthesized for the first time.See [5] for communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 440–442, April, 1971.     

Atranes

The infrared absorption spectra over the range 400–1700 cm^–1 of ten organyl- and organoxysilatranes, p-CH₃C₆H₄O] are investigated. The SiN coordinate link in these compounds is largely unreflected in the fundamental vibration frequencies of the bonds of the central silicon atom or the internal vibration frequencies of the substituents X linked to that atom. However, all the IR spectra have an absorption band in the 570 cm^–1 region, related to the valence vibrations (SiN), or manifesting itself as the frequency (Si-O) of the XSi (O)₃ group, substantially lowered because of interaction between the Si-O and Si-N bonds. Evidence in favor of this bond is shift of the (Si-H) frequency in the spectrum of silatrane(X=H).For Part V see [1].     

Comparative conformational analysis of 2,2-dimethyl and 2,2,5-trimethyl-1,3-dioxanes and their 2-heteroanalogs with silicon and germanium atoms

Comparative conformational analysis of 2,2-dimethyl- and 2,2,5-trimethyl-1,3-dioxanes as well as their 2-heteroanalogs with silicon and germanium atoms has been performed by means of computer simulation using HF/pVDZ, hybrid DFT PBE/3ξ, and RI-MP2/λ2 methods. The potential energy surface for all the studied compounds has revealed the presence of the chair and 2,5-twist conformers. The latter form, in the case of substituted 1,3-dioxa-2-silacyclohexanes at the HF/pVDZ level, is a transition state rather than an intermediate minimum. The molecules of 2-sila- and 2-germa-1,3-dioxacyclohexanes exhibit an enhanced conformational flexibility as compared to the 1,3-dioxanes.     

Spectroscopic effects and intramolecular interactions in the1H and13C NMR spectra of five-membered N-vinyllactams

In 1-vinylpyrrolidone, 1-vinyl-1,2,4-triazole-5-ones, 1,3-divinylimidazolidine-2-thione, and 1-vinylbenzimidazole-1-thione the vinyl groups exist predominantly in the s-trans-, but in 1-vinyl-4,5-diphenylimidazole-2-ones in the s-cis(0)-conformations relative to the exocyclic heteroatom. In 1-vinylbenzimidazole-2-ones, 3-vinylbenzoxazole-2-one, and 1-vinylindole-2,3-diones the vinyl group is present as a mixture of the s-cis(0)- and s-trans(0)-conformations. According to¹H and¹³C NMR results there are specific intramolecular interactions in 1-vinylpyrrolidone and in 1,3-divinylimidazolidine-2-thione resembling weak hydrogen bonding between the -hydrogen atoms of the vinyl group and the oxygen or the sulfur atom. In 1-vinylsuccinimide, 2-vinylphthalimide, and 1,3-divinyl-4,5-diphenylimidazole-2-one there is the same type of interaction with the -cis-hydrogen atom of the vinyl group, while in 1,3-divinyl-1,2,4-triazole-5-one there is interaction between the same hydrogen atom and the nitrogen atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1983–1990, September, 1990.     

Microwave Spectrum of 1,3-Dioxolane in the v=4-8 States of Hindered Pseudorotation

The microwave spectrum of 1,3-dioxolane (C₃H₆O₂) (8 GHz - 53 GHz) has been studied. We identified 247 b type transitions in the v=4, 5, 6, 7, 8 states of excited pseudorotation: rotational transition; vibration-rotation transitions between the v=5 and v=6 states and between the v=7 and v=8 states. Rotational constants, centrifugal distortion constants, and coupling constants between general rotation and hindered pseudorotation have been determined. The intervals _{v v'} between the pseudorotational energy levels have been evaluated: ₅₆=298,618 MHz and ₇₈=201,078 MHz.     

5-Bromouracil and 5-bromouracil–histidine complexes with metal(III) ions and their antitumour activity

Complexes of the [AILCl₂], [ML(OH)Cl] and [MLL(H₂O)Cl] type, where HL = 5-bromouracil; HL = histidine; M = Cr^III or Fe^III and M = Al^III, Cr^III or Fe^III were synthesized and characterized. The complexes are polymers with high temperature decomposition points and are insoluble in H₂O and common organic solvents. 5-Bromouracil is coordinated to the metal ion through the O atom of C₍₄₎=O and the N atom of N₍₁₎, while histidine coordinates through the O atom of —CO₂ ^– and the N atom of the —NH₂ groups. The _eff values, electronic spectral bands and e.s.r. spectra suggest a polymeric six-coordinate spin-free octahedral stereochemistry for the Cr^III and Fe^III complexes. The in vivo antitumour effect of 5-bromouracil and its complexes was examined on C₃H/He mice versus P815 murine mastocytoma. As is evident from their T/C values Cr^III and Fe^III complexes display significant and higher antitumour activity compared to 5-bromouracil while the Al^III complexes show lower activity. The in vitro results of the complexes on the same cells indicate that Cr^III and Fe^III complexes show higher inhibition on ³H-thymidine and ³H-uridine incorporation in DNA and RNA replication, respectively.     

Synthesis and mesomorphic properties of four-ring liquid crystals containing 2,3-difluorophenyl and 1,3-dioxane units

Two series of novel liquid crystalline materials were synthesized: 2-(2,3-difluoro-4-alkoxyphenyl)-5-[4-(4-alkylcyclohexyl)phenyl]-1,3-dioxanes (A _m-n and 2-(2,3-difluoro-4-alkylphenyl)-5-[4-(4-alkylcyclohexyl)phenyl]-1,3-dioxanes (B _m-n ). Their mesmorphic properties were characterized by polarizing optical microscopy and differential scanning calorimetry. All these compounds exhibit broad mesomorphic phases, and most of them show wide smectic C phases and the phase sequence Cr-SmC-SmA-N-I. The relationship between properties and chemical structures is discussed in detail.     

Zum rotameren Verhalten des Phenyl- und Phenyltricarbonylchrom-liganden in 2-substituierten 1,3-Dioxanen: Ein Vergleich

Dipole moment measurements, NMR-spectroscopical methods and dipole-dipole interaction calculations applied to 2-benchrotrenyl-1,3-dioxanes and a comparison with o-substituted 2-phenyl derivatives furnish evidence, that in both cases the rotameric state is mainly determined by the steric demand of the substituent being attached to phenyl: the declination angle () of the Cr(CO)₃-group from the bisectional cisoid relation (with respect to H on C-2) is identical with that for the ortho substituent and amounts to about 60 degs. The influence of the Cr(CO)₃-fragment on the conformational behaviour of the benzene moiety in geminal 2,2-disubstituted derivatives is consistent with these results: the assumption of an axial and gonal conformation for the phenyl ring, which had recently been established for 2-alkyl-2-phenyl-1,3-dioxanes, is no longer valid for the 2-alkyl-2-phenyltricarbonylchromium compounds.

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Mit 4 Abbildungen

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40. Mitt. über Stereochemie von Metallocenen; 39. Mitt. siehe Lit.

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Herrn Prof. Dr.H. Nowotny mit besten Wünschen zum Geburtstag gewidmet.     

Occurrence of the Unusual 2C5 (1C4) Chair Conformation in Two Carbohydrates and the Reverse Anomeric Effect. X-Ray Structures of 3,4,5,7-Tetra-O-Acetyl-2,6-Anhydro-D-Glycero-D-Ido-Heptonamide (1) and 3,4,5,7-Tetra-O-Acetyl-2,6-Anhydro-D-Glycero-L-Gluco-Heptonamide (2)

Abstract

The title compounds 1 and 2 (both C₁₅O₁₅NH₂₁) crystallized in the monoclinic space group P2₁ (Z = 2) with a=8.864(1), b=8.346(1), c =13.569(1)Å, β =114.12(1), V=918.1(2)A3, D(calc) = 1.358 g/cc for compound 1, and a=15–045(1), b=8.106(1), c=7.491(1)Å, β =97.23(1)°, V=906.4(3)Å3 D(calc)= 1.375 g/cc, for compound 2. The structures were solved by direct methods and refined by the full-matrix least squares technique to R indices of 0.010 and 0.046, respectively. Both compounds are in the α ? D configuration and adopt the unusual ²C₅, (¹C₄) chair conformation with the carbamoyl groups on the anomeric carbon atoms equatorially oriented. In this conformation the orientations of the substituents are 2e, 3a, 4a, 5a and 6a in 1 and 2e, 3a, 4a, 5e and 6a in 2 which leads to unfavorable 1,3-diaxial interactions. The “reverse anomeric effect” which induces the ²c₅ chair conformation in these compounds, may have its origin in the unfavorable steric interactions found in the ⁵c₂ (⁴C₁) conformation where the carbamoyl group is axially oriented. Furthermore, the ²C₅ conformation is stabilized by the N-H … O intramolecular hydrogen bond between the carbamoyl nitrogen atom and the pyranosyl ring oxygen atom. Semi-empirical energy calculations reveal that the rotational freedom of the carbamoyl group is greater for the equatorial orientation (²C₅) than for the axial orientation (⁵C₂).     

Observedtrans influence of donor atoms in monocharged bidentate ligands: Crystal structure of the acetone solvate of 2-carboxyquinolinatocarbonyltriphenylphosphinerhodium(I)

Summary 2-Carboxyquinolinatocarbonyltriphenylphosphinerhodium(I), [Rh(Quin)(CO)(PPh₃)], was prepared by replacement of CO by PPh₃ in the corresponding dicarbonyl. The compound crystallizes in the triclinic space group Åb=17.168(6) Å,c=9.254(5) Å, =101.49(5)°, =95.74(4)°, =98.41(4)°, d_cxp=1.45g cm^–3 and Z=2. The crystal structure was dermined from 3496 observed reflections. The final R value was 0.061. This structure determination indicates that the nitrogen atom of the chelate ring has the largesttrans influence since the carbonyl grouptrans to this atom was substituted by the PPh₃ ligand. The effects of different donor atoms in bidentate ligands, as well as the ring size of the chelate ring, on the relativetrans influence of the donor atoms are discussed.     

Conformational analysis of 5,5-bis(halomethyl)-1,3-dioxanes

Investigation of stationary points on the potential energy surface of a number of 5,5-bis(halomethyl)-1,3-dioxanes using DFT-approximation of PBE/3ζ revealed the only path of chair form interconversion proceeding through an intermediate minimum corresponding to a 2,5-twist-conformer.     

Regioselectivity in the reactions of the acetonate ion with electron-deficient arenes

The reactions of the acetonate ion with 1,3-dinitro-5-X-, 1,3-X₂-5-nitro- (X = NO₂, CN, COOCH₃, CONH₂, COO^–, and H), and 1,3,5-tricyanobenzenes were studied by ¹H NMR and electronic absorption spectroscopy and by quantum-chemical methods. The kinetic factor is decisive for the initial attack of the carbanion on the C(2) atom of unsymmetrical arenes. However, -adducts in which a nucleophile is added to the C(4) atom are more stable thermodynamically. In the case of 1,3-X₂-5-nitrobenzenes (X = CN, COOCH₃, or CONH₂), the -adducts with the acetonate group in para-position to the X group unexpectedly proved to be very stable. The structures of the -adducts based on trinitro- and 1,3-dinitro-5-cyanobenzenes were determined by X-ray diffraction analysis. Quantum-chemical calculations (the AM1 and PM3 semiempirical methods and the density functional method) were used to interpret the reaction regioselectivity and the molecular and electronic structures of the -adducts.