Search results for "hexane"
showing 10 items of 467 documents
ChemInform Abstract: UEBER ARSEN-HALTIGE HETEROCYCLEN 3. MITT. KRISTALLSTRUKTUR VON 2,6-DIMETHYL-4,4-DIPHENYL-1,4-OXOARSENANIUMBROMID-MONOHYDRAT
1975
Abstract The crystal structure of the title compound has been determined from single crystal X-ray data and refined to a conventional R factor of 0.046. The coordination of the As atom is tetrahedral with a mean As—C distance of 1.92 A. The six-membered heterocycle has chair conformation with two equatorial methyl and one equatorial and one axial phenyl substituent. The transannular 1,4-As⋯O distance is 3.11 A, interactions are discussed. The connection of the structure is more van der Waals than ionic type. Some unspecific gaps are statistically occupied by one molecule of crystal water.
Selenium Imides: 77Se NMR Investigations of the SeCl2−tBuNH2 Reaction and X-ray Structures of Se3(NtBu)3, tBuNSe(μ-NtBu)2SO2, and tBuNSe(μ-NtBu)2SeO
2000
The reaction of SeCl2 with tert-butylamine in various molar ratios in THF at −78 °C has been investigated by 77Se NMR spectroscopy. In addition to the known Se−N heterocycles Se6(NtBu)2 (1) and Se9(NtBu)6 (2), the acyclic imidoselenium(II) dichlorides ClSe[N(tBu)Se]nCl (4, n = 1; 5, n = 2) and two new cyclic selenium imides [Se3(NtBu)2]n (3, n = 1 or 2) and Se3(NtBu)3 (6) have been isolated and identified. An X-ray analysis shows that 6 is a six-membered ring in a chair conformation with |d(Se−N)| = 1.833 A. Crystal data: 6, trigonal, P3c1, a = 9.8660(3) A, c = 20.8427(7) A, V = 1757.0(1) A3, Z = 6. The 1H, 13C, and 77Se NMR data for 1−6 are reported, and some reassignments of earlier lite…
Über polygermane
1985
Abstract [(Cl 3 CCOO)Ph 2 Ge] 2 reacts with wet acetone to give Ph 8 Ge 4 O 2 , and with dry H 2 S to give Ph 8 Ge 4 S 2 . With Na 2 S or NaHSe, Ph 4 Ge 2 Cl 2 yields Ph 8 Ge 4 S 2 and Ph 8 Ge 4 Se 2 , respectively. Only Ph 6 Ge 3 S 2 or Ph 6 Ge 3 Se 2 , but no Ph 6 Ge 3 O 2 , can be obtained from a mixture of Ph 4 Ge 2 Cl 2 , Ph 2 GeCl 2 and Na 2 S or NaHSe. The mass spectra show a high stability of the cations Ph 6 Ge 3 S 2 + and Ph 6 Ge 3 Se 2 + . The 13 C NMR phenyl signals for C( ipso ) shift to high field in the series O, S, Se and 6-membered, 5-membered rings. The crystal structures of Ph 8 Ge 4 O 2 ( R = 0.031) and Ph 6 Ge 3 S 2 ( R = 0.036) have been determined. The 6-membered ring…
(E)-2-{[1-(3,11-Dimethyl-4-methylene-10-oxo-1-phenyl-4,5,10,11-tetrahydro-1H-benzo[b]pyrazolo[3,4-f][1,5]diazocin-5-yl)ethylidene]amino}-N-methyl-N-(…
2013
The central eight-membered ring of the title compound, C40H36N8O2, deviates from the ideal boat conformation because the bond between the exo-ethylene group and the adjacent N atom is twisted by 60.0 (4)° due to steric hindrance. Its adjacent benzene and pyrazole rings are oriented almost perpendicular to each other, making a dihedral angle of 85.8 (3)°. In the crystal, the molecules are linked by C(ar)—H...O hydrogen bonds, generating a three-dimensional network.
Modular P-Chirogenic Aminophosphane-Phosphinite Ligands for Rh-Catalyzed Asymmetric Hydrogenation: A New Model for Prediction of Enantioselectivity
2007
An original series of P-chirogenic aminophosphane-phosphinite (AMPP) ligands has been synthesized from (+)- or(–)-ephedrine in 23 to 61 % overall yields by a versatile three-step methodology. The AMPP ligands, bearing either one or two P-chirogenic centers, were used in the form of rhodium complexes for the catalyzed hydrogenation of α-acetamidocinnamate as a test reaction. Notably, even with AMPP ligands all derived from (+)-ephedrine, variation of the substituent on a P-center allowed the phenylalanine derivatives to be obtained in either (S) or (R) absolute configurations, with ee values ranging from 99 % (S) to 88 % (R). The asymmetric induction was analyzed with the aid of X-ray struct…
Benzoannulated quinone-type electron acceptors: evolution of the molecular and electronic structures upon reduction
1998
Abstract The molecular and electronic structures of DCNQI and its π-extended derivatives benzo-DCNQI and DCAQI have been investigated using ab initio 6-31G ∗ calculations. The steric hindrance introduced by lateral benzoannulation determines the loss of planarity of the DCNQI moiety for DCAQI. The most stable conformation of DCAQI corresponds to a butterfly-type structure, in which the DCNQI ring adopts a boat conformation and the lateral benzene rings remain planar. This structure lies 2.75 kcal mol −1 below the fully planar conformation. MP2/6-31G ∗ calculations including full geometry optimization confirm the greater stability of the butterfly structure. The geometries of the anions and …
Selective Derivatization of Resorcarenes. 3. C2-Symmetrical and Transcavity Bridged Bis-Benzoxazines Derived from C2v-Symmetrical Tetratosylates
1998
The regioselective condensation of resorcarene tetratosylates 3/4 with formaldehyde and various primary amines readily gives bis-benzoxazines 5/6 in 65−86% yield. The chiral, C2-symmetrical structure of these compounds has been proved by NMR-spectroscopy and single-crystal X-ray analysis. Bis-benzoxazines 5f and 5i assume in the crystalline state a boat conformation in which the two resorcinol rings bearing the oxazine fragments are nearly parallel. The tosylated resorcinol units are horizontally arranged in a propeller-like fashion, and two intramolecular hydrogen bonds are formed between the phenolic hydroxy groups and the oxygens of the neighboring sulfonyl fragments. Molecular mechanics…
Influence of theZ/EIsomerism on the Pathway Complexity of a Squaramide‐Based Macrocycle
2020
The rising interest on pathway complexity in supramolecular polymerization has prompted the finding of novel monomer designs able to stabilize kinetically trapped species and generate supramolecular polymorphs. In the present work, the exploitation of the Z/E (geometrical) isomerism of squaramide (SQ) units to produce various self-assembled isoforms and complex supramolecular polymerization pathways in methylcyclohexane/CHCl3 mixtures is reported for the first time. This is achieved by using a new bissquaramidic macrocycle (MSq) that self-assembles into two markedly different thermodynamic aggregates, AggA (discrete cyclic structures) and AggB (fibrillar structures), depending on the solven…
Crystal structure and Hirshfeld surface analysis of 3-oxours-12-ene-27a,28-dioic acid (quafrinoic acid)
2017
The title compound, known as quafrinoic acid, is a pentacyclic triterpene isolated from Nauclea Pobeguinii. The compound is composed of five fused six-membered rings and the molecular conformation is stabilized by intramolecular C—H⋯O interaction, forming S6 and S8 rings.
Predictability of properties of ternary systems solvent/solvent/polymer from interaction parameters of the binary systems—III. Analysis of binary pot…
1990
Abstract The assumption that the ternary parameter, g τ , and its derivative with respect to polymer concentration, ( ∂g τ / ∂φ 3 ) μ 1 , φ 3 → 0 , can be described by three binary interaction parameters, g o i 3 ( i = 1, 2) and g 12 , implies that these must be independent functions. This feature has been demonstrated by using g o i 3 values obtained from A/B/polymer(P) and C/D/P ternary polymer systems to predict the ternary properties, namely preferential solvation (λ), second virial coefficient ( A 2 ) and intrinsic viscosity ([η]), of a A/C/P ternary system. Two distinct polymers, polystyrene(PS) and poly(dimethylsiloxane)(PDMS), have been utilized in three solvent mixtures, benzene(BZ…