Beiträge zur Chemie des Schwefels, 116 [1]Kristall-und Molekülstrukturen von 1.2.4.5-Benzotetrathiepin und 3-Methyl-1.2.4.5-benzotetrathiepin / Contributions to the Chemistry of Sulfur, 116 [1]Crystal and Molecular Structures of 1,2,4,5-Benzotetrathiepine and 3-Methyl-1,2,4,5-benzotetrathiepine

1979 ◽  
Vol 34 (3) ◽  
pp. 426-430 ◽  
Author(s):  
F. Fehér ◽  
B. Engelen
Keyword(s):  
Structure Analysis ◽  
Spectroscopic Data ◽  
Membered Ring ◽  
Molecular Structures ◽  
Methyl Group ◽  
Chair Form ◽  
X Ray ◽  
Crystal And Molecular Structures

Abstract The structures of 1,2,4,5-benzotetrathiepine and 3-methyl-1,2,4,5-benzotetrathiepine were determined by X-ray structure analysis. The constitution of the molecules, which was proposed by way of spectroscopic data, could be verified. The conformation of the seven-membered rings is the chair form. The position of the methyl group in 3-methyl-1,2,4,5-benzotetrathiepine is equatorial with respect to the seven-membered ring. Details of the conformations are discussed. Bond distances and angles are compared with those in other molecules, which have similar structures.

Untersuchungen an Stickstoff-Brom-Verbindungen, IV / Studies on Nitrogen-Bromine Compounds, IV

1977 ◽  
Vol 32 (12) ◽  
pp. 1416-1420 ◽  
Author(s):  
Omar Jabay ◽  
Hans Pritzkow ◽  
Jochen Jander
Keyword(s):  
Crystal Structure ◽  
Nitrogen Atom ◽  
Structure Analysis ◽  
Electron Acceptors ◽  
Molecular Structures ◽  
Hydrogen Atoms ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
Solid Nitrogen ◽  
Intermolecular Contacts

The crystal and molecular structures of N-bromobenzamide (NBB), N-bromosuccinimide (NBS), and N,N-dibromobenzenesulfonamide (NBBS) were determined by X-ray structure analysis. The nitrogen atoms in NBB and NBS have a trigonal planar coordination (sp2) and the N—Br distances lie in the same range (1.82 A, 1.84 A). The N—Br distance in NBBS, where the nitrogen atom is sp3-hybridized, is somewhat longer (1.88 A). In these structures the molecules are connected by O···H—N (NBB), O···Br—N (NBS) or N···Br—N (NBBS) intermolecular bonds forming endless chains; positivated hydrogen atoms or, in case that they are absent, positivated bromine atoms act as electron acceptors with oxygen or sp3- hybridized nitrogen atoms. These results suggest, that in solid nitrogen tribromide, the crystal structure of which cannot be determined, the nitrogen atoms will be sp3-hybridized and intermolecular contacts via N—Br···N will occur.

Darstellung und Charakterisierung von Spezies der Zusammensetzung η5-C5H5Cr(NO)2SR (R = C6H5, C6F5, t–C4H9) und [η5-C5H5CrNO]2(ER)2 (E = O, S, Se, Te, R = Alkyl, Aryl); Röntgenstrukturanalysen von [η5-C5H5(NO)Cr(μ-SeC6H5)2Cr(NO)-η5-C5H5] und [η5-C5H5(NO)Cr(μ-Se-n-C4H9)(μ-OH)Cr(NO)-η5-C5H5] / Synthesis and Characterization of Species of Composition η5-C5H5Cr(NO)2SR (R = C6H5, C6F5, t-C4H9) and [η5-C5H5CrNO]2(ER)2 (E = O, S, Se, Te, R = Alkyl, Aryl); Röntgenstrukturanalysen von [η5-C5H5(NO)Cr(μ-SeC6H5)2Cr(NO)-η5-C5H5] and [η5-C5H5(NO)Cr(μ-Se-n-C4H9)(μ-OH)Cr(NO)-η5-C5H5]

1982 ◽  
Vol 37 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Johannes Rott ◽  
Ernst Guggolz ◽  
Albert Rettenmeier ◽  
Manfred L. Ziegler
Keyword(s):  
Mass Spectra ◽  
Membered Ring ◽  
Molecular Structures ◽  
Binuclear Complexes ◽  
Alkyl Aryl ◽  
X Ray ◽  
H Nmr ◽  
Crystal And Molecular Structures ◽  
Nmr Methods

The title compounds have been synthesized and characterized by elemental analysis, IR and 1H NMR methods and mass spectra. The crystal and molecular structures of the binuclear complexes [η-C5H5(NO)Cr(μ-SeC6H5)2Cr(NO)-η5-C5H5] and [η5-C5H5(NO)Crμ-Se-n-C4H9)(μ-OH)Cr(NO)-μ5-C5H5] have been determined by X-ray structure analysis. The latter is shown to have a four-membered ring consisting of two chromium atoms, one selenium, and one oxygen atom.

Sense of sequential 1,5-sigmatropic rearrangements of dimethyl-3,3-dialkyl-3H-pyrazole-4,5-dicarboxylates. Crystal and molecular structures of two dimethyl-4,5-dialkyl-1H-pyrazole-1,3-dicarboxylates

1991 ◽  
Vol 69 (3) ◽  
pp. 373-378 ◽  
Author(s):  
Christopher S. Frampton ◽  
Michael W. Majchrzak ◽  
John Warkentin
Keyword(s):  
Dicarboxylic Acid ◽  
Key Words ◽  
Dimethyl Ester ◽  
Molecular Structures ◽  
X Ray Diffraction ◽  
Methyl Group ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
Sigmatropic Rearrangements ◽  
Methoxycarbonyl Group

3,3-Dialkyl-3H-pyrazole-4,5-dicarboxylic acid dimethyl esters (4), obtained by cycloaddition of R1R2C=N+=N− (R1 = R2 = CH3; R1 = CH3, R2 = CH2CH3) to CH3O2CC≡CCO2CH3, rearrange thermally by 1,5-sigmatropic alkyl shifts to both N and C. The latter rearrangement is followed by two successive 1,5-sigmatropic shifts of a methoxycarbonyl group. Final products of the threefold rearrangement were shown to be 4,5-dialkyl-1H-pyrazole-1,3-dicarboxylic acid dimethyl esters (6), rather than the isomeric 3,4-dialkyl-1H-pyrazole-1,5-dicarboxylic acid dimethyl esters (7), by means of single crystal X-ray diffraction. Those products therefore result from alkyl migration to C-4 of 4, followed by sequential migration of the methoxycarbonyl group, initially at C-4, to C-3 and then to N-2 of 4. In the initial alkyl migration step, ethyl migrates in preference to methyl, and in subsequent migration steps the methoxycarbonyl group migrates faster than the ethyl or methyl group. Crystals of 4-ethyl-5-methyl-1H-pyrazole-1,3-dicarboxylic acid dimethyl ester (6b) are monoclinic, of space group P21/n, with a = 7.907(1) Å, b = 11.087(2) Å, c = 13.199(3) Å, V = 1124.9(4) Å 3, Dc = 1.34 g cm−3, Dm = 1.33 g cm−3 for Z = 4, and R1 = 0.0772 (R2 = 0.0626) for 1474 reflections (R1 = 0.0428, R2 = 0.0422 for 903 reflections with I > 3σ(I)). The structure of 6a is similar. Key words: 3,3-dialkyl-3H-pyrazoles, 1,5-sigmatropic rearrangements of; 4,5-dialkyl-1H-pyrazoles, crystal and molecular structures; 1,5-sigmatropic rearrangements of pyrazoles, sense of.

Röntgenstrukturuntersuchungen an Trimethylsilylaluminiumverbindungen / X-Ray Crystal Study of Trimethylsilylaluminium Compounds

1983 ◽  
Vol 38 (1) ◽  
pp. 34-41 ◽  
Author(s):  
Lutz Rösch ◽  
Gerald Altnau ◽  
Carl Krüger ◽  
Y.-H. Tsay
Keyword(s):  
Structure Analysis ◽  
Ion Pair ◽  
Molecular Structures ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
Contact Ion Pair ◽  
Linear Chains ◽  
Pair Interactions

Abstract Structure, Tris(trimethylsilyl)aluminium, Sodium-tetrakis(trimethylsilyl)aluminate The crystal and molecular structures of three trimethylsilylaluminium compounds -tris(trimethylsilyl)aluminium coordinated to a diethylether molecule (1), sodium-tetrakis-(trimethylsilyl)aluminate coordinated to two toluene molecules (2b) and unsolvated sodium-tetrakis(trimethylsilyl)aluminate (2a) -have been determined by X-ray structure analysis. In all three compounds the aluminium is tetrahedrally coordinated, the Al-Si-distances lying between 2.44 and 2.49 Å. (1) is monomeric and (2a) and (2b) form linear chains resulting from contact-ion pair interactions.

Formation of heterocyclic arylboronates by thermally induced 1,4-aryl migration in diarylboron chelates of C-(1-hydroxyalkyl)nitrones. Crystal and molecular structures of some of the rearrangement products and of one of the educts

2001 ◽  
Vol 79 (2) ◽  
pp. 226-237
Author(s):  
Wolfgang Kliegel ◽  
Gottfried Lubkowitz ◽  
Jens O Pokriefke ◽  
Steven J Rettig ◽  
James Trotter
Keyword(s):  
Spectroscopic Data ◽  
Direct Methods ◽  
Molecular Structures ◽  
Time Dependent ◽  
Isomerization Reaction ◽  
Crystal Data ◽  
Thermally Induced ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
Transition State Geometry

Synthesis of heterocyclic arylboronates has been carried out by thermally induced rearrangement of diarylboron chelates of C-(1-hydroxyalkyl)nitrones. The structures have been determined from spectroscopic data and from X-ray analyses. Thermoanalytical and time-dependent NMR measurements give information on the nature of the isomerization reaction. Crystal data (at 293 K for 2j, 180 K for the others): 1m, monoclinic, P21/n, a = 14.059(3), b = 12.5531(13), c = 14.8531(6) Å, β = 95.8067(12)°, Z = 4; 2j, triclinic, [Formula: see text]1, a = 10.4729(11), b = 13.5896(11), c = 9.5803(7) Å, α = 104.764(6), β = 103.279(7), γ = 107.278(7)°, Z = 2; 2m, monoclinic, P21/n, a = 14.9442(13), b = 11.990(2), c = 16.0613(4) Å, β = 114.0153(7)°, Z = 4; 9, monoclinic, P21/n, a = 11.123(2), b = 18.433(3), c = 13.4852(4) Å, β = 108.2075(7)°, Z = 4. The structures were solved by direct methods and refined by full-matrix least-squares procedures to R(F, I [Formula: see text] 3σ(I)) = 0.036, 0.052, 0.043, and 0.040, respectively, for AFC6 data for 2j and CCD data for 1m, 2m, and 9. All four molecules contain six-membered OBONCC rings, with an approximately planar ON=CC segment in the educt 1m and approximately planar OBOC segments in the rearrangement products. A probable transition state geometry is derived for the isomerization process.Key words: diarylboron chelates, C-(1-hydroxyalkyl)nitrones, heterocyclic arylboronates, organoboron compounds, rearrangement, crystal structures.

Newμ-Oxo Octanuclear Complexes of 3d Elements Stabilized by Dialkylcarbamato Ligands. Synthesis and X-ray Crystal and Molecular Structures†

2002 ◽  
Vol 41 (11) ◽  
pp. 2814-2816 ◽  
Author(s):  
Daniela Belli Dell'Amico ◽  
Consuelo Bradicich ◽  
Fausto Calderazzo ◽  
Alessandro Guarini ◽  
Luca Labella ◽  
...  
Keyword(s):  
Molecular Structures ◽  
X Ray ◽  
Crystal And Molecular Structures ◽  
3D Elements

scholarly journals Five-membered ring annelation in [2.2]paracyclophanes by aldol condensation

2014 ◽  
Vol 10 ◽  
pp. 2021-2026 ◽  
Author(s):  
Henning Hopf ◽  
Swaminathan Vijay Narayanan ◽  
Peter G Jones
Keyword(s):  
Structural Analysis ◽  
Spectroscopic Data ◽  
Acid Treatment ◽  
Aldol Condensation ◽  
Membered Ring ◽  
X Ray

Under basic conditions 4,5,12,13-tetraacetyl[2.2]paracyclophane (9) cyclizes by a double aldol condensation to provide the two aldols 12 and 15 in a 3:7 ratio. The structures of these compounds were obtained from X-ray structural analysis, spectroscopic data, and mechanistic considerations. On acid treatment 12 is dehydrated to a mixture of the condensed five-membered [2.2]paracyclophane derivatives 18–20, whereas 15 yields a mixture of the isomeric cyclopentadienones 21–23. The structures of these elimination products are also deduced from X-ray and spectroscopic data. The sequence presented here constitutes the simplest route so far to cyclophanes carrying an annelated five-membered ring.

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