Thiophene molecular structure

Fig. 1-6). The structure obtained for thiazoie is surprisingly close to an average of the structures of thiophene (169) and 1,3,4-thiadiazole (170) (Fig. 1-7). From a comparison of the molecular structures of thiazoie, thiophene, thiadiazole. and pyridine (171), it appears that around C(4) the bond angles of thiazoie C(4)-H with both adjacent C(4)-N and C(4)-C(5) bonds show a difference of 5.4° that, compared to a difference in C(2)-H of pyridine of 4.2°, is interpreted by L. Nygaard (159) as resulting from an attraction of H(4) by the electron lone pair of nitrogen. 

Rg. 1-7. Molecular structures of thiophene and 1,3,4-thiadiazole bond lengths in A (left), bond angles in degrees (right). 

Thiophene, 3,5-diethyl-2,4-diphenyl-synthesis, 4, 900 Thiophene, dihydroconformation, 4, 34 cycloaddition reactions, 4, 850 H NM 4, 10 methiodide, 4, 86 molecular structure, 4, 7 1-oxide... 

Figure 27 Molecular structure of thiophene used in the NMR NOE study [139].

Dipolar cycloaddition of 2,4-(trimethylsilyl)- and 2,4-(trimethylgermyl)-substituted thiophene-1,1-dioxides as well as silylated 2,2 -bithiophene-1,1-dioxides was investigated. It was shown that only the C(4)=C(5) double bond of 2,4-disubstituted thiophene-1,1-dioxides interacts with acetonitrile oxide to give thienoisoxazoline dioxides. Bithiophene derivatives were inactive or their reaction with nitrile oxide was accompanied by desilylation. Cycloaddition of benzonitrile oxide with all mentioned sulfones did not occur. The molecular structure of 3a-methyl-5.6a-bis(trimethylgermyl)-3a,6a-dihydrothieno 2.3-c/ isoxazole 4,4-dioxide was established by X-ray diffraction (263). ... 

Synthesis, Determination of Physical Properties, Molecular Structure and Spectroscopy of Thiophene and its Homologs. 

III. Molecular Structure and Physical Properties of Benzo[6]thiophenes... 

II Conjugation alone cannot be relied upon to significantly enhance the optical nonlinearities. The conformational effects and the role of the substituents so that understanding of the molecular structure-property relation can be improved have been studied (89JPC7916). In the case of the thiophene oligomers, a rapid increase in the y value (large microscopic nonlinearity) as a function of N is found. 

The pyrolysis properties of four model compounds were examined. Their molecular structures are shown in Table II. The three and four-ring molecules, containing a benzo [b] thiophenic unit were synthesized by Dr. Cagniant (L.S.C.O., Metz University). A polycyclohexanesulfide is an aliphatic sulfide synthesized by Dr. N. Spassky (Laboratory of Macromolecular Chemistry, Paris VI University). Polymeric aromatic sulfide was represented by a polybenzosulfide provided by Philips Petroleum. 

Density functional theory (DFT) calculations of two types of push-pull chromophores built around thiophene-based 7t-conjugating spacers rigidified by either covalent bonds or noncovalent intramolecular interactions (Figure 6) have been carried out to assign the relevant electronic and vibrational features and to derive useful information about the molecular structure of these NLO-phores <2003CEJ3670>. 

Highly accurate molecular geometries for thiophene, deuteriothiophene, and C-labeled thiophene have been obtained by microwave spectroscopy. The molecular structure has also been determined by ED. Results from ED compare reasonably well with microwave spectral analysis, except for the C-H bond lengths, which are somewhat smaller than those determined from microwave spectroscopy. 

The molecular structure of thiophene has also been determined by liquid crystal LC (liquid chromatography) NMR spectroscopy <1984MP779, 1988MCL267> as well as ED and rotational spectroscopy. 

Although the molecular structure of thiophene has been actively investigated, there have not been many reports on those of the methyl derivatives. The molecular structure of 2,5-dimethylthiophene has been determined by gas electron diffraction (GED) and the results compared with ab initio calculations carried out at the 3-21G" level. 

In ethyl 2-amino-4-phenylthiophene-3-carboxylate 28, steric repulsion between the ethoxy group and the phenyl ring is reduced by the phenyl ring being twisted out of the plane by an angle of 70.2°. Determination of the molecular structure of 2-thiophenecarboxylic acid shows the dihedral angle between thiophene and the carboxyl group to be 1.49°. 

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