Search results for "Chemical shift"

13C NMR study of aromatic ring-substituted (E)-3-phenylpropenals and (2E,4E)-5-phenylpenta-2,4-dienals

1990

13C and 1H chemical shifts together with C,H and H,H coupling constants are presented for (E)-3-phenylpropenal, (2E,4E)-5-phenylpenta-2,4-dienal and their o-OCH3- and o-, m- and p-NO2-substituted derivatives. The SCSs calculated for the aldehyde chains show similar effects on the ring carbons, except in the para position where the shorter chain causes a 3.3 ppm deshielding and the longer chain a 1.0 ppm shielding effect. This shift difference is reflected in all the ring-substituted derivatives of the two series of aldehydes, but not in the one-bond C,H coupling constants. The effect of aromatic ring substitution on 2J(C,CHO) seems to be mainly inductive in origin. The importance of the str…

Push-Pull Oligomers with 2,2-Dicyanovinyl Groups as Electron Acceptors

2007

Three conjugated oligomer series with terminal donor–acceptor substitution were studied: oligo(1,4-phenylenevinylene)s DAOPVs 4a–d (n = 1–4), oligo(1,4-phenyleneethynylene)s DAOPEs 6a–d (n = 1–4) and oligo(2,5-thienyleneethynylene)s DAOTEs 8a–e (n = 1–5). Dialkylamino or methoxy groups served as electron donors and 2,2-dicyanovinyl groups as strong electron acceptors. The push-pull effect polarizes the molecular chains – an effect which is documented by the splitting of the 13C chemical shifts of two carbon atoms of the double or triple bonds in the chain. For higher oligomers (n ≥ 3), the effect is mainly localized at the chain ends. The long-wavelength absorption results in a charge-trans…

Über tetraaryl-methan-analoga in der gruppe 14

1994

Abstract The title compounds have been synthesized by Grignard reactions or pyrolysis of diplumbanes respectively. The crystal structures of m -Tol 4 Pb and Ph 4 Pb (redetermination) have been determined. All eight compounds (Ph/Tol) 4 (Sn/Pb) are S 4 symmetric and contracted along this unique axis. The 13 C-NMR chemical shifts and the couplings 1 J ( 119 Sn/ 207 Pb 13 C) as well depend additively upon the methyl substituents. The ratios 1 K ( 207 Pb 13 C): 1 K ( 119 Sn 13 C) of the reduced coupling constants are all near to 1.61; a comparison with values from the literature for alkyl, alkenyl and alkinyl substituents is given. The ratio δ( 207 Pb):δ( 119 Sn) results in 2.28. IR (700 dow…

1H,13C,17O and19F NMR spectroscopic study of isomeric ring-substituted monofluoro-(E)-3-phenylpropenals

1993

Isomeric ring substituted monofluoro-(E)-3-phenylpropenals (cinnamaldehydes) were synthesized in order to provide, with the NMR-active 19F nucleus, an insight into the influence of substituents and the transmission of electronic effects between the aromatic ring and the side-chain. Their 1H, 13C and 17O NMR chemical shifts and their nJ(H,H), nJ(H,F), nJ(C,H) and nJ(C,F) values were determined. Generally, the nJ(C,F) coupling constants correlate with the length of the coupling route and thus simplify the assignments of the 13C NMR spectra. Only the side-chain carbons C-2 and C-3 in the ortho-substituted compounds showed an exception to this rule. Many long-range nJ(H,F) (n = 4–7) values were…

13C NMR spectroscopic study of diphenyl ether and 28 of its polychlorinated derivatives

1993

The 13 C NMR chemical shifts and coupling constants for diphenyl ether and 28 environmentally interesting polychlorinated diphenyl ethers were measured and analysed

Novel Applications of Dynamic NMR in Organic Chemistry

2004

Abstract This review article is oriented on NMR applications in studying various dynamic processes of organic molecules. The topic as a whole is too large to be covered exhaustively in one article or by one author. Therefore, the literature searches are limited mainly for the years 1999–2001. Further, many interesting branches joined essentially with organic chemistry such as supramolecular and organometallic chemistry are left outside this article because there exist recent reviews on these topics. Similarly, the theoretical background of dynamic NMR is not included. The nature of dynamic NMR itself is changing with the recent progress in computational possibilities to estimate the differe…

ChemInform Abstract: Synthesis and Spectroscopic Characterizations of Both 1-Ethyl-4,8- dihydro-10-methoxy-3-methyl-8-R1-6-R2-dipyrazolo(3,4-b:4′,3′-…

2010

The non-selective methylation of compounds 3a-d using ethereal diazomethane, allowed the synthesis of isomers 4 and 5 which were useful intermediates for the preparation, by a simple approach, of the title compounds 7 and 9. A complete assignment of the chemical shifts to the carbon atoms of the compounds 7 and 9 was performed by different nmr experiments, such as DEPT and XHDEPT for onebond CH correlations and COLOC experiments for long-range C-H correlations.

Novel Applications of Dynamic NMR in Organic Chemistry

2003

Abstract This review article is oriented on NMR applications in studying various dynamic processes of organic molecules. The topic as a whole is too large to be covered exhaustively in one article or by one author. Therefore, the literature searches are limited mainly for the years 1999–2001. Further, many interesting branches joined essentially with organic chemistry such as supramolecular and organometallic chemistry are left outside this article because there exist recent reviews on these topics. Similarly, the theoretical background of dynamic NMR is not included. The nature of dynamic NMR itself is changing with the recent progress in computational possibilities to estimate the differe…

Predominance of resonance over polar effects on1H,13C and15N NMR substituent chemical shifts inN-arylglycines

1998

Benzodiselenagermoles and spirobisbenzodiselenagermoles

1993

Synthesis of benzodiselenagermoles and bisbenzodiselenagermoles was carried out by transmetallation group 4 group 14 between diselenophenylenezirconocenes and dialkyl-, diaryl- or alkylaryldichlorogermanes, aryltrichlorogermane or germanium tetrachloride. The new compounds were studied by 1H, 77Se NMR and mass spectrometry. In the case of compounds with substituted phenyl groups, double irradiation and 2D NMR experiments were performed to determine the chemical shifts of the two selenium atoms. The crystal structure of a spirobisbenzodiselenagermole has been established by X-ray diffraction analysis.