<sup>15</sup>N NMR spectroscopy of 3‐substituted 5‐trichloromethyl‐1,2‐dimethyl‐1<i>H</i>‐pyrazolium chlorides

Martins, Marcos A. P.; Pereira, Cláudio M. P.; Sinhorin, Adilson P.; Rosa, Adriano; Zimmermann, Nilo E. K.; Bonacorso, Hélio G.; Zanatta, Nilo

doi:10.1002/mrc.987

Cited by 7 publications

(6 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Such correlations between charges and chemical shifts were observed only for rigid compounds. [20,21] The molecules studied are able to rotate around single bonds as well as can undergo inversion at NH nitrogen atoms, and these processes preclude observation of a simple correlation between charge and chemical shift. Good correlations (R 2 > 0.9) were, however, found for the calculated values of the C A -O bond length and the experimental δ 17 O NMR results (Table 2; correlation parameters given for the equation: δ exp 17 O = ρL C -O + intercept).…”

Section: O Nmr Chemical Shifts -Theoretical Calculationsmentioning

confidence: 99%

¹⁷O NMR studies of substituted 1,3,4‐oxadiazoles

Gierczyk

Zalas

Kaźmierczak

et al. 2011

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

show abstract

Section: O Nmr Chemical Shifts -Theoretical Calculationsmentioning

confidence: 99%

¹⁷O NMR studies of substituted 1,3,4‐oxadiazoles

Gierczyk

Zalas

Kaźmierczak

et al. 2011

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

show abstract

“…We have not found any simple correlation between the calculated Mulliken or NBO charges on oxygen atoms or on neighboring atoms with the experimental values of chemical shifts. Such correlations between charges and chemical shifts were observed only for rigid compounds 20, 21. The molecules studied are able to rotate around single bonds as well as can undergo inversion at NH nitrogen atoms, and these processes preclude observation of a simple correlation between charge and chemical shift.…”

Section: Resultsmentioning

confidence: 93%

Topologically Chiral Covalent Assemblies of Molecular Knots with Linear, Branched, and Cyclic Architectures

Lukin

Kubota

Okamoto

et al. 2004

Chemistry A European J

View full text Add to dashboard Cite

Selectively functionalized molecular knots (knotanes) of the amide-type have been used as building blocks in syntheses of higher covalent assemblies composed of up to four knotane units. Preparation of linear and branched tetraknotanes consisted of the consecutive selective removal of allyl groups followed by linking of the intermediate hydroxyknotanes with biphenyl-4,4'-disulfonyl chloride. Macrocyclic knotane oligomers involving two, three, and four knotane moieties were obtained by high-dilution cyclization of dihydroxyknotane and biphenyl-4,4'-disulfonyl chloride. Due to their relation with cyclophanes, the latter class of oligomeric knotanes was termed "knotanophanes". Chiral resolution analysis of new oligoknotanes has been attempted on chemically bonded Chiralpak AD stationary phases, however met severe difficulties due to their complex isomeric compositions, and in most cases a significant overlap of the isomer fractions was observed. In spite of the limits of presently available chiral stationary phases that allowed only partial resolution of the synthesized topologies, oligoknotanes have been shown to be of high fundamental interest due to their unprecedented chirality. The chirality descriptions of topologically chiral unsymmetrical dumbbell 4, and the linear tetraknotane 5 are analogous to the Fischer projections of erythrose/threose and hexaric acid, respectively, while the isomeric composition of the branched tetraknotane 8 is completely unique. Moreover, the linear and branched tetraknotanes are constitutional isomers. Chirality of knotanophanes represents, in turn, analogies to known cyclic forms of peptides or sugars with multiple stereogenic centers.

show abstract

“…Correlations between the charge and the chemical shifts were observed only for rigid molecules. 13,14 The possibility of rotation and deformation of disubstituted 1,3,4-oxadiazole system precludes the observation of a simple relation between the calculated charge and spectral parameters.…”

Section: Resultsmentioning

confidence: 98%

“…In our previous paper, the effect of substituents on the 13 C and 15 N chemical shifts was studied for 2-aryl-1,3,4-oxadiazoles. 6 The present work presents our NMR studies of 2-(arylamino) …”

Section: Introductionmentioning

confidence: 99%