Wyniki wyszukiwania - Biblioteka Nauki

Ten serwis zostanie wyłączony 2025-02-11.

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Effects of intermolecular interactions on the 1H, 13C and 14N NMR chemical shifts of N,N-Dimethylformamide dissolved in monosubstituted benzenes

100%

Jackowski K. , Makulski W. , Trenkner-Olejniczak Z.

Bulletin of the Polish Academy of Sciences. Chemistry

2000

tom Vol. 48, No. 1

81-89

1 H,13 C and 14 N NMR chemical shifts have been used to monitor the dilution process of JV,7V-dimethylformamide (DMF) in monosubstituted benzenes. Both the proton and carbon chemical shifts of non-equivalent methyl groups in DMF are spectacularly influenced by ASIS (Aromatic Solvent Induced Shift) effects at the low concentration of a solute. On the other hand, the destruction of DMF liquid structure itself is better seen when the 13C chemical shift of a carbonyl carbon and the 14N shift are verified. A good correlation between the latter NMR chemical shifts has been found. It is shown on the basis of GIAO-CHF model calculations that the destruction of solute dipole-dipole dimers may be responsible for the increase of carbonyl carbon and nitrogen shielding constants of DMF in solvents.

Influence of Intermolecular Interactions on Nuclear Magnetic Shielding Constans of OCS

100%

Jackowski K. , Les A. , Makulski W. , Wozniak K.

2002

tom Vol. 76 / nr 4

575-580

The gauge-included atomic orbital (GIAO) method has been applied within the coupled Hartree-Fock (CHF) approximation to compute 13C, 17Oand 33SNMRchemical shifts for solid OCS. Increasing clusters of OCS molecules taken out of crystal lattice have been used in an additive approximation to estimate the effect of intermolecular interactions on shielding of the carbon, oxygen and sulphur nuclei. There is a very good agreement achieved for NMR chemical shifts between the results of calculations and experimental measurements obtained for 13C and also some discrepancies for 17Oand 33S nuclei, probably due to deficiency of ab-initio calculations (lack of electron correlation). The results reveal that the 33S NMR signal of OCS is strongly dependent on intermolecular interactions.