NMR Chemical Shifts Of Compounds Research Articles

New 1,3,4-thiadiazol derivatives: Synthesis, computational study and X-Ray

In this study, 4-hydroxyphenyl-3H-1,2,4-triazol-3-one derivatives (1a-d), cyanomethoxyphenyl-3-alkyl/aryl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-acetonitriles (2a-d) and bis amino-1,3,4-thiadiazol-5-alkyl/aryl-2,4-dihydro-3H-1,2,4-triazol-3-one (3a-d) were synthesized. The new compounds were characterized by elemental analyses, IR, 1H NMR, 13C NMR and mass spectral studies. The molecular structure of compound 2c was determined by X-ray diffraction. Vibrational data, 1H NMR and 13C NMR chemical shifts of compound 3 b were obtained by DFT/B3LYP/6–311++G(d,p) method and theoretical spectral data were compared with the experimental ones. Furthermore, Gauswiev 5.0 was used to visualize the results of the computation MEP surface for compound 3 b.

Experimental and Theoretical Studies on Molecular Structures, Nanostructural Features, and Photophysical Properties of 5-Amino-1-Alkylimidazole-4-Carboxamide Compounds

A detailed interpretation of experimental spectral data on 1H and 13C NMR chemical shifts of compounds determined from the DFT calculation is reported. The DFT calculated values are in good agreement with the experimental results. The NBO analysis is used to investigate the stability of 1-alkylAICA. The HOMO and LUMO analysis is performed to study the charge transfer property within the molecule as well as various molecular properties viz EHOMO, ELUMO, energy gap, ionization potential, electron affinity, electronegativity, chemical potential, electrophilicity, global hardness as well global softness, and so on. The formation of a 1D nano structure of 1-alkylAICA compounds is detected by SEM studies. The UV and fluorescence study is performed to observe the variation of their photophysical properties on going from the monomer to the nanostructure. TDDFT is applied to analyze experimentally measured absorption and emission spectra. A fluorescence life-time measurement is performed for the series of 1-AlkylAICA.

Experimental and theoretical studies on molecular structures, nanostructural features and photophysical properties of 5-amino-1-alkylimidazole-4-carboxamide compounds

A detailed interpretation of experimental spectral data on 1H and 13C NMR chemical shifts of compounds determined from the DFT calculation is reported. The DFT calculated values are in good agreement with the experimental results. The NBO analysis is used to investigate the stability of 1-alkyl-AICA. The HOMO and LUMO analysis is performed to study the charge tran­sfer property within the molecule as well as various molecular properties viz. EHOMO, ELUMO, energy gap, ionization potential, electron affinity, electronegativity, chemical potential, electrophilicity, global hardness as well global softness, and so on. The formation of a 1D nano-structure of 1-alkyl-AICA compounds is detected by SEM studies. The UV and fluorescence study is performed to observe the variation of their photophysical properties on going from the monomer to the nanostructure. TDDFT is applied to analyze experimentally measured absorption and emission spectra. A fluorescence life-time measurement is performed for the series of 1-alkyl-AICA.

Syntheses, spectral characterization, single crystal X-ray diffraction and DFT computational studies of novel thiazole derivatives

A novel thiazole (E)-1-((E)-2-methyl-3-phenylallylidene)-2-(4-phenylthiazole-2-yl)hydrazine 2 and its derivatives 3–8 were synthesized by cyclo condensation of (1E)-1-((E)-2-methyl-3-phenylallylidene)thiosemicarbazide 1 with substituted 2-bromoacetophenones. The synthesized thiazole derivatives were characterized by FT-IR, 1H NMR and 13C NMR analyses. For compound 8 single crystals X-ray diffraction analysis and density functional theory (DFT) calculation were carried out. The compound 8 crystallizes in the monoclinic space group P21/c with a=7.4601 (3)Å, b=5.7259 (2)Å, c=41.0823 (13)Å, α=90°, β=91.715 (2)° and γ=90°. The molecular geometrical parameters, frontier molecular orbital energies (HOMO, LUMO), their energy gap (ΔE), molecular electrostatic potential (MEP) and natural bond orbital (NBO) analysis of the compounds 2 and8 have been calculated by using DFT/B3LYP with 6-311G (d, p) level. In addition, IR frequencies, 1H and 13C NMR chemical shifts of compound 8 were also calculated by using DFT calculations at the same level basis set. The calculated geometrical parameters, IR frequencies, 1H and 13C NMR chemical shifts of the compound 8 were in good agreement with the observed single crystal-XRD data, IR, 1H and 13C NMR spectral values.

Synthesis of diosgenin p-nitrobenzoate by Steglich method, its crystal structure and quantum chemical studies

In the present study, a novel one pot synthetic route for the synthesis of diosgenin p-nitrobenzoate (2) is described from cheap, commercially available naturally occurring sapogenin–diosgenin. The molecular geometry, IR frequencies, Gauge-including atomic orbital (GIAO), 1H and 13C NMR chemical shifts of compound 2 has been calculated in the ground state by using the Hartree–Fock (HF) and density functional method (DFT/B3LYP) using 6-31G(d,p) basis set. The structure of diosgenin p-nitrobenzoate (2) has been confirmed by single crystal X-ray diffraction. The compound crystallizes in monoclinic form having space group P21 with cell parameters a=7.719(2)Å, b=8.425(2)Å and c=22.578(6)Å, α=90.00, β=98.46 and γ=90.00. The oxygen atoms O5 and O4 of the nitro and carbonyl ester, respectively display weak intermolecular N1O5⋯H7′ and C1′O4⋯H4′ interactions having dimensions of 2.61 and 2.59Å, respectively to form intricate 1D network. The study of the electronic properties such as HOMO and LUMO energy were performed using time dependent DFT (TD-DFT) calculations. The calculated HOMO and LUMO energy values indicate that charge transfer takes place within the molecule. The compound was screened for cytotoxicity and anti-adipogenic activity.

ChemInform Abstract: Structure of Two New Sesquiterpenoid Insect Antifeedants from Celastrus rosthornianus

Two new sesquiterpene polyol esters have been isolated from the root bark of Celastrus rosthornianus. Their structures were elucidated, on the basis of 1H NMR, 13C NMR, NOESY, 1H–13C chemical-shift correlation, 1H–13C long range correlation (COLOC) and mass spectrometry, as 1β-acetoxy-2β,8β,9α-tribenzoyloxy-4α,6α-dihydroxy-β-dihydroagarofuran 3 and 1β-acetoxy-8β,9α-dibenzoyloxy-2β-(furan-β-carbonyloxy)-4α,6α-dihydroxy-β-dihydroagarofuran 4. The complete assignment of 13C NMR chemical shifts of compounds 3 and 4 on the basis of 1H–13C chemicalshift correlation spectral data and insecticidal tests on compound 3 against the larvae of Pieris rapae were also carried out.

Synthesis and structure of N-arylimines of β-tellurocyclohexenals with the intramolecular coordination N → Te bonds

A series of N-arylimines of β-tellurocyclohexenals 11 have been synthesized and the molecular and crystal structures of the compounds 11a– e and also β-(dimethyltelluronium)cyclohexenal perchlorate 12 studied by X-ray crystallography. All the compounds contain strong intramolecular coordination N → Te (O → Te) bonds of the hypervalent type. In 11a– e, the lengths of the N → Te bonds are within the range of 2.690–2.147 Å and are 1.0–1.5 Å shorter than the sum of the van der Waals radii of respective atoms. In the N-arylimines 11b– e with the electronegative groups attached to the tellurium center, the lengths of the N → Te bonds are very close to that characteristic of a standard covalent N–Te bond. The experimental observed geometries are well reproduced by the DFT calculations performed at B3LYP/LanL2DZ level of approximation. The energies of the intramolecular coordination N → Te bonds vary from 23 kJ mol −1 for 11a to 119 kJ mol −1 for 11e. The calculated energy of the O → Te bond in 12 was found to be 50 kJ mol −1. The 125Te NMR chemical shifts of compounds 11 span the wide range of 734.3–1622.4 ppm. The largest downfield 125Te NMR chemical shifts are observed in the case of the compounds 11e, f in which the most electronegative atoms are attached to the tellurim centers.

5-Trifluoromethyl-1,2-dimethyl-1H-pyrazolium chlorides: synthesis and [formula omitted], [formula omitted], [formula omitted] and [formula omitted] NMR chemical shifts

The one-pot synthesis of nine novel 5-trifluoromethyl-1,2-dimethyl-1H-pyrazolium chlorides 2 from the cyclocondensation of 4-alkoxy-1,1,1-trifluoro-3-alken-2-ones 1 [CF 3C(O)CH=C(R 1)OR, where R 1=H, Me, n-Pr, n-Hex, Ph, 4-Me-C 6H 4, 4-F-C 6H 4, 4-Cl-C 6H 4, 4-NO 2-C 6H 4, and R=Me, Et] with 1-2-dimethyl hydrazine, in quantitative yields, is reported. The 1 H , 13 C , 19 F and 35 Cl NMR chemical shifts of compounds 2 also are described.

Structure of two new sesquiterpenoid insect antifeedants from Celastrus rosthornianus

Two new sesquiterpene polyol esters have been isolated from the root bark of Celastrus rosthornianus. Their structures were elucidated, on the basis of 1H NMR, 13C NMR, NOESY, 1H–13C chemical-shift correlation, 1H–13C long range correlation (COLOC) and mass spectrometry, as 1β-acetoxy-2β,8β,9α-tribenzoyloxy-4α,6α-dihydroxy-β-dihydroagarofuran 3 and 1β-acetoxy-8β,9α-dibenzoyloxy-2β-(furan-β-carbonyloxy)-4α,6α-dihydroxy-β-dihydroagarofuran 4. The complete assignment of 13C NMR chemical shifts of compounds 3 and 4 on the basis of 1H–13C chemicalshift correlation spectral data and insecticidal tests on compound 3 against the larvae of Pieris rapae were also carried out.

ChemInform Abstract: Deuterium Isotope Effects as a Probe for C‐C Hyperconjugation.

AbstractThe deuterium isotope effects on 13C NMR chemical shifts of compounds (I)‐(VIII) bearing a perdeuterated tert. butyl are shown to correlate linearly with π bond orders.