Search results for "RESONANCE"

NMR Study of the (Z)-Phenylhydrazones of 5-Alkyl- and 5-Aryl-3-benzoyl-1,2,4-oxadiazoles: Support for the Interpretation of Kinetic Results on the Re…

2005

An analysis of the 1H, 13C, and 15N NMR substituent chemical shifts (SCSs) of the title compounds in CDCl3 solution has been carried out by using the SCSs of other classes of compounds (arenes, methyl esters or amides), Hammett substituent constants or kinetic data. The results obtained provide information concerning the ground-state electronic distribution of the compounds examined. The results relevant to the carbon and nitrogen atoms of the 1,2,4-oxadiazole ring can be considered of special interest, as the effects of the substit- Introduction For several years our research group has been involved in the use of NMR spectroscopic data (1H, 13C, 15N, and 17O) to obtain information about th…

New tracer compounds for secondary organic aerosol formation from β-caryophyllene oxidation

2013

Abstract Five products from β-caryophyllene oxidation (β-caryophyllonic acid (I), 3,3-dimethyl-2-(3-oxobutyl)cyclobutanecarboxylic acid (βCA198) (II), β-nocaryophyllonic acid (III), β-caryophyllinic acid (IV), and 2-(2-carboxyethyl)-3,3-dimethylcyclobutanecarboxylic acid (βCA200) (V)) were synthesized and their structures confirmed by nuclear magnetic resonance spectroscopy. Reaction chamber experiments with β-caryophyllene at two different ozone mixing ratios were performed and the carboxylic acid oxidation products in the particle phase were characterized by APCI–MS and HPLC–ESI–MS. All five synthesized acids were found as β-caryophyllene oxidation products in the reaction chamber aerosol…

Synthesis and Unusual NMR-Spectroscopic Behavior of a Strained Bicyclic Ammonium Salt

2018

Cycloaddition reactions of benzothiete and hetero dienophiles for the synthesis of heterocyclic systems

1986

Abstract Benzothiete ( 1 ) undergoes cycloaddition reactions with hetero dienophiles with NN-, NO- or CO- double bonds, leading to six-membered heterocyclic ring systems of 2H-3,4-dihydro-1,2,3-benzothiadiazine ( 3 ), 4H-3,1,2-benzoxathiazine ( 4 ) and 4H-3,1-benzoxathiin.

Cyclometallation reactions in complexes of the type Rh(oq)(CO)(P(o-BrC6F4)Ph2)

1986

Abstract The complex [uRh(oq)Br(P( o -Cu 6 F 4 )Ph 2 )(H 2 O)] 2 is obtained by refluxing a solution of Rh(oq)(CO)(P( o -BrC 6 F 4 )Ph 2 ) (oq = 8-oxyquinolinate) in toluene. The structure of this compound has been determined by X-ray diffraction and refined to R = 0.061 and R w = 0.065 factors. The cell has monoclinic symmetry, space group P 2 1 / n ; a 19.513(2), b 17.049(1), c 16.898(1) A and β 99.69(1)°. The structure consists of two independent Rh(oq)Br(P( o -C 6 F 4 )Ph 2 )H 2 O) units linked by hydrogen bonds between the coordinated water molecules and oq ligands to form a distorted boat (six atom ring of junction between the two units). In each unit the metal atom has a distorted oc…

Configurational effects in17O NMR chemical shifts of hydroxyl-substituted, bicyclo [2.2.1]heptenes and -heptanes, their methylated derivatives and so…

1993

Well resolved natural abundance 17O NMR spectra of 27 mono-, di-, tri- and tetrahydroxybicyclo[2.2.1]heptenes and -heptanes (norbornenes or norbornanes), their methylated derivatives and some related compounds were measured for 0.5 M or saturated solutions in acetonitrile at 65°C. In addition, the 17O NMR chemical shifts of 14 aliphatic and alicyclic alcohols were also determined for reference purposes. The 17O NMR chemical shifts of all compounds were assigned. Both methyl- and hydroxyl-induced deshielding β-effects were consistent with those reported in the literature. Similarly, observed shielding γ-effects were in agreement with the earlier observations and characteristic especially for…

Structure and fluxional behaviour of heptaleneirontricarbonyl and heptalenebis (Irontricarbonyl)

1987

Abstract The synthesis of heptaleneirontricarbonyl ( 4 ) is described. The structures of 4 and of the closely related heptalenebis(irontricarbonyl) ( 3 ) are elucidated by NMR spectroscopy ( 1H and 13C) and by X-ray crystallography. Compounds 3 and 4 are shown by dynamic NMR to undergo an isodynamic 1 ,2-migration of the Fe(CO3)-groups as well as a carbonyl scrambling. The relevant kinetic data allow for a mechanistic discussion of the dynamics and a comparison with other irontricarbonyl complexes.

Straightforward synthesis of bioconjugatable azo dyes. Part 2: Black Hole Quencher-2 (BHQ-2) and BlackBerry Quencher 650 (BBQ-650) scaffolds

2014

Abstract A further extension of the efficient synthetic methodology described in Part 1, to the aromatic bis-diazo scaffold of Black Hole Quencher-2 dye is presented. Bioconjugatable derivatives bearing either azido, terminal alkyne, or maleimide reactive group were easily obtained as well as the free-phenol form of BlackBerry® Quencher 650 (BBQ-650®) initially developed by Berry & Associates, Inc. Company. The efficient conjugation ability of azido- and maleimide-quenchers was demonstrated through the facile preparation of the first water-soluble and formylated BHQ-2 dyes and a FRET-based probe suitable for the in vitro/in cellulo detection of a cancer-associated protease namely urokinase-…

Synthesis and biopharmaceutical characterisation of new poly(hydroxyethylaspartamide) copolymers as drug carriers.

2001

Abstract Four new poly(hydroxyethylaspartamide)-based copolymers bearing (a) poly(ethylene glycol) 2000, (b) poly(ethylene glycol) 5000, (c) poly(ethylene glycol) 2000 and hexadecylalkyl, (d) poly(ethylene glycol) 5000 and hexadecylalkyle, as pendant groups were synthesised. The copolymers were obtained by partial aminolysis of polysuccinimide with poly(ethylene glycol) and hexadecylalkyl amino derivatives followed by reaction with ethanolamine. Naked polyhydroxyaspartamide was obtained by polysuccinimide reaction with ethanolamine. The nuclear magnetic resonance, infrared, light scattering and elemental analysis allowed for the extensive physico-chemical characterisation of the carriers. T…

Group 13 complexes of dipyridylmethane, a forgotten ligand in coordination chemistry.

2015

The reactions of dipyridylmethane (dpma) with group 13 trichlorides were investigated in 1 : 1 and 1 : 2 molar ratios using NMR spectroscopy and X-ray crystallography. With 1 : 1 stoichiometry and Et2O as solvent, reactions employing AlCl3 or GaCl3 gave mixtures of products with the salt [(dpma)2MCl2](+)[MCl4](-) (M = Al, Ga) as the main species. The corresponding reactions in 1 : 2 molar ratio gave similar mixtures but with [(dpma)MCl2](+)[MCl4](-) as the primary product. Pure salts [(dpma)AlCl2](+)[Cl](-) and [(dpma)AlCl2](+)[AlCl4](-) could be obtained by performing the reactions in CH3CN. In the case of InCl3, a neutral monoadduct (dpma)InCl3 formed regardless of the stoichiometry emplo…