Molecular complexes. Part 12.1 Dimeric toluene, torsional vibrations, dipoles and isomeric complexes in 1H NMR studies of weak arene complexes. Temperature dependence of CH signals

2001 ◽  
pp. 2089-2095 ◽  
Author(s):  
Helmut Stamm ◽  
Hanns-Otto Strumm ◽  
Karl-Heinz Loebel ◽  
Hannelore Jäckel ◽  
Ulrich Hoffmanns ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
1H Nmr ◽  
Molecular Complexes ◽  
Torsional Vibrations ◽  
Arene Complexes ◽  
Nmr Studies

Molecular Complexes, 13. Weak Arene Complexes of Nitroaromatics. 1H NMR Studies of Conformations and Polar Effects. syn-anti Selectivity of 5-Nitrofurfural

2002 ◽  
Vol 57 (11) ◽  
pp. 1305-1314 ◽  
Author(s):  
Helmut Stamm ◽  
Hanns-Otto Strumm ◽  
Hannelore Jäckel ◽  
Barbro Beijer ◽  
Gerhard Schilling ◽  
...  
Keyword(s):  
1H Nmr ◽  
Aromatic Hydrocarbons ◽  
Molecular Complexes ◽  
Association Constants ◽  
Arene Complexes ◽  
Nmr Studies ◽  
H Nmr ◽  
Nmr Method

The refined 1H NMR method (AUS concept, CCl4) provided association constants K and approximate complex shifts IK for complexes of nitroaromatics A with aromatic hydrocarbons D. 5-Nitrofurfural (1) and benzene (B) or toluene (T) form syn-1B or syn-1T, respectively; a proton dependence of K indicates about 10% anti complexes. The dimer T2 of T additionally yields some 1T2 since IK values are 29-34% higher than for 1B. With naphthalene (N) or phenanthrene all protons of 1 provide the same K. Picrylacetone (2) and B form 2B and at least one 2BB adduct; published parameters of 2B and 2BB are inconsistent. 2 and N or M (1,3,5-trimethylbenzene) form only 1:1 complexes. All results are in accord with CH2COMe standing perpendicular to picryl. 2,4-Dinitrophenylacetone (3) in a rather flat conformation coordinates with a single stacking N centred over C-6; 3 yields two isomeric stacking complexes 3B and at least one edge-on 3B complex. 2-Chloro-5-nitropyridine (5) forms stacking complexes under repulsion of D by the ring N. In contrast to 1 and 4-nitrobenzaldehyde (6) 1,4-dinitrobenzene (7) and T form only a 1:1 complex that is stabilized by dipole-dipole attraction. Equal and unequal shielding of proton pairs (ortho or meta) in complexes of type 6B is discussed.

1H NMR studies of [N-MeAib1, Tyr(Me)4]ANGII and [N-MeAib1, Tyr(Me)4, Ile8]ANGII in dimethylsulfoxide by nuclear Overhauser effect (NOE) enhancement spectroscopy: cis-trans Isomerism of the His-Pro bond

1990 ◽  
Vol 55 (4) ◽  
pp. 1106-1111 ◽  
Author(s):  
John Matsoukas ◽  
Paul Cordopatis ◽  
Raghav Yamdagni ◽  
Graham J. Moore
Keyword(s):  
1H Nmr ◽  
Nuclear Overhauser Effect ◽  
Nmr Studies ◽  
Restricted Rotation ◽  
Overhauser Effect ◽  
Major Isomer ◽  
Conformational Properties ◽  
Nuclear Overhauser

The conformational properties of the Sarmesin analogues [N-MeAib1, Tyr(Me)4]ANGII and [N-MeAib1, Tyr(Me)4, Ile8]ANGII in hexadeutero-dimethysulfoxide were investigated by Nuclear Overhauser Effect (NOE) Enhancement Studies. Cis-trans isomers (ratio 1 : 6) due to restricted rotation of the His-Pro bond were observed. Interresidue interactions between the His Cα proton and the two Pro Cδ protons revealed that the major isomer was the trans.

ChemInform Abstract: HPLC and 1H NMR Studies of Alkaline Hydrolysis of Some 7-(Oxyiminoacyl) cephalosporins.

ChemInform ◽  
2010 ◽  
Vol 25 (11) ◽  
pp. no-no
Author(s):  
B. VILANOVA ◽  
F. MUNOZ ◽  
J. DONOSO ◽  
F. GARCIA BLANCO
Keyword(s):  
1H Nmr ◽  
Alkaline Hydrolysis ◽  
Nmr Studies ◽  
Hydrolysis Of

scholarly journals Temperature Dependence of Limiting Fluorescence Anisotropy of POPOP in Cellulose Acetate Film

1985 ◽  
Vol 40 (6) ◽  
pp. 559-561
Author(s):  
A. Kawski ◽  
A. Kubicki ◽  
I. Weyna ◽  
I. Janić
Keyword(s):  
Temperature Dependence ◽  
Cellulose Acetate ◽  
Fluorescence Anisotropy ◽  
Thermal Relaxation ◽  
Effect Of Temperature ◽  
Torsional Vibrations ◽  
Slow Increase ◽  
Cellulose Acetate Film ◽  
Luminescent Centre

The effect of temperature (103 K < T < 303 K) upon the limiting fluorescence anisotropy r0 of POPOP was investigated in a cellulose acetate film. A slow increase in r0 was observed when reducing the temperature. Based on the Jabłoński theory, the frequency of the torsional vibrations of POPOP was determined to be w = 1.3 x 1012s−1. The depolarization due to these torsional vibrations was found to occur immediately following excitation during the thermal relaxation of the luminescent centre, thus somewhat lowering the value of the fundamental fluorescence anisotropy rf to the limiting r0 value.

ChemInform Abstract: 1H NMR Studies of the System Ti3SbHx

ChemInform ◽  
1989 ◽  
Vol 20 (14) ◽  
Author(s):  
N. RAJALAKSHMI ◽  
K. V. S. R. RAO ◽  
A. WEISS
Keyword(s):  
1H Nmr ◽  
Nmr Studies

Crystal structure of trans-[W(CO)4(η2-C2H4)2] and IR and 1H NMR studies of the reactions of this and related ethene carbonyl complexes of tungsten(0), [W(CO)n(η2-C2H4)6- n] ( n=3–5)

1999 ◽  
Vol 23 (4) ◽  
pp. 407-416 ◽  
Author(s):  
Teresa Szymańska-Buzar ◽  
Krystyna Kern ◽  
Anthony J. Downs ◽  
Timothy M. Greene ◽  
Leigh J. Morris ◽  
...  
Keyword(s):  
Crystal Structure ◽  
1H Nmr ◽  
Carbonyl Complexes ◽  
Nmr Studies

1H NMR studies of the adsorption of water on silicalite

1998 ◽  
Vol 23 (3-4) ◽  
pp. 189-196 ◽  
Author(s):  
V.V. Turov ◽  
V.V. Brei ◽  
K.N. Khomenko ◽  
R. Leboda
Keyword(s):  
1H Nmr ◽  
Nmr Studies ◽  
Adsorption Of Water

scholarly journals Circular dichroism and 1H NMR studies of Co2+- and Ni2+-substituted concanavalin A and the lentil and pea lectins.

1987 ◽  
Vol 262 (35) ◽  
pp. 16985-16994
Author(s):  
I Bertini ◽  
M S Viezzoli ◽  
C Luchinat ◽  
E Stafford ◽  
A D Cardin ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
1H Nmr ◽  
Concanavalin A ◽  
Nmr Studies ◽  
Circular Dichroïsm
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