Study of substituent effects on conformational equilibrium (E⇆Z) of 2-(4-substituted anilino)-5-nitropyridines by infrared spectra, X-ray crystallography, and CNDO/2 calculations

1986 ◽  
pp. 1969-1978 ◽  
Author(s):  
Mamoru Takasuka ◽  
Hiroshi Nakai ◽  
Motoo Shiro
Keyword(s):  
Infrared Spectra ◽  
Conformational Equilibrium ◽  
Substituent Effects ◽  
X Ray ◽  
X Ray Crystallography

The geometry of 4-(1-ethoxyethylidene)-5-oxazolones and thiazolones: 1H and 13C studies and the crystal structure of 4-[(Z)-1-ethoxyethylidene]-2-phenyl-5-oxazolone

1985 ◽  
Vol 63 (12) ◽  
pp. 3618-3630 ◽  
Author(s):  
R. A. Bell ◽  
R. Faggiani ◽  
C. J. L. Lock ◽  
R. A. McLeod
Keyword(s):  
Crystal Structure ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Side Chain ◽  
Oxazole Ring ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cell Dimensions ◽  
Ring Nitrogen ◽  
E And Z Isomers

A series of E and Z isomers of substituted 4-(1-ethoxyethylidene)-5-oxazolones and thiazolones have been prepared and their 1H and 13C spectra recorded. The vinylic methyl 1H chemical shifts showed minimal differences between E and Z isomers whereas the vinylic OCH21H signals differed by 0.15–0.43 ppm, with the Z isomer being consistently the more deshielded. Both vinylic methyl and OCH2 groups showed different 13C resonances for each isomer, with the Z isomers being the more deshielded. The Z geometry was conclusively defined for one isomer of 4-(1-ethoxyethylidene)-2-phenyl-5-oxazolone, 5, by X-ray crystallography and this was sufficient to assign the geometry of the remaining pairs of E and Z isomers. Oxazolone 5 has the space group P21/n and cell dimensions a = 9.219(3), b = 19.899(5), c = 7.459(1) Å, β = 118.01(2)°, and has four formula units in the unit cell. Intensities were measured with use of MoKα radiation and a Nicolet P3 diffractometer. The crystal structure was determined by standard methods and refined to R1 = 0.0709, R2 = 0.0696 based on 1419 independent reflections. The molecule is essentially planar and most bond lengths and angles are normal. Exceptions are the very short C(olefin)—O(ether) bond (1.339(4) Å) and the large ether C—O—C angle (122.1(3)°) caused by extreme delocalization in the O(ether)CCCO(carbonyl) system. The planarity causes a number of strong intramolecular repulsive interactions, causing an exceptionally small external olefin angle, O(ether)CC(methyl), of 108.1(4)°. The ethoxyl side chain of 5 adopts a conformation in the solid state which places the methylene of the OCH2 group adjacent to the oxazole ring nitrogen. This conformation is proposed to persist in solution phases and is consistent with the observed 13C chemical shifts and known γ and δ substituent effects.

The stereochemistry of nitrate esters. II. Symmetric stretching frequencies of the nitrato group in nitrate esters of l,4;3,6-di-anhydrohexitols (4,8-dihydroxy-cis-2,6-dioxabicyclo[3.3.0]octanes)

1967 ◽  
Vol 45 (19) ◽  
pp. 2191-2194 ◽  
Author(s):  
L. D. Hayward ◽  
D. J. Livingstone ◽  
M. Jackson ◽  
Valerie M. Csizmadia
Keyword(s):  
Infrared Spectra ◽  
Benzene Solution ◽  
Intramolecular Interaction ◽  
Molecular Conformations ◽  
X Ray ◽  
Nitrate Esters ◽  
X Ray Crystallography ◽  
Structure Configuration ◽  
Configuration And Conformation

In the infrared spectra of mono- and di-nitrate esters of the l,4;3,6-dianhydrides of d-mannitol, d-glucitol, and l-iditol in benzene solution (0.04 M in nitrato groups), the frequencies of the va(NO2) and v(ON) bands (singlets) were 1 645 ± 3 and 843 ± 3 cm−1, respectively, whereas the vs(NO2) band occurred at frequencies characteristic of either an endo (1 282 ± 1 cm−1) or an exo (1 274 ± 1 cm−1) configuration of the nitrato group; the ratios of the band areas were 1.5:1.0:1.0, respectively.The stereospecific frequency of the vs(NO2) band was attributed to non-bonded intramolecular interaction between the nitrato group and vicinal oxy groups on the basis of the spectra run in a series of solvents and the molecular conformations determined by X-ray crystallography. This new stereochemical probe permitted the assignment of the structure, configuration, and conformation in a series of nitrate esters.

Crystallographic and Spectroscopic Evidence of O-Bonding in 3d-MetaI Dicyanomethanidonitrite Complexes

2001 ◽  
Vol 56 (1) ◽  
pp. 100-104 ◽  
Author(s):  
M. Hvastijová ◽  
J. Kohout ◽  
J. W. Buchler ◽  
H. W. Katzenmeier ◽  
J. Kožíšek ◽  
...  
Keyword(s):  
Oxygen Atom ◽  
Infrared Spectra ◽  
Spectroscopic Evidence ◽  
X Ray ◽  
X Ray Crystallography ◽  
Pyridine Complexes ◽  
Pyridine Complex ◽  
Pyridine Nitrogen ◽  
Oxygen Atoms

Abstract The coordination of the dicyanomethanidonitrite group through the nitroso oxygen atom in the tetrakis(pyridine) complexes [M{ONC(CN)2}2(py)4], M = Ni, Co, Cu, and in the bis(pyridine) complex [Cu{ONC(CN)2}2(py)2] was proved by X-ray crystallography of the Ni11 complex and re-evaluated infrared spectra. The Ni11 and Co11 complexes exhibit almost octahedral structures composed of four pyridine nitrogen atoms and two oxygen atoms of dicyanomethanidonitrite ions. Both copper(II) complexes display a considerable axial distortion of the pseudooctahedral arrangement. In the bis(pyridine) Cu11 complex the ONC(CN)2 groups are involved in the bridging function by use of the oxygen and nitrile nitrogen atoms.

scholarly journals Substituent effects in phosphine ligands

2011 ◽  
Vol 30 (1) ◽  
Author(s):  
C. Alicia Renison ◽  
D. Bradley G. Williams ◽  
Alfred J. Muller
Keyword(s):  
Nmr Spectroscopy ◽  
High Resolution ◽  
Molecular Modelling ◽  
31P Nmr ◽  
Substituent Effects ◽  
Phosphine Ligands ◽  
31P Nmr Spectroscopy ◽  
Electronic Effects ◽  
X Ray ◽  
X Ray Crystallography

The study illustrates the use of the P-atom to evaluate steric and electronic effects in P-containing organic compounds. The work involves the synthesis of substituted triarylphosphines and their corresponding Rh Vaska complexes. High resolution X-ray crystallography, molecular modelling, 31P NMR spectroscopy and IR will be used to quantify substituent effects.

Sign in / Sign up

Export Citation Format

Share Document