Conformations of methoxy(hydroxy)-substituted benzenes and benzaldehydes in the gas phase

Вокин, А. И.; Frolov, Yu. L.; Medvedev, S. A.; D’yachkova, S. G.

doi:10.1007/bf00697039

Cited by 2 publications

(2 citation statements)

References 12 publications

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“…11 Geometry optimization has been carried out for the different planar conformations of vanillin (Fig. 7), identified by the different orientation of the substituents.…”

Section: Optimized Geometrymentioning

confidence: 99%

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Changes in the vibrational spectral modes by the nonbonded interactions in the NLO crystal vanillin

Binoy¹,

Joe²,

Jayakumar³

2005

J Raman Spectroscopy

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The crystal of the famous flavoring agent vanillin is known for its nonlinear optical activity. Density functional theory at B3LYP/6-31G(d) level has been used to compute energies of different conformers of vanillin to find their stability, the optimized geometry of the most stable conformer and its vibrational spectrum. The conformer VAN1 with torsion angles 0°, 180°and 0°respectively for C 2 -C 1 -C 7 -O 14 , C 2 -C 1 -C 7 -H 13 and C 3 -C 4 -O 10 -H 19 is found to be most stable. Geometry predicted by DFT and XRD reveals that geometrical parameters of hydroxyl group are altered substantially because of intermolecular hydrogen bonding. Vibrational analysis based on the NIR FT Raman, FT IR and computed spectrum reveals that the CH in-plane bending of the aldehyde group interacts with its stretching mode via Fermi resonance, and evidence for intermolecular hydrogen bonding can be observed as the broadness of the band in the stretching region in IR spectrum. The unusual lowering of carbonyl stretching wave number is attributed to the electron-releasing effect of C O group in the acceptor subunit due to intramolecular charge transfer, leading to NLO activity, in addition to the intermolecular interaction and p-conjugation. Other vibrational spectral contributions of NLO activity such as violation of selection rule for tangential C-C stretching mode 8 and overlooking of complementarities are also observed. Nonbonded interactions affecting each vibrational mode are found, and the resulting shifting of band position is discussed. Firstorder hyperpolarizability, computed at HF/3-21G level, is used to analyze the conformation dependent NLO activity.

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“…11 Geometry optimization has been carried out for the different planar conformations of vanillin (Fig. 7), identified by the different orientation of the substituents.…”

Section: Optimized Geometrymentioning

confidence: 99%

“…10 Conformations of vanillin in gas phase have been investigated using photoelectron spectroscopy and semiempirical AM1 computation. 11 Studies on intramolecular hydrogen bonding in vanillin by CNDO/2 have also appeared in literature. 12 Crystal structure of the title compound vanillin has been reported.…”

Section: Introductionmentioning

confidence: 99%

Changes in the vibrational spectral modes by the nonbonded interactions in the NLO crystal vanillin

Binoy¹,

Joe²,

Jayakumar³

2005

J Raman Spectroscopy

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Stereoelectronic Effects on ¹H Nuclear Magnetic Resonance Chemical Shifts in Methoxybenzenes

2006

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Investigation of all O-methyl ethers of 1,2,3-benzenetriol and 4-methyl-1,2,3-benzenetriol (3-16) by 1H NMR spectroscopy and density-functional calculations disclosed practically useful conformational effects on 1H NMR chemical shifts in the aromatic ring. While the conversion of phenol (2) to anisole (1) causes only small positive changes of 1H NMR chemical shifts (Delta delta < 0.08 ppm) that decrease in the order Hortho > Hmeta > Hpara, the experimental O-methylation induced shifts in ortho-disubstituted phenols are largest for Hpara, Delta delta equals; 0.19 +/- 0.02 ppm (n = 11). The differences are due to different conformational behavior of the OH and OCH3 groups; while the ortho-disubstituted OH group remains planar in polyphenols due to hydrogen bonding and conjugative stabilization, the steric congestion in ortho-disubstituted anisoles outweighs the conjugative effects and forces the Ar-OCH3 torsion out of the ring plane, resulting in large stereoelectronic effects on the chemical shift of Hpara. Conformational searches and geometry optimizations for 3-16 at the B3LYP/6-31G** level, followed by B3LYP/6-311++G(2d,2p) calculations for all low-energy conformers, gave excellent correlation between computed and observed 1H NMR chemical shifts, including agreement between computed and observed chemical shift changes caused by O-methylation. The observed regularities can aid structure elucidation of partly O-methylated polyphenols, including many natural products and drugs, and are useful in connection with chemical shift predictions by desktop computer programs.

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Conformations of methoxy(hydroxy)-substituted benzenes and benzaldehydes in the gas phase

Cited by 2 publications

References 12 publications

Changes in the vibrational spectral modes by the nonbonded interactions in the NLO crystal vanillin

Changes in the vibrational spectral modes by the nonbonded interactions in the NLO crystal vanillin

Stereoelectronic Effects on ¹H Nuclear Magnetic Resonance Chemical Shifts in Methoxybenzenes

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Conformations of methoxy(hydroxy)-substituted benzenes and benzaldehydes in the gas phase

Cited by 2 publications

References 12 publications

Changes in the vibrational spectral modes by the nonbonded interactions in the NLO crystal vanillin

Changes in the vibrational spectral modes by the nonbonded interactions in the NLO crystal vanillin

Stereoelectronic Effects on 1H Nuclear Magnetic Resonance Chemical Shifts in Methoxybenzenes

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Stereoelectronic Effects on ¹H Nuclear Magnetic Resonance Chemical Shifts in Methoxybenzenes