Correlation analysis of the 13C chemical shifts of substituted Benzaldehyde 2-aminobenzoylhydrazones. Study of the propagation of substituent effects along a heteroatomic chain

Kari Neuvonen, F. Fülöp, Helmi Neuvonen, Mario Simeonov, Kalevi Pihlaja

Research output: Contribution to journalArticle

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Abstract

The 13C chemical shifts of eight series of para- or meta-substituted benzaldehyde 2-aminobenzoylhydrazones possessing both amide and imine functionalities were measured. The 13C chemical shifts were used to study the transmission of electronic substituent effects along the heteroaromatic side-chain of the substituted aromatic ring. In addition to the C=N bond, the benzoylhydrazones possess in their side-chain polarizable C=O and phenyl π-units. The benzylidenic ring-substituent chemical shifts were analysed by the dual substituent parameter approach to separate the inductive and resonance effects. The negative ρI and ρR values observed (i.e. reverse substituent effects) indicate a significant π-polarization of the C=N bond. The highly negative ρR values, especially those in the case of meta substitution, suggest a contribution from a marked secondary field-transmitted resonance effect. The results are compared with those obtained for other hydrazones or imines. Variation of the electron-withdrawing ability of the N2 substituent is seen to have a systematic effect on the ρI values. Reverse substituent effects are also observed at the C-1″ site of the 2-aminobenzoyl ring while C-4″ shifts show normal behaviour, consistent with the general concept of the π-polarization that each π-unit of the side-chain is polarized largely as a localized system. Accordingly, the π-polarization effect is seen efficiently to propagate also along a heteroaromatic chain. On the other hand, the C=O sites exhibit normal, although fairly slight, dependence on the benzylidenic substituent indicating an insignificant role of π-polarization at that site. The effects of the solvent, CDCl3 νs. DMSO-d6, on the ρI and ρR values are also considered.

Original languageEnglish
Pages (from-to)55-66
Number of pages12
JournalJournal of Physical Organic Chemistry
Volume10
Issue number1
Publication statusPublished - Jan 1997

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Chemical shift
chemical equilibrium
Polarization
Imines
propagation
Hydrazones
polarization
Dimethyl Sulfoxide
Amides
imines
rings
Substitution reactions
hydrazones
benzaldehyde
Electrons
amides
substitutes
shift
electronics

ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Correlation analysis of the 13C chemical shifts of substituted Benzaldehyde 2-aminobenzoylhydrazones. Study of the propagation of substituent effects along a heteroatomic chain. / Neuvonen, Kari; Fülöp, F.; Neuvonen, Helmi; Simeonov, Mario; Pihlaja, Kalevi.

In: Journal of Physical Organic Chemistry, Vol. 10, No. 1, 01.1997, p. 55-66.

Research output: Contribution to journalArticle

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abstract = "The 13C chemical shifts of eight series of para- or meta-substituted benzaldehyde 2-aminobenzoylhydrazones possessing both amide and imine functionalities were measured. The 13C chemical shifts were used to study the transmission of electronic substituent effects along the heteroaromatic side-chain of the substituted aromatic ring. In addition to the C=N bond, the benzoylhydrazones possess in their side-chain polarizable C=O and phenyl π-units. The benzylidenic ring-substituent chemical shifts were analysed by the dual substituent parameter approach to separate the inductive and resonance effects. The negative ρI and ρR values observed (i.e. reverse substituent effects) indicate a significant π-polarization of the C=N bond. The highly negative ρR values, especially those in the case of meta substitution, suggest a contribution from a marked secondary field-transmitted resonance effect. The results are compared with those obtained for other hydrazones or imines. Variation of the electron-withdrawing ability of the N2 substituent is seen to have a systematic effect on the ρI values. Reverse substituent effects are also observed at the C-1″ site of the 2-aminobenzoyl ring while C-4″ shifts show normal behaviour, consistent with the general concept of the π-polarization that each π-unit of the side-chain is polarized largely as a localized system. Accordingly, the π-polarization effect is seen efficiently to propagate also along a heteroaromatic chain. On the other hand, the C=O sites exhibit normal, although fairly slight, dependence on the benzylidenic substituent indicating an insignificant role of π-polarization at that site. The effects of the solvent, CDCl3 νs. DMSO-d6, on the ρI and ρR values are also considered.",
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N2 - The 13C chemical shifts of eight series of para- or meta-substituted benzaldehyde 2-aminobenzoylhydrazones possessing both amide and imine functionalities were measured. The 13C chemical shifts were used to study the transmission of electronic substituent effects along the heteroaromatic side-chain of the substituted aromatic ring. In addition to the C=N bond, the benzoylhydrazones possess in their side-chain polarizable C=O and phenyl π-units. The benzylidenic ring-substituent chemical shifts were analysed by the dual substituent parameter approach to separate the inductive and resonance effects. The negative ρI and ρR values observed (i.e. reverse substituent effects) indicate a significant π-polarization of the C=N bond. The highly negative ρR values, especially those in the case of meta substitution, suggest a contribution from a marked secondary field-transmitted resonance effect. The results are compared with those obtained for other hydrazones or imines. Variation of the electron-withdrawing ability of the N2 substituent is seen to have a systematic effect on the ρI values. Reverse substituent effects are also observed at the C-1″ site of the 2-aminobenzoyl ring while C-4″ shifts show normal behaviour, consistent with the general concept of the π-polarization that each π-unit of the side-chain is polarized largely as a localized system. Accordingly, the π-polarization effect is seen efficiently to propagate also along a heteroaromatic chain. On the other hand, the C=O sites exhibit normal, although fairly slight, dependence on the benzylidenic substituent indicating an insignificant role of π-polarization at that site. The effects of the solvent, CDCl3 νs. DMSO-d6, on the ρI and ρR values are also considered.

AB - The 13C chemical shifts of eight series of para- or meta-substituted benzaldehyde 2-aminobenzoylhydrazones possessing both amide and imine functionalities were measured. The 13C chemical shifts were used to study the transmission of electronic substituent effects along the heteroaromatic side-chain of the substituted aromatic ring. In addition to the C=N bond, the benzoylhydrazones possess in their side-chain polarizable C=O and phenyl π-units. The benzylidenic ring-substituent chemical shifts were analysed by the dual substituent parameter approach to separate the inductive and resonance effects. The negative ρI and ρR values observed (i.e. reverse substituent effects) indicate a significant π-polarization of the C=N bond. The highly negative ρR values, especially those in the case of meta substitution, suggest a contribution from a marked secondary field-transmitted resonance effect. The results are compared with those obtained for other hydrazones or imines. Variation of the electron-withdrawing ability of the N2 substituent is seen to have a systematic effect on the ρI values. Reverse substituent effects are also observed at the C-1″ site of the 2-aminobenzoyl ring while C-4″ shifts show normal behaviour, consistent with the general concept of the π-polarization that each π-unit of the side-chain is polarized largely as a localized system. Accordingly, the π-polarization effect is seen efficiently to propagate also along a heteroaromatic chain. On the other hand, the C=O sites exhibit normal, although fairly slight, dependence on the benzylidenic substituent indicating an insignificant role of π-polarization at that site. The effects of the solvent, CDCl3 νs. DMSO-d6, on the ρI and ρR values are also considered.

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