Primary and secondary deuterium‐induced isotope effects for 13C NMR parameters of benzaldehyde

P. Vujanić, E. Gács-Baitz, Z. Meić, T. Šuste, V. Smrečki

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Abstract

Deuterium‐induced isotope effects on 13C chemical shifts and 1J(13C‐α, 1H) coupling constants in benzaldehyde were measured. Over 30 different effects on 13C chemical shifts were revealed. The effects through one (1Δ) and two bonds (2Δ) have mean values of 282.1 ± 9.6 and 109.5 ± 3.1 ppb, respectively, which is consistent with previously observed trends. Exceptions are [α‐2H] benzaldehyde and [o‐2H] benzaldehyde, where 2Δ values at the quaternary carbon C‐1 of only 72.6 and 69.6 ppb, respectively, were determined. While 3Δ at the C‐2,6 site in [p‐2H] benzaldehyde is absent, three different 3A effects in [o‐2H] benzaldehyde were observed. The longest range effect is 5Δ = −1.9 ppb, observed in [p‐2H] benzaldehyde. The role of the position and the number of incorporated deuterium atoms with respect to the range, magnitude and sign of these effects is discussed. Some of the observed effects are rationalized through interactions with lone‐pair electrons at the oxygen atom. A number of carbon‐deuterium coupling constants, nJ(13C,2H), through one, two and three bonds were measured. A single primary deuterium isotope effect on 1J(13C‐α,1H) in [α‐2H] benzaldehyde was determined, whereas no secondary effect through three or more bonds on the same coupling constant was observed.

Original languageEnglish
Pages (from-to)426-430
Number of pages5
JournalMagnetic Resonance in Chemistry
Volume33
Issue number6
DOIs
Publication statusPublished - 1995

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Keywords

  • C NMR
  • benzaldehyde
  • deuterium isotope effects
  • multiple quantum correlation
  • NMR

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)

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