Conformational equilibria of β-alanine and related compounds as studied by NMR spectroscopy

Françoise Gregoire, Sindy H. Wei, Erik W. Streed, Kenneth A. Brameld, Diana Fort, Linda J. Hanely, Jamie Walls, William A. Goddard, John D. Roberts

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

The vicinal proton-proton couplings of the dipolar form of β-alanine in water, alcohol-water, and dimethyl sulfoxide-water solutions indicate little conformational preference and are consistent with an essentially statistical equilibrium of the gauche or trans conformations. The position of the equilibrium is only slightly affected, over a temperature range of about 130°, by changes in dielectric constants ranging from 30 to 80 or by massive changes in ionic strength. Quantum-mechanical calculations at the HF/6-31G** and LMP2/cc-pVTZ levels were found to give rather good parallels with experiment, although suggesting the gauche conformation to be 2-3 kcal/mol more stable in water or methanol than actually observed. A number of related compounds, such as N,N,N-trimethyl-β-alanine and N,N-diethyl-β-alanine, as well as the conjugate acid and conjugate base of B-alanine, also show no significant conformational preference in water solution. In conformity with these results, the zwitterionic form of piperidine-3-carboxylic acid (nipecotic acid) has about die same preference for equatorial carboxylate as cyclohexanecarboxylic acid itself. Taurine shows no significant conformational preference except in basic solution, where the couplings indicate about 53% of the gauche conformation. In contrast, N,N,N-trimethyltaurine is predominantly trans in acidic or neutral solution. Tile conformational equilibria of the N,N,N-trimethyltaurine species are most likely governed by steric hindrance, because there are rather large tetrahedral groups at each end of the ethano chains. Yet, even here the energy difference between gauche and trans is only about 1.2 kcal.

Original languageEnglish (US)
Pages (from-to)7537-7543
Number of pages7
JournalJournal of the American Chemical Society
Volume120
Issue number30
DOIs
StatePublished - Aug 5 1998
Externally publishedYes

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Alanine
Nuclear magnetic resonance spectroscopy
Magnetic Resonance Spectroscopy
Water
Conformations
Acids
Protons
Dimethyl sulfoxide
Taurine
Tile
Carboxylic Acids
Dimethyl Sulfoxide
Ionic strength
Carboxylic acids
Osmolar Concentration
Methanol
Alcohols
Permittivity
Temperature
Experiments

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Gregoire, F., Wei, S. H., Streed, E. W., Brameld, K. A., Fort, D., Hanely, L. J., ... Roberts, J. D. (1998). Conformational equilibria of β-alanine and related compounds as studied by NMR spectroscopy. Journal of the American Chemical Society, 120(30), 7537-7543. https://doi.org/10.1021/ja974311u

Conformational equilibria of β-alanine and related compounds as studied by NMR spectroscopy. / Gregoire, Françoise; Wei, Sindy H.; Streed, Erik W.; Brameld, Kenneth A.; Fort, Diana; Hanely, Linda J.; Walls, Jamie; Goddard, William A.; Roberts, John D.

In: Journal of the American Chemical Society, Vol. 120, No. 30, 05.08.1998, p. 7537-7543.

Research output: Contribution to journalArticle

Gregoire, F, Wei, SH, Streed, EW, Brameld, KA, Fort, D, Hanely, LJ, Walls, J, Goddard, WA & Roberts, JD 1998, 'Conformational equilibria of β-alanine and related compounds as studied by NMR spectroscopy', Journal of the American Chemical Society, vol. 120, no. 30, pp. 7537-7543. https://doi.org/10.1021/ja974311u
Gregoire, Françoise ; Wei, Sindy H. ; Streed, Erik W. ; Brameld, Kenneth A. ; Fort, Diana ; Hanely, Linda J. ; Walls, Jamie ; Goddard, William A. ; Roberts, John D. / Conformational equilibria of β-alanine and related compounds as studied by NMR spectroscopy. In: Journal of the American Chemical Society. 1998 ; Vol. 120, No. 30. pp. 7537-7543.
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AU - Fort, Diana

AU - Hanely, Linda J.

AU - Walls, Jamie

AU - Goddard, William A.

AU - Roberts, John D.

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