Abstract
The interesting deuterium isotope effects of gossypols have been reinvestigated and the very large two-bond isotope effect, 2ΔC-6(OD), is ascribed to electric field effects. Common to the investigated compounds is the presence of intramolecular hydrogen bonds. A feature strongly related to the strength of the intramolecular hydrogen bond is intermolecular OH exchange. Electron-attracting substituents at the 3- and 5-positions of 2-hydroxyacyl aromatics increase the acidity of the 2-OH proton and therefore the intermolecular exchange, but not the hydrogen bond strength, whereas alkyl groups ortho to the intramolecularly hydrogen bonded OH prevent the OH group from swinging out and therefore prevent intermolecular exchange. Conformational equilibria were studied in 2-hydroxy-3-nitro-6-methoxyacetophenone. Surprisingly, the form with the weaker intramolecular hydrogen bond to the nitro group is dominant at ambient temperature, whereas it is the opposite at 160 K. For 2-hydroxy-5-methyl-3-nitroacetophenone a similar pattern is seen, but with much less of the form having hydrogen bonding to the nitro group at ambient temperature. 2-Acetyl-1, 8-dihydroxy-3,6-dimethylnaphthalene is involved in tautomerism of the enolic β-diketone type and large deuterium isotope effects on the 13C and OH chemical shifts are observed. © 1997 John Wiley & Sons, Ltd.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.