A proposed standard sample for nuclear Overhauser effect measurements

✍ Scribed by Alex D. Bain; Eugene P. Mazzola; Samuel W. Page

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 209 KB
• Volume: 36
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199806)36:6<403::aid-omr285>3.0.co;2-a

✦ Synopsis

A standard sample for the measurement of protonÈproton nuclear Overhauser e †ects (NOE) is proposed. 1,5-Dichloro-2,4-dimethoxybenzene (DCDMB) shows an essentially full (50%) enhancement of the proton H-3 when the protons of the Ñanking methoxyl groups are saturated. The molecule is appropriate as a standard for the following reasons. The molecule is stable and easily synthesized. All the lines in the spectrum appear as singlets, so selective population transfer e †ects cannot obscure the NOE. The proton at position 6 provides a monitor of other relaxation mechanisms that would reduce the NOE. The NOE was veriÐed by two complementary experiments. One is the standard technique of measuring the intensity with and without irradiation. A second method, based on spinÈlattice relaxation rate experiments, provides unbiased data and gives an statistical estimate of the errors. Within experimental error, the NOE for DCDMB is 50%.