Question

9-fluorenol NMR: I've provided two sets of NMR's. The theoretical vs. the experimental. In the theoretical I understand all the shifts except for the 2.06, representative of the H alpha to the OH group. Methine protons usually have a shift around 1.7ppm and protons alpha to an (OH) are deshieled adding +2.5ppm, according to my textbook, which would make me think that the actual shift be 4.2ppm. Why is this not the case? Could I be mistaking this nuclei for another?

I've attached my experimental NMR and I'm wondering what's causing alot of these seeemingly incorrect shifts. Is this due to impurities, and how would impurtities effect the NMR results. The huge integration 3.55ppm is 492. We used chlorofor as a solvent for NMR tubes so I was thinking maybe this caused the huge peak. Thanks.

IMAGES: http://imgur.com/a/gWTXM

Answer 1

As in case of arromatic hydrogen these hydrogen have downfield shift due to diamegnatic anisotropic effects due to which arromatic H feels increased megnatic field , Here you also have to see the diamegnetic shielding of this H due to presence of ring current , But here here this ring current is in such a way that H at neighbour of OH group feels a decreased megnatic field . Thus now in will show peak even at high applied megnatic field . Hence peak is at 2.06. Because as applied megnatic field is increased we moves towards right on chemical shift axis.