Steve's+HNMR+Analysis+of+1-hydroxy-2-methoxy-4-allylbenzene_text


 * 1-hydroxy-2-methoxy-4-allylbenzene (C10H12O2) **

The benzene ring 3 proton coupling resulted in 2 peaks in the 6.5 -7.0 ppm range. There is a doublet present at ~6.9 ppm. This is likely from the C-5 proton. It is coupling with the adjacent C-H, forming a doublet. The C-3 proton and the C-6 proton have similar absorbencies since they are both bound to a C-O and a CH=; consequently, their peaks overlap at ~6.7 ppm. A doublet from the C-6 proton is overlapping the singlet from the C-3 proton forming the subsequent peak. In general, benzene protons absorb at ~7.0-8.0 ppm. This data is therefore consistent. The protons on the methoxy group attached to C-2 are responsible for the singlet at ~3.8 ppm. There are no protons to couple with the 3 protons on the methoxy group since the only adjacent atom is oxygen. Furthermore, C-H adjacent to oxygen atoms have absorbencies in the vicinity of 3-4 ppm which is consistent with this spectrum. The allylic carbon protons yielded a doublet via coupling to the single adjacent proton bound to the alkene carbon. The signal is ~3.3 ppm partially because of the neighboring C=C, but mainly due to the adjacent benzene ring; allylic protons and protons adjacent to aromatic rings tend to absorb at ~1.5-2 and 2.0-2.5 ppm, respectively. Consequently, deshielding from both sides pushed the reading into the 3.0-3.5 ppm range. Ha resulted in a 6.1 ppm reading. This is attributed to significant deshielding via the double bond; this shift tends range fall within 5.0-6.0 ppm. A shift closer to 6.0 ppm, notwithstanding NMR error, in caused by further deshielding from the opposite side – in this case, the allylic proton. Stereochemistry resulted in nonequivalent protons on the same carbon. Ha coupled with Hb, Hc, and the allylic protons, generating a triplet of doublets of doublets: Hb and Hc had absorbencies of ~5.2 ppm. Again, due to stereochemistry, these protons are different and therefore couple to one another. Hc likely had a slightly larger shift due to being cis with Ha. Both protons couple to one another and the adjacent proton Ha; thus, doublets of doublets are normally generated for each, 4 peaks. However, the overlap is substantial and caused a multiplet to form. The remaining proton, the hydroxyl, resulted in the broad, short peak at ~6.3 ppm. Alcohols frequently absorb at 2.0-5.0 ppm. The proton in this spectrum underwent a significant shift to the 6.0-6.5 ppm range. This can be attributed to the nearby benzene ring. Because there are no adjacent hydrogens, a singlet emerged.
 * [Good - the only problem is that the spectrum is inverted - it can be corrected using JSpevView by clicking on a button JCB]**

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