Thesis-Final 03 June 2011 pdf - Jacobs University

Results and discussion Chapter 3
Identification of the product was supported by 1 H-NMR spectra. The 1 H-NMR
spectrum shows that the two methyl protons of acetyl group at 1.30 and 1.46 ppm
with three proton intensity and assigned to H-12 and H-13 protons. Furthermore four
signals at 2.38, 2.51, 2.64 and 3.02 ppm correspond to the four non-equivalent protons
of the two sets of CH 2 groups. The most highfield peak of CH 2 occurred as doublet of
doublet at 2.38 ppm and was assigned to 2-H ax , then another pear of the same
methylene group which was occurred at 2.51 ppm as multiplet was assigned to 2-H eq .
The non-equivalent protons of another methylene group at 2.64 ppm as doublet with
the 11.4 Hz coupling constant were assigned to 6-H eq and then the multiplet at 3.02
ppm assigned to 6-H ax . The two diastereotopic protons of the Troc group which are
identical to each other appeared as two doublets at 4.71 and 4.80 ppm.; both protons
have coupling constant around 12 Hz, typical of a 2 J HCH coupling. The 1 H-NMR
spectrum shows two doublet of doublet and one doublet of doublet of doublet at 4.31,
4.52 and 4.76 ppm, corresponding to the three protons HCO next to an oxygen atom.
Because of the chemical shift considerations the most downfield proton at 4.76 ppm
was assigned to H-5, the proton next to the lactone functionality. From the 1 H 1 H-
COSY spectrum the signal at 4.31 ppm, which occurred as doublet of doublet,
identified as H-4 due to crosspeaks to H-5. The doublet of doublet of doublets at 4.52
ppm was assigned to H-3 proton.
Figure 49: 13 C-NMR spectrum of 1-(β, β, β-trichloroethoxycarbonyl)-3, 4-Oisopropylidene
quinide, (47)
72