3.3 Assignment of the signals for the quantification by qHNMR
For deriving 1H NMR based quantification some
prerequisite conditions have to be met such as complete solubility of
the analyte, proper relaxation delay within the scans, no overlapping of
the peaks and no side reactions in the mixture (Bharti & Roy 2012),
which also happen to be the limitations of this technique. In our case,
with reference to the overlapping of the peaks, there was no overlap of
the peaks of OA, MO and EMO that are selected for the quantification
purpose and all are completely soluble in the CDCl3 with
no side reaction. The 1H NMR equation has been derived
keeping in the view of the basic principle of qHNMR that integrated peak
area value directly corresponds to the number of protons responsible for
that peak which in turn will provide the molar concentration of the
corresponding molecule (Bharti & Roy 2012). It has been observed that
with the progress of the epoxidation reaction, the double bond present
in the MO gets converted into the oxirane ring resulting in the
appearance of new signal c at 2.87 ppm and disappearance of
signal c1 at 5.3 ppm. However, the methoxy
signal, a remained intact in both MO and EMO as shown inFig. 3. Thus the formation of EMO in the reaction mixture could
be quantified either by following the peak area corresponding to the
disappearing alkene proton (\(I_{c_{1}}\)) as given in equation
1 or by following the peak area corresponding to the appearing oxirane
proton (Ic) as given in equation 2 .
\(\%\ \text{EMO}=100-\frac{{3\times I}_{c_{1}}}{{2\times I}_{a}}\ \times 100\)