Isovanillin(621-59-0)
1HNMR
NMR is an effective analytical method to structural analysis of organic compounds. In making the structure analyzed by NMR, it is common to first go check from the positional relationship of hydrogen with each other. Some of that approach, there is a two-dimensional NMR measurement technique called COSY (COrrelation SpectroscopY). Before this COSY is used, it was done by the one-dimensional NMR measurement technique called homo decoupling.
Homo decoupling isovanillin in Figure 1 1 shows the H-NMR spectrum. by irradiating the selectively radio wave to the signal of b, along with the elimination of the b of the signal, you can erase the coupling from the b of the signal. As a result, the signal of c has changed from four to two. That is, during the b signal and c of the signal, it indicates that there was a coupling, b and c are found to exist at a position closer via coupling. However, in the homo-decoupling, since it is necessary to perform measurements on one signal each, was time-consuming assays.
Figure 1: homo decoupling of isovanillin 1 H-NMR spectrum (top: irradiating the signal b, lower: no irradiation)
On the other hand, the HH COSY spectrum, it is possible to observe the presence or absence of coupling of all hydrogen at one time (Fig. 2). The presence or absence of coupling between each signal can be confirmed by the presence or absence of a signal at the intersection of each signal. In isovanillin, because the point of intersection of a and c, the signal at the intersection of b and c have been observed, you can see that there is a coupling between them. In other words, a and c, b and c, we know to be present in a position close through a bond. In this way, COSY is the positional relationship of hydrogen with each other, is an excellent measurement method can be examined at a time.
Figure 2: HH COSY spectrum of isovanillin
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