Integration ratio, nuclear magnetic resonance

Regiostructures for soluble poly(CHD) and its copolymers are determined by solution nuclear magnetic resonance (NMR) spectroscopy. For the poly(CHD) unit, the Ho, Ha, and Hb protons (Figure 18.2) are identified with signals at, respectively, 5.73, 2.01, and 1.56 ppm. There are equal numbers of Ho and Ha protons in the 1,4-unit of poly(CHD), while the ratio of Ho to Ha protons in the 1,2-unit is 2 3. Therefore, regioregularity can be estimated by the Ho/Ha integral value ratio. 

Traditionally, either gas chromatography combined with mass spectroscopy (GC-MS), density measurements, or refractometry is used to determine the relative concentration of the permeant mixtures [68]. However, proton nuclear magnetic resonance ( H NMR) is another excellent method to quantify concentrations because of its ease of use and high accuracy. The molar ratio of the mixture is calculated from the ratio of the integration of peaks corresponding to the components in the mixture. Once the ratios of permeants are known, selectivity can be calculated. To demonstrate that H NMR is an accurate method for determining the composition of liquid mixtures, a trial run was carried out using measured volumes of water and methanol (Fig. 33.17). 

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