Methylhexadiene polymer

Ozonolysis. Ozonolysis of the methylhexadiene polymer was conducted (21)at room temperature on a solution of 1,03 g. polymer in 20 ml. tetrahydrofuran with the aid of the Wellsbach ozonizer. The end point for the ozonolysis was observed after about 15 min. by the reaction of excess ozone with starch-iodide solution. Triphenylphosphine was added to the reaction mixture and allowed to react at room temperature for 60 hr. The resulting product was analyzed by GLC (Hewlett Packard 5750, Porapak Q 10 ft. x 1/8 in. column at 110°C, helium pressure 60 psi, thermal conductivity detector at 190°C, injector 200°c). 

The 300 MHz H-NMR spectrum of the 5-methylhexadiene polymer is shown in Figure 3. The peak intensity in the olefinic region was found to be 7.7% of the total intensity and is close to the theoretical value of 8.3. The general features of the spectrum are also in agreement with the arrangement of 1,2-structural units in a regular head-to-tail sequence. The measured chemical shifts and assignments are listed in Table I. 

The 13C-NMR spectrum of the 5-methylhexadiene polymer in CDCI3 solution is given in Figure 4. The spectrum (six peaks) is consistent with the structure of a polymer resulting from a regular head-to-tail 1,2-polymerization. The peak at 33.31 ppm consists of two overlapped peaks. These are attributed to the methylene carbons adjacent to the double bond and to the backbone methine carbon these two peaks are in the same position by coincidence. 

In contrast to the spectrum of isotactic trans-l,4-hexadiene polymer (Figure 5), the 300 MHz -H-NMR spectra of the 5-methylhexadiene polymer in both CCI4 and CgDg solutions exhibit only one peak for its backbone methylene protons. As in the case of cis-l,4-hexadiene polymer (14), the backbone methylene protons were not resolvable. The absence of a doublet for the methylene protons in these polymers does not necessarily preclude the possibility that they are isotactic. 

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