The Formation of Butane in the Polymerization of Methyl Methacrylate with Butyllithium
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Polymer Journal, Vol. 12, No. 8, pp 535-537 (1980) SHORT COMMUNICATION The Formation of Butane in the Polymerization of Methyl Methacrylate with Butyllithium Koichi HATADA, Tatsuki KITAYAMA, and Heimei YUKI Department of Chemistry, Faculty of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560, Japan. (Received February 28, 1980) KEY WORDS Methyl Methacrylate I Perdeuterated Methyl Methacrylate I Anionic Polymerization I Butyllithium I Toluene I Tetrahydrofuran I Butane Formation I Mass Spectroscopy I Butene I It has been found that a small amount of butane merization reactions in toluene: (1) the poly is formed when the polymerization of methyl merization of MMA terminated by CH30D methacrylate is initiated with butyllithium and (MMA-CH30D system) and (2) that of MMA-d8 terminated with acetic acid. The origin of the butane terminated by CH3 0H (MMA-d8-CH3 0H system). was not clear, although the proton abstraction from The reactions were quenched at 10 min following the monomer is assumed. 1 the initiation. The spectra of butane (BuH) and In this work the polymerizations of undeuterated butane-d-1, CH3 CH2 CH2CH2 D, (BuD) are also (MMA) and perdeuterated (MMA-d8 ) methyl shown for comparison. The BuH and BuD were methacrylates were initiated with undeuterated obtained by the reaction of BuLi with CH30H and butyllithium (BuLi) and terminated by CH3 0D and CH30D, respectively. By inspecting these four CH3 0H, respectively. Deuterium distributions in spectra, it can be seen that the butane from the the butane formed were determined by combined MMA-CH3 0D system mainly consists of BuD and gas-liquid phase chromatography-mass spectrom the butane from the MMA-d8-CH30H system is etry. Based on these results, the origin of the butane mainly BuH. The results clearly indicate that a is discussed in this paper. certain amount of BuLi remained unreacted even MMA-d8 was prepared from acetone after 10 minutes following the initiation, and cyanohydrin-d7 and methanol-d4 according to the reacted with methanol to produce butane in the 2 method of Crawford. MMA or MMA-d8 termination reaction. (lOmmol) was polymerized with BuLi (1 mmol) in BuLi + CH3 0D-------. BuD + CH30Li either toluene or tetrahydrofuran (10 ml) at - 78oC (MMA-CH3 0D system) a glass ampoule and terminated by adding a small amount of CH30H or CH30D. The volatile BuLi CH 0H -------. BuH CH 0Li compounds were then distilled from the reaction + 3 + 3 (MMA-d -CH 0H system) mixture on the vacuum line. From the distillate, the 8 3 low-boiling fraction was collected again by frac Gas-chromatographic analysis showed that the tional distillation and subjected to analysis for the butane formed corresponds to about 10% of the butane fraction by combined vapor-phase chro BuLi used. matography-mass spectrometry. The mass spectra It has been reported that in the polymerization of were recorded by a JMS-OlSG-2 mass spectrom MMA with fluorenyllithium in toluene at - 78°C, eter (JEOL) combined with a gas-liquid phase the initiator disappeared instantaneously on mixing chromatograph. the reactants. 3 BuLi has a greater tendency to exist In Figure 1 are illustrated the mass spectra of the in an associated form in a nonpolar solvent in butanes formed in the products of the two poly- contrast to fluorenyllithium. Thus, the remaining 535 K. HATADA, T. KITAYAMA, and H. YUKI (A) BuD (C) MMA-GH30D system 59 59 II II .Ill lr 20 ]) 40 50 60 m/e 20 30 40 50 60 m/e (B) BuH (D) MMA-dg-CH30H system 58 58 Ill I II 20 30 40 50 60 m/e 20 30 40 50 60 m/e Figure 1. Mass spectra of butane-1-d (BuD) (A), butane (BuH) (B), the butane from MMA-CH3 0D (C) and MMA-d8-CH30H (D) systems in toluene for lOmin. unreacted BuLi in the polymerization of MMA in toluene should be in a stable association form even in the presence of a small amount of this polar > monomer. A similar phenomenon was observed by +' ·rl Vankerckhoven and Van Beylen in the poly Ul >:: merization ofmethacrylonitrile with BuLi in toluene (!) 58 +' at - 78°C, and the existence of the strongly >:: 56 associated and inactive form of BuLi was H suggested.4 In the mass spectrum of the butane fraction for I the MMA-CH30D system after 12 h of reaction in 20 30 40 so 60 m/e toluene (Figure 2), the intensities of the peaks at mfe= 58 and 56 increase considerably compared Figure 2. Mass spectrum of the butane fraction from with those in the spectrum of the butane from the MMA-CH3 0D system in toluene for 12h. polymerization fm I 0 min (Figure 1). The increasing peak intensity at mje=58 indicates that the hy drogen abstraction from the monomer or the is not clear at the present. polymer by the remaining BuLi occurs gradually Figure 3 shows the mass spectra of the butane during the polymerization reaction. On the other from MMA-CH3 0D and MMA-d8-CH3 0H poly hand, enhancement in the peak intensity at mje =56 merization systems for 10 min. in tetrahydrofuran. probably means that the prolonged polymerization The amount of butane measured by gas-liquid time brings about the formation of butene from the chromatography was about 5% of the BuLi used. remaining BuLi. The mechanism for this formation Comparison of these spectra with those in Figure 1 536 Polymer J., Vol. 12, No. 8, 1980 Formation of Butane in the Polymerization of MMA with BuLi (A) MNA-CHJOD (B) NNA-dg-CH30H system system .,_, /Jl r: Q) .j.J 5658 58 c 56 H 59 59 I I ll1 20 30 40 50 60 m/e 20 30 40 50 60 rn/e Figure 3. Mass spectra of the butane fractions from MMA-CH30D (A) and MMA-d8-CH30H (B) systems in tetrahydrofuran for I 0 min. clearly indicates that the butane from the poly m/ e =56 in the spectra. merizations in tetrahydrofuran contained an ap preciable amount of the butane formed through the Acknowledgment. The authors are grateful to proton abstraction from the monomer or the Dr. S. Kusumoto of Osaka University for making polymer. The high polarity of the solvent may break measurements of mass spectra and also to Mrs. F. down the association form of BuLi to reduce the Yano for her clerical assistance in the preparation of amount of the remaining BuLi and enhance the this manuscript. abstraction reaction. The peak intensity at mfe= 58 in the spectrum of the butane from the MMA REFERENCES CH30D system was stronger than that of the peak at mfe=59 in the spectrum of the butane from the N. Kawabata and T. Tsuruta, Makromol. Chern., 86, 231 (1965). MMA-d8-CH30H system. This might indicate the 2. 1. W. C. Crawford, Br. Patent 405 699 (1934). isotope effect in the proton abstraction reaction by 3. D. L. Glusker, E. Stiles, and B. Y oncoskie, J. Polym. butyllithium in tetrahydrofuran. The formation of Sci., 49, 297 (1961). butene was also enhanced in tetrahydrofuran, as is 4. H. Vankerckhoven and M. Van Beylen, Eur. Polym. evidenced by the increasing intensity of the peak at J., 14, 189 (1978). Polymer J., Vol. 12, No. 8, 1980 537 .