ABSTRACT:Polymerizations of trityl (TMA), diphenylmethyl (DMA) and benzyl (BMA) methacrylates were carried out mainly by n-butyllithium (n-BuLi) and the tacticities of the polymers were studied by NMR spectroscopy. Polymerization of TMA by n-BuLi gave a highly isotactic polymer in toluene as well as in tetrahydrofuran (THF). The polymer obtained in radical polymerization by AIBN catalyst had about 60 % isotacticity in triads.From these results the growing-chain-controlled mechanism was proposed to this polymerization. In the polymerization of DMA by n-BuLi a highly isotactic polymer was obtained in toluene at lower temperatures and a highly syndiotactic one in THF. The radical polymerization gave a predominantly syndiotactic polymer. Temperature dependence of the NMR signal-width of the isotactic polymer indicates that the conformational arrangement of the polymer chain in solution is much rigid up to a fairly higher temperature. These results suggest that the growing-chain-controlled mechanism may contribute to some extent to the stereoregulation of DMA in toluene. BMA behaved very similarly to methyl methacrylate in the polymerization by n-BuLi. Probably the same polymerization mechanisms can be applied for both monomers. Polymerization ofTMA, DMA and BMA by phenylmagnesium bromide or diethylaluminum diphenylamide was also investigated.KEY WORDS Stereospecific Polymerization / Poly (Trityl Methacrylate) / Poly (Diphenylmethyl Methacrylate) / Poly (Benzyl Methacrylate) / Poly (Methyl Methacrylate) / n-Butyllithium / Phenylmagnesium bromide / Diethylaluminum Diphenylamide / Growing-Chain-Controlled Mechanism of Stereoregulation / NMR Spectroscopy / Stereospecific polymerizations of methyl 1 -3 and other alkyl methacrylates 4 -9 by anionic initiator have been extensively studied. However there have been few systematic studies 10 concerning the effect of the ester group on the tacticity of polymer. EXPERIMENTAL MaterialsTMA was prepared from silver methacrylate and trityl chloride in diethyl ether. 12 The crude product was purified by recrystallization from petroleum ether. mp 102-103°C (lit. 12 101-1030C), Anal. Found: C, 84.00; H, 6.08%. Calcd for C23H 200 2 : C, 84.12; H, 6.14%. The NMR spectrum (10 % CC14 solution) showed peaks at 1.90 ppm (singlet, 2.95H) assigned to the methyl protons, 5.49 and 6.13 ppm (two singlets 2.00H) assigned to the p-protons of the vinyl group and about 7.20 ppm (multiplet, 15.2H) assigned to the phenyl protons.In a previous communication 11 we briefly reported the polymerization of trityl methacrylate by anionic and radical initiators and found that this monomer gave a highly isotactic polymer regardless of the polymerization medium, the temperature and the type of initiator. In the present work the polymerizations of trityl (TMA), diphenylmethyl (DMA) and benzyl (BMA) methacrylates were carried out mainly by n-butyllithium (n-BuLi) and the effect of the bulkiness of the ester group on the tacticity of the polymer was investigated. 36DMA was prepared by the reaction of 45 g of silve...

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from powder diffraction data. Glycyl-L-tyrosine is known to crystallize as dihydrate from an aqueous-methanol solution [1]. Recently, we obtained the trihydrate from an aqueous solution, and carried out single-crystal structure analysis [2]. Humidity-and temperature-dependent phase transitions of both hydrates were examined by powder X-ray diffraction analysis. The dihydrate is stable at room temperature in the relative humidity (rh) range from 80% to 0% and the structural transition proceeds around 50 °C at 0% rh. On the other hand, the trihydrate loses a part of crystal water at 0% rh, and further dehydrates around 80 °C. At the first step, we have successfully determined the crystal structure of the dihydrate from powder diffraction data. The structure coincides with that determined by singlecrystal structure analysis. In addition the cell parameters of the partly dehydrated state of the trihydrate at 0% rh have been determined and structure analysis from powder diffraction data is in progress.

Im Temperaturbereich von 350 ‐ 450°C wird Isobutyraldehyd (I) in Gegenwart verschiedener Oxide zu Methacrolein (II) dehydriert.