Butyl isopropenyl

Butyl isopropenyl ketone was prepared by the reaction of methacryloyl chloride with BuLi in ether at -78°C. The crude product was purified by the fractional distillation under reduced nitrogen pressure. Bp 56.5°C(14mmHg). ]., 4363. Anal. Found ... 

In the polymerization of MMA by BuLi the initiator was reported to react first with many more carbonyl groups than with vinyl double bonds at low temperatures O). Therefore, the butyl carbonyl group must be incorporated through the copolymerization of MMA with butyl isopropenyl ketone formed by the former reaction. 

Now it will be necessary to elucidate the location of the butyl isopropenyl ketone unit in the polymer chain. The spin-lattice relaxation time, Tj., of the protons in the polymer and oligomer was measured. The Ti of methylene protons adjacent to the carbonyl group was nearly the same level as the T of methyl protons in the terminal butyl group or terminal methine proton (Table ) but much longer than the T of the protons in interior sequences of polymer (13). These indicate that the butyl carbonyl group in the polymer or oligomer locates at or near to the forefront or the end of the chain. 

The trimer showed the peaks of 127, 158 and 258, while the dimer showed the peaks of 127 and 158. The results strongly indicate that the ketone unit locates at the chain end of the oligomer, which could not be determined by NMR spectroscopy. Then, it is reasonable to assume that the oligomer molecule containing a terminal methine proton has one butyl isopropenyl ketone unit at the chain end. 

There is also some posibility that the butyl Isopropenyl ketone formed was again attacked by BuLi to produce an anion as follows ... 

Some initiator may also remain unreacted. The side products formed, butyl isopropenyl ketone and methanolatemagnesium chloride, are not inactive under these conditions. They contribute to the formation of oligomers (by incorporation of dormant butyl isopropenyl ketone chain ends) and to the formation of syndiotactic polymer (by coordination of CHaOMgCl with propagating chain ends). 

However, the structural survey of the low molecular weight products by Kawabata and Tsuruta58 seems to indicate that carbonyl addition was not a predominant side-reaction since the amount of butyl isopropenyl ketone (BIPK) formed was very small, particularly in the polymerization in toluene. The problem was solved almost completely by totally deuterated monomer technique.59-63 The poly(MMA-rf8) prepared with n-C4H9Li in toluene showed in lH NMR signals due to the methyl (0.79 ppm) and methylene... 

Some abnormalities were reported in the initiations of methyl methacrylate polymerizations in toluene by butyllithium. Their nature is such that they suggest the possibility of more than one reaction taking place simultaneously. One, which must be the major one, is that of the oiganomet-allic compound reacting with the carbon-to-carbon double bond as shown above. The other, minor one, may be with the carbon-to-oxygen double bond. The major reaction produces methyl methacrylate anions. The minor reaction, however, yields butyl isopropenyl ketone with an accompanying formation of lithium methoxide ... 

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