Cyclopropanones polymerization

Cyclopropanone Polymerization. Triethylamine is an efficient initiator for the polymerization of cyclopropanone. This initiator caused polymerization to start almost immediately as evidenced by the rapid increase in temperature and the formation of a precipitate within 2-3 minutes. From the data in Table 1 there does not appear to be any correlation between the amount of initiator added and the molecular weight of the resultant polymer. One possible explanation for this is that the polymer was synthesized under heterogeneous conditions thus limiting the access of monomer to growing polymer chains. 

Another intriguing aspect of the polymerization of cyclopropanone was the possibility that the resulting polymer could provide an indirect route to the hithertofore unreported polymer of acetone. 

The carbonyl group in cyclopropanone readily adds many types of nucleophiles, even at low temperature, e.g. water, amines, acids, Grignard reagents. The unusual tendency toward adduct formation extends to polymerization and is a consequence of the strain energy released by the sp2->-sp3 rehybridization of a carbon atom constrained by a three-membered ring. 

The polymerization of cyclopropanone is initiated °) by traces of water and is inhibited 15> by moisture scavengers such as acetyl chloride. The terminal groups are apparently hemiketal units since a,co-diacetoxy-poly(oxycyclopropylidenes) 85 are isolated from a mixture of cyclopropanone hydrate, diazomethane and excess ketene. 80>... 

Cyclopropanones are usually not isolated as discrete entities since they rapidly undergo polymerization or ring-opening, especially in the presence of acids or bases. For this reason, much of the chemistry of cyclopropanone and its derivatives has been observed through the behavior of transient intermediates such as hemiketals formed in situ from precursors ... 

A significant advance in the study of cyclopropanones resulted from studies by the Turro and the de Boer groups on the formation of cyclopropanones in solution by the reaction of ketenes with diazoalkanes. These investigators found that it is possible to store the parent ketone only for short periods at low temperature because of its unusual reactivity and propensity for polymerization. Subsequent work has shown that cyclopropanone seems to show chemical behavior similar to that of ketene. Thus, it is attacked by nucleophilic species such as water, alcohol and amines and reacts rapidly with itself to form... 

As mentioned earlier, many types of nucleophilic reagents will add to the carbonyl group of cyclopropanones, including water, alcohols, amines and Grignard reagents. This type of reaction is most probably involved in the ready polymerization observed in these systems. For example, cyclopropanone forms a polymer, polycyclopropanone (33), when warmed... 

Thomas and his coworkers have studied the gas-phase thermolysis and photolysis of cyclopropanone in detail" ". They have found that the thermal reaction of gaseous cyclopropanone follows a first-order rate to give only the polymerized product in what appears to be a surface-catalyzed process. The heat of formation of cyclopropanone was measured to be -f 3.8 kcal mol" and this value was used to predict an activation energy of 30.5 kcal mol" for its homogeneous decomposition via the oxyallyl biradical. 

Polymerization of cyclopropanone in the absence of inhibitors occurs readily when the monomer in solution is warmed to above The polymerization of cyclopropanone is initiated... 

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