Poly lithium carbon dioxide reaction

Amination (11) and solution carbonation (8) reactions were carried out as described previously. For solid-state carbonations, a benzene solution of poly(styryl)lithium was freeze-dried on the vacuum line followed by introduction of high-purity, gaseous carbon dioxide (Air Products, 99.99% pure). Analysis and characterization of polymeric amines (11) and carboxylic acids (8) were performed as described previously. Benzoyl derivatives of the aminated polystyrenes were prepared in toluene/pyridine (2/1. v/v) mixtures with benzoyl chloride (Aldrich, 99%). 

The carbonation of polymeric anions using carbon dioxide is one of the most useful and widely used functionalization reactions. However, there are special problems associated with the carbonation of polymeric organolithium compounds317 . For example, Wyman, Allen and Altares318) reported that the carbonation of poly-(styryl)lithium in benzene with gaseous carbon dioxide produced only a 60% yield of carboxylic acid the acid was contaminated with significant amounts of the corresponding ketone(dimer) and tertiary alcohol(trimer) as shown in Eq. (70). 

With regard to the carbonation of polymeric anions with counter ions other than lithium, Pannell325) has reported that poly(styryl)potassium reacts with carbon dioxide in tetrahydrofuran to form carboxyl-terminated polymer without the complicating side reactions which generate higher molecular weight species. 

The carbonation of polymeric carbanions using carbon dioxide is one of the simplest, most useful, and widely used functionalization reactions. However, there are special problems associated with the simple carbonation of polymeric organolithium compounds. Eor example, when carbonations with high-purity, gaseous carbon dioxide are carried out in benzene solution at room temperature using standard high vacuum techniques, the carboxylated polymer is obtained in only 27-66% yield for PSLi, PILi, and poly(styrene-b-isopre-nyl)lithium. The functionalized polymer is contaminated with dimeric ketone (23-27%) and trimeric alcohol (7-50%)... 

In order to optimize specific anionic functionalization reactions such as carbonation with carbon dioxide, the effect of chain end structure (stability and steric requirements) has often been investigated. The steric and electronic nature of the anionic chain end and the chain-end aggregation can be modified by reaction with 1,1-diphenylethylene as shown in Eq. (13). When the direct carbonation is effected in benzene at room temperature with the diphe-nylalkyllithium species formed by addition of poly(styryl)lithium to 1,1-diphenylethylene (Eq. 31), the carboxylated polymer can be isolated in 98% yield compared to only a 47% yield for poly(styryl)lithium without end-capping under the same conditions [141] ... 

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