Agents, polymeric phosphonium

Polymerization was initiated with alkylating agents such as CH3I, CeHsC Br, or CH3OSO2CF3. Depending on the nucleophilicity of the counterion, propagation proceeds on phosphonium ion active species (triflate counterion) or on covalent alkyl bromide species. 

Use Organic preparations, phosphonium halides, doping agent for n-type semiconductors, polymerization initiator, condensation catalyst. Note A synthetic dye, chrysaniline yellow, is sometimes called phosphine. 

A way to limit these reactions consists of replacing Li+ by a bulkier cation (quaternary ammonium, phosphonium, etc.) or by adding in the reaction medium, a solvating agent that increases the apparent radius of the lithium ion the attack of carbonyl groups by ion pairs can thus be thwarted, the probability of termination reduced, and the control of polymerization improved in this way. 

Another potential problem with DCC is that at the completion of the reaction some DCU remains in solution with the product, necessitating additional purification. Water-soluble carbodiimide derivatives such as l-Cyclohexyl-3-(2-morpholinoethyl)carbodiimide Metho-p-toluenesulffonate and l-Ethyl-3-(3 -dimethylaminopropyl)carbodiimide Hydrochloride (EDCI) obviate this problem, as they are removed by a simple extraction. Many newer coupling agents have been developed for peptide synthesis and other acylation reactions. These include Benzotriazol-l-yloxytris(dimethylamino)phosphonium Hexafluorophosphate (BOP)," 0-Benzotriazol-l-yl-N,N,N, N -tetramethyluronium Hexafluorophosphate (HBTU)," Bis(2-oxo-3-oxazolidinyl)phosphinic Chloride (BOP-Cl), and (1 //-1,2,3-benzotriazol-1 -yloxy)tris(pyrTolidino)phosphonium hexafluorophosphate (PyBOP). In addition to linear and polymeric amides, lactams of various ring sizes have been synthesized using these methods (eq 1)."... 

---