Divinylbenzene dioxide

To illustrate the specific operations involved, the scheme below shows the first steps and the final detachment reaction of a peptide synthesis starting from the carboxyl terminal. N-Boc-glycine is attached to chloromethylated styrene-divinylbenzene copolymer resin. This polymer swells in organic solvents but is completely insoluble. ) Treatment with HCl in acetic acid removes the fert-butoxycarbonyl (Boc) group as isobutene and carbon dioxide. The resulting amine hydrochloride is neutralized with triethylamine in DMF. 

The SFC analysis of barbiturates has been reported by Smith and Sanagi [16]. The method utilzed packed columns of ODS bonded silica (200 x 3 mm ID) or polystyrene-divinylbenzene polymer (150 x 4.6 mm ID) with a carbon dioxide mobile phase and FID detection. The barbiturates were strongly adsorbed on the ODS column and were not observed to elute. The drugs did elute with reasonable retention times on the polymer column. Unfortunately, there was peak tailing, and adsorption remained a problem with all the barbiturates studied. The authors were prevented from adding methanol as a polar modifier to the mobile phase because the detection was by FID. 

Smith and Sanagi reported the packed-column SFC of benzodiazepines (diazepam, lorazepam, lormetazepam, nordazepam, temazepam, es-trazolam, chlordiazepoxide, triazolam, cloxazolam, ketazolam, and lopra-zolam) with methanol-modified carbon dioxide as the mobile phase [29]. The effect of methanol concentration on separation was studied on three columns polystyrene-divinylbenzene, octadecylsilane, and cyanopropyl-bonded silica columns. They concluded that proportion of methanol has marked effect on the selectivity of compounds containing different functional groups. 

Figure 10. Retention volume for benzene versus carbon dioxide pressure on the styrene/divinylbenzene resin.

Crosslinked Polystyrene. Polystyrene lightly crosslinked during polymerization by 0.01-0.25% divinylbenzene provides foams, expanded by carbon dioxide or other gases, with greater expandability and resistance to collapse at elevated temperatures (102, 103). Other divinylbenzene copolymers are reported, employing as blowing agent saturated aliphatic or fluoroaliphatic volatile liquids, tetramethylsilane, and azobis-isobutyronitrile (99,106, 108). 

Porous polymer beads of uniform size arc manufactured from styrene cross-linked with divinylbenzene (Section 28F-2). The pore size of these beads is uniform and is controlled by the amount of cross-linking. Porous polymers have found considerable use in the separation of gaseous polar species such as hydrogen. sulfide, oxides of nitrogen, water, carbon dioxide, methanol, and vinyl chloride. A typical application of an open tubular column lined with a porous polymer (PLO Tcolumn) is shown in Figure 27-2lb,... 

A parallel study has reported the synthesis of crosslinked polymer microspheres in supercritical carbon dioxide [54]. Heterogeneous free-radical polymerization of divinyl benzene and ethyl benzene were carried out at 65 C and 310 bar using AIBN initiator to form the crosslinked polymer. It is shown that in the absence of surfactants as stabilizers, polymerization of the mixture containing 80 % divinyl benzene + 20 % ethyl benzene leads to poly(divinylbenzene) microspheres of about 2.4 micron diameter [Figure 14]. In the presence of a carbon dioxide-soluble diblock copolymer as a stabilizer, polymerization of the mixture with the same monomer ratio proceeds as an emulsion and lead to smaller crosslinked particles (ca. 0.3 micron). Thermal analysis shows that the crosslinked polymer that is formed from these polymerizations is stable up to 400 C. 

Emerson, D.W. Chlorine Dioxide Generated by Reaction of Sodinm Chlorite with N-halosulfonamide or N-alkyl-N-halosulfonamide Gronps on Styrene-Divinylbenzene Copolymers. Ind. Eng. Chem. Res. 1993,32, 1228. 

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