CROSS-LINKING OF STARCH WITH BIFUNCTIONAL PRECURSORS OF NITROALKENES

Granular starch was cross-linked with 1,3-di-O-acetyl-2-nitro-1,3-prop anediol (1), 1,3-di-O-pivaloyl-2-nitro-1,3-propanediol (2), 2-nitro-3- O-pivaloyl-1-propene-3-ol (3), 1,3-di-O-acetyl-aci-2-nitro-1,3-propane diol (4), 1,3-di-O-pivaloyl-aci-2-nitro-1,3-propanediol (5) and 1,6-di -O-acetyl-2,5-dinitro-1,6-hexanediol (6). The bifunctional precursors for the nitro-alkenes 1, 2, 3, and 4 were readily synthesized in high yields from nitromethane, paraformaldehyde and acetic anhydride (1, 3) or pivaloyl chloride (2, 4), respectively. The reaction rate for the cross-linking was very high, and for 1 and 3, the reaction reached com pletion within 1 h (at room temperature). The swelling capacities of t he products obtained when starch was cross-linked with precursors for the nitroalkenes 1-4 and 6 were lower in comparison to epichlorohydrin cross-linked starch. These results indicate a high reaction efficienc y at low degrees of substitution. Cross-linked 2-nitroalkyl starch eth ers were synthesized in a one-pot synthesis by addition of 1 or 3 and 2-nitroalkyl acetates to granular suspensions of starch. (C) 1998 Else vier Science Ltd. All rights reserved.