The reaction of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles instead of amides when the cations have reasonable stability. The reactions of oxime derivatives of 1-substituted-phenyl-2-propanones and 3-substituted-phenyl-2-butanones in aqueous solvents gave both rearrangement and fragmentation products, the ratio of which was dependent on substituents. Transition state (TS) optimizations and intrinsic reaction coordinate (IRC) calculations for the reaction of 1-phenyl-2-propanone oximes showed that there is a single TS for each substituted compound. The IRC path from the TS either led to a rearrangement product or a fragmentation product depending on the substituent; the IRC path changes from rearrangement to fragmentation when substituent X becomes more electron donating. Ab initio dynamics simulations were found to follow the IRC path for X ¼ p-NH 2 and p-MeO giving fragmentation products, and almost so for X ¼ p-NO 2 giving the rearrangement products. However, in a borderline case where X is less donating than p-MeO or less withdrawing than p-NO 2 , the trajectories did not follow the minimum energy path on the potential energy surface, but gave both rearrangement and fragmentation products directly from the single TS. This is a novel example of path bifurcation for a closed shell anionic reaction. It was concluded that a reactivity-selectivity argument based on the traditional TS theory may not always be applicable even to a well-known textbook organic reaction.

The reactions of oximes to amides, known as the Beckmann rearrangement, may undergo fragmentation to form carbocations + nitriles when the migrating groups have reasonable stability as cations. The reactions of oxime sulfonates of 1-substituted-phenyl-2-propanone derivatives (7-X) and related substrates (8-X, 9a-X) in aqueous CH(3)CN gave both rearrangement products (amides) and fragmentation products (alcohols), the ratio of which depends on the system; the reactions of 7-X gave amides predominantly, whereas 9a-X yielded alcohols as the major product. The logk-logk plots between the systems gave excellent linear correlations with slopes of near unity. The results support the occurrence of path bifurcation after the rate-determining TS of the Beckmann rearrangement/fragmentation reaction, which has previously been proposed on the basis of molecular dynamics simulations. It was concluded that path-bifurcation phenomenon could be more common than thought and that a reactivity-selectivity argument based on the traditional TS theory may not always be applicable even to a well-known textbook organic reaction.

Fast-responsive deswelling of poly(N-isopropylacrylamide) gel after a freeze-dry (FD) treatment was investigated by means of SEM images and a kinetic method using a N-isopropylacrylamide (NIPAAm) monomer from the viewpoint of the mesoscopic structure comprising a partitioned polymer-network. It was deduced from SEM images that an elastic frame comprising a partitioned polymer-network is formed by a hydrophobic interaction between polymer chains in the FD-treated gel. Fast-deswelling of the FD-treated gel results from the elasticity of a partitioned polymer-network caused water to release. The kinetic parameters on deswelling of both the conventional gel and the FD-treated gel were determined in the presence of an NIPAAm monomer. This monomer in solution is considered to play two directly-opposed roles in making a skin on the surface of the conventional gel: One is for disturbing the formation of hydrogen bonding between amide groups in the polymer; the other is for accelerating the separation of hydrated water from isopropyl groups in the polymer. Cracking the surface of a conventional gel was investigated in connection with the monomer.

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The reaction of melamine with ammonium dihydrogenphosphate has been investigated by solid-state NMR spectroscopy under different conditions. Synthesized melamine diphosphate (MDP) was characterized by X-ray powder diffraction, solid-state NMR spectroscopy and was also tested for flame retardant ability. The flammability of polypropylene (PP) containing melamine diphosphate, pentaerythritol (PER) or dipentaerythritol (DPER) was characterized by limiting oxygen index (LOI).