Cycloisomerization of a,b-acetylenic oximes leading to substituted isoxazoles was achieved using AuCl 3 as catalyst, under moderate reaction conditions. The reaction can be applied to various acetylenic oximes and gives good to excellent yields. The methodology is amenable for the selective synthesis of 3-substituted, 5substituted or 3,5-disubstituted isoxazoles by simply altering the substituents on the acetylenic oximes.
Many linear polymers containing water‐attracting groups spread uniformly at the airwater interface. The spreading property of polymethyl methacrylate is due to the ester groups which serve as anchors and promote spreading. The spreading of polystyrene, although it is a pure hydrocarbon, appears probably to be due to the end groups in each polymer molecule, introduced at the termination of the chains which act as anchors and facilitate spreading.
The surface pressure extended by the films of the high polymers is a sort of two‐dimensional swelling pressure. The distinguishing feature of these films is their high compressibility in the rectilinear portion of the F–A curve.
The limiting areas for F–A curves are not independent of the concentrations of spreading solutions as might be expected. The primary cause of this phenomenon in the case of high polymers appears to be a more or less coherent sponge‐ or felt‐like structure which develops at high concentration. The linear polymers, like polystyrene, become coiled up statistically and at higher concentration the coils become interlocked and produce an imperfectly spread film.
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