In independent experiments, four carbons in the 4-pentenal skeleton have been labeled with deuterium or methyl and the fate of each label has been determined as the pentenal was transformed into a cyclopentanone derivative by RhCl(PPh3)3(1) at 24-26 °C. The catalyst converted 4-hexenal to 2-methylcyclopentanone (2) in CHC13 and C6H6. Approximately equivalent amounts of hydrocarbon decarbonylation products and RhCl(CO)(PPh3)2 were also formed. 3-Methyl-4-pentenal was isomerized to 3-methylcyclopentanone by 1. 4-Hexenal possessing deuterium at C-2 was isomerized to 2 which contained deuterium at C-5. ínm-4-Hexenal-1 -d was cyclized to 2-3-d and 2-2-d in 9:1 ratio when the reaction was carried to a low conversion. The deuterium in the 2-3-d product was found to be cis to the C-2 CH3 group. ris-4-Hexenal-/-d was isomerized by 1 to afford 2-3-d possessing deuterium trans to the C-2 CH3 group. NMR analyses of these products were assisted by the synthesis and characterization of 2-cis-2,3-d2 by treatment of 2-methylcyclopent-2-en-1 -one with D2 and 1. The 2-cis-2,3-d2 could be converted to a 1:1 mixture of 2-3-d diastereomers on treatment with HC1 in MeOH/H20. The results demonstrated that the cyclization of 4-hexenal-f-rf occurred by a syn addition of the C-D bond to the olefinic bond to generate 2-3-d. The presence of C2H4 in reaction mixtures of 1 and 4-hexenal-1-d resulted in the formation of substantial 2-d0 and C2H3D. The deuterium locations in the 1-pentene, 2-pentene, and ethylcyclopropane decarbonylation products derived from reaction of 4-hexenal-1-d with 1 were determined. The results were interpreted in terms of a hydroacylation mechanism involving an acylrhodium(III) hydride complex and organometallic intermediates derived therefrom. The hydroacylation and decarbonylation products appear to be generated via common intermediates.Acylmetal hydride species have been proposed as possible participants in a group of very important transformations which are promoted by transition metal complexes in solution. These include hydroformylation,1
Attempts have been made, particularly by American workers, to exploit differences in crystalline and amorphous polymer spectra to determine crystalline/amorphous ratios. In most published work authors have been forced to rely on calibration by other methods, especially density. They have justified the use of the spectroscopic method principally on the grounds of speed in obtaining results. We propose a spectroscopic method, applicable to a number of polymers, which is entirely independent of other measurements. We are thus able to compare our results with those obtained by other methods and have in some cases been able to draw useful conclusions from apparent anomalies. Our method depends upon measurement of pure amorphous bands. We consider these to arise from the multiplicity of rotational isomers present in the amorphous phase. The pure amorphous spectrum of many polymers can be obtained, and by this means an absolute calibration of amorphous content is possible. Crystalline bands cannot be so calibrated; they are dangerous to use quantitatively, although superficially more attractive because of their sharpness. The application of the method to some common polymers including polythene, polyethylene terephthalate, and polytetrafluorethylene is described; the results are compared with values obtained by x‐ray and density methods.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.