By the N-decoupling technique the spectrum of the N-H proton in pyrrole-2-carboxylic acid and pyrrole-2-aldehyde was clearly unveiled. Using the full spectra including the N-H band, the N.M.R. parameters of the two pyrrole derivatives were determined with a high degree of accuracy by computer simulation. It was demonstrated that two types of long-range coupling exist for the aldehyde proton of pyrrole-2-aldehyde. From partial decoupling experiments by using the third r.f. field the relative signs of all coupling constants were determined to be the same for the two pyrrole derivatives, except for a long-range coupling, J cho-nh , in pyrrole-2-aldehyde. Based on an assumption that the long-range couplings of the aldehyde proton originate from the pi electrons, it was concluded that the absolute signs of all coupling constants among the ring protons of pyrrole-2-aldehyde were positive.
Polyethylene was mechanochemically produced by milling of alumina powder at room temperature in the presence of ethylene monomer. Nearly 50% of the produced polyethylene was chemically bonded with the matrix of the alumina. The other 50% of the polymer was extracted by the organic solvents. The polyethylene extracted by the hot n-heptane was characterized as having a structure similar to that of the branched polyethylene of low density, and the toluene extracted polyethylene had a structure similar to that of the high density polyethylene. The molecular weights of the mechanochemically produced polyethylene were found to distribute from 102 to 106 by gel permeation chromatography. The weight average molecular weight was estimated as 260,000 after the 3 days milling. Mechanochemical polymerization of ethylene was also demonstrated by milling of silica in the presence of ethylene monomer. Polymerization of propylene by milling of alumina under propylene atmosphere was performed. The obtained polymer was found to be an atactic by IR measurement and the molecular weight of the extracted product was determined as ≃ 400 by the vapor pressure osmometer.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNovel cycloaddition of dimethylacetylene to the dimethylacetylene radical cation: direct observation by ESRM. Shiotani, K. Ohta, Y. Nagata, and J. SohmaCite this: J. Am. Chem. Soc. 1985, 107, 8, 2562–2564Publication Date (Print):April 1, 1985Publication History Published online1 May 2002Published inissue 1 April 1985https://pubs.acs.org/doi/10.1021/ja00294a067https://doi.org/10.1021/ja00294a067research-articleACS PublicationsRequest reuse permissionsArticle Views91Altmetric-Citations26LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
