The solid reaction products from pyrolysis of polyethylene terephthalate in the presence and absence of red phosphorus were characterized by CP/MAS 13C‐NMR, FR‐IR, and MAS 31P‐NMR spectroscopy. Over the temperature range of 300–400°C, polyethylene terephthalate was converted in a sealed vial to a highly crosslinked polymer of terephthalic acid. Pyrolysis in the presence of red phosphorus, which functions as a flame retardant by increasing the amount of char, yielded an intractible polyaromatic phosphate ester. After thermal cleavage of polyethylene terephthalate with formation of free carboxyl and vinyl ester groups, there are two competing reaction pathways. The smaller molecular weight fragments may enter the vapor phase where they undergo further degradation primarily to CO2, CO, and acetaldehyde, as described by others. However, if volatilization of the oligomeric fragments is inhibited, an alternate reaction pathway gives rise to the formation of highly crosslinked char. Red phosphorus decreases the volatility of the oligomeric fragments by converting them to phosphates and thereby enhances char formation.
Cross-polarisation magic-angle-spinning and high resolution I3C n.m.r. spectra indicate that hydrogen bonding and crystal packing forces alter the structure of morphine sulphate in the crystalline state from that available for receptor binding in aqueous solution.The isomeric structure of (-)-morphine was first proven by X-ray crystallography of the hydroiodide dihydrate sa1t.l oriented only in the equatorial direction as in (1).This and subsequent X-ray crystallography of the hydrochloride trihydrate salts2 indicated that both morphine and codeine exist in the crystal as structure (1). The piperidine ring, which includes C-9, -14, -13, -15, and -16, exhibited a
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.