Varying amounts of radiation decomposition during storage i n the dry form have been found in the cases of ~k l a b e l e d valine, norvaline, norlewine, choline chloride, calcium glycolate and cholesterol, These data indicate t h a t investigators using labeled organic compounds should make frequent checks of the purity of these compoun8.s i n order t o exclude
nBuLi: To nBuLi (2.9 g. 46 mmol), constantly stirred at -8O"C, precooled pentane was added dropwise until a homogeneous solution was obtained (ca. 20 mL). After one week at -90 "C colorless blocks crystallized with a melting point of -34(2) 'C. rBuLi: tBuLi (2.2 g, 34 mmol) was treated as described for nBuLi (ca. 18 mL pentane added). Crystallization over one week yielded colorless elongated blocks. (rBuLi. Et,O),: From various pentane/Et,O ratios the best results were obtained by first adding 5 mL pentane and then 12 mL E t 2 0 (each precooled to -60 "C) dropwise to solid tBuLi (2.2 g, 34 mmol) at -80 'C. At -90 'C colorless blocks with a melting point of -38(2) "C were formed from the pale yellow solution.
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.