21960-71-4Relevant academic research and scientific papers
Selectivity of Dihalocarbenes in Cycloaddition Reactions
Giese, Bernd,Lee, Woo-Bung,Meister, Juergen
, p. 725 - 735 (2007/10/02)
Dihalocarbenes 1a-e yield in the 2-methyl-2-butene/2-methylpropene competition system the cyclopropanes 2a-e and 3a-e.Whereas selectivity increases at 293 K in the sequence CBr2 CClBr CCl2 CFCl CF2, at 393 K the order of carbene selectivity is reversed: CF2 CFCl CCl2 CClBr CBr2 (Table 1).At 360 K (isoselective temperature) the carbenes 1a-e react with equal selectivity.The reason for this is that activation enthalpies and activation entropies are changed in the same direction with variation of carbene substituents from fluorine to bromine (Table 2).Thereby the selectivities of CClBr and CBr2 increase with increasing temperature (Figure 2). - Above and below 360 K the order of the slopes of carbenes 1a-e are reversed in the Skell-Moss diagram (Figure 3).
