Their central carbon is sp2 hybridized and they are subject to nucleophilic attack as an intermediate in the Sn1 and E1 reactions.
This class of compounds may undergo the Wagner-Meerwein rearrangement, and they contain a carbon with a characteristic NMR shift of over 300 ppm downfield from a TMS standard. Tropylium is a rare example of a (*) stable one that can form a salt with poor anionic nucleophiles. They are stabilized by inductive effects and hyperconjugation, which explains why tertiary ones are more stable than primary ones. Their central carbon is sp2 hybridized and they are subject to nucleophilic attack as an intermediate in the Sn1 and E1 reactions. For 10 points, name this class of reaction intermediates featuring a positively charged trivalent carbon atom.
This class of compounds may undergo the Wagner-Meerwein rearrangement, and they contain a carbon with a characteristic NMR shift of over 300 ppm downfield from a TMS standard.
{Carbocation} [or {carbonium} ion] (3) [DF]