Carbenes carbocations

Nanosecond techniques have now been superceded by picosecond and femtosecond techniques, allowing detection in time domains as short as 10 s. Yet, nanosecond techniques remain powerful tools in the arsenal of the physical organic chemist quite simply, many radical, carbene, carbocation, carbanion reactions take place in the nano- and microsecond time scales. 

Until now, the detailed mechanism involved in the MTG/MTO process has been a matter of debate. Two key aspects considered in mechanistic investigations are the following the first is the mechanism of the dehydration of methanol to DME. It has been a matter of discussion whether surface methoxy species formed from methanol at acidic bridging OH groups act as reactive intermediates in this conversion. The second is the initial C—C bond formation from the Ci reactants. More than 20 possible mechanistic proposals have been reported for the first C-C bond formation in the MTO process. Some of these are based on roles of surface-bound alkoxy species, oxonium ylides, carbenes, carbocations, or free radicals as intermediates (210). 

Carbene structure, of thiazolium salts in basic medium, 31.34 Carbocation, in thiazolium salts, 32 Carbocyanines. see Trimethine thiazolo-cyanines... 

Carbocations, Carbanions, Free Radicals, Carbenes, and Nitrenes... 

CARBOCATIONS, CARBANIONS, FREE RADICALS, CARBENES, AND NITRENES... 

In this chapter, we will consider examples of RIs characterized by a hypervalent or valency-deficient carbon, such as carbocations, carbenes, carbanions, and carbon radicals. In the first part, we will consider examples that take advantage of stabilization and persistence to determine their structures by single crystal X-ray diffraction. In the second part we will describe several examples of transient reactive intermediates in crystals. ... 

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