Chameleon species

The particular substitution pattern of lithium carbenoids, the fact that both an electropositive metal and an electronegative substituent X are bound to the same carbon atom, causes the ambiphilic character of this species. The chameleon-like reactivity becomes evident from the resonance formulas of the carbenoid lb (equation 1) Whereas the carbanionic character is expressed by the resonance formula la, the electrophilic character is represented by Ic. In an analogous way, the reactivity of vinylidene carbenoids 2b is expressed by the mesomeric structures 2a and 2c. 

Ogliaro, F., De Visser, S.P., Groves, J.T., and Shaik, S. (2001) Chameleon states. Fligh-valent metal-oxo species of cytochrome P450 and its ruthenium analogue, Angew. Chem., Intern. Ed. 40, 2874-2878. 

Suppose you owned a collection of very extraordinary chameleons that were able to change colors instantaneously from white to black or black to white every 1 s. If you took a picture of them with a shutter speed of 10 s, each of the little critters would appear to be gray. But if you decreased the exposure time to 0.01 s, the photograph would show black ones and white ones in roughly equal numbers but no gray ones Thus, to capture the individual colors, your exposure time must be significantly shorter than the lifetimes of the species, in this case the 1-s lifetime of each colored form. 

Chameleon states High-valent metal-oxo species of cytochrome P450 and its ruthenium analogue. Angew. Chem. Int. Ed. 40, 2874-2878. 

Figure 5.34 "Stereoelectronic chameleon" the two faces of the OMe group. Methoxy serves as a donor in cationic and radical reactions, but behaves as an acceptor towards anionic species.

Aggregation behavior has also been reported for a number of lizard species (for review see Mason 1992). During the breeding season male chameleons (Chameleo chameleo) aggregate but still appear to maintain territories (Ogilvie 1966). These territories may be maintained by chemical cues rubbed onto the substrate from a temporal pouch. These glands secrete an odoriferous material. 

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