3-ethyl-3-pentyl cation

Electrostatic potential map for 3-ethyl-3-pentyl cation shows most positively-charged regions (in blue) and less positively-charged regions (in red). 

The following example illustrates this point. We shall see (Sec. 16.5) that the neopcntyl cation is particularly prone to rearrange to the more stable ten-pentyl cation. Neopentyl bromide reacts (slowly) with ethoxide ion by an 8 2 mechanism to yield neopentyl ethyl ether it reacts (slowly) with ethyl alcohol by an SnI reaction to yield almost entirely rearranged products. 

Fig. 1. Important types of cations in ionic liquids. R and R" are lineal chains ethyl, propyl, butyl, pentyl, hexyl.

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