1.4- Pentadiene, electrostatic potential

Electrostatic potential map for 1,3-pentadiene shows negatively-charged regions (in red) and positively-charged regions (in blue). 

Obtain the energies, carbon-carbon bond distances and electrostatic potential maps for 3-ethyUdene-l,3-pentadiene and 1,3,5-heptatriene. Which data are consistent with the usual resonance argument and which are not ... 

Figure 14.3 Electrostatic potential maps of 1,3-butadiene (conjugated) and 1,4-pentadiene (nonconjugated) show additional electron density (red) in the central C—C bond of 1,3-butadiene, corresponding to partial double-bond character.

Pentadiene is an isolated diene. The electron density in each 7t bond of an isolated diene is localized hei wecn two carbon atoms. In 1,3-butadiene, however, the electron density of both n bonds is delocalized over the four atoms of the diene. Electrostatic potential maps in Figure 16.1 clearly indicate the difference between these localized and delocalized Jt bonds. 

Draw all of the contributing resonance structures and the resonance hybrid for the carbocation that would result from ionization of bromine from 5-bromo-1,3-pentadiene. Open the computer molecular model at the book s website depicting a map of electrostatic potential for the pentadienyl carbocation. Based on the model, which is the most important contributing resonance structure for this cation Is this consistent with what you would have predicted based on your knowledge of relative carbocation stabilities ... 

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