Electrostatic potential map for

Electrostatic potential map for lithium hydride shows negatively-charged regions (in red) and positively-charged regions (in blue). 

Next, examine electrostatic potential maps for the same set of compounds. Focus your attention on the value of the potential around hydrogen. For which molecule is it most positive For which is it most negative Is there a correlation between the value of the potential and the difference in electronegativities Plot charge on hydrogen (vertical axis) vs. difference in electronegativities (horizontal axis). Is there a correlation ... 

Draw Lewis structures for allyl cation. Where is the positive charge Examine atomic charges as well as the electrostatic potential map for localized and delocalized forms of allyl cation. Which carbon (s) carries the charge in each ... 

Compare electrostatic potential maps for planar and pyramidal forms of 2-methyl-2-propyl anion. For which is the negative charge more delocalized Is this the lower-energy structure For this case, does charge delocalization lead to stabilization Explain. 

Display electrostatic potential maps for both bisected and perpendicular conformers of cyclopropylcarbinyl cation. For which is the charge more delocalized Is the more delocalized cation also the lower-energy cation ... 

Examine electrostatic potential maps for free hydronium and for hydronium complexed to three and nine water molecules hydronium+3 water and hydronium+9 water, respectively). What happens to the positive charge as more and more water molecules are involved Rationalize your result. 

Compare atomic charges and electrostatic potential maps for imidazole NH protonated and imidazole Nprotonated. In which ion is the positive charge more delocalized Compare carbon-nitrogen bond distances in each ion to those in imidazole as a standard. Are these distances consistent with the bonding patterns shown above for each ion Draw whatever Lewis structures are needed to describe each ion s geometry and charge distribution. 

Next, display electrostatic potential maps for acetUi chloroacetate, trichloroacetate, 2-chlorohutyrate a 4-chlorobutyrate anions. Compare potentials at the positi between the two oxygens. Classify the anions as havi large, intermediate or small charge in this region. 

Display electrostatic potential maps for water, ethanol, formic acid and propanoic acid, and examine the value of the electrostatic potential at the most electron-poor site. What causes a larger change in electrostatic potential, switching the alkyl group for H, or changing the structure of the acidic functional group ... 

Nucleophilic atoms can also be identified by inspection of electrostatic potential maps. Reactive sites appeal as negative electrostatic potentials. Examine electrostatic potential maps for trimethylamine, methyl fluoride, and phenol. Identify the most nucleophilic atom in each molecule. Are these the same as you identified above using Lewis structures Are all sides of the nucleophilic atoms equally electron rich, or only particular regions ... 

Nucleophiles can also act as acids and bases, and this behavior substantially alters their nucleophilicity. At pH 5, trimethylamine exists mainly as its conjugate acid, trimethylammonium cation. First draw a Lewis structure, and then examine the electrostatic potential for trimethylammonium ion. On the basis of the map, which is the better nucleophile, the cation or the corresponding neutral amine At pH 12, phenol exists mainly as its conjugate base, phenoxide anion. First draw a Lewis structure (or series of Lewis structures), and then examine the electrostatic potential map for phenoxide anion. Which is the better nucleophile, phenoxide or phenol ... 

What other factors might be responsible for difference in activation energies Compare atomic charges anc electrostatic potential maps for the Sn2 transition states Does the increase in steric crowding lead to enhanced o diminished charge delocalization Explain. How, if at all would this be expected to affect the energy barrier Why ... 

Display and examine electrostatic potential maps for ethyl cation, 2-propyl cation and 2-methyl-2-propyl cation. Which cation shows the greatest localization of positive charge If you find that the methyl groups delocalize the positive charge, where does the charge go Write resonance contributors for the three cations to rationalize your conclusion. (Note You may need to draw resonance contributors that contain a CC double bond and are missing a CH bond see also Chapter 7, Problem 8.)... 

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