Phenyl diazonium ion

Aniline, PI1NH2, reacts with sodium nitrite, NaN02, and aqueous acid to give phenyl diazonium ion, PhN2. This ion can be isolated, but it also reacts readily with certain nucleophiles to give substitution products, e.g. 

Examine the geometries (in particular, CN bond distances) of methyl diazonium, tert-butyl diazonium and phenyl diazonium ions. Which, if any, of these ions is best described as a weak complex between a cation and N2 Which is furthest away from this description Is your result consistent with the observed reactivity patterns Explain. 

Draw all of the resonance contributors needed to describe each ion. Why is phenyl diazonium ion so much more stable than either of the alkyl diazonium ions ... 

Phenyl diazonium ion, PhN2, reacts with nucleophiles in several ways. Water displaces N2 to give phenol, while dimethylamine adds to the terminal N. 

Examine the structure, atomic charges and electrostatic potential map of phenyl diazonium ion. Which atom(s) appears to carry most of the positive charge Is the electron distribution around this atom(s) uniform, or are some regions more electron rich and others more electron poor Draw appropriate resonance contributors. 

Next, consider the reactivity of phenyl diazonium ion. Are either of the reactions shown above consistent with nucleophilic attack at the ion s most electron-poor site Examine the lowest-unoccupied molecular orbital (LUMO) of phenyl diazonium ion. What electrophilic sites are identified by the LUMO Are either of the reactions shown above consistent with an orbital-controlled addition ... 

Experimental observations indicate that electron-rich aromatic nucleophiles, such as phenoxide, add to phenyl diazonium ion in the same way as dimethylamine. 

What controls selectivity Draw the products that would result from O addition and from ortho C addition (as well as "para C addition shown above) of phenoxide anion and phenyl diazonium ion. Compare the energies of these products (para C product, ortho C product and O product). Which is most stable Is this the observed product Can thermodynamics explain the outcome ... 

Electrostatic potential map of phenyl diazonium ion. shows most positively-charged regions (in blue) and less positively-charged regions (in red). 

LUMO of phenyl diazonium ion reveals the most electrophilic sites. 

Write out the SrnI process for phenyl diazonium ion reacting with iodide anion to produce nitrogen gas and phenyl iodide. Use s.e.t. from iodide anion to start the process. 

The reaction between phenyl diazonium ion and aniline results into the formation of an intermediate ion, which upon loss of a proton yields the coupled product p-aminoazobenzene. 

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