Negative charge delocalization

The dinitramide ion is stable in both acidic and basic solutions between pH 1-15 at room temperature but is slowly decomposed in the presence of strong concentrated acid. In contrast to alkyl V,V-dinitramines (Section 6.11.2) where the central nitrogen atom is highly electron deficient, the dinitramide anion has its negative charge delocalized over both nitrogen and oxygen atoms with the consequence that the N-N bonds are less susceptible to rupture. However, the dinitramide anion is not as stable as the nitrate anion ammonium dinitramide melts at 92 °C and decomposition starts at 130 °C. 

Negative charge delocalized in the 5-carbon ring of cyclopentadiene (see cyclopentadiene below)... 

An X-ray structural analysis of bis[4-methoxyphenyl] tellurium 4-methylbenzenesulfon-imide showed that the S —N bond in this trigonal pyramidal molecule has considerable double bond character with the negative charge delocalized over the sulfonyl oxygen atoms1. 

The following reaction shows the SN2 displacement of tosylate ion ( OTs) from (.V)-2-butyl tosylate with inversion of configuration. The tosylate ion is a particularly stable anion, with its negative charge delocalized over three oxygen atoms. 

Use resonance forms to show that the dipolar sigma complex shown in the sulfonation of benzene has its positive charge delocalized over three carbon atoms and its negative charge delocalized over three oxygen atoms. 

Stability of carboxylate ions. Carboxylic acids are more acidic than alcohols because carboxylate ions are more stable than alkoxide ions. A carboxylate ion has its negative charge delocalized over two oxygen atoms, compared with only one oxygen atom bearing the negative charge in an alkoxide ion. 

Exceptionally we have drawn the enol ate of diethyl malonate as a carbanion. This is not generally recommended but you will see it and in this case, with the negative charge delocalized over the two ester groups, it is relatively harmless. 

Resonance forms of phenoxide anion show the negative charge delocalized onto the ring only at carbons 2, 4, and 6 ... 

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