Carboxylic Acids and their Derivatives 2 Question 50
50. Give reasons for :
“Carbon-oxygen bond lengths in formic acid are $1.23 \AA$ and $1.36 \AA$ and both the carbon-oxygen bonds in sodium formate have the same value, i.e. $1.27 \AA$.”
$(1988,2 \mathrm{M})$
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Solution:
- Both formic acid and sodium formate exhibit the phenomenon of resonance as :
In formic acid, the extent of delocalisation is less compared to sodium formate because of charge separation in the former case. Due to this reason, the bond length between carbon and $s p^{3}$ oxygen in formic acid is slightly greater than the same between carbon and $s p^{2}$ oxygen. In formate ion, there is no separation of charge and both the resonance structures are equivalent giving equal bond length of both carbon oxygen bonds.
