The most stable of:
(a) $\ce{(CH3)2C(OH)2}$
(b) $\ce{CH3 C Cl (OH)2}$
(c) $\ce{CH3CN}$
is $\ce{CH3CN}$, because the other two are geminal diols. How can we tell that geminal diols are unstable?
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Sign up to join this communityThe most stable of:
(a) $\ce{(CH3)2C(OH)2}$
(b) $\ce{CH3 C Cl (OH)2}$
(c) $\ce{CH3CN}$
is $\ce{CH3CN}$, because the other two are geminal diols. How can we tell that geminal diols are unstable?
Formation Of Gemdiol
Carbonyl compounds react with water to give gem diols. This reaction is catalysed by acid. The reaction is reversible reaction.
Gem diols are highly unstable compounds hence equilibrium favours the backward direction. The extent to which an aldehyde or ketone is hydrated depends on the stability of gem diol.
Stability of gem diols depend on the following factors:
(i) Steric hindrance by +I group around α-carbon decreases the stability of gem diols. +I group decreases stability of gem diol and hence decreases extent of hydration.
(ii) Stability of gem diols mainly depends on the presence of –I group on α-carbon. More is the –I power of the group more will be stability of gem diols.
(iii) Intramolecular hydrogen bonding increases stability of gem diols. –I groups present on carbon having gem diol group increases strength of hydrogen bond.
More is the strength of hydrogen bond more will be the stability of gem diol.
Overall stability : (CH3)2C(OH)2 < CH3CCl(OH)2 < CH3CN
Geminal diols are unstable due to repulsion between the two oxygens present on the same carbon.If a compound is able to disperse the electron pair of oxygens by phenomenon like hydrogen bonding,resonance,-H effect(hyperconjugation) etc,their stability will increase.