Pseudo Unimolecular Reaction





The reactions having molecularity \geq 2 but order of reaction is one are called pseudo unimolecular reactions.

E g.

(i)         CH_3COOC_2H_5 + H_2O \to CH_3COOH + C_2H_5OH \\[3mm] \text{Rate} = k[CH_3COOC_2H_5]

Thus order of reaction is one but molecularity of the reaction is two.

 

(ii)      C_{12}H_{22}O_{11} + H_2O \to C_6H_{12}O_6 + C_6H_{12}O_6 \\[3mm] \text{Rate} = k[C_{12}H_{22}O_{11}]

Thus order of reaction is one but molecularity of reaction is two.

 

(iii)     (CH_3CO)_2O + 2C_2H_5OH \to 2CH_3COOC_2H_5 + H_2O \\[3mm] \text{Rate} = k[(CH_3CO)_2O]

Thus order of reaction is one but molecularity of reaction is three.

Similarly the reactions having molecularity \geq 3 but order of reaction is two are called pseudo bimolecular reactions.



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