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Why does a Grignard reaction not react to water?

Answer 1

Are you sure the premises of your question are correct?

#R-MgX + H_2O rarr R-H + Mg(OH)X#

A Grignard will react rapidly and irreversibly with water as shown to give the magnesium salt and parent alkane. Sometimes this reaction is used to label alkanes with deuterium (#""^2H#) or tritium (#""^3H#) labels:

#RCH_2MgX + D_2O rarr RCH_2D + Mg(OH)X#

#D=""^2H#

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Answer 2

Zoe Alexander

A Grignard reaction does not react with water because the Grignard reagent (organomagnesium compound) is highly reactive towards protic functional groups such as water. When exposed to water, the Grignard reagent undergoes a reaction called protonolysis, where the magnesium alkoxide and the corresponding hydrocarbon are formed. This reaction competes with the desired Grignard reaction, leading to a loss of the desired product and complicating the reaction mixture. Therefore, it is essential to ensure that the reaction environment is anhydrous to prevent interference from water.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.