Why do we need anhydrous ether to form a grignard reagent?

Answer 1

Because water is the natural enemy of the Grignard reagent.

Ether solvents are carefully dried over and distilled from alkali metals; glassware is dried under vacuum over a soft bunsen flame (a heady mix with ethereal solvents!). Often the reaction is conducted under an atmosphere of dry dinitrogen or argon. These precautions are taken when performing Grignard and organolithium chemistry.

Water is the Grignard reagent's natural enemy, which is why these precautions are necessary:

#R-MgCl + H_2O rarr R-H + MgCl(OH)#
This reaction is rapid and irreversible, and water is of such low molecular weight that a little goes a long way to reduce yield. Sometimes we can exploit this reactivity. Suppose we wanted to add a deuterium label to an alkyl chain for some other experiment; i.e. you need #R-D#, where #D# #=# #""^2H#. The simplest way of making this would be to prepare the Grignard from the (cheap!) alkyl halide, and quenching it with with heavy water, #D_2O#, i.e.:
#R-MgX + D_2O rarr R-D + MgX(OD)#
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Answer 2

Anhydrous ether is used to form a Grignard reagent because water reacts with the Grignard reagent, leading to its decomposition and the formation of undesired byproducts. The anhydrous environment prevents water from interfering with the reaction.

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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.

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.

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.

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.

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