Protonation of Grignard reagents to give alkanes

by James

Description:  Treatment of Grignard reagents with acid leads to alkanes. Alternatively,  use of deuterated acids leads to the resulting deuterated compounds.

Notes: X here is a halide (Cl, Br or I). Note that deuterium (D) is a heavy isotope of hydrogen which behaves in a chemically identical fashion.


Notes: Since Grignards are such strong bases, even weak acids like water or alcohols work great. Example 4 shows an example of using this reaction to introduce deuterium into a molecule (deuterium is just the heavy isotope of hydrogen).

Mechanism:  Addition of acid (in this case just water) leads to protonation of the carbon (Step 1, arrows A and B).

Notes: Instead of water, any reasonably acidic species could have been used here, such as an alcohol, carboxylic acid, acid, etc.


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