The addition of Grignard reagents to aldehydes and ketones is known as the Grignard reaction. Formaldehyde gives primary alcohols; other aldehydes give secondary alcohols; and ketones give tertiary alcohols. The reaction is of very broad scope, and hundreds of alcohols have been prepared in this manner. R may be alkyl or aryl. In many cases the hydrolysis step is carried out with dilute HCl or H2SO4, but this cannot be done for tertiary alcohols in which at least one alkyl group is alkyl because such alcohols are easily dehydrated under acidic conditios. In such cases (and often for other alcohols as well) an aqueous solution of ammonium chloride is used instead of a strong acid. Other organometallic compounds can also be used, but in general only of active metals; e.g., alkylmercurys do not react. In practice, the only organometallica compounds used to any extent, besides Grignard reagents, are alkyl- and aryllithiums, and alkylzink reagents where enantioselective addition is desired. For the addition of aceylenic groups, sodium may be the metal used: RC%CNa, while vinylic alanes are the reagents of choice for the addition of vinylic groups. Many methods have been reported for the addition of allylic groups. Among these are the use of allyltrialkyltin compounds (in the presence of BF3-etherate), allyltrialkylsilanes (in the presence of a Lewis acid), as well as other allylic metal compounds. (March, 1992)
Stereoselectivity:
March, J. Advanced Organic Chemistry, 4th ed., reaction 6-29
Introduction to the Grignard reaction
A more detailed introduction to the Grignard reaction
The Nobel Prize in Chemistry 1912
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