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The Grignard reagent is rarely isolated It is formed in solution and used immediately in the desired reaction. The alkylmetal bond is highly polar, with the partial negative charge on the C atom, which makes the C atom highly nucIeophilic The Grignard reagent ((R MgJ3r) ) can attack a carbonyl group in an aldehyde or ketone as follows:
Addition of dilute aqueous acid solution to the metal alkoxide furnishes the alcohol. The important synthetic consequence of this procedure is that we have prepared a product with more carbon atoms than present in the starting material. A simple starting material can be transformed into a more complex molecule.
a. What is the product of the reaction between methanal and the Grignard reagent formed from 1-bromobutane after the addition of dilute acid?
b. By using a Grignard reagent, devise a synthesis for hexan-2-ol
c. By using a Grignard reagent, devise a synthesis for 2-methylhexan-2-ol. d. Grignard reagents can also be formed with aryl halides, such as chlorobenzene. What would be the product of the reaction between the Grignard reagent of chlorobenzene and propanone? Can you think of an alternative synthesis of this product, again using a Grignard reagent?
e. The basicity of the C atom bound to the magnesium in the Grignard reagent can be used to make Grignard reagents of terminal
f. By using a Grignard reagent, suggest a synthesis for hept-2-yn-1-oi
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