Grignard reaction

The Grignard reaction (ɡʁiɲaʁ) is an organometallic chemical reaction in which carbon alkyl, allyl, vinyl, or aryl magnesium halides (Grignard reagent) are added to the carbonyl groups of either an aldehyde or ketone. This reaction is important for the formation of carbon–carbon bonds. (R2 could also be a hydrogen)Grignard reactions and reagents were discovered by and are named after the French chemist François Auguste Victor Grignard (University of Nancy, France), who published it in 1900 and was awarded the 1912 Nobel Prize in Chemistry for this work. The reaction of an organic halide with magnesium is not a Grignard reaction, but provides a Grignard reagent. Because carbon is more electronegative than magnesium, the carbon attached to magnesium functions as a nucleophile and attacks the electrophilic carbon atom that is present within the polar bond of a carbonyl group. The addition of the Grignard reagent to the carbonyl typically proceeds through a six-membered ring transition state. Based on detection of radical coupling side products, an alternative single electron transfer (SET) mechanism that involves the initial formation of a ketyl radical intermediate has also been proposed. A recent computational study suggests that the operative mechanism (polar vs. radical) is substrate dependent, with the reduction potential of the carbonyl compound serving as a key parameter. Grignard reagents#Reactions of Grignard reagentsThe classical Grignard reaction typically refers only to the reaction between a ketone or aldehyde group and a Grignard reagent to form a primary or tertiary alcohol. While some chemists understand the definition to mean all reactions from electrophilic molecules with Grignard reagents. So, for the modern definition there is some dispute on what defines the Grignard reaction today. March's Advanced Organic Chemistry, a reputable graduate level text, defines it as "The addition of Grignard reagents to aldehydes and ketones...". The IUPAC Goldbook, a similarly reputable text, does not address either side.