Grignard reagents are a class of organomagnesium compounds formed by reacting magnesium metal with organic halides. They are highly reactive and are typically represented as R-Mg-X, where R is an organic group, Mg is magnesium, and X is a halogen (like chlorine, bromine, or iodine). These reagents are valuable in organic chemistry for forming carbon-carbon bonds. When Grignard reagents react with water or alcohols, they can decompose, so they must be handled in dry conditions. They are commonly used in various reactions, such as the synthesis of alcohols, by reacting with carbonyl compounds like aldehydes and ketones.