Hello there

If I tell you about the formation of Grignard reagent then it is formed by the reaction of magnesium metal with alkyl or alkenyl halides. Generally,Grignard reagents are good nucleophiles which react to the electrophiles such as carbonyl compounds which includes- aldehydes, ketones esters carbon dioxide and also with epoxides.

Coming to the structure then its generic formula is R-Mg-X, here 'X' is a halogen and 'R' is an organic group which is usually an alkyl or aryl.

For more information about the same you can refer the link:

https://school.careers360.com/chemistry/grignard-reagent-topic-pge

I hope it helps you!

Thank you!