What exactly is this reagent CH3MgCl and what does it do?

grignard (i dont know if i spelled that right)...it attacks the carbonyl carbon ...opens up the double bond (C=O) & forms an alcohol. So now that carbonyl carbon has 1 OH group, 2 carbon chain that it used to have before & 1 (newly added) methyl group from CH3MgCl

Oh okay, I see... but where does the extra CH3 come from?

It starts with 2 and 1 from the reagent...but the other?

Oh okay, I see... but where does the extra CH3 come from?

It starts with 2 and 1 from the reagent...but the other?
well the the carbonyl carbon will have 1 Oxygen atom with double bonds...& the other 2 bonds could be both hydrogen, both carbon chain, or combination of both. Inshort after grignard is complete...you will have 1 new carbon chain that you got from grignard reagent & everything else will be same except that carbonyl is now alcohol