"Organic Syntheses"

Organometallic reagents contain a carbon atom bonded to a metal. The most commonly used metals in these reagents are lithium (organolithium reagents), copper (organocuprates), and magnesium (Grignard reagents).¹
Magnesium is a very electropositive metal, making the C-Mg bond very polar and very reactive. The following reaction (found in Organic Syntheses) describes the synthesis of 3,5-bis(trifluoromethyl)acetophenone from 3,5-bis(trifluoromethyl)bromobenzene. During this reaction, (i-PrMgCl) forms a Grignard reagent. The Grignard reagent is formed when the starting material is introduced to a magnesium atom, which is bonded to chlorine. The magnesium is then inserted into the C-Br bond, and the chlorine atom replaces the bromine. An intermediate is now formed.  The addition of acetic anhydride forms a ketone, 3,5-bis(trifluoromethyl)acetophenone, as the final product. As a result a new C-C bond has been formed between the benzene ring and the carbon atom which is bonded to the oxygen. The IUPAC name for this compound is (1-[3,5-Bis(trifluoromethyl)phenyl]-ethanone). The following is nearly an identical scheme from the report, except this scheme shows the intermediate to still contain the bromine atom and not the chlorine.

Synthesis of 3,5-bis(trifluoromethyl)acetophenone

¹Smith, J. Organic Chemistry. 2^nd ed.; McGraw-Hill, 2008, pp 739.

http://orgsyn.org/orgsyn/pdfs/v82p0115.pdf

www.google.com/images