Using a Premade Grignard Reagent To Synthesize Tertiary Alcohols in a Convenient Investigative Organic Laboratory Experiment

Abstract

A commercially available Grignard reagent (3.0 M solution of phenyl magnesium bromide in ether) was used in a convenient Grignard synthesis in a second-year organic chemistry laboratory without any of the typical failures associated with the Grignard reaction. The reaction setup used oven-dried glassware and no extraordinary measures were taken to keep the reaction under inert atmosphere. The Grignard reagent was dispensed into students' reaction vessels by the instructor. The students then slowly added a solution of a ketone. The yields of the resulting tertiary alcohols were good to excellent. Additional activities included determination of recrystallization solvent and characterization of their purified products using TLC, mp, IR, and NMR spectroscopy. This lab was used as the student's first exposure to a synthesis-type experiment and occurred early in the second-semester organic course corresponding to the lecture material concerning Grignard reactions.

Synthesis of Arylpropiolic Acids via Carboxylation of Arylacetylenic Grignard Reagents

“…To the best of our knowledge, no organic chemistry laboratory experiment has been developed that demonstrates the use of Grignard reagents both as a base and as a nucleophile in the synthesis of organic compounds. In fact, a brief survey of the new Grignard reaction laboratory experiments that have been developed recently and published in this journal only show the use of Grignard reagents as nucleophiles. − …”

Investigating a Chemoselective Grignard Reaction in an Undergraduate Discovery Lab To Predict Reactivity and Final Products

“…In the presence of two different aryl halogens, the more reactive halogen will react with magnesium selectively. 7−9 In this case, since the C aryl −Br bond is weaker and more labile than the C aryl −Cl bond, the organomagnesium bromide (2) forms selectively over the organomagnesium chloride (4). Second, the students reacted the Grignard reagent with dimethylformamide (DMF) to synthesize 4-chlorobenzaldeScheme 1.…”

“…In teaching laboratories, students often prepare the Grignard reagent of bromobenzene and react it with carbon dioxide or benzophenone to yield benzoic acid or triphenylmethanol, respectively . Over the years, the emphasis on discovery-based pedagogy has resulted in the design of many new Grignard experiments. − However, until very recently, no attention has been given to experiments where students prepare a Grignard reagent selectively from the more reactive halogen in a dihalogenated species . Furthermore, most Grignard exercises result in the formation of highly predictable products such as tertiary alcohols.…”