Organic Chemistry : Using Grignard Reagents

Study concepts, example questions & explanations for Organic Chemistry

varsity tutors app store varsity tutors android store

Example Questions

Example Question #3 : Organic Reducing Agents

What is the product of the reaction between magnesium and any alkyl halide, in anhydrous ether?

Possible Answers:

An organolithium

An alcohol

An aldehyde

An alkane

A Grignard reagent

Correct answer:

A Grignard reagent

Explanation:

The reaction between magnesium and an alkyl halide in anhydrous ether results in a Grignard reagent.

An organolithium would result from the same process, but the magnesium would need to be replaced by two equivalents of lithium. Alcohols are products of reactions between a Grignard reagent and a carbonyl. 

Example Question #1 : Using Grignard Reagents

What type of reaction would ensue if the ketone compound shown was introduced to  (a Grignard reagent in water).

Possible Answers:

Grignard addition reaction

Oxidation-reduction reaction

No reaction

Correct answer:

No reaction

Explanation:

Grignard reagents are known for their ability to readily attack carbonyls at the point of their carbons. However, Grignard reagents do not work in the presence of protic solvents. Rather than reacting with the desired molecule, the Grignard is so unstable that it will readily accept a proton from a protic solvent. The Grignard then becomes inert and no reaction ensues with the desired molecule.

Example Question #2 : Using Grignard Reagents

3-bromopropene was treated with 

What is the final major product?

Possible Answers:

Cyclohexene

6-bromohex-4-ene

Hexene

Hexanol

Correct answer:

Hexene

Explanation:

Any time we have a Grignard reagent and a primary haloalkane, we will see a substitution reaction, identical to an  reaction. In this case, the Grignard can easily attack the haloalkane as the bromine leaves to create hexene.

Example Question #6 : Organic Reducing Agents

Img 0711

What reactant(s) is/are needed to drive this reaction?

Possible Answers:

Correct answer:

Explanation:

The carbons on the epoxide compound experience a slightly positive charge. As a result, a Gringard reagent can easily attack the less substituted side of the epoxide to break the ring and to form a six membered carbon chain.  is used to protonate the negatively charged oxygen atom.

Img 0712

Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: