# Grignard reaction product involving a ketone

• chris_0101
In summary, the conversation discusses the Grignard reaction, specifically the conversion of a ketone to an alcohol. The individual attempted the reaction and produced an alcohol with two ethyl groups, a phenyl group, and an OH group attached to the central carbon. However, the correct answer showed an alkene instead of an alcohol. The individual is seeking clarification on why this occurred and when the extra step of deprotonation takes place. They come to the conclusion that the presence of sulfuric acid led to dehydration, resulting in the production of an alkene.
chris_0101

## Homework Statement

Basically I have to show the product of this reaction:

## Homework Equations

Grignard reaction mechanism:
The conversion of a ketone to an alcohol

## The Attempt at a Solution

My attempt of this reaction produces an alcohol with two ethyl groups attached to the central carbon as well as a phenyl group and an OH group attached to the central carbon, so the IUPAC name would be 3-phenyl-3-pentanol.

However, the answer is:

Can someone please explain why the reaction produced an alkene instead of an alcohol. I do not know why this occurred and need some clarification. Also, when does this extra step occur.

Thanks.

Think a little about step 3.

What occurs is step 3? I know that the H2SO4 is deprotonated to become HSO4. This produces the alcohol part of the compound, which is what I got. I am going to assume that deprotonation of HSO4 occurs, thus producing water and the alkene as shown in the answer. Is this right?

Look up "dehydration". Sulfuric acid is a powerful dessicant.

The Grignard reaction, also known as the Grignard reagent synthesis, is a chemical reaction involving the addition of an organomagnesium halide (Grignard reagent) to a ketone or aldehyde, resulting in the formation of a tertiary alcohol. However, it is important to note that the reaction can also produce an alkene as a byproduct under certain conditions.

The most common cause of an alkene byproduct in a Grignard reaction is the presence of excess Grignard reagent or prolonged reaction times. This can lead to the over-reduction of the ketone, resulting in the formation of an alkene instead of an alcohol.

In order to prevent the formation of an alkene byproduct, it is important to carefully control the amount of Grignard reagent used and the reaction time. Additionally, certain ketones may be more prone to over-reduction than others, so it is important to choose the appropriate ketone for the reaction.

In the case of your specific reaction, it is possible that the excess Grignard reagent or prolonged reaction time led to the formation of the alkene byproduct. It is important to carefully analyze the conditions of the reaction and make adjustments as needed in order to achieve the desired product.

## 1. What is a Grignard reaction?

A Grignard reaction is a type of chemical reaction in which a Grignard reagent (an organometallic compound) reacts with a carbonyl compound (such as a ketone) to form a new carbon-carbon bond.

## 2. How does a Grignard reaction involving a ketone work?

In a Grignard reaction involving a ketone, the Grignard reagent (typically an alkyl or aryl magnesium halide) acts as a nucleophile and attacks the carbon atom of the ketone's carbonyl group. This results in the formation of a new carbon-carbon bond and ultimately a new product.

## 3. What is the product of a Grignard reaction involving a ketone?

The product of a Grignard reaction involving a ketone is usually an alcohol. This is because the Grignard reagent adds to the carbonyl group of the ketone, resulting in the formation of a new carbon-carbon bond and a new hydroxyl group.

## 4. What are some uses of Grignard reaction products involving ketones?

Grignard reaction products involving ketones have a variety of uses in organic synthesis. They can be used to create more complex molecules, such as amino acids, through further reactions. They can also be used to form carbon-carbon bonds in the synthesis of pharmaceuticals, natural products, and other organic compounds.

## 5. Are there any limitations or drawbacks to using Grignard reactions involving ketones?

While Grignard reactions involving ketones can be a powerful tool in organic synthesis, there are some limitations and drawbacks to consider. For example, the reaction can be sensitive to moisture and air, and it may not work well with certain functional groups. It is also important to carefully control the reaction conditions to avoid unwanted side reactions.

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