Problem 103
Question
Which of the following products is formed when benzaldehyde is treated with \(\mathrm{CH}_{3} \mathrm{MgBr}\) and the addition product so obtained is subjected to acid hydrolysis? (a) a primary alcohol (b) phenol (c) secondary alcohol (d) tert-Butyl alcohol
Step-by-Step Solution
Verified Answer
The product formed is a secondary alcohol.
1Step 1: Identify the Reactants and Reaction Type
The reactants in this chemical reaction are benzaldehyde (C6H5CHO) and methylmagnesium bromide ( \(\mathrm{CH}_3\mathrm{MgBr}\)) which is a Grignard reagent. This signifies that the reaction is a Grignard reaction, which is used for forming carbon-carbon bonds.
2Step 2: Grignard Reagent Attack on Benzaldehyde
The Grignard reagent, \(\mathrm{CH}_3\mathrm{MgBr}\), acts as a nucleophile and attacks the electrophilic carbon in the carbonyl group \( (C=O) \) of benzaldehyde. This forms a tetrahedral alkoxide intermediate.
3Step 3: Formation of the Alkoxide Intermediate
In this step, the \(\mathrm{CH}_3\) group from \(\mathrm{CH}_3\mathrm{MgBr}\) adds to the carbonyl carbon of benzaldehyde, displacing the \(\mathrm{O}^{-}\) in the alkoxide intermediate structure, leading to the formation of \(\mathrm{C}_6\mathrm{H}_5\mathrm{CH}( \mathrm{O}^{-})\mathrm{CH}_3\).
4Step 4: Acid Hydrolysis of the Alkoxide
The alkoxide intermediate is subjected to acid hydrolysis by adding water in the presence of an acid (commonly \(\mathrm{HCl}\)). This step involves protonation of the oxygen leading to the formation of an alcohol. During this process, the alkoxide group \(\mathrm{O}^{-}\) is converted to an alcohol group \(\mathrm{OH}\).
5Step 5: Examine the Product Formed
After hydrolysis, the compound formed is \(\mathrm{C}_6\mathrm{H}_5\mathrm{CH}(\mathrm{OH})\mathrm{CH}_3\), which is a secondary alcohol. This indicates that the product formed is a secondary alcohol, as it contains a carbon atom bonded to an \(\mathrm{OH}\) group and two other carbon-containing groups.
Key Concepts
Understanding BenzaldehydeRole of Methylmagnesium Bromide in ReactionsAcid Hydrolysis ExplainedFormation of Secondary Alcohols
Understanding Benzaldehyde
Benzaldehyde is an organic compound commonly used in chemical reactions. It is represented by the formula \( \text{C}_6\text{H}_5\text{CHO} \). This molecule belongs to the aldehyde family, characterized by the presence of a carbonyl group \( \text{(C=O)} \) bonded to a hydrogen atom. In benzaldehyde, the carbonyl group is directly connected to a benzene ring.
Benzaldehyde is an aromatic aldehyde, making it a common reagent in both laboratory and industrial chemical synthesis. Its unique structure allows it to participate in various chemical reactions, such as the Grignard reaction, which is the focus of our exercise.
When benzaldehyde reacts with a Grignard reagent, it enables the formation of a new carbon-carbon bond, an essential transformation in organic chemistry that can lead to the production of alcohols, among other compounds.
Benzaldehyde is an aromatic aldehyde, making it a common reagent in both laboratory and industrial chemical synthesis. Its unique structure allows it to participate in various chemical reactions, such as the Grignard reaction, which is the focus of our exercise.
When benzaldehyde reacts with a Grignard reagent, it enables the formation of a new carbon-carbon bond, an essential transformation in organic chemistry that can lead to the production of alcohols, among other compounds.
- Consists of a carbonyl group attached to a benzene ring
- Utilized in creating new C-C bonds through Grignard reactions
Role of Methylmagnesium Bromide in Reactions
Methylmagnesium bromide (\( \text{CH}_3\text{MgBr} \)) is a prominent example of a Grignard reagent. These are typically composed of an organic alkyl group connected to a magnesium halide, and they play a crucial role as nucleophiles in organic synthesis.
This Grignard reagent, \( \text{CH}_3\text{MgBr} \), has a methyl group that carries a partial negative charge. This means it is super reactive and ready to attack positive centers, like the carbon in a carbonyl group, such as the one found in benzaldehyde.
Because of its reactivity, methylmagnesium bromide effectively initiates a nucleophilic addition reaction with benzaldehyde, breaking open the \( \text{C=O} \) bond and forming a more complex structure called an alkoxide intermediate. Grignard reagents are vital for constructing more intricate organic molecules from simpler ones.
This Grignard reagent, \( \text{CH}_3\text{MgBr} \), has a methyl group that carries a partial negative charge. This means it is super reactive and ready to attack positive centers, like the carbon in a carbonyl group, such as the one found in benzaldehyde.
Because of its reactivity, methylmagnesium bromide effectively initiates a nucleophilic addition reaction with benzaldehyde, breaking open the \( \text{C=O} \) bond and forming a more complex structure called an alkoxide intermediate. Grignard reagents are vital for constructing more intricate organic molecules from simpler ones.
- Grignard reagent with \( \text{CH}_3 \) as the functional group
- Acts as a nucleophile in reactions
- Facilitates the formation of alkoxide intermediates
Acid Hydrolysis Explained
Acid hydrolysis is a significant step in many organic reactions, including the conversion of alkoxides to alcohols. The reaction requires an aqueous acidic solution, commonly \( \text{HCl} \), to proceed.
In the context of the Grignard reaction, once methylmagnesium bromide reacts with benzaldehyde, an alkoxide ion is produced. This intermediate possesses a negatively charged oxygen atom. Upon acid hydrolysis, this negative charge attracts protons (hydrogen ions) from the surrounding acidic solution.
Consequently, the oxygen becomes protonated, converting the alkoxide ion into an alcohol group. This transformation results in the formation of an alcohol from the original alkoxide intermediate. Acid hydrolysis not only stabilizes the compound but also is crucial for isolating the alcohol in its final form.
In the context of the Grignard reaction, once methylmagnesium bromide reacts with benzaldehyde, an alkoxide ion is produced. This intermediate possesses a negatively charged oxygen atom. Upon acid hydrolysis, this negative charge attracts protons (hydrogen ions) from the surrounding acidic solution.
Consequently, the oxygen becomes protonated, converting the alkoxide ion into an alcohol group. This transformation results in the formation of an alcohol from the original alkoxide intermediate. Acid hydrolysis not only stabilizes the compound but also is crucial for isolating the alcohol in its final form.
- Converts alkoxides to alcohols through protonation
- Requires an acidic environment, usually \( \text{HCl} \)
- Key step in finalizing the alcohol product from Grignard reactions
Formation of Secondary Alcohols
A secondary alcohol is defined by having an -OH group connected to a carbon atom, which in turn is attached to two other carbon atoms. The product of the reaction between benzaldehyde and methylmagnesium bromide, followed by acid hydrolysis, is precisely this type of alcohol.
When benzaldehyde is treated with \( \text{CH}_3\text{MgBr} \), the resulting intermediate upon hydrolysis forms \( \text{C}_6\text{H}_5\text{CH(OH)CH}_3 \). Here, the central carbon, to which the hydroxyl \( \text{(OH)} \) group is attached, is connected to both a benzene ring and a methyl group, categorizing the product as a secondary alcohol.
Secondary alcohols are significant due to their presence in various industrial applications and their potential to be further transformed into a variety of other functional groups. Recognizing this alcohol formation is critical in understanding complex organic synthesis techniques and the transformations they enable.
When benzaldehyde is treated with \( \text{CH}_3\text{MgBr} \), the resulting intermediate upon hydrolysis forms \( \text{C}_6\text{H}_5\text{CH(OH)CH}_3 \). Here, the central carbon, to which the hydroxyl \( \text{(OH)} \) group is attached, is connected to both a benzene ring and a methyl group, categorizing the product as a secondary alcohol.
Secondary alcohols are significant due to their presence in various industrial applications and their potential to be further transformed into a variety of other functional groups. Recognizing this alcohol formation is critical in understanding complex organic synthesis techniques and the transformations they enable.
- Characterized by an -OH group linked to a central carbon with two other carbon attachments
- Product from Grignard reaction and subsequent acid hydrolysis
- Important intermediates and products in organic chemistry
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