Question

From which of the following tertiary butyl alcohol is obtained by the action of methyl magnesium iodide? (a) \(\mathrm{CO}_{2}\) (b) \(\mathrm{HCHO}\) (c) \(\mathrm{CH}_{3} \mathrm{CHO}\) (d) \(\mathrm{CH}_{3} \mathrm{COCH}_{3}\)

Short answer

Tertiary butyl alcohol is obtained from (d) \(\mathrm{CH}_{3} \mathrm{COCH}_{3}\) with methyl magnesium iodide.

Step-by-step solution

Understanding the Compounds

Identify each compound and understand its structure. - \(\mathrm{CO}_{2}\) is carbon dioxide.- \(\mathrm{HCHO}\) is formaldehyde.- \(\mathrm{CH}_{3}\mathrm{CHO}\) is acetaldehyde.- \(\mathrm{CH}_{3}\mathrm{COCH}_{3}\) is acetone.

Reaction of Methyl Magnesium Iodide

Methyl magnesium iodide (MeMgI) is a Grignard reagent. Grignard reagents react with carbonyl compounds to form alcohols.

Applying Grignard Reagent to Each Compound

- For \(\mathrm{CO}_{2}\): The reaction with methyl magnesium iodide does not produce tertiary butyl alcohol.- For \(\mathrm{HCHO}\): The reaction with methyl magnesium iodide produces ethanol, not tertiary butyl alcohol.- For \(\mathrm{CH}_{3}\mathrm{CHO}\): The reaction with methyl magnesium iodide produces secondary alcohol, not tertiary.- For \(\mathrm{CH}_{3}\mathrm{COCH}_{3}\): The reaction with methyl magnesium iodide produces tertiary butyl alcohol, as the carbon of the carbonyl becomes connected to three methyl groups.

Choosing the Correct Compound

From the above analysis, \(\mathrm{CH}_{3}\mathrm{COCH}_{3}\) (acetone) reacts with methyl magnesium iodide to form tertiary butyl alcohol.

Key concepts

Tertiary Butyl Alcohol

Tertiary butyl alcohol, also known as tert-butanol, is an alcohol classified as tertiary because the hydroxyl group (OH) is attached to a carbon atom that is connected to three other carbon atoms. It is a colorless liquid that can form solid under low temperatures. In the context of Grignard reactions, tertiary butyl alcohol is a product of specific reactions between carbonyl compounds and Grignard reagents.

When tertiary butyl alcohol is formed, particularly in a laboratory setting, it often results from the action of Grignard reagents like methyl magnesium iodide on certain carbonyl compounds, such as acetone. The structure, consisting of a central carbon atom bonded to three methyl groups and one hydroxyl group, illustrates why it is called tertiary: Three carbon connections leaving no room for formulating a simpler structure such as primary or secondary alcohols.

Understanding this structure is crucial for recognizing how different alcohols are classified and synthesized within organic chemistry.

Methyl Magnesium Iodide

Methyl magnesium iodide is a type of Grignard reagent used widely in organic chemistry. This compound is very reactive and appears as a complex with other reagents or solvents during reactions. Its formula is denoted as MeMgI, where 'Me' signifies a methyl group. Grignard reagents like methyl magnesium iodide are used to form carbon-carbon bonds, making them crucial in synthesizing alcohols from carbonyl compounds.

When methyl magnesium iodide encounters carbonyl compounds, such as aldehydes or ketones, it can add a new carbon chain to the central carbon of the compound, ultimately generating alcohol. When it reacts with acetone (a carbonyl compound featuring a double-bonded oxygen), it forms tertiary butyl alcohol. This property is leveraged frequently in organic synthesis to create various alcohols by selectively choosing the carbonyl starting compound.

Students often encounter Grignard reactions during their study of organic chemistry, serving as ideal examples to illustrate the rules governing the behavior of organometallic compounds.

Carbonyl Compounds

Carbonyl compounds are a group of organic compounds that contain a carbon atom double-bonded to an oxygen atom (C=O). This group is characterized by this carbonyl group, which significantly impacts the chemical reactivity of the compounds. They are pivotal participants in several organic reactions, including reactions with Grignard reagents.

In the exercise, we're discussing several carbonyl compounds like formaldehyde, acetaldehyde, and acetone. Each of these interacts differently with methyl magnesium iodide due to the presence of different carbon structures surrounding the carbonyl group. For instance:

• Formaldehyde (
  aHCHO
  a) yields primary alcohols when reacted with Grignard reagents.
• Acetaldehyde (
  aCH_3CHO
  a) produces secondary alcohols.
• Acetone (
  aCH_3COCH_3
  a) forms tertiary alcohols, specifically tertiary butyl alcohol, when methyl magnesium iodide is utilized.

The powerful feature of carbonyl compounds is their ability to form more complex molecules by engaging in such additions and transformations, becoming indispensable building blocks in organic chemistry.

Organic Chemistry Reactions

Organic chemistry involves reactions that are fundamental to creating a diversity of complex organic compounds. Among these, Grignard reactions hold a special place as they facilitate the formation of carbon-carbon bonds, essential for building larger molecules from simpler ones.

In the context of the Grignard reaction explored in the exercise, the interaction between methyl magnesium iodide and carbonyl compounds exemplifies how chemists can construct alcohols with detailed specificity. This is achieved through the mechanism of the Grignard reagent acting as a nucleophile, adding to the electrophilic carbon in the carbonyl group, resulting in new alcohol structures.

The formation path of alcohols using these organic reactions teaches us about the selectivity and versatility of chemical processes, enabling the production of a wide array of substances from simple carbon and oxygen containing starting materials. As students journey through organic chemistry, learning about these reactions equips them with the knowledge to predict product formation and manipulate pathways for desired syntheses.