Question

Write equations showing the oxidation of a primary alcohol and the oxidation of a secondary alcohol to produce an aldehyde and a ketone, respectively. Indicate the structure of each alcohol and of the principal organic products of the oxidations.

Short answer

Solution: 1. Ethanol (CH3CH2OH) is a primary alcohol with the structure: H H | | H - C - C - O - H | | H H 2. Oxidation of ethanol produces acetaldehyde (CH3CHO) with the equation: CH3CH2OH + [O] → CH3CHO + H2O. Acetaldehyde has the structure: H | H - C - C = O | H 3. Isopropanol (CH3CHOHCH3) is a secondary alcohol with the structure: H H | | H - C - C - O - H | | H H | H 4. Oxidation of isopropanol produces acetone (CH3COCH3) with the equation: CH3CHOHCH3 + [O] → CH3COCH3 + H2O. Acetone has the structure: H H | | H - C - C = O | | H H | H

Step-by-step solution

Choose a primary alcohol and indicate its structure

We will use ethanol (CH3CH2OH) as a primary alcohol. Its structure can be represented as follows: H H | | H - C - C - O - H | | H H

Write the equation for the oxidation of the primary alcohol to produce an aldehyde

When ethanol is oxidized, it forms acetaldehyde (CH3CHO). Here's the equation for this oxidation: CH3CH2OH + [O] → CH3CHO + H2O The structure of acetaldehyde is as follows: H | H - C - C = O | H

Choose a secondary alcohol and indicate its structure

We will use isopropanol (CH3CHOHCH3) as a secondary alcohol. Its structure can be represented as follows: H H | | H - C - C - O - H | | H H | H

Write the equation for the oxidation of the secondary alcohol to produce a ketone

When isopropanol is oxidized, it forms acetone (CH3COCH3). Here's the equation for this oxidation: CH3CHOHCH3 + [O] → CH3COCH3 + H2O The structure of acetone is as follows: H H | | H - C - C = O | | H H | H

Key concepts

Primary Alcohol Oxidation

Understanding the oxidation process of primary alcohols to aldehydes involves a step-by-step transformation. Ethanol, a common primary alcohol, is represented as \textsc{H}_3\textsc{CCH}_2\textsc{OH}. During oxidation, an oxidizing agent, symbolized as [O], removes hydrogen atoms, leading to the formation of acetaldehyde (\textsc{CH}_3\textsc{CHO}). The balanced chemical equation for this reaction is: \[ \textsc{CH}_3\textsc{CH}_2\textsc{OH} + [O] \rightarrow \textsc{CH}_3\textsc{CHO} + \textsc{H}_2\textsc{O} \]
This transformation is essential in organic chemistry as it illustrates the concept of increasing the oxygen content or decreasing the hydrogen content to oxidize organic compounds.

Secondary Alcohol Oxidation

Secondary alcohols undergo a different oxidation pathway compared to primary ones. Isopropanol (\textsc{CH}_3\textsc{CHOHCH}_3) is oxidized to form acetone (\textsc{CH}_3\textsc{COCH}_3), a ketone. The oxidizing agent [O] removes hydrogen, creating a double bond with oxygen in the carbonyl group. The equation representing this reaction is: \[ \textsc{CH}_3\textsc{CHOHCH}_3 + [O] \rightarrow \textsc{CH}_3\textsc{COCH}_3 + \textsc{H}_2\textsc{O} \]
The process illustrates the conversion of the hydroxyl group into a carbonyl, which is characteristic of ketone formation from secondary alcohols.

Chemical Equations in Organic Chemistry

Chemical equations in organic chemistry serve as a blueprint for understanding the structural changes compounds undergo during chemical reactions. They balance the number of atoms for each element on both sides of the equation and indicate the phases of reactants and products. Oxidation reactions are typically indicated by the presence of an oxidizing agent, such as [O], which illustrates the electron exchange process involved in converting alcohols to carbonyl compounds.

When writing a chemical equation, it's crucial to represent the structure of molecules accurately and use the correct stoichiometry to reflect the conservation of mass. Understanding these notations helps students decipher the process of bond formation and cleavage during chemical reactions.

Aldehyde Formation

Aldehydes are formed through the oxidation of primary alcohols, where the alcohol's terminal carbon gains a double bond with oxygen, resulting in a carbonyl functional group at the end of the carbon chain. For instance, when ethanol is oxidized to acetaldehyde, the equation \[ \textsc{CH}_3\textsc{CH}_2\textsc{OH} + [O] \rightarrow \textsc{CH}_3\textsc{CHO} + \textsc{H}_2\textsc{O} \] demonstrates this change.

The transition from a single-bonded oxygen in the alcohol to a double-bonded oxygen in the aldehyde is a key aspect of organic functional group interconversion. This process is widely used in various chemical industries and synthetic organic chemistry.

Ketone Formation

Ketones are created by the oxidation of secondary alcohols, where the oxygen atom forms a double bond with a carbon atom within the carbon skeleton. This reaction changes the secondary alcohol's hydroxyl group into a carbonyl group, situated between two carbon atoms. Using isopropanol's oxidation as an example, the chemical equation \[ \textsc{CH}_3\textsc{CHOHCH}_3 + [O] \rightarrow \textsc{CH}_3\textsc{COCH}_3 + \textsc{H}_2\textsc{O} \]
illustrates ketone formation. This is an important reaction, especially in the creation of fragrances, solvents, and the synthesis of more complex organic molecules.