Question

Give the structural formula and systematic name for the organic product, if any, from each of the following reactions: (a) pentanal and \(\mathrm{KMnO}_{4}\) (b) 2-octanone and LiAlH \(_{4}\)

Short answer

(a) Pentanoic acid, CH3(CH2)3COOH (b) 2-Octanol, CH3(CH2)5CHOHCH3.

Step-by-step solution

Understand the Reaction Conditions for (a)

Pentanal is an aldehyde, and when it reacts with a strong oxidizing agent like potassium permanganate (\(\mathrm{KMnO}_4\)), it undergoes oxidation. Aldehydes are typically oxidized to carboxylic acids under these conditions.

Predict the Product for (a)

Pentanal will be oxidized to pentanoic acid. The structural formula of pentanoic acid is \(\text{CH}_3(\text{CH}_2)_3\text{COOH}\), where the aldehyde group \(\text{CH}=\text{O}\) is converted into a carboxylic acid group \(\text{COOH}\).

Name the Product for (a)

The systematic name for the product is pentanoic acid. This is derived from 'pentane', which indicates five carbon atoms, with the suffix '-oic acid' to denote the carboxylic acid functional group.

Understand the Reaction Conditions for (b)

2-Octanone is a ketone, and when it reacts with lithium aluminum hydride (LiAlH\(_4\)), which is a strong reducing agent, it undergoes reduction. Ketones are reduced to secondary alcohols under these conditions.

Predict the Product for (b)

2-Octanone will be reduced to 2-octanol. The structural formula of 2-octanol is \(\text{CH}_3(\text{CH}_2)_5\text{CHOH}\text{CH}_3\), where the ketone group \(\text{C}=\text{O}\) converts to a hydroxyl group \(\text{C}-\text{OH}\).

Name the Product for (b)

The systematic name for the product is 2-octanol. This name indicates an eight-carbon chain ('octane') with a hydroxyl group on the second carbon ('-2-ol').

Key concepts

Organic Chemistry

Organic chemistry is the branch of chemistry that deals with the structure, properties, composition, reactions, and preparation of carbon-containing compounds. These compounds include not just hydrocarbons, but also compounds with other elements such as oxygen, nitrogen, sulfur, phosphorus, and various metals. Understanding organic chemistry is crucial because it forms the foundation for the synthesis of a wide variety of important products ranging from pharmaceuticals to plastics. Key concepts in organic chemistry include:

• Understanding the structure and bonding of carbon atoms, which exhibit unique bonding capabilities allowing for a myriad of complex structures.
• Studying functional groups—specific groups of atoms within molecules that have distinct chemical properties.
• Learning about the mechanisms of organic reactions, which explain how and why reactions occur.

With organic chemistry, we delve into the chemical processes that govern the mechanisms of living organisms and many industrial processes. By mastering these fundamentals, you can explore the endless applications of organic compounds.

Oxidation and Reduction

Oxidation and reduction, often referred to as redox reactions, are essential processes in chemistry. In organic chemistry, these processes involve the loss or gain of electrons or hydrogen atoms during a reaction. Oxidation refers to the loss of electrons, which can also correspond to an increase in the oxidation state or the addition of oxygen. Conversely, reduction involves the gain of electrons, a decrease in oxidation state, or the removal of oxygen.In the context of the reaction of pentanal with \(\mathrm{KMnO}_4\\):

• Pentanal is oxidized to pentanoic acid as the aldehyde group \(\text{CH}=\text{O}\) is transformed into a carboxylic acid group \(\text{COOH}\).
• The oxidizing agent \(\mathrm{KMnO}_4\) donates oxygen, facilitating this conversion by removing electrons from the aldehyde.

Reduction, as demonstrated with 2-octanone and LiAlH\(_4\):

• 2-Octanone is reduced to 2-octanol. Here, the ketone group \(\text{C}=\text{O}\) gains hydrogen and transforms into a hydroxyl group \(\text{C}-\text{OH}\).
• LiAlH\(_4\) acts as a reducing agent, providing electrons and hydrogen ions to facilitate the reaction.

Redox reactions are crucial in biochemistry and industry, playing key roles in energy production, synthesis, and more.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They're essential building blocks in organic chemistry because they define the properties and reactivity of organic compounds.Consider these important functional groups involved in our reactions:

• Aldehyde Group: The aldehyde group (\(\text{CH}=\text{O}\)) is present in pentanal. Aldehydes are typically reactive and can be easily oxidized to form carboxylic acids.
• Carboxylic Acid Group: Pentanoic acid contains a carboxylic acid group (\(\text{COOH}\)). This functional group is characterized by its acidity and ability to donate protons (H\(^+\)).
• Ketone Group: 2-Octanone contains a ketone group (\(\text{C}=\text{O}\)). Ketones are related to aldehydes but are considered less reactive due to the R-group attached to the carbonyl carbon.
• Hydroxyl Group: The reduced product, 2-octanol, has a hydroxyl group (\(\text{C}-\text{OH}\)), which is the defining feature of alcohols, making them versatile in chemical reactions.

Recognizing and understanding functional groups allow chemists to predict the properties and reactions of organic molecules effectively.

Aldehydes and Ketones

Aldehydes and ketones are two important classes of organic compounds containing the carbonyl group, \(\text{C}=\text{O}\). Though they share this feature, their chemical and physical properties differ due to their distinct structures.

Aldehydes

Aldehydes have the carbonyl group located at the end of a carbon chain, denoted as \(\text{R}-\text{CHO}\). This position makes them highly reactive because the hydrogen attached to the carbonyl can be easily manipulated. Pentanal, for example, can be readily oxidized to form pentanoic acid.

• Aldehydes can be easily oxidized to carboxylic acids.
• Their reactivity often makes them intermediates in various organic reactions.

Ketones

Ketones have the carbonyl group situated between two carbon atoms, \(\text{R}-\text{CO}-\text{R'}\). Because of this internal positioning, ketones are generally less reactive compared to aldehydes.

• Ketones do not oxidize as easily as aldehydes, but they can be reduced to secondary alcohols like 2-octanol.
• The stability of ketones makes them common in both industrial and biological systems.

By understanding aldehydes and ketones, you can harness their unique properties for designing chemical reactions and pathways.