Problem 60 - Chemistry and Chemical Reactivity

Question

Give the structural formula and name for the organic product from the following reactions. (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CHO}+\mathrm{LiAlH}_{4}\) (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}+\mathrm{KMnO}_{4}\)

Step-by-Step Solution

Answer

(a) 1-Pentanol (\(\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{OH}\)); (b) Butanoic acid (\(\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{COOH}\)).

Step 1: Identify Reaction Type for Reaction (a)

The reaction involves butanal (\(\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CHO}\)) and lithium aluminum hydride (\(\mathrm{LiAlH}_4\)) as the reagent. \(\mathrm{LiAlH}_4\) is a reducing agent, commonly used to reduce aldehydes to primary alcohols.

Step 2: Determine the Organic Product for Reaction (a)

Reduce butanal (\(\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CHO}\)) with \(\mathrm{LiAlH}_4\) to convert the aldehyde group (\(-CHO\)) to a primary alcohol group (\(-CH_2OH\)). The resulting structure is \(\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{OH}\), which is 1-pentanol.

Step 3: Identify Reaction Type for Reaction (b)

The reaction involves butanol (\(\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{OH}\)) and potassium permanganate (\(\mathrm{KMnO}_4\)) as the reagent. \(\mathrm{KMnO}_4\) is an oxidizing agent, which oxidizes primary alcohols to carboxylic acids.

Step 4: Determine the Organic Product for Reaction (b)

Oxidize 1-butanol (\(\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{OH}\)) with \(\mathrm{KMnO}_4\) to convert the primary alcohol group (\(-CH_2OH\)) to a carboxylic acid group (\(-COOH\)). The resulting structure is \(\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{COOH}\), which is butanoic acid.

Key Concepts

Reduction Reaction

In organic chemistry, reduction reactions are pivotal in modifying functional groups to create new compounds with distinct properties. A reduction reaction typically involves the gain of electrons or the addition of hydrogen to an organic molecule. An excellent example is the reduction of aldehydes to primary alcohols. For instance, when butanal \( \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CHO} \) reacts with lithium aluminum hydride \( \mathrm{LiAlH}_4 \), a well-known reducing agent, it undergoes a transformation. The aldehyde functional group \(-CHO\) is converted into a primary alcohol group \(-CH_2OH\).
This change yields 1-pentanol \( \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{OH} \). Here’s why it matters:

• Introduction of a Hydroxyl Group: This increases the compound's reactivity and alters its polarity.
• Reagents Like \( \mathrm{LiAlH}_4 \): These are so potent that they can reduce various systems under mild conditions.
• Applications: Useful in pharmaceutical manufacturing and creating fine chemicals.

Mastering these reactions expands your toolkit in organic synthesis, enabling you to predict and create different organic products based on their structure.

Oxidation Reaction

Oxidation reactions, a counterpart to reduction reactions, involve the loss of electrons or hydrogen, often paired with the gain of oxygen. In organic reactions, they transform simpler compounds into those with additional complexity, heightening their applications. Using the example of butanol \( \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{OH} \), when reacted with potassium permanganate \( \mathrm{KMnO}_4 \), an efficient oxidizing agent, a primary alcohol is oxidized into a carboxylic acid.
This means the alcohol group \(-CH_2OH\) moves to a carboxylic acid group \(-COOH\), resulting in butanoic acid \( \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{COOH} \). The importance of oxidation reactions includes:

• Enhanced Functional Diversity: By adding or converting functional groups, molecules become more versatile for various applications.
• Reagent Potency: Potassium permanganate is robust enough to achieve this oxic transformation effortlessly.
• Environmental and Industrial Uses: They're crucial for building blocks in biochemistry and industrial synthesis processes.

In understanding oxidation, one appreciates how organic molecules evolve chemically and functionally.

Functional Groups

Functional groups are the core of organic chemistry. They are specific groupings of atoms within molecules that dictate how these molecules behave and react. In the context of our reactions:

• Aldehydes and their Importance: The aldehyde group \(-CHO\) in butanal gives it a distinct reactivity often targeted in reduction reactions, as seen in its conversion to 1-pentanol.
• Alcohols as Versatile Players: The active alcohol group \(-CH_2OH\) in butanol showcases how versatile and reactive alcohols are, making them prone to oxidation into acids.
• Carboxylic Acids – The End Goals: With butanoic acid formed from oxidation, the carboxylic acid group \(-COOH\) is a strong presence in organic synthesis due to its high reactivity and role in creating larger, complex molecules.

Grasping the essence of functional groups allows chemists to predict how molecules will interact chemically, making this knowledge essential for anyone delving into organic synthesis and reactions.