Question

Alcohols are very useful starting materials for the production of many different compounds. The following conversions, starting with 1 -butanol, can be carried out in two or more steps. Show the steps (reactants/catalysts) you would follow to carry out the conversions, drawing the formula for the organic product in each step. For each step, a major product must be produced. (See Exercise 62.) (Hint: In the presence of \(\mathrm{H}^{+},\) an alcohol is converted into an alkene and water. This is the exact reverse of the reaction of adding water to an alkene to form an alcohol.) a. \(1-\) butanol \(\longrightarrow\) butane b. \(1-\) butanol \(\longrightarrow 2\) -butanone

Short answer

To convert 1-butanol into butane, follow these steps: 1. Dehydration of 1-butanol using concentrated H2SO4 to form 1-butene. 2. Hydrogenation of 1-butene using Pt or Pd catalyst to form butane. To convert 1-butanol to 2-butanone, follow these steps: 1. Oxidation of 1-butanol using PCC to form butyraldehyde. 2. Oxidation of butyraldehyde using KMnO4 in basic solution to form 2-butanone.

Step-by-step solution

Reaction pathway for 1-butanol to butane (a)

To convert 1-butanol into butane, we will follow these steps: 1. Dehydration of 1-butanol to form 1-butene (an alkene): - Reactant: 1-butanol - Catalyst: Concentrated sulfuric acid (H2SO4) - Major product: 1-butene 2. Hydrogenation of 1-butene to form butane (an alkane): - Reactant: 1-butene - Catalyst: Platinum (Pt) or Palladium (Pd) on activated carbon - Major product: Butane

Reaction pathway for 1-butanol to 2-butanone (b)

To convert 1-butanol to 2-butanone, we will follow these steps: 1. Oxidation of 1-butanol to form butyraldehyde (an aldehyde): - Reactant: 1-butanol - Catalyst: Pyridinium chlorochromate (PCC) - Major product: Butyraldehyde 2. Oxidation of butyraldehyde to form 2-butanone (a ketone): - Reactant: Butyraldehyde - Catalyst: Potassium permanganate (KMnO4) in basic solution - Major product: 2-butanone

Key concepts

1-Butanol Conversion

The conversion of 1-butanol, a type of alcohol, to different chemical compounds is a crucial skill in organic chemistry. Alcohols like 1-butanol are versatile reagents that can be transformed through various reactions into a range of different organic products, including alkanes, alkenes, ketones, and aldehydes. For example, the steps outlined in the textbook problem show how 1-butanol can be converted to butane and 2-butanone through different chemical pathways. Understanding these pathways is essential because each step of the transformation requires specific conditions and catalysts to achieve the desired major product.

Key to successful 1-butanol conversion is knowing the right type of reaction to use. Dehydration, hydrogenation, and oxidation are some of the processes that can be applied to 1-butanol to convert it to other organic compounds. Each step needs to be carefully planned to ensure that the reactants and catalysts will deliver the selected major product efficiently.

Dehydration Reaction

Dehydration reactions are a class of chemical reactions wherein water is removed from a molecule, typically involving the loss of an -OH group and a hydrogen atom (H). In the context of 1-butanol conversion, when 1-butanol is treated with a strong acid like concentrated sulfuric acid (H2SO4), a dehydration reaction takes place, resulting in the formation of 1-butene, an alkene. This type of reaction is not only limited to the production of alkenes but also pivotal in synthesizing ethers.

During dehydration, the acid acts as a catalyst, which accelerates the reaction without being consumed. For students, understanding the role of a catalyst in such reactions is critical, as it affects the reaction conditions such as temperature and reaction time. Moreover, knowing that dehydration can be a reversible process helps students grasp the equilibrium between alcohols and alkenes, which is influenced by the nature of the acid used and the reaction conditions.

Oxidation Reaction

Oxidation reactions in organic chemistry refer to the processes where an organic compound loses electrons, often gaining oxygen or losing hydrogen. One common application is the oxidation of alcohols like 1-butanol to produce carbonyl compounds such as aldehydes and ketones. The textbook solution illustrates two successive oxidation steps: first converting 1-butanol into butyraldehyde (an aldehyde), and then further oxidizing butyraldehyde to 2-butanone (a ketone).

The specific conditions for oxidation reactions are vital. For instance, pyridinium chlorochromate (PCC) is used to convert 1-butanol to butyraldehyde, a milder oxidizing agent that stops at the aldehyde stage without further oxidation to a carboxylic acid. In contrast, stronger oxidizers, such as potassium permanganate (KMnO4) in basic solution, are required to convert the aldehyde into a ketone. This precision in choosing the appropriate oxidizing agent is essential for students to control the outcome of a reaction and obtain the desired product.