Question

A reaction for converting ketones to lactones, called the Baeyer-Villiger reaction, is used in the manufacture of plastics and pharmaceuticals. 3-Chloroperbenzoic acid is shock-sensitive, however, and prone to explode. Also, 3 -chlorobenzoic acid is a waste product. An alternative process being developed uses hydrogen peroxide and a catalyst consisting of tin deposited within a solid support. The catalyst is readily recovered from the reaction mixture. (a) What would you expect to be the other product of oxidation of the ketone to lactone by hydrogen peroxide? (b) What principles of green chemistry are addressed by use of the proposed process?

Short answer

The other product of oxidation of the ketone to lactone by hydrogen peroxide is water (H2O), and the proposed process addresses several principles of green chemistry such as the use of safer reactants, waste prevention, catalytic processes, and renewable feedstocks.

Step-by-step solution

Understand the Baeyer-Villiger Reaction

The Baeyer-Villiger reaction is an organic reaction that involves the conversion of ketones into esters or lactones by the addition of a peracid. In this case, hydrogen peroxide (H2O2) is used as the peracid.

Identify the other product of the reaction

During the Baeyer-Villiger reaction, a ketone is oxidized to a lactone, while the peracid (hydrogen peroxide) will be reduced to another product. To identify the other product, we need to consider the reduction of hydrogen peroxide. The reduction of hydrogen peroxide can be represented by the following half-reaction: H2O2 + 2 H^+ + 2e^- -> 2 H2O In this reaction, hydrogen peroxide is reduced by receiving 2 electrons and 2 protons, transforming into water (H2O) as the other product of the oxidation of the ketone to lactone.

Discuss the principles of green chemistry addressed by the proposed process

Green chemistry aims to design products and processes that minimize the use and generation of hazardous substances. The proposed process involving hydrogen peroxide and a tin catalyst addresses several principles of green chemistry: 1. Use of safer reactants: Hydrogen peroxide is a less hazardous alternative to 3-chloroperbenzoic acid, which is shock-sensitive and prone to explode. 2. Waste prevention: The proposed process avoids the formation of 3-chlorobenzoic acid as a waste product, which could have environmental and disposal issues. 3. Catalytic processes: The use of a tin catalyst deposited within a solid support can help reduce the amount of reactants needed, making the process more efficient and generating less waste. The catalyst can be easily separated from the reaction mixture and reused, contributing to waste reduction. 4. Renewable feedstocks: Hydrogen peroxide is a simple and readily available chemical that can be produced from environmental sources like water and oxygen, making it more sustainable than other peracids. In conclusion, the other product of oxidation of the ketone to lactone by hydrogen peroxide is water (H2O), and the proposed process addresses several principles of green chemistry such as the use of safer reactants, waste prevention, catalytic processes, and renewable feedstocks.

Key concepts

Green Chemistry

Green chemistry aims to create processes and products that cause minimal damage to health and the environment. By using less toxic materials and producing fewer waste products, we can achieve more sustainable chemical processes.

In the Baeyer-Villiger Reaction, traditionally, 3-chloroperbenzoic acid is used, which is sensitive and can explode, posing safety risks in handling and storage.

However, adopting hydrogen peroxide as an alternative reactant dramatically increases safety. Instead of forming harmful waste products like 3-chlorobenzoic acid, this method principally produces water, a benign byproduct.

Some green chemistry principles include:

• Reducing or eliminating hazardous substances.
• Preventing waste generation rather than treating and disposing of it.
• Utilizing renewable resources.

Catalytic Processes

Catalytic processes involve the use of catalysts to accelerate chemical reactions. A catalyst speeds up a reaction without being consumed, enabling the use of less reactant and resulting in fewer byproducts.

In the improved Baeyer-Villiger Reaction, a tin catalyst placed on a solid support is used alongside hydrogen peroxide. This plays a crucial role in increasing efficiency and reducing waste.

Some benefits of using catalytic processes include:

• Lower energy requirements.
• Less reactant is needed, reducing material costs.
• Reduction in waste through the recycling of the catalyst.

By applying catalytic processes, the overall environmental footprint of the reaction is reduced, contributing positively to the goals of green chemistry.

Ketones to Lactones Conversion

The Baeyer-Villiger Reaction catalyzes the conversion of ketones into lactones. This is crucial in manufacturing products such as plastics and pharmaceuticals.

In this reaction, the ketone undergoes oxidation, during which the reactant (hydrogen peroxide) becomes water. This conversion is essential due to the functional versatility and utility of lactones in various applications.

Key aspects of this conversion include:

• Lactones are cyclic esters that serve as useful intermediates in synthetic chemistry.
• The reaction is specific, ensuring minimal byproducts.
• This reaction can be efficiently catalyzed, improving yield and sustainability.

The transition from ketones to lactones is streamlined and environmentally considerate, highlighting both chemical innovation and sustainability.