Problem 119 - Chemistry and Chemical Reactivity

Question

ATOM ECONOMY: One type of reaction used in the chemical industry is a substitution, where one atom or group is exchanged for another. In this reaction, an alcohol, 1-butanol, is transformed into 1 -bromobutane by substituting Br for the -OH group in the presence of sulfuric acid. \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}+\mathrm{NaBr}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow\) $$ \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}+\mathrm{NaHSO}_{4}+\mathrm{H}_{2} \mathrm{O} $$ Calculate the \(\%\) atom economy for the desired product, \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}.\)

Step-by-Step Solution

Answer

The atom economy for this reaction is 50.15%.

Step 1: Understand Atom Economy Formula

To calculate the percent atom economy, use the formula: \( \text{Atom Economy} = \left( \frac{\text{Molar Mass of Desired Product}}{\text{Molar Mass of All Reactants}} \right) \times 100\% \). This formula helps us understand what percentage of the reactants' mass is converted into the desired product.

Step 2: Calculate Molar Mass of Desired Product

The desired product is 1-bromobutane (\( \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br} \)).Calculate its molar mass: C (12.01) × 4 + H (1.008) × 9 + Br (79.90).\(\text{Molar Mass of } \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br} = 43.04 + 9.072 + 79.90 = 137.992 \text{ g/mol} \).

Step 3: Calculate Molar Mass of All Reactants

The reactants include 1-butanol (\( \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH} \)), NaBr, and \( \mathrm{H}_{2} \mathrm{SO}_{4} \).Calculate their molar masses: - 1-butanol: C (12.01) × 4 + H (1.008) × 10 + O (16.00) = 74.12 g/mol- NaBr: Na (22.99) + Br (79.90) = 102.89 g/mol- \( \mathrm{H}_{2} \mathrm{SO}_{4} \): H (1.008) × 2 + S (32.07) + O (16.00) × 4 = 98.08 g/molSum: \( 74.12 + 102.89 + 98.08 = 275.09 \text{ g/mol} \).

Step 4: Calculate Atom Economy

Substitute the molar masses into the atom economy formula: \[ \text{Atom Economy} = \left( \frac{137.992}{275.09} \right) \times 100\% = 50.15\% \].

Key Concepts

Substitution Reaction

Substitution reactions are a vital part of many chemical processes. They occur when one atom or group in a compound is replaced by another. In the example, 1-butanol is transformed into 1-bromobutane. The -OH group of the alcohol is replaced by a bromine atom. This reaction is facilitated by sulfuric acid, making it a classic example of a substitution reaction in organic chemistry.
These reactions are crucial because they allow the modification of functional groups in a molecule, which is important in synthesizing new compounds. They are widely used in the chemical industry for manufacturing diverse products, ranging from pharmaceuticals to polymers. Understanding substitution reactions can help you predict the outcome of chemical reactions and design the synthesis of desired products.

Molar Mass Calculation

Molar mass calculation is essential for understanding the amount of each atom present in a compound. It involves multiplying the atomic mass of each element in a molecule by the number of times the element appears and summing them up. For example, in 1-bromobutane (\(\text{C}_4\text{H}_9\text{Br}\)), the molar mass is calculated as:

• Carbon: 12.01 × 4
• Hydrogen: 1.008 × 9
• Bromine: 79.90

This results in a molar mass of 137.992 g/mol. Calculating this accurately is crucial for determining other reaction parameters, like atom economy.

Chemical Industry

The chemical industry is an extensive field that produces thousands of products from raw materials such as oil and metals. It relies heavily on chemical reactions like substitution to create a wide array of substances. These substances range from everyday materials such as plastics and paints to more specialized items like fertilizers and pharmaceuticals.
Sustainability is becoming increasingly important in the chemical industry. This involves using processes that maximize efficiency and minimize waste, which brings us to concepts like atom economy. By using reactions that optimize the desired output, industries can reduce their environmental impact and improve profitability.

• Optimize reactions to reduce waste.
• Create sustainable and efficient processes.

Desirable Product

In any chemical reaction, the desirable product is the specific substance intended as the final output. The focus is on maximizing its yield and purity while maintaining efficiency in reaction processes. For instance, in the conversion of 1-butanol to 1-bromobutane, 1-bromobutane is the desired product. Achieving a high yield of it is crucial not only for economic reasons but also for maintaining sustainable practices.
To determine how effectively desired products are generated without excess waste, the concept of atom economy is applied. Atom economy measures the proportion of reactants that become part of the final product. A higher atom economy indicates a more efficient process, which is desirable in producing chemical products with minimal waste.