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Why is important to allow the saturated solution to cool down slowly during the recrystallization?

Why is important to allow the saturated solution to cool down slowly during the recrystallization?

Chemistry
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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Why is important to allow the saturated solution to cool down slowly during the recrystallization?

**Transcription and Description for Educational Website** **Title: Williamson Ether Synthesis of p-Cresol with α-Chloroacetic Acid** **Chemical Reaction Scheme:** The diagram shows the reaction of p-cresol (a phenol) with α-chloroacetic acid. The reagents used are: 1. Water (H₂O) and Potassium Hydroxide (KOH) 2. Water (H₂O) and Hydrochloric Acid (HCl) The reaction product is an ether with the release of HCl as a byproduct. **Figure 1: Reaction of p-cresol with α-chloroacetic acid** --- **Objective:** We will carry out the reaction shown above to illustrate the Williamson ether synthesis and to identify the product by the melting point. The reaction yields a 75% return. **Procedure:** 1. **Preparation:** - Dissolve 4.0 g of KOH pellets in 8 mL of water in a 250-mL round bottom flask. Avoid using NaOH. - Add 2.0 grams of p-cresol to the flask and swirl for homogeneity. - Add three boiling stones and attach a reflux condenser. Heat to a gentle boil. 2. **Reaction:** - Add 6 mL of 50% aqueous α-chloroacetic acid gradually using a separatory funnel. - Continue refluxing for 10 minutes after adding the acid solution. 3. **Post-Reaction:** - Transfer the solution to a small beaker while still hot. If solids are present, add about 10 mL of water to dilute, then transfer to a 100-mL beaker. - Cool the solution to room temperature and acidify with concentrated 12 M HCl until pH is acidic (pH=2). 4. **Precipitation and Filtration:** - Ensure the mixture is properly cooled to form a solid precipitate. - Filter and collect the precipitate using a Büchner funnel vacuum setup. - Dry and re-crystallize the solid product if necessary, adding more water and repeating the process. - Limit water use to less than 50 mL to maintain crystal integrity. - Use vacuum filtration for the final product and dry completely. 5. **Analysis:** - Weigh the dried solid for yield determination. - Measure
Transcribed Image Text:**Transcription and Description for Educational Website** **Title: Williamson Ether Synthesis of p-Cresol with α-Chloroacetic Acid** **Chemical Reaction Scheme:** The diagram shows the reaction of p-cresol (a phenol) with α-chloroacetic acid. The reagents used are: 1. Water (H₂O) and Potassium Hydroxide (KOH) 2. Water (H₂O) and Hydrochloric Acid (HCl) The reaction product is an ether with the release of HCl as a byproduct. **Figure 1: Reaction of p-cresol with α-chloroacetic acid** --- **Objective:** We will carry out the reaction shown above to illustrate the Williamson ether synthesis and to identify the product by the melting point. The reaction yields a 75% return. **Procedure:** 1. **Preparation:** - Dissolve 4.0 g of KOH pellets in 8 mL of water in a 250-mL round bottom flask. Avoid using NaOH. - Add 2.0 grams of p-cresol to the flask and swirl for homogeneity. - Add three boiling stones and attach a reflux condenser. Heat to a gentle boil. 2. **Reaction:** - Add 6 mL of 50% aqueous α-chloroacetic acid gradually using a separatory funnel. - Continue refluxing for 10 minutes after adding the acid solution. 3. **Post-Reaction:** - Transfer the solution to a small beaker while still hot. If solids are present, add about 10 mL of water to dilute, then transfer to a 100-mL beaker. - Cool the solution to room temperature and acidify with concentrated 12 M HCl until pH is acidic (pH=2). 4. **Precipitation and Filtration:** - Ensure the mixture is properly cooled to form a solid precipitate. - Filter and collect the precipitate using a Büchner funnel vacuum setup. - Dry and re-crystallize the solid product if necessary, adding more water and repeating the process. - Limit water use to less than 50 mL to maintain crystal integrity. - Use vacuum filtration for the final product and dry completely. 5. **Analysis:** - Weigh the dried solid for yield determination. - Measure
**Introduction** Ethers can be produced from two alcohols. However, unless you want to have symmetrical ethers (i.e., diethyl ether derived from ethanol), ether synthesis from different alcohols in the same reaction mixture will produce a variety of products. To produce an unsymmetrical ether (i.e., tert-butyl methyl ether, MTBE), one component must be an alkyl halide, and the other component is an alkoxide (or phenoxide) ion. The alkoxide ion can be any alkoxide but the alkyl halide is usually going to be a primary or methyl halide since the reaction usually follows an \( S_N2 \) mechanism. The reason for this is that a primary halide would have less chance of undergoing elimination, hence you can end with the product you want. In this experiment, p-cresol and chloroacetic acid will be used. The phenol can easily be converted into the phenoxide ion. This procedure is typical for reactions used to produce asymmetrical ethers. The Williamson ether synthesis is one of several organic chemistry reactions referred to as “Named Reactions”, which employ the name of the scientist who developed it. Many of the reactions used in organic chemistry are described as being named reactions. The Fischer Esterification reaction was a “named reaction”, referring to Emil Fischer who discovered and popularized it as a method to produce esters. Likewise, the Grignard Reaction was similarly named after its discoverer. In today's experiment, the Williamson ether synthesis is another named reaction, developed by Dr. Alexander W. Williamson who was a professor at University College in London in the latter part of the 1800's. This reaction has been around for a long time and has been used successfully to synthesize many different ethers. For this reaction to occur at a high yield, the alcohol portion can be either \( 1^{\circ} \), \( 2^{\circ} \), or \( 3^{\circ} \), which can then be converted into an alkoxide nucleophile using basic conditions (i.e., NaOH can be used as the base). The alkoxide ion then reacts via an \( S_N2 \) mechanism with a primary alkyl halide (in the current experiment chloroacetic acid will be used which also cannot undergo elimination). For example, if the alkyl halide was either \( 2^{\circ} \) or \( 3^{\circ} \
Transcribed Image Text:**Introduction** Ethers can be produced from two alcohols. However, unless you want to have symmetrical ethers (i.e., diethyl ether derived from ethanol), ether synthesis from different alcohols in the same reaction mixture will produce a variety of products. To produce an unsymmetrical ether (i.e., tert-butyl methyl ether, MTBE), one component must be an alkyl halide, and the other component is an alkoxide (or phenoxide) ion. The alkoxide ion can be any alkoxide but the alkyl halide is usually going to be a primary or methyl halide since the reaction usually follows an \( S_N2 \) mechanism. The reason for this is that a primary halide would have less chance of undergoing elimination, hence you can end with the product you want. In this experiment, p-cresol and chloroacetic acid will be used. The phenol can easily be converted into the phenoxide ion. This procedure is typical for reactions used to produce asymmetrical ethers. The Williamson ether synthesis is one of several organic chemistry reactions referred to as “Named Reactions”, which employ the name of the scientist who developed it. Many of the reactions used in organic chemistry are described as being named reactions. The Fischer Esterification reaction was a “named reaction”, referring to Emil Fischer who discovered and popularized it as a method to produce esters. Likewise, the Grignard Reaction was similarly named after its discoverer. In today's experiment, the Williamson ether synthesis is another named reaction, developed by Dr. Alexander W. Williamson who was a professor at University College in London in the latter part of the 1800's. This reaction has been around for a long time and has been used successfully to synthesize many different ethers. For this reaction to occur at a high yield, the alcohol portion can be either \( 1^{\circ} \), \( 2^{\circ} \), or \( 3^{\circ} \), which can then be converted into an alkoxide nucleophile using basic conditions (i.e., NaOH can be used as the base). The alkoxide ion then reacts via an \( S_N2 \) mechanism with a primary alkyl halide (in the current experiment chloroacetic acid will be used which also cannot undergo elimination). For example, if the alkyl halide was either \( 2^{\circ} \) or \( 3^{\circ} \
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