Draw the products of the following reactions: b. pentanoic acid + PBr 3 + Br 2 , followed by hydrolysis

Hello, everyone. Today, we have the following problem predict the product of the reaction given below. So when a carboxylic acid such as the starting reactant that we have, now, when a carboxylic acid is reacted with these following re agents that we have here on this arrow, it yields what's known as an alpha bromo acid. So this entire process is undergone through a reaction known as the hell all hard Zelinsky reaction. So the first thing that is going to occur is once we see that we have these reagents, and we know that this is the reaction we're going to identify an alpha carbon. So the alpha carbon is the carbon that is exactly adjacent to the carbonyl carbon. So this double bonded oxygen carbon bond is our Carboni. And that carbon that's attached to the oxygen is the car is the carbonyl carbon. And so the atom that's adjacent to that, that carbon is the alpha carbon and that alpha carbon is going to contain a proton. And so when this carboxylic acid is reacted with phosphorus, tribromide and bromine and then followed up with water to undergo hydrolysis, it is going to essentially replace that hydrogen or that proton. And so when we draw our product, it is going to be the exact same skeletal structure. However, instead of that hydrogen, we are replacing that with bromine. And once again, this reaction is known as the Hel Vardy and it yields our product which is an alpha bromo acid alpha, referring to the bromine being on the alpha carbon bromo because there's a bromine there and acid because this is a carboxylic acid as well. And so with that, we have predicted the product of the given reaction, which is known as the hell Wsky reaction overall. I hope this helped. And until next time.

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24. Enolate Chemistry: Reactions at the Alpha-Carbon

Hell-Volhard-Zelinski Reaction

Organic Chemistry

24. Enolate Chemistry: Reactions at the Alpha-Carbon

Hell-Volhard-Zelinski Reaction

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2:23 minutes

Problem 49b

Textbook Question

Draw the products of the following reactions: b. pentanoic acid + PBr₃ + Br₂, followed by hydrolysis

Verified step by step guidance

Step 1: Recognize the starting material, pentanoic acid, which is a carboxylic acid with five carbon atoms. The reaction involves PBr3 and Br2, followed by hydrolysis.

Step 2: Understand the role of PBr3 and Br2. PBr3 converts the carboxylic acid group (-COOH) into an acyl bromide (-COBr). This step activates the molecule for further reaction.

Step 3: The acyl bromide reacts with Br2 in the presence of PBr3, leading to alpha-bromination. This occurs at the alpha-carbon (the carbon adjacent to the carbonyl group) due to its increased reactivity.

Step 4: After alpha-bromination, hydrolysis (reaction with water) converts the acyl bromide back into a carboxylic acid. The bromine atom remains attached to the alpha-carbon.

Step 5: The final product is alpha-bromopentanoic acid, where the bromine atom is attached to the alpha-carbon of the pentanoic acid structure.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Reactivity of Carboxylic Acids

Carboxylic acids, like pentanoic acid, are organic compounds characterized by the presence of a carboxyl group (-COOH). They can undergo various reactions, including halogenation and conversion to acid halides. Understanding their reactivity is crucial for predicting the products when they react with reagents like PBr3 and Br2.

Role of PBr3 in Organic Synthesis

Phosphorus tribromide (PBr3) is commonly used to convert alcohols into alkyl bromides. In this reaction, PBr3 reacts with the hydroxyl group of pentanoic acid, facilitating the substitution of the -OH group with a bromine atom. This step is essential for the subsequent bromination of the resulting compound.

Hydrolysis of Alkyl Halides

Hydrolysis is a reaction where water is used to break chemical bonds, often resulting in the formation of alcohols from alkyl halides. After the initial reaction with PBr3 and Br2, hydrolysis of the resulting alkyl bromide will yield a bromo-substituted carboxylic acid. This step is critical for determining the final products of the reaction sequence.

Draw the products of the following reactions: b. pentanoic acid + PBr3 + Br2, followed by hydrolysis

Key Concepts

Reactivity of Carboxylic Acids

Role of PBr3 in Organic Synthesis

Hydrolysis of Alkyl Halides

Draw the products of the following reactions: b. pentanoic acid + PBr₃ + Br₂, followed by hydrolysis