What products would you obtain from acidic and basic...

Key Concepts

Reaction Mechanisms

The reaction mechanisms for both acidic and basic hydrolysis of amides involve the formation and collapse of tetrahedral intermediates, a hallmark of nucleophilic acyl substitution reactions. Understanding these mechanisms is crucial for predicting how different conditions affect the reactivity and overall outcome of the reaction, including the nature and stability of the products formed.

Base-Catalyzed Hydrolysis

In basic conditions, hydroxide ions directly attack the carbonyl carbon of the amide, forming a tetrahedral intermediate that collapses, expelling the amine as a leaving group. The resulting carboxylic acid is deprotonated immediately under the basic environment to form a carboxylate salt. This reaction is typically irreversible due to the stability of the carboxylate and the thermodynamic drive provided by the strong base.

Amide Hydrolysis

Amide hydrolysis is a transformation where the amide functional group is broken down, typically resulting in the formation of a carboxylic acid and an amine. This reaction is significant because the amide bond is stabilized by resonance, making it relatively unreactive under mild conditions and requiring either acidic or basic environments to proceed effectively.

Acid-Catalyzed Hydrolysis

Under acidic conditions, amide hydrolysis proceeds by protonation of the carbonyl oxygen, which increases the electrophilic character of the carbonyl carbon. This facilitates nucleophilic attack by water, leading to a tetrahedral intermediate that, after a series of proton transfers, ultimately decomposes to yield a carboxylic acid and a protonated amine (ammonium ion) as products.

Transcript

00:02 Suppose we're hydrolyzing amides in acidic or basic mediums.

00:09 Well, the first step is to find the amide bond.

00:13 And that's the bond that will connect the acyl carbon to the nitrogen, right? so it needs to have a c -o -n.

00:28 And that will be the structure of an amide.

00:33 And, well, really, in an acidic, in acidic conditions what happens is that bond gets cleaved so we get our acid on one side because this bond right here is cleaved and we get an acid and we get an an ammonium compound and the reason why we get an ammonium compound is because nitrogen is has a bigger nitrogen's peak p .k .a.

01:13 Is bigger than oxygen's pka.

01:17 And what that means is that it is a stronger base, which means it takes more hydrogens than oxygen would.

01:25 So in acidic conditions, the first protonated substance will, in fact, be the amine.

01:33 And that will be protonated first.

01:36 And adding more acid makes our carboxylic acid group an acid as well.

01:43 Let's try in a basic medium.

01:47 In a basic medium, well, we can't protonate as well, but we will cleave that bond nonetheless because hydrolysis of any carboxylic acid derivative can occur in acidic and basic mediums.

02:04 But in a basic medium, we won't make an actual carboxylic acid.

02:09 We'll make a carboxylate anion, and since it's in basic conditions, we will have just a regular amine or an ammonia compound.

02:29 Let's try this example.

02:32 Now, this one is a little bit more confusing because this is the same molecule.

02:40 Notice how these molecules are connected, right? or the both functional groups are part of the same molecule even if we were to cleave this bond.

02:50 But nonetheless, we will still cleave this bond.

02:57 So let's start with that.

03:01 And we know that in acidic conditions, we protonate our nitrogen, giving it a positive charge, and we complete the carboxylic acid.

03:14 And this will be our final product.

03:16 It will cleave that bond, but the nitrogen group is still part of that molecule.

03:21 Because it was part of it from the other side of the carboxylic acid.

03:30 And if we were to do this in the basic medium, well, it would look very similar to the previous answer.

03:41 Whoops.

03:45 Except we would have a negative charge here.

03:49 And i did put the negative there...