A. What two amides are obtained from the reaction of acetyl...

Key Concepts

Nucleophilic Acyl Substitution

This is a fundamental organic reaction mechanism where an acyl chloride, which has an electrophilic carbonyl carbon, is attacked by a nucleophile (typically an amine) to form an intermediate that eventually leads to the formation of an amide. It explains how different amines can replace the chloride, providing the basis for amide formation in these reactions.

Amines as Nucleophiles

Amines are nucleophilic due to the presence of a lone pair of electrons on the nitrogen atom. In acyl chloride reactions, primary amines (such as ethylamine and propylamine) readily attack the electrophilic carbonyl carbon, leading to distinct amide products. Their nucleophilicity is central to the formation of amides through nucleophilic acyl substitution.

Steric Hindrance Impact on Nucleophilicity

Steric hindrance refers to the decreased reactivity of a nucleophile caused by bulky groups around the reactive center. In the context of the reaction with triethylamine, its bulkiness prevents it from effectively attacking the acyl chloride, thereby reducing its role as a nucleophile. This explains why only one amide product is obtained when a base such as triethylamine is present, as it does not participate in amide formation.

Role of Base in Acid-Base Reactions

In reactions involving acyl chlorides, bases are often used to neutralize the acid (HCl) produced during the reaction, thereby driving the equilibrium toward amide formation. Triethylamine, being a tertiary amine, is effective as an acid scavenger but, due to its steric bulk and lack of nucleophilicity, does not react further with the acyl chloride, ensuring that only the amide from the more nucleophilic primary amine is formed.

Transcript

00:01 Okay, this problem is asking us to explain why we get two products in this reaction, and we only get the one product in this reaction.

00:07 Okay, so let's look at this first one.

00:09 Okay, so as we can see, we have acetyl chloride, and that is going to be reacting with both ethylamine and proplamine.

00:14 Okay, so what does that mean? it means that we're going to have a difference in the nucleophilicity in these two compounds, right? so if we analyze ethylame versus propamine, in reality, they have very similar nucleophilicities in relation to this acetyl chloride, right? because i both have one nitrogen, they both have two hydrogens, and they both have the single carbon chain.

00:34 Okay, so they're going to be very similar in terms of their reactivity with acetyl chloride.

00:38 So that means that we're going to get the formation of two products, one in which the nucleophile is myethlamine, and one in which my nucleophile was my proplamine.

00:46 Okay, so the two products are going to be as follows.

00:48 I'm going to retain my ch3, i'm going to get my carbonyl, and i'm going to replace that chlorine with my nitrogen of my ethylame.

00:56 Okay, so that means i'm going to have my two carbons.

00:58 With my one hydrogen, and then if propamine behaved as a nucleophile, it would get this product, in which i retain my phryl as well, i retain my carbonyl, but i'm replacing that chlorine with my propamine.

01:12 So i'm going to get my nitrogen, my three carbons instead of two, and then my single hydrogen.

01:16 Okay, so that is why i have the formation of two products, simply because the difference in nucleophilicity of both these compounds is very minute.

01:24 Right, we're going to get a mixture of what about in this example, in which i still have my cedar chloride, but i have two different reactants, okay, and they're actually going to be considerably different because i have the one carbon chain associated with this ethlamine, and i have my triethlamine over here.

01:40 So i have three carbon chains one two three versus the one carbon chain.

01:43 Okay, so why are we only getting the formation of one product in this example? okay, so in reality, my ethylamine is going to be a much better nucleophile than my triethlamine, but triethlamine is still considered nucleophilic.

01:55 So if we're to have a nucleophilic ethylamine, we would get a situation in which the nitrogen attacks that carbonyl.

02:02 We eventually move the electrons onto the auction.

02:04 We eventually get rid of that chlorine, and we eventually form this product, my amide.

02:08 We get my ch3 retained.

02:12 We get my carbonyl retained, but we replace that chlorine with my nitrogen of my ethylameine.

02:16 So we're just getting rid of one of those hydrogens, and we're getting those two carbons.

02:20 So that is the product, if only my ethylamine reacts.

02:24 Okay...

Please give Ace some feedback