Addition of Amine Derivatives: Videos & Practice Problems

When ammonia derivatives react with carbonyls, they form various imine derivatives. For instance, replacing an H in NH₂ with another amine yields imines, while hydrazine produces hydrazones, and hydroxylamine results in oximes. Each derivative follows a similar nucleophilic addition mechanism, leading to distinct functional groups. Understanding these reactions is crucial for recognizing how different amines interact with carbonyls, enhancing knowledge of organic synthesis and functional group transformations.

Brady's Reagent

There was a lot going on on that benzene molecule, but there was only one part of it that could react with the ketone, and that was the hydrazine. This is just a derivative of hydrazine. In fact, this molecule is actually called 2,4-DNP, and it's used as Brady's test. This is a molecule that you might actually use in your organic chemistry lab this semester because it's a very famous test for ketones. What happens is that when you make the phenylhydrazone product, that phenylhydrazone will precipitate out of the solution. And it usually precipitates in a yellow, orange, or red color. If you get that precipitate, you have a ketone present. This is actually a test that's used to detect ketones. Let's see what the phenylhydrazone product would look like. Well, we know that obviously I'm not going to draw the whole mechanism because that's not what this question is asking. Just asking to predict the product. I would go ahead and I would draw my imine. But I need to attach the hydrazone part. In fact, it's going to be a phenylhydrazone. I'm going to add NH. Let's see what else is attached to it. We've got a benzene ring. That benzene ring has 2 nitro groups, so let's add those. N2O2, N2O2 and that would be it. That's our molecule. This is basically a phenyl hydrazone. Hydrazone. In fact, it's a 2,4-dinitrophenylhydrazone because this is the 2,4-dinitro part, 2,4. Do you think you can figure out where the name comes from? It's 2,4-dinitrophenylhydrazone. That's why it's called 2,4-DNP. It's a great example of an imine derivative and it's actually a reaction that you might see later this semester. So if it comes up, you'll say, hey, I learned that at Clutch. Maybe you tell your lab partners that they'll know about Clutch too and more people know about us. Awesome. All right. So let's move on to the next topic.

Here’s what students ask on this topic:

What are the products when hydrazine reacts with a carbonyl compound?

When hydrazine (NH₂-NH₂) reacts with a carbonyl compound (such as an aldehyde or ketone) in an acidic environment, the product formed is a hydrazone. The reaction mechanism involves nucleophilic addition of the hydrazine to the carbonyl carbon, followed by elimination of water. The general reaction can be represented as:

${R-C}_{=O}+{\mathrm{NH}}_{2-\mathrm{NH}2}\to {R-C}_{=N-\mathrm{NH}2}+{H-O}_H$

The product, hydrazone, has the general structure R-C=N-NH₂.

How does hydroxylamine react with carbonyl compounds?

Hydroxylamine (NH₂OH) reacts with carbonyl compounds (aldehydes or ketones) to form oximes. The reaction mechanism involves nucleophilic addition of hydroxylamine to the carbonyl carbon, followed by elimination of water. The general reaction can be represented as:

${R-C}_{=O}+{\mathrm{NH}}_{2-\mathrm{OH}}\to {R-C}_{=N-\mathrm{OH}}+{H-O}_H$

The product, oxime, has the general structure R-C=N-OH.

What is the difference between imine and hydrazone formation?

Imine and hydrazone formation both involve the reaction of a carbonyl compound with a nitrogen-containing nucleophile, but they differ in the specific nucleophiles used and the resulting products. Imine formation involves the reaction of a carbonyl compound with ammonia (NH₃) or a primary amine (R-NH₂), resulting in an imine (R-C=N-R'). The general reaction is:

${R-C}_{=O}+{R-\mathrm{NH}}_2\to {R-C}_{=N-R}+{H-O}_H$

Hydrazone formation involves the reaction of a carbonyl compound with hydrazine (NH₂-NH₂), resulting in a hydrazone (R-C=N-NH₂). The general reaction is:

${R-C}_{=O}+{\mathrm{NH}}_{2-\mathrm{NH}2}\to {R-C}_{=N-\mathrm{NH}2}+{H-O}_H$

What is the mechanism of imine formation from a carbonyl compound and ammonia?

The mechanism of imine formation from a carbonyl compound and ammonia involves several steps:

1. Nucleophilic Addition: Ammonia (NH₃) attacks the carbonyl carbon, forming a tetrahedral intermediate.
2. Proton Transfer: Proton transfer occurs within the intermediate, leading to the formation of a protonated alcohol.
3. Elimination of Water: The protonated alcohol loses a water molecule, forming an iminium ion.
4. Deprotonation: The iminium ion loses a proton to form the final imine product.

The overall reaction can be summarized as:

${R-C}_{=O}+{\mathrm{NH}}_3\to {R-C}_{=N-H}+{H-O}_H$

What are the different types of imine derivatives formed from ammonia derivatives?

Different types of imine derivatives are formed from various ammonia derivatives reacting with carbonyl compounds. Here are some common examples:

• Hydrazone: Formed from hydrazine (NH₂-NH₂) and a carbonyl compound. The structure is R-C=N-NH₂.
• Oxime: Formed from hydroxylamine (NH₂OH) and a carbonyl compound. The structure is R-C=N-OH.
• Phenylhydrazone: Formed from phenylhydrazine (C₆H₅-NH-NH₂) and a carbonyl compound. The structure is R-C=N-NH-C₆H₅.
• Schiff Base: Formed from a primary amine (R-NH₂) and a carbonyl compound. The structure is R-C=N-R'.

Each derivative follows a similar nucleophilic addition mechanism, leading to distinct functional groups.