Naming Ammonium Salts - Online Tutor, Practice Problems & Exam Prep

Ammonium salts, characterized by one or more alkyl groups attached to a positively charged nitrogen atom, follow a naming convention similar to amines, with the suffix changing from "amine" to "aminium." To draw structures, ensure nitrogen makes four bonds, adding hydrogen atoms as needed. For naming, identify the largest carbon chain and list substituents alphabetically, using numerical prefixes for identical groups. This systematic approach is essential for understanding the properties and reactions of ammonium salts in organic chemistry.

Common Naming Concept 1

In this video, we're going to take a look at how to name ammonium salts. Now, ammonium salts, sometimes called ammonium ions, are compounds with one or more alkyl groups connected to a positively charged nitrogen atom. Now, here we're going to say the ammonium salts have a similar naming system to amines, whereas amines we say substituent and then we end the name with amine. Here, we're going to say substituent and end the name with ammonium ion. Now before we continue, I know that ammonium ion also exists as NH4+. We're not really concerned with that particular form of ammonium. What we're concerned with are the ones that are connected to carbons. All right. So that's what we're using the definition of an ammonium ion or salt as at least one alkyl group connected to a still positively charged nitrogen atom. So keep that in mind as we name these different types of structures.

Drawing Ammonium Salts Concept 2

Now, in addition to knowing how to name ammonium salts, it's going to become important to know how to draw them. Recall that nitrogen has a plus one charge whenever it makes 4 bonds. Here in this example, it says, "Draw the structure for isopropylphenyl ammonium ion." Alright, so step 1 tells me, based on the name, to add the alkyl groups to the nitrogen atom. Here's the nitrogen. Connected to it is an isopropyl. Phenyl just means a benzene ring. Next, if the nitrogen atom isn't making 4 bonds, add enough hydrogen atoms until it does. So right now, nitrogen is only making 2 bonds. It needs to get to 4, so we add 2 hydrogens. And in step 3, we just add a plus one charge to the nitrogen atom because now it's making 4 bonds. So this would be the structure for our isopropylphenyl ammonium ion.

IUPAC Naming Concept 3

Now, when it comes to naming Ammonium salts, we're going to say the set of rules for naming Ammonium salts are similar to amines plus a modifier ending. Here, we're going to modify the ending from amine, which is what we'd have if we had an amine, to aminium, because it's an ammonium salt now. Just before we use the same naming convention, we designate the numerical locations of substituents. We talk about the location of the nitrogen, which forms the parent chain, and then we have the modified ending. We're going to think of it if it was an amine, it'd end with amine, but because it's a positive nitrogen, it's an ammonium ion. So amine changes to aminium.

So, if we take a look here, it says provide the systematic name for the following ammonium salt. Alright. So step 0 says that if it's symmetrical, we can follow the rules for naming them under common rules. But here it's not symmetrical, so we can ignore step 0. Step 1: if asymmetrical, we have to identify the largest carbon chain connected to the nitrogen atom and name it as an ammonium ion. So, if we take a look here, we have an isopropyl, a methyl, an ethyl, and a cyclopentane ring. The cyclopentane ring is the largest one. So here, we end it with that, so we'd say cyclo cyclopentane. But if it wasn't amine, it would end with amine. But here, we're really just changing the ending to aminium. So that's the end of the name.

Next, we're going to name other alkyl groups alphabetically. Oops. Okay. So, actually, use numerical location to indicate the location of nitrogen. Here, since it's on a ring, we don't have to state 1-cyclopentaminium. We don't have to do any of that stuff because it's on a ring. So we go straight to step 2. Name other alkyl groups alphabetically as N-substituents. If they are identical alkyl groups, use numerical prefixes (di, tri, etc.). Now, this grayed-out box is just something we've always done when it comes to naming, and it's used commas to separate numbers from numbers and uses dashes to separate letters from numbers. Letters are not separated from letters, something we've always done. So it's something you should always have in the back of your mind.

Now let's talk about these N-substituents. So what do we have here? We have methyl, we have ethyl, and we have isopropyl. So in alphabetical order, ethyl first. N-ethyl, then I next, N-isopropyl, N-methylcyclopentanaminium. It will be the name of the structure. I know it's a mouthful in terms of this, but this is the way we'd have to name this particular ammonium salt using the IUPAC naming system.

Draw structure for N,N-diethyl-2-hexanaminium.

• A.
• B.
• C.
• D.

Draw structure for propylammonium ion.

• A.
• B.
• C.
• D.

Provide the IUPAC name for the following ammonium salt.

• A. sec-butyl cyclohexyl ammonium ion
• B. N-isopropylcyclohexanaminium 
• C. N-cyclohexyl-2-propanaminium
• D. N-propylcyclohexanaminium

Which of the following represents m-bromo-N-ethyl-N-isopropylbenzenaminium?

• A.
• B.
• C.
• D.

Here’s what students ask on this topic:

What are ammonium salts and how are they named?

Ammonium salts are compounds where one or more alkyl groups are attached to a positively charged nitrogen atom. The naming convention for ammonium salts is similar to that of amines, but with a key difference: the suffix changes from 'amine' to 'aminium.' For example, if you have an amine named 'methylamine,' the corresponding ammonium salt would be named 'methylaminium.' The systematic approach involves identifying the largest carbon chain connected to the nitrogen atom, naming it as the parent chain, and then listing other substituents alphabetically. Numerical prefixes are used for identical groups, and the nitrogen's location is indicated if necessary.

How do you draw the structure of an ammonium salt?

To draw the structure of an ammonium salt, follow these steps: First, identify the alkyl groups attached to the nitrogen atom based on the name. For example, in 'isopropylphenylaminium ion,' you would attach an isopropyl group and a phenyl group (benzene ring) to the nitrogen. Next, ensure the nitrogen atom makes four bonds by adding hydrogen atoms if needed. Finally, add a +1 charge to the nitrogen atom because it is making four bonds. This systematic approach ensures that the structure accurately represents the ammonium salt.

What are the rules for naming asymmetrical ammonium salts?

When naming asymmetrical ammonium salts, follow these steps: First, identify the largest carbon chain connected to the nitrogen atom and name it as the parent chain with the suffix 'aminium.' Next, list other alkyl groups alphabetically as N-substituents. If there are identical alkyl groups, use numerical prefixes like di-, tri-, etc. For example, if you have an ammonium salt with a cyclopentane ring, an ethyl group, a methyl group, and an isopropyl group, the name would be 'N-ethyl-N-isopropyl-N-methylcyclopentanaminium.'

Why is it important to know how to name and draw ammonium salts?

Knowing how to name and draw ammonium salts is crucial for understanding their properties and reactions in organic chemistry. Proper naming ensures clear communication among chemists and helps in identifying the structure and function of the compound. Drawing the correct structure is essential for predicting reactivity, understanding mechanisms, and designing experiments. This knowledge is foundational for advanced studies and practical applications in fields like pharmaceuticals, materials science, and chemical engineering.

What is the difference between ammonium ions and ammonium salts?

Ammonium ions (NH₄⁺) are simple ions consisting of a nitrogen atom bonded to four hydrogen atoms, carrying a +1 charge. In contrast, ammonium salts are compounds where one or more alkyl groups replace some or all of the hydrogen atoms attached to the nitrogen, resulting in a positively charged nitrogen atom bonded to carbon atoms. The naming and structural conventions for ammonium salts are more complex due to the presence of these alkyl groups, whereas ammonium ions are straightforward and do not involve carbon atoms.