Condensed Formula - Online Tutor, Practice Problems & Exam Prep

Condensed formulas represent the bonding of atoms in a compound without showing all individual bonds. For example, CH₃CH₂CH₃ illustrates a straight-chain alkane. Parentheses indicate branched structures, such as (CH₃) in a more complex molecule. Additionally, subscripts in parentheses denote repeating units, allowing for further condensation, as seen in CH₃(CH₂)₂CH₃. Understanding these representations is crucial for grasping molecular structures and their complexities in organic chemistry.

Condensed Formula Concept 1

Now, the Condensed Formula shows how the atoms in a compound are bonded without showing all the bonds. Carbon and hydrogen atoms are grouped together in blocks. For example, in CH₃, the 3 hydrogens on the compound are packed together, grouped together. In CH₂, the 2 hydrogens on the carbon are grouped together, and in CH, the carbon and the hydrogen are grouped together.

If we take a look here, we have our structural formula. This formula shows all the bonds being created between our atoms. We're showing all the carbon-carbon bonds, and all the carbon-hydrogen bonds. Now, with condensed, we would package in this CH₃, bringing those 3 hydrogens together, and the reason we draw it backward like this is to show that it's the carbons that are connecting to each other, and not hydrogen to carbon. Because if we wrote it the other way, it would almost look like the 3 hydrogens are connecting to my carbon, but they're not. It's the carbons that are connected to each other.

Here we have our CH₂, so bring in those 2 hydrogens with the carbon, giving us CH₂ here. And then here on the right end, we have CH₃ again, bringing in those 3 hydrogens to give us CH₃.

We can go even further and condense it even more by erasing the bonds that show the carbon-carbon linkages. So here, I erase this bond and this bond, and just bring everything in closer, so my fully condensed formula would be CH₃CH₂CH₃. This is how we go from our structural formula to our condensed formula.

Condensed Formula Example 1

Here it says draw a condensed formula for a compound with the following molecular formula, C₄H₁₀. Here we're given a hint: arrange all carbon atoms in a row. Alright. So we'd have our carbons all connected to each other, our 4 carbons, and remember carbon wants to make 4 bonds. And in order to do that, we distribute hydrogens to all of them. So this here represents my structural formula, where I'm showing each of the bonds between carbon-carbon and carbon-hydrogens. But remember, we want the condensed so now we package things in. Here we have a carbon connected to 3 hydrogens, so that's CH₃. Then we have carbon connected to 2 hydrogens, that's CH₂. Again, another CH₂. And then finally, we have a carbon connected to 3 hydrogens again, that'd be a CH₃. So this will represent our Condensed Formula, CH₃CH₂CH₂CH₃. This would be our final answer.

Parenthesis and Parenthesis w/ Subscripts Concept 2

In this video, we're going to talk about condensed formulas, including parentheses and parentheses with subscripts. Here we're going to say that groups that are in parentheses are branches or branch structures. For example, we have CH₃ here. If we take a look at this structural formula, we see that we have these three carbons here in a row together. And branching off of that middle carbon is our CH₃ group. Now, if we change this structural formula into our condensed formula, we'd start out by saying, we have a CH₃ group here, which is shown here. That then comes after that a CH group right here. Branching off of that CH group is our CH₃ group up here. To designate it as a branched structure, we put it in parentheses, and then we continue down our chain. After this CH is our CH₃. So after this branched group here, branch structure, we write CH₃. So as our molecules or compounds become more and more complex, we're going to sometimes need to utilize parentheses to talk about the branched structures coming off of my main chain. Right? So this is just one way we can illustrate that this CH₃ in this particular structure represents a branched structure. Alright. So we're going to start doing more and more complex ones, and we're going to incorporate more and more parentheses.

Condensed Formula Example 2

Here it says write a condensed formula for the following compound. So here we have CH₃ connected to a CH, which has a Cl coming off of it, that CH is connected to another CH that has a Br coming off of it, and then we end with another CH₃. So how would we write this? Well, we're going to have our CH₃ to start, that's connected to our CH group. Remember we use parentheses to show our branches; that's Cl as a branch, so we put parentheses Cl. Then we have another CH, which has its own branch of Br, so in parentheses, and then we conclude it with our CH₃. So this will represent our condensed formula with our two branches of Chlorine and Bromine.

Condensed Formula with Subscript Concept 3

Our continued discussion of condensed formulas now takes a look at parentheses with subscripts. In this case, they indicate repeating units. So, for example, CH₂. If we examine the structural formula of this hydrocarbon, we see CH₃CH₂CH₂CH₃. If we want to convert this to a condensed formula, we learn that we could denote it as CH₃ and then CH₂, CH₂, and CH₃. But we can further condense it even more by indicating that the two CH₂ in the middle can be combined. Putting them in parentheses, and then adding a subscript at the bottom, indicates that there are two CH₂ groups in the middle of this hydrocarbon. Hence, this would be another version of a condensed formula, where we have now repeating units.

Condensed Formula Example 3

This example question asks, "Draw a structure for the following condensed formula." Here we have CH₃, and then in parentheses, CH₂, and then a subscript of 3, followed by CH₃ again. So here, we're going to say we're starting out with CH₃, so we have a carbon connected to 3 hydrogens. It is now connected to 3 of these CH₂s. So we're going to have CH₂ here in the middle, another CH₂ here in the middle, and then finally our 3rd CH₂ here in the middle. That last one is connected to the CH₃ at the end. So this would represent our structural formula when given this condensed formula.

Write a condensed formula for the given structure.

• A. CH₃CH(CH₃)CH(NH₂)CH₃
• B. C₅H₁₃N
• C. CH₃CH(CH₂)CH₃(NH₂)CH₃
• D. (CH)₂(CH₃)₃NH₂

Convert CH₃(CH₂)₂CHBrCH₃ into structural formula.

• A.
• B.
• C.
• D.

Here’s what students ask on this topic:

What is a condensed formula in organic chemistry?

A condensed formula in organic chemistry is a way to represent the bonding of atoms in a compound without showing all individual bonds. It groups carbon and hydrogen atoms together in blocks, such as CH₃ or CH₂, to simplify the structure. For example, the condensed formula CH₃CH₂CH₃ represents a straight-chain alkane with three carbon atoms and eight hydrogen atoms. This method helps in visualizing the molecular structure more compactly.

How do parentheses and subscripts work in condensed formulas?

In condensed formulas, parentheses indicate branched structures or repeating units. For example, in a branched structure, (CH₃) denotes a methyl group attached to the main chain. Subscripts in parentheses indicate the number of repeating units. For instance, CH₃(CH₂)₂CH₃ means there are two CH₂ groups in the middle of the molecule. This notation helps in further condensing the formula and simplifying complex structures.

Why are condensed formulas important in organic chemistry?

Condensed formulas are important in organic chemistry because they provide a simplified way to represent complex molecular structures. They help in visualizing the arrangement of atoms without drawing all individual bonds, making it easier to understand and communicate molecular structures. This is particularly useful for large molecules and helps in identifying functional groups, branches, and repeating units efficiently.

Can you give an example of converting a structural formula to a condensed formula?

Sure! Let's take the structural formula of butane: CH₃-CH₂-CH₂-CH₃. To convert this to a condensed formula, we group the carbon and hydrogen atoms together: CH₃CH₂CH₂CH₃. We can further condense it by recognizing the repeating CH₂ units: CH₃(CH₂)₂CH₃. This shows the same molecule in a more compact form.

How do you represent branched structures in condensed formulas?

Branched structures in condensed formulas are represented using parentheses. For example, if a methyl group (CH₃) branches off the main chain, it is placed in parentheses. Consider the structural formula: CH₃-CH(CH₃)-CH₃. The condensed formula would be CH₃CH(CH₃)CH₃, indicating that the CH₃ group is attached to the second carbon of the main chain.