Condensed Formula - Online Tutor, Practice Problems & Exam Prep

In organic chemistry, condensed formulas provide a simplified representation of molecules by grouping together atoms bonded to a central atom, typically carbon. For example,

${\mathrm{CH}}_3\left({\mathrm{CH}}_2\right)2{\mathrm{CH}}_3$

represents a hydrocarbon with a chain of carbon atoms, where

${\mathrm{CH}}_3$

signifies a carbon bonded to three hydrogens and

${\mathrm{CH}}_2$

indicates a carbon bonded to two hydrogens. Parentheses in condensed formulas denote branched structures or repeating units, with subscripts specifying the number of repeating groups. This streamlined notation allows chemists to quickly convey complex molecular structures without drawing all the individual bonds, facilitating easier analysis and understanding of the molecule's composition and connectivity.

Condensed Formula

Now condensed formula shows how the atoms in a compound are bonded without showing all the bonds. Now carbon and hydrogen atoms are grouped together in blocks. So what I mean by that is we have chapter 3 where the three hydrogens on the compounds are packed together, grouped together. Chapter 2, the two hydrogens on the carbon are grouped together and then chapter the carbon and the hydrogen are grouped together.

If we take a look here, we have our structural formula. Here our structural 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, so bring in those three hydrogens. And the reason we draw backwards 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 this way, it would almost look like my 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 Chapter 2, so bring in those two hydrogens with the carbon. So we have CH2 here. And then here on the right end here we have CH3 again, bring in those three hydrogens to give us CH3.

Now we can go even further in in condense it even more by erasing those 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 chapter three, Chapter 2, Chapter 3. So this is how we go from our structural formula to our condensed formula.

Condensed Formula Example

Here it says draw a condensed formula for compound with the following molecular formula C₄H₁₀. Here we're given a hint. Arrange all carbon atoms in a row. All right, so we'd have our carbons all connected to each other, our four carbons. And remember, carbon wants to make four 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 three hydrogen, so that's CH₃. Then we have carbon connected to two hydrogens. That's CH₂, again another CH₂, and then finally we have a carbon connected to three hydrogens.

Again that be a CH₃, so this will represent our condensed formula. CH₃CH₂CH₂CH₃. This would be our final answer.

Parenthesis and Parenthesis w/ Subscripts

In this video, we're going to talk about condensed formulas including parentheses and parentheses with subscripts. So here we're going to say that groups that are in parentheses are branches or branch structures. So example, we have Chapter 3 here. If we take a look at this structural formula, we'd see that we have these three carbons here in a row together, and branching off of that middle carbon is our chapter three group.

Now if we change the structural formula into our condensed formula, we'd start out by saying we have CH3 group here, which is shown here. That then comes after that CH2 group right here. Branching off of that CH2 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 the CH2 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.

All right, 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

Here it says write a condensed formula for the following compound. So here we have chapter 3 connected to a Ch which contains 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 CH₃O.

How would we write this? Well, we're going to have our CH₃ to start that's connected to our chapter roop. Remember, we put we use parentheses to show our branch branches that CL is a branch. So we put parentheses CL. Then we have another chapter which has its own branch of branch, so in parentheses.

And then we conclude it with our Chapter 3. So this will represent our condensed formula with our two branches of chlorine and bromine.

Condensed Formula with Subscript

In our continued discussion of condensed formulas, now we take a look at parentheses with subscripts. In this case they indicate repeating units O. For example Chapter 2. If we take a look at the structural formula of this hydrocarbon, we have what Chapter 3, Chapter 2, Chapter 2, Chapter 3.

If we want to convert this to condensed, we learn that we could have done Chapter 3, and then we could do Chapter 2, Chapter 2, and then Chapter 3. But we can further condense this even more. We're going to say that these two Ch twos in the middle, we can combine them even more.

Putting them in parentheses and then putting a little subscript at the bottom tells me that there are two Ch twos in the middle of this hydrocarbon. So here this would be another version of a condensed formula where we have now repeating units.

Condensed Formula Example

In this example question it says draw a structure for the following condensed formula. Here we have Chapter 3, and then in parentheses chapter 2, and then a subscript of three, followed by chapter 3 again. So here we're going to say we're starting out with chapter 3.

So we have a carbon connected to three hydrogens. It is now connected to three of these chapter twos. So we're going to have Chapter 2 here in the middle, another Chapter 2 here in the middle, and then finally our third Chapter 2 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 the condensed structural formula in organic chemistry?

In organic chemistry, a condensed structural formula is a system of writing the molecular formula of a compound in a way that shows the arrangement of atoms within the molecule but omits the lines representing chemical bonds. It's more informative than a simple molecular formula, which only provides the number of each type of atom present, but less detailed than a full structural formula that depicts the precise geometric arrangement of these atoms.

For example, ethanol can be represented by the molecular formula $C_2{H}_{6}O$, which doesn't tell you much about its structure. The condensed structural formula, however, is ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}$, which indicates that there are two carbon atoms connected, with the first carbon bonded to three hydrogen atoms and the second carbon bonded to two hydrogen atoms and an OH group (hydroxyl group). This gives you a clearer idea of the molecule's actual structure without showing all the bond lines as you would see in a full structural formula or a three-dimensional model.

How to write a condensed formula in organic chemistry?

Writing a condensed formula in organic chemistry involves representing the molecule in a simplified manner that shows the atoms in each functional group without drawing all the bonds. Here's how you can write one:

1. Identify the Main Chain: Start by identifying the longest continuous chain of carbon atoms, which will serve as the backbone of your compound.
2. List the Atoms Sequentially: Write the atoms in the order they appear in the chain. Carbon (C) atoms are typically listed first, followed by hydrogen (H) atoms that are bonded to them.
3. Group Functional Groups and Branches: If there are any functional groups or branches (side chains) off the main chain, write them next to the carbon atom to which they are attached. Use parentheses to group atoms in the side chain together if they are attached to the same carbon atom.
4. Indicate Multiplicity: Use subscripts to indicate the number of identical atoms or groups attached to a single carbon atom. For example, ${\mathrm{CH}}_3$ for a methyl group.
5. Show Double and Triple Bonds: Use the appropriate bond symbols (= for double bonds, ≡ for triple bonds) to indicate unsaturation in the main chain or branches.

For example, the condensed formula for isopropyl alcohol would be written as ${\mathrm{CH}}_3\mathrm{CH}\left(\mathrm{OH}\right){\mathrm{CH}}_3$, where