Skip to main content

Start typing, then use the up and down arrows to select an option from the list.

1. A Review of General Chemistry

Condensed Structural Formula

1. A Review of General Chemistry

Condensed Structural Formula

Previous TopicNext Topic

What if you want to describe a molecule, but you have nothing but a keyboard? (No fancy pictures or drawings). This is was actually a big dilemma in the chemistry world, which is why we now have condensed structure.

Condensed Rules

1

concept

How to interpret condensed structures.

6m

Play a video:

Was this helpful?

Hey, guys. So now we're gonna talk about another way to represent organic structures, and that's called the condemned structure. So the condensed method is a common way to describe the connectivity connectivity, how molecules connected off a molecule using Onley text. So my speculation is that the logic behind this is that professors and chemists wanted a way to represent these molecules using only a text editor. Back in the day, there weren't these fancy drawing programs. In fact, all they had was typewriters, right? And they wanted some way Teoh be able to know Tate what a molecule looked like without having to draw fancy structures. All right, and that's where they came upon the condensed structure. Now, one thing that's important for this class is that you're gonna have to really learn how to inter convert between bond line and condensed very quickly. The reason is because your professor, just to trick you, will use both structures interchangeably. One question might be in bond line. Another question might be in condensed and typically just from my years of tutoring experience. I know that students really don't like to think and condemned structure because because it's kind of tricky. So I'm gonna do today is gonna really show you OK, how to interpret it. So let's go ahead and look at There's two different types of start off with the full condemned structure. So the full condensed structure is literally Onley text. And as you can see, we're taking a bond line structure and we're going to represent it in just only one line of text. Now, a lot of this is straight forward, meaning that you can see that this first ch three here is represented by that stage three there. Okay, so then you think, Oh, this isn't so bad. The confusing part is that parentheses can be used to represent different things, depending on the subscript in front of them. So let's go ahead and look at that. The first interesting parentheses that you should know is this one that I've indicated in Blue, which is a C H two plus a sub script. Okay, so notice that I have ch two bracket three. What that means is that I have a repeating unit that's gonna happen over and over and over again. So when I have ch two with a three, that doesn't mean I have three ch two sticking out of one place. What it means is I have three ch two attached in order, like in a line. Does that make sense? So far? The reason that saves us a lot of time is because some of these molecules can get really, really long. Imagine having a molecule that's 100 carbons long. Do you want to write? Ah, 100 ch twos? No, it's way easier just to put ch two in parentheses with a 100 underneath it. And that means I'm going to repeat this unit 100 times. Cool. So far. Awesome. So let's keep going. Then. We have this red one. The red one is parentheses alone. If you have parentheses alone, that indicates that you have a branch coming off of the gene. All right. Now, what's going to be interesting here is that sometimes this parentheses is optional, meaning that your professor may not always be so nice as to put that parentheses there. To say that there's a branch, sometimes you're just gonna have to know. All right, let's look at the logic here. I have a carbon right here, and that carbon is attached to two other things. It's attached to one half of the chain on the left and one half of the chain on the right. Right? By the way, this carbon, Let's go ahead and locate it. It's this one right here. Okay, So let's just make sure that we know what we're talking about. Okay? So that carbon has a part of the chain on the left and a part of the chain on the right. Okay. But it also has supposed to have two other things coming off of it. Because, remember, Carbon wants to have four bonds. Right? So what are those two other things? Well, there's an H. That means that I have one age sticking off there, okay? And I also have an O. H. Now notice that in this case I was nice and I put it in parentheses. What that meant was that it's very easy to say. Oh, the O. H. Is the thing that's coming off here. Done. I have my four bonds perfect, but sometimes you might see it as just C H O. H. And then what? You would need to know. Is that okay? One of them, the H is going in one direction. The O. H. Is going in the other, but you know that both of them are attached to that carbon. Because remember that that carbon needs four bonds. That's kind of the way that we think about it. You always think in terms of how can I make carbon have four bonds. Finally, as you can see, there's one more type of parentheses. Sorry about getting a little sidetracked, but I wanted you guys to see an example of that. And then the last one is that if I have something else that's in parentheses other than CH two, and it has a number in front of it. So in this case, I'm giving you ch three with the two in the magenta brackets, Okay? And what that means is that these things are not attached in a line. They're both attached to the same carbon. Okay, so basically, the only time that I have things in a line repeating is if it's ch two, that would mean that it would be linear. So go ahead and write that down linear, linear, meaning that it's all in one line. But if I have two things that are not ch three or three right here. These these would indicate branching. Okay, because of the fact that both of these ch threes must be coming off of one carbon. And what that would be is that they would be attached to this one right here. Okay, Now, let's look at the logic with this one. So let's look at this carbon. Where is that carbon? That carbon is right here. Okay. So that carbon needs to have four things attached to it, right? Well, first of all, it has the whole left part of the chain. Easy. And then it has Let's look at it. Let's see what's after the carbon after the carbon. I haven't h and I have a ch two. I mean, and I have a ch three, and then I have another stage three because it says to those are the three other things that attached that carbon. So this would be bond to bond three and bond four. And if we were going to go ahead and draw that, you would see that I have an h here, and then I have ch three here and then I have ch three here do you get that? At the end of the day, the carbon still has four bonds, so it's fine. But if you ever draw structure, if you if you ever translated structure that does not give carbon for bonds, then you know you made a mistake.

Content

The condensed structure shows us the connectivity of the molecule. The use of parentheses is important:

Parentheses with no subscripts: Branch on the chain.
Parenthesis with subscripts: Multiple branches on a chain.
CH₂within parentheses + subscripts: Repeating CH₂units within a chain.

Condensed Mixed Structures

2

example

How to draw condensed mixed structures.

5m

Play a video:

Was this helpful?

All right, So now let's look at one that's a little bit easier. And that's the condensed mixed structure. The condensed mixed structure is one in which I have a ring. So I'm just gonna put here rings. Okay. The reason is because rings are very, very difficult. If you think about it, rings would be very difficult to draw in a text because a ring could be a certain shape. It's two dimensional. And most text editors don't give you the ability to draw up and across its on Lee to go across. Think that you're on a typewriter. Would you be able to type a ring? No. So what you do with the condensed mixed structure is that the ring is the only thing that stays this bond line, and then everything else that's branching off of it goes to condensed. So as you can see, what I do is I take this thing converted over here, and now all of the branches coming off of the ring become a condensed formula. Does that make sense? So far? Cool. I also wanted to talk about a few other things right here. Notice that with this, let's start off with this one could kind of easy. Okay, What I have is think about it. I have parentheses that has doesn't have ch two in parentheses. No, it's something other than ch two, right? It's actually ch three. So that must mean What does it mean that all the ch threes or in a line? No, that would only be if it was ch to. What it means is that all three ch threes are coming off of the same carbon. Does that make sense? And that's what we see right here. I have carbon and then ch three ch three ch three. Does that make sense? Cool. I hope so. Now let's go toe one. That's a little bit trickier. That is this one over on the left hand side. So now what is this weird line that I drew like, where did that come from? This line is a pretend line. Okay, so don't pay attention to it too much. All I'm trying to do is separate the right side from the left side to show you how we draw it differently. Okay. Now, because condensed structure has to do with connection has to do with what is connected to what? When you're on the left hand side of a mixed structure, you always have to draw in reverse. You have to put the letters backwards. Okay? The reason is because I have to show exactly what order they're connected in. So let's look at this. This right here is an O attached to a ch three. Would you agree with that? Cool. But if I just write If I instead of writing this, let's say that I wrote Oh, c h three like that. Would that be correct? That would actually be incorrect. So go ahead and put an X on that. Okay, that would be wrong. The reason is because it looks like the O is attached to one of the h is right. That doesn't make a lot of sense. So the way we need to show this is that the, uh oh is actually connected to the carbon first. And then the carbon is connected to three. H is right. So then the way that we draw it is O. C. And then h three after that, Does that make sense? This Onley applies when you're on the left side. Because if you're on the right side, then it just makes sense the way it actually is. You would just ride it out. According to the connectivity, The left side is the part that gets a little bit tricky now. Some of you guys might be asking this question, Johnny, but what if it's at the top or at the bottom? Because that's not really how about if it's in between? So how about if I had a line right here and I wanted to put text there? Well, if it's right in the middle, then obviously go to the right because I could just do ch three. Oh, or whatever I could do in this case, it would be, oh, ch three if it had been there. Okay, So obviously what I'm trying to say is that you would only go to the left. You would only reverse it if you absolutely have to, because it's on the left hand side. Does that make sense? But if it's at the top of the bottom, just go to the right, like normal, because there's plenty of room to draw it. Okay, so let's goto the last example. Which is this one down here that has a double bond toe carbon into oxygen. That's this thing right there. Okay, This is a situation where if you have a double bond, many times your professor is going to put an equal sign there. An equal sign represents double bond, which is pretty easy. If it was a triple bond, then they would put one of the equal signs that has three bars. Okay, but sometimes your professors will be really tricky, and they will just write this like C o ch three, and they will skip the equal sign. That's tricky, right? How are you supposed to know that? That is a double bond without being told that it's a double bond. Can you guys think about it? Is there any way to know? The answer is it goes back to carbon having four bonds. Okay, if this is a carbon and oxygen and if that carbon needs four bonds, then what that means is that this carbon must be attached to that oxygen with a double bond. The reason is because I have a bond on the left, have a bond on the right, and then I must have to bonds that are missing those two bonds that are missing are the ones that are attached to the Oh, that make it a double bond right there. Does. That kind of makes sense now, Like I'm like, I was saying, most professors are gonna be nice, and they're going to give you that double bond. But I'm just trying to show you, just in case you professor decides to be a tool and not put that in there so that you guys will know that you can actually calculate it based on carbon having four bonds. Okay, so I'm gonna give you plenty of practice. Don't worry.

Content

This is similar to normal condensed structure, except there is a bondline ringed component. Always draw your condensed letters in terms of connectivity!

If to the right of the ring:Draw branch normally.
If to the left of the ring:Draw branch in reverse.

3

Problem

Problem

Convert the condensed structure into a bondline structure

A

B

C

D

Remember, the exact direction of your zig-zag pattern doesn’t matter as long as everything is connected correctly. Single bonds can rotate freely, so let’s not spend lots of time worrying about the exact angles you drew.

Previous TopicNext Topic

Additional resources for Condensed Structural Formula

PRACTICE PROBLEMS AND ACTIVITIES (9)