Now that we understand the differences in energy between the different rotations of a Newman Projection, I want to really go in-depth on how to draw and interpret a Newman Projection. Alright? So there is a method to the madness and it's just a series of steps that I want to teach you. Alright? So let's say that you have the following example. This is a very common problem that you could see on your exam. Draw the most energetically favorable Newman Projection for that 5 carbon chain down the C2, C3 bond. Okay? So how do we even begin to approach this? We need to use steps.
4. Alkanes and Cycloalkanes
Drawing Newman Projections
4. Alkanes and Cycloalkanes
Drawing Newman Projections: Study with Video Lessons, Practice Problems & Examples
Created using AITo analyze a condensed structure, convert it to a bond line structure, focusing on the bond of interest, such as C2-C3. Visualize the bond using a Newman projection, adding implied hydrogens only around the bond of interest. Draw the front and back carbons with their respective groups, ensuring to identify the most stable conformation, typically the anti conformation with a dihedral angle of 180 degrees. This method aids in understanding conformational analysis and stability in organic compounds.
As we learned already, we use Newman projections to visualize the rotations of conformers. Now we will learn the steps involved to draw the perfect one.
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example
Introduction to Drawing Newman Projections
Video duration:
34sVideo transcript
Six Steps to Drawing Newman Projections
Worked Example:Draw the most energetically favorable Newman Projection for CH3CH2CH2CH2CH3 down the C2 – C3 bond.
1. Convert problem into bondline structure
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Step 1 to Drawing Newman Projections
Video duration:
19sVideo transcript
The first thing that I always do is, if you're given a condensed structure, which is often the case, you need to convert the problem into a bond-line structure. Okay? So what that means is that I want to take this 5 Carbon chain, or whatever I'm given, and turn it into bond line. So that's the first thing I'm going to do. Five carbons right there. So, this is pentane.
2. Highlight the bond of interest
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Step 2 to Drawing Newman Projections
Video duration:
1mVideo transcript
The second thing I'm going to do is I'm going to highlight the bond of interest. What is the bond of interest? What? It's this, C2C3. That's your professor telling you that he wants you to focus on a certain bond that's going to rotate. Okay? Just like when I was talking to you about conformers that you could have sigma with S cis or S trans, he's picking out which sigma bond you're going to use, which sigma bond you're going to rotate. That's going to be this sigma bond right there. Because basically, what you want to do is you want to go from the second carbon to the third carbon. That's what C2C3 means. C2C3. Alright? Now, it could have also been this one, just letting you know, it could have also been this one because if you were counting your one from over here, then this would have been your 2 and your 3. Okay? But I'll just go ahead and use this other one. So this is my 2, this is my 3. Perfect. So, I highlighted the bond of interest. You don't need to necessarily write the numbers as long as you just know which bond it is.
3. Draw an eyeball glaring down the length of the bond
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Step 3 to Drawing Newman Projections
Video duration:
28sVideo transcript
What we want to do is, this part sounds silly, I'm going to redraw this, but I actually want you to do the eyeball thing. I want you to draw an eyeball looking down the length of that bond. Okay? So, I want you to draw an eyeball and make it look straight at that carbon. Okay, so pretend that's you, squinting your eyes at it and you're going to try to figure out what this thing is going to look like if I was looking straight at it.
4. Surround only the bond of interest with ALL implied hydrogens
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Step 4 to Drawing Newman Projections
Video duration:
37sVideo transcript
Now the way you're going to do that is that you surround only the bond of interest with all implied hydrogens. That means if there's any implied hydrogens on that carbon or on that carbon, I need to add them. Okay? How about the hydrogens on that carbon? Do I add those as well? No, because that's not the bond of interest. The bond of interest is only going to be from 2 to 3. So what that means is I'm going to add 2 H's here and I'm also going to add 2 H's here. Okay? But I'm not going to add H's anywhere else because that's not the bond of interest.
5. Draw a front carbon with 3 groups in the front and a back carbon with 3 groups in the back
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Step 5 to Drawing Newman Projections
Video duration:
1mVideo transcript
Now what we're going to do is we're going to draw a front carbon with 3 groups in the front and then a back carbon with 3 groups in the back like I was doing when I told you guys about the way the Newman Projection works. So I'm going to say that, for example, little dot. Okay little dot. Okay? And I would draw that it has 3 things coming off of it. Okay? You can draw your little triangle thing or whatever that's called, however you want. You can start with it with a point up or you can start with a point down. It doesn't matter as long as the other one is consistent. So basically, what I would say is then, okay, what are the three things that that red carbon is attached to? Well, it seems to be attached to an H on the top, an H on the top, and then a CH3 at the bottom. That is this CH3 right here. Get that? Then I look back at the blue one. The blue one, imagine that it's kind of peeking out from behind the red one. So the blue one is going to be a circle behind and then I'm going to draw the 3 groups that the blue one has. So the blue one has what? It seems to have 2 H's, H and H. And then what else does it have? Well, it has a 2 carbon chain coming off of it. So that would be what you could just write as CH2CH3. Does that make sense? Okay? Another way to write that would have been to write ET, which stands for Ethyl. Okay? Another way to write CH3 would be to write ME, which stands for Methyl. Okay? And there are abbreviations for a bunch of these different ones. Alright. And your professor might use those more than he actually uses the letters.
6. Determine which dihedral angle would correspond
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Step 6 to Drawing Newman Projections
Video duration:
1mVideo transcript
So now that we've drawn that Newman projection, that is a valid Newman projection. That could be right. The only thing is that I don't know if it's the energy state that the professor was asking for because the professor could ask for any energy state. He could ask for anti. He could ask for gauche. He could ask for eclipse. Maybe even something in the middle. So I have to make sure that this is the exact one that he wants. Okay? So then to determine which dihedral angle would correspond, I have to go up here and see what he said. Well, he specifically said to draw the most energetically favorable. What does energetically stable mean? Stable. Okay? So we're looking for the most stable conformation. What is the most stable conformation? That's going to be anti. Remember, anti is the most stable. So let's go down and see if that's what I drew. And what's the bond dihedral angle, by the way, for anti? 180°. Let's go down and see if that's what I drew. What I have is a large group in the back and a large group in the front. They appear to be 180° degrees away from each other, so this would be anti. So this would be your right answer, and this would be what would get you the points on the exam. Okay? So even if I drew the wrong conformation at the beginning, you could still rotate it into the right conformation. The important part is that you're following all of these steps.
Hint:This question asked for the most energetically favorable = most stable. Which conformation is most stable?
The right answer was anti. You got it. So it turns out this time we drew it correctly on the first try. But there will be other examples where we will have to rotate the Newman Projection into the correct position.
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Problem
ProblemDraw the most energetic Newman Projection of CH3CH(C6H5)CH3
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Hint:Not all Newman Projections can form an anti, gauche and eclipsed conformation. If you have no clear large group on one side of the projection, you’ll just be stuck with projections called staggered (not overlapping) and eclipsed (overlapping).
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ProblemDraw the most stable Newman Projection of CH3CH2 CH2OH through the C2 – C1 bond.
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Do you want more practice?
More setsNewman projections are head-on representations of molecules looking down the bonds between two carbons typically used to visualize rotation around a single bond. We refer to these different rotations of Newman Projections as conformations.
They portray the stereochemistry of substituents on two carbons, with a large circle representing the back (or distal) carbon and a small dot representing the front (or proximal) carbon.
Drawing Newman Projections
Bondline, Sawhorse, and Newman
Where bondline (aka skeletal structure) looks at a molecule perpendicular to its bonds, a Newman projection looks at a molecule down the bond between two atoms. From left to right, we’re looking at ethane as it gets rotated slightly. We start from bondline, rotate the molecule so that the carbon on the left shifts closer to us to view as sawhorse, and then we continue rotating it to look at the molecule head-on.
Bondline to Newman
Let’s draw a Newman together. First things first, we need to pick out the template we’ll use: the “Y” or the “peace sign.”
Newman projection templates
It’s not so hard to determine which one to use; all we need to do is look at the orientation of the substituents on the atom closest to our eyeball. Let’s make one with good, ol’ ethane.
Ethane eyeball
Okay, so I’ve gone ahead and drawn an eyeball to show exactly where we’re looking. The carbon closer to the eyeball has three hydrogens—one in plane facing straight down and the two others facing up on wedge and dash. Looking at the the templates, which one has a substituent on the front carbon facing straight down? The “Y!” Let’s add our color-coded hydrogens to the template!
Ethane Newman
The brown and yellow hydrogens are fairly easy because they’re in plane and facing straight down and up, respectively. Let’s walk through the other substituents. Remember that the big circle represents the back carbon, and the place where all the lines connect is the front carbon. Wedge means it’s coming out of the page (toward you), and dash means it’s going into the page (away from you).
In bondline, we can see that the light blue hydrogen would be to the left of the eyeball and above the carbon-carbon bond so it must be on the left in our Newman. The red carbon is on the back carbon, facing down, and to the right of the eyeball so it must be on the back carbon on the right.
Okay, now let’s get some more practice and try butane! What template should we use for this molecule from the eyeball’s perspective? I’ve drawn it looking down the C2-C3 bond.
Butane eyeball
Notice here that the carbon closest to the eyeball has a yellow methyl group (CH3) facing straight up in plane and two hydrogens facing down and on wedge and dash. What template should we use? The peace sign, of course! Let’s go ahead and add the substituents.
Butane Newman
The methyls were pretty easy because they were facing straight up and down on different carbons, but the hydrogens might’ve been a bit tricky. This time, since we’re looking from the right of the molecule, the wedged substituents would be on the left of our Newman projection.
Conformations
Wait a second… Don’t single bonds freely rotate? Yes! This is where we have to consider conformations. Looking at butane, let’s keep the front carbon (C2) exactly the same and rotate the back carbon (C3). It’s always better to keep one static and rotate the other; rotating both at the same time can get confusing.
Staggered Newman
In both Newman projections, our front carbon’s and back carbon’s substituents are 60 degrees apart from each other. We refer to this as a staggered conformation. There is a slight difference between the first Newman and the second, though.
In the first Newman, the front and back carbons’ methyl groups are as far apart as possible: 180 degrees. When the largest substituents are 180 degrees apart, we refer to that confirmation as anti, a specific type of staggered confirmation.
In the second Newman, the methyl groups are only 60 degrees apart. When the largest substituents are 60º or 120º apart, we refer to the conformation as gauche. What happens when the front and back carbons’ substituents are 0º apart and they overlap? Let’s take a look below:
Eclipsed Newman
In both Newman projections, the groups are overlapping. When substituents line up like that, the molecule has a higher energy (lower stability) because of the steric interactions between the front and back carbons’ substituents. This kind of conformation is called eclipsed. Just like before, there is a slight difference between the two Newman projections here.
The first Newman has two hydrogens overlapping and two pairs of a methyl overlapping with a hydrogen. Since our two largest groups, the methyls in this case, aren’t overlapping we’d call this conformation eclipsed.
The second Newman actually does have the two largest groups overlapping, so we’d call that totally eclipsed. This form of eclipsed conformation is actually the highest in energy (lowest stability) because larger groups have larger steric interactions; put simply, they bump into each other more.
Energy Diagrams
Let’s put all of that together and look at a visual representation of the different energy levels of our conformations using hexane as an example. First, let’s draw hexane in its highest-energy conformer looking down the C3-C4 bond.
Totally eclipsed hexane
That wasn’t so hard, right? Notice that I actually drew two equivalent projections, but the second one uses “Et” for ethyl instead of CH2CH3. Let’s take a look at the energy levels as the dihedral angle (the angle between the front and back carbons’ substituents) changes.
Energy diagram
All the way to the left of the diagram, we’ve got a totally eclipsed hexane with the highest energy of any of the conformations. As we rotate to have a dihedral of 60º, we drop in energy since we end up in a gauche conformation. 120º is another eclipsed conformation, so it jumps up again. Rotating to 180º gives us the lowest energy, and that makes sense because our two largest groups are anti. 240 degrees is the same as 120 degrees, 300 is the same as 60, and 360 is the same as our starting point.
Cyclohexane Newman Projections
Cyclohexane chair conformations can also be portrayed through a Newman projection, but it’s a little bit different. We actually use what amounts to two Newman projections stuck together, and we call it a double Newman. Let’s draw one for (1R,2R,4S)-4-chloro-2-iodo-1-methylcyclohexane.
Cyclohexane Newman
Basically, all we have to do is create two separate Newman projections and link them together through two different carbons. It really helps to choose two carbons that don’t have substituents for this. I’ve color-coded the different carbons here to help keep track.
Notice that my double Newman can be split into two different Newman projections with the “Y” template. That’s because, on the chair conformation, the iodine is axial down and the chlorine is equatorial up. Let’s convert the chair conformation to planar and see if it’s a bit easier to see what that would look like.
Planar to Newman
Converting the planar cyclohexane to Newman is a bit easier, right? See how I’ve drawn two extra eyeballs? The red eyeball is looking down the bond between the chlorine’s carbon and the red carbon, and that bond’s Newman projection is on the left of the double Newman. The blue eyeball is looking down the bond between iodine’s carbon and the blue carbon in the back, and that bond’s Newman projection is on the right.
Here’s what students ask on this topic:
How do you convert a condensed structure to a bond line structure for Newman projections?
To convert a condensed structure to a bond line structure, follow these steps: Identify the carbon chain and draw it as a zigzag line, where each vertex represents a carbon atom. Add any substituents or functional groups to the appropriate carbons. For example, a condensed structure like CH3CH2CH2CH3 would be drawn as a four-carbon zigzag line. This conversion helps in visualizing the molecule more clearly for Newman projections.
Created using AIWhat is the bond of interest in a Newman projection and how do you identify it?
The bond of interest in a Newman projection is the specific sigma bond you are analyzing for rotation. To identify it, look for the bond specified in the problem, often denoted by the carbons it connects, such as C2-C3. Highlight this bond in your bond line structure, as it will be the axis around which you visualize the molecule in the Newman projection.
Created using AIHow do you draw the front and back carbons in a Newman projection?
In a Newman projection, the front carbon is represented by a dot, and the back carbon is represented by a circle. From the dot, draw three lines representing the bonds to the front carbon's substituents. From the circle, draw three lines representing the bonds to the back carbon's substituents. Ensure the groups are positioned correctly to reflect the molecule's 3D structure.
Created using AIWhat is the most stable conformation in a Newman projection and how do you identify it?
The most stable conformation in a Newman projection is typically the anti conformation, where the largest groups on the front and back carbons are 180 degrees apart. This minimizes steric hindrance. To identify it, look for a dihedral angle of 180 degrees between the largest groups. This conformation is energetically favorable due to reduced repulsion between bulky groups.
Created using AIHow do you determine the dihedral angle in a Newman projection?
The dihedral angle in a Newman projection is the angle between two substituents on adjacent carbons. To determine it, visualize the molecule from the perspective of the bond of interest. Measure the angle between the substituents on the front and back carbons. Common angles are 0 degrees (eclipsed), 60 degrees (gauche), and 180 degrees (anti).
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Additional resources for Drawing Newman Projections
PRACTICE PROBLEMS AND ACTIVITIES (30)
- Use a Newman projection about the indicated bond to draw the most stable conformer for each compound. a. 3-me...
- Use a Newman projection about the indicated bond to draw the most stable conformer for each compound. b. 3,3-...
- Convert each Newman projection to the equivalent line–angle formula, and assign the IUPAC name. g. h.
- Convert each Newman projection to the equivalent line–angle formula, and assign the IUPAC name. a. b.
- Draw a Newman projection, similar to [FIGURE 3-25} down the C1—C6 bond in the equatorial conformation of met...
- Draw Newman projections of the following molecules viewed from the direction of the blue arrows. b.
- b. Draw a potential-energy diagram for rotation about the C-2-C-3 bond of pentane through 360°, starting with ...
- For rotation about the C-3-C-4 bond of 2-methylhexane, do the following: a. Draw the Newman projection of the ...
- c. Draw Newman projections of the two conformers of the trans isomer. d. Which of the conformers predominates ...
- (••) Given the following structures, show the Newman projection that would result from looking down the indica...
- (••) Given the following structures, show the Newman projection that would result from looking down the indica...
- Using the Newman projections shown, draw each molecule in its line-angle drawing with all hydrogens and substi...
- Using the Newman projections shown, draw each molecule in its line-angle drawing with all hydrogens and substi...
- (•) Given the first Newman projection and the direction and degree of rotation, fill in the resulting Newman p...
- (•) Given the first Newman projection and the direction and degree of rotation, fill in the resulting Newman p...
- (•) Given the first Newman projection and the direction and degree of rotation, fill in the resulting Newman p...
- (•) Given the first Newman projection and the direction and degree of rotation, fill in the resulting Newman p...
- (••) Given the following structures, show the Newman projection that would result from looking down the indica...
- (••) Given the following structures, show the Newman projection that would result from looking down the indica...
- Draw Newman projections along the C3―C4 bond to show the most stable and least stable conformations of 3-ethy...
- For each molecule, draw the Newman projection you would observe if you looked down the Cₐ - Cᵦ bond in the dir...
- (••) Given the following structures, show the Newman projection that would result from looking down the indica...
- (•••) Looking down the indicated bond, show the three most stable conformations and choose the one that is mos...
- (••) For each of the following structures, which staggered Newman projection skeleton from Assessment 3.51 sho...
- Is each of the following a cis isomer or a trans isomer?d. <IMAGE>e. <IMAGE>f. <IMAGE>
- Convert each Newman projection to the equivalent line–angle formula, and assign the IUPAC name.c. <IMAGE>...
- Using Newman projections, draw the most stable conformer for each of the following:c. 3,3-dimethylhexane, view...
- For the following molecule, draw the Newman projection (around the 2,3-bond) with a dihedral angle of 180° bet...
- Conformational studies on ethane-1,2-diol (HOCH2—CH2OH) have shown the most stable conformation about the cen...
- b. Draw the conformer that is present in greatest concentration.