Ch. 4 - Alkanes and CycloalkanesWorksheetSee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins
Johnny Betancourt

Newman 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 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 templatesNewman 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 eyeballEthane 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 NewmanEthane 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 eyeballButane 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 NewmanButane 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 NewmanStaggered 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 NewmanEclipsed 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 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 diagramEnergy 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 NewmanCyclohexane 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 NewmanPlanar 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. 



Johnny Betancourt

Johnny got his start tutoring Organic in 2006 when he was a Teaching Assistant. He graduated in Chemistry from FIU and finished up his UF Doctor of Pharmacy last year. He now enjoys helping thousands of students crush mechanisms, while moonlighting as a clinical pharmacist on weekends.


Additional Problems
Write a structural formula for the most stable conformation of each of the following compounds:  (a)  2,2,5,5-Tetramethylhexane (Newman projection of conformation about C-3—C-4 bond) 
Draw the lowest and the highest energy Newman Projection looking down the C1-C2 bond for 1-bromo-2-methylpropane.
Name the following molecule. 
Draw a Newman projection for the following compound as viewed down the indicated bond.
Use a Newman projection to draw the most stable conformation of 3-methylpentane, looking down the C2—C3 bond.  
For the line angle drawing: give the IUPAC name for the compound AND draw the most stable Newman projection, looking down the bond indicated with the thick line. (E.G. the first compound, draw the Newman projection looking down the #1 C. The circle of the Newman projection represents the C facing us.)
For the line angle drawing: give the IUPAC name for the compound AND draw the most stable Newman projection, looking down the bond indicated with the thick line. (E.G. the first compound, draw the Newman projection looking down the #1 C. The circle of the Newman projection represents the C facing us.)
For the line angle drawing: give the IUPAC name for the compound AND draw the most stable Newman projection, looking down the bond indicated with the thick line. (E.G. the first compound, draw the Newman projection looking down the #1 C. The circle of the Newman projection represents the C facing us.)
For the line angle drawing: give the IUPAC name for the compound AND draw the most stable Newman projection, looking down the bond indicated with the thick line. (E.G. the first compound, draw the Newman projection looking down the #1 C. The circle of the Newman projection represents the C facing us.)
For the line angle drawing: give the IUPAC name for the compound AND draw the most stable Newman projection, looking down the bond indicated with the thick line. (E.G. the first compound, draw the Newman projection looking down the #1 C. The circle of the Newman projection represents the C facing us.)
One possible stereoisomer of 2-bromopentane is pictured below. Assuming that sterically a CH3 is bigger than a Br, provide the following: a. A sawhorse representation, with C2 in the front and C3 in the back, with the Br on C2 and the CH2CH3 on C3 pointing UP. b. The Newman projection of the most stable conformer of this molecule with the CH2CH3 on C3 pointing UP on the back carbon. c. The Newman projection of the least stable conformer of this molecule with the CH2CH3 on C3 pointing UP on the back carbon. d. The Newman projection having the Br and Ha antiperiplanar. e. The sawhorse representation of what you drew in d.
Draw a Newman projection of the following compound as viewed from the angle indicated:
Assume a methyl group is larger than a chloro group and draw the lowest energy conformation of 2-chlorohexane as a Newman projection viewed down the C2-C3 bond. Use the alkyl group abbreviations Me, Et, Pr, etc for the alkyl substituents on C2 and C3.
The conformations of (+)-epichlorohydrin (1), viewed along the Ca—Cb bond, can be analyzed in exactly the same manner as the acyclic alkanes discussed in Chapter 4 (J. Phys. Chem. A 2000, 104, 6189–6196). (a) Draw all staggered conformations for 1 viewed along this bond.
Find the correct Newman projection of Molecule A from C3 to C4.  
Using the numbering from your IUPAC name for the following molecule (ketone group has the priority), find the correct the Newman projection from C3 to C4.  
Consider (1R, 3R)-1,3-dimethylcyclohexane. Draw its Newman projection. Paying attention to stereochemistry, draw an acceptable regular 3D structure.
Provide the Newman projection of the following compound
Provide a structural formula for the compound below. Be sure to identify stereoisomers properly. Viewing down the C3-C4 bond of 3,4-dimethylhexane, give a sawhorse formula for the highest energy conformation
On the template provided, draw the Newman projection for the most stable conformation of the molecule shown. Draw the Newman viewing from Carbon #3 to Carbon #2 (IUPAC numbering). The hydrogen on carbon #3 has been added to get you started.
Draw the lowest and the highest energy Newman projections for 2,3- dimethylbutane looking down the C2-C3 bond.
Sight down the C-2—C-3 bond, and draw Newman projection formulas for the  (a) Most stable conformation of 2,2-dimethylbutane
Draw the Newman projection through C1-C2 for the least stable conformation of 2-methyl-1-butanol.
Convert each of the following to a Newman Projection along the C2-C3 bond
When looking down the assigned arrow, draw the Newman projection formula for this molecule:
When looking down the assigned arrow, draw the Newman projection formula for this molecule:
Which of the following is a Newman projection for the following compound as viewed down the indicated bond in the conformation shown?