4. Alkanes and Cycloalkanes

Newman Projections

4. Alkanes and Cycloalkanes

# Newman Projections

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Get a 10 bullets summary of the topicWe use Newman projections to visualize the rotations of conformers. Some are more stable than others. Let's take a look.

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## How sigma bond rotation is visualized

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So Newman projections are way of analyzing which sigma bond rotation will be the most stable. We have some rules about which rotations are **better** and which are ** worse**!

Three Types of Conformations

The __dihedral angle__ (*theta)*, is equal to the angle between the two largest groups on either side of the projection.

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## The energy states of 3 different Newman Projections.

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Plotting a Newman Energy Diagram

As you’ll see, when we plot (*theta*) against energy, we wind up getting a predictable pattern of peaks and valleys that can be used to better understand the different rotations.

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## How to draw a Newman Projection Energy Diagram.

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Professors may ask you to draw this, so don’t just tune it out! You need to understand the basics of energy diagrams for this topic.

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Additional resources for Newman Projections

PRACTICE PROBLEMS AND ACTIVITIES (12)

- Which of the following conformers of isobutyl chloride is the most stable?
- 1. Construct a graph, similar to [FIGURE 3-11] , of the torsional energy of 3-methylpentane along the C2―C3 bo...
- Draw a graph, similar to [FIGURE 3-11] , of the torsional energy of 2-methylbutane as it rotates about the C2—...
- a. Draw a graph, similar to [FIGURE-9] , of the torsional strain of 2-methylpropane as it rotates about the bo...
- The chair conformer of fluorocyclohexane is 0.25 kcal/mol more stable when the fluoro substituent is in an equ...
- Calculate the dihedral angle (θ) for the conformations shown. (a)
- Calculate the dihedral angle (θ) for the conformations shown. (c)
- For each of the pairs in Assessment 3.29, which conformation would you expect to be more prominent at equilibr...
- Choose the conformation in each pair that is most stable. If both are equally stable, then write “no differenc...
- (••••) LOOKING AHEAD In Chapter 5, we introduce reaction coordinate diagrams as a plot of potential energy ver...
- Which conformation in each of the following pairs has the least strain energy? (c)
- For the following molecule, draw the Newman projection (around the 2,3-bond) with a dihedral angle of 180° bet...