Chapter 3 Practice Problems – Answers

Q3.1: Draw and label Newman Projections for the antiperiplanar, fully eclipsed, both partially eclipsed, and both gauche conformations of 1-iodopropane. For simplicity, use a perspective that has the carbon with the iodine closer to the viewer in each case.

Drawing a line-angle structure first will help.

Other perspectives are also fine.

e.g. any of these is acceptable for the antiperiplanar Newman Projection:

Q3.2: For each of the following molecules add the remaining substituents to complete Newman Projections of the current, most stable, and least stable conformations. It is not necessary to draw out full groups; using the abbreviations provided is acceptable. However, knowing what the abbreviations represent will assist in answering the question.

It is strongly recommended to build and use molecular models.

Remember that perspective can change (conformation AND orientation).

Q3.3: Assume each of the following adopts the lowest energy conformation available to it. Fill in the blanks for each set of molecules by assessing the strains they experience.

Q3.4: For each six-membered ring draw both chair conformations and then label (highlight, colour-code, etc.) all substituents other than H’s as axial or equatorial. A template of each chair is provided to set the perspective. For practice purposes you should attempt to draw these chair conformations (in the same perspective) by hand.

Using a molecular model will help.

Pay very close attention to perspective,

which may be different from the original line-angle structure.

For D re-drawing the line-angle structure flipped over will help.

Q3.5: For each chair conformation below add the substituents to the line-angle structure (including hashed/wedged notation) and indicate whether the chair conformation shown is more or less stable than the other chair conformation. You do not need to draw the other chair conformation, though doing so may assist in answering the question.

Using a molecular model will help.

Drawing the other chair conformation is not required but acceptable.