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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
Ch. 26 - Transition Metals
IUPAC Naming
Alkyl Groups
Naming Cycloalkanes
Naming Bicyclic Compounds
Naming Alkyl Halides
Naming Alkenes
Naming Alcohols
Naming Amines
Cis vs Trans
Conformational Isomers
Newman Projections
Drawing Newman Projections
Barrier To Rotation
Ring Strain
Axial vs Equatorial
Cis vs Trans Conformations
Equatorial Preference
Chair Flip
Calculating Energy Difference Between Chair Conformations
Additional Guides
t-Butyl, sec-Butyl, isobutyl, n-butyl

Before we can really understand chair conformations, we have to practice drawing them! These tricky little suckers can be hard to get right.  

Method for Drawing Chairs

Concept #1: How to draw chairs.


Now that we understand the positions of cyclohexane, I'm actually going to take like five minutes just to teach you how to draw it. I know that sounds kind of juvenile, but once again, there are so many people that struggle to draw this weird shape that it's not even worth it not to go over it. We should just go over it once, make sure that you have at least one solid way how to draw it and then we'll move on from there.
So how to draw cyclohexane. I've actually seen a lot of different explanations in different books, the easiest one that I've found is this. I always just draw two slightly angled parallel lines like that. Then all I do is I cap off both ends. What that means is I use an up cap for the down one and I use a down cap for the bottom one. That one actually came out really nice. You would think I'm like a pro. Well, I kind of am, but they usually come out not that nice.
That's how to draw a cyclohexane. And then obviously if you want to draw the other one, you should be able to draw both. You would draw the slightly parallel lines the other way and then you'd cap them the other way. That one came out okay too. These are totally legit – like this would totally work in a test. I'm sure that some of you girls can draw this way nicer than I can, but whatever. I'm just saying this works. 

  1. Draw two slightly angled parallel lines. 
  1. Cap both ends off

How did you do?


It's ok if you didn't draw it beautifully the first time - practice makes perfect!

Cis and Trans

Concept #2: How to distinguish cis from trans.


What I want to teach you guys is how to determine cis and trans. Cis and trans is not based on whether your positions are axial or equatorial. That's one of the biggest misconceptions in this chapter. A lot of students say, “Oh, but they're both equatorial so that means that they should be cis. Or one is equatorial and one is axial, so they should be trans.” Wrong. That's not how you decide it at all.
Cis and trans is actually going to be based on whether the groups are facing the same face of the ring. What I mean by face is just top or bottom. What that means is that I'm not going to be looking at positions. I'm going to be looking at direction.

Cis or trans is based on whether the groups are facing the same face (top or bottom) of the ring.

  • It has nothing to do with the axial and equatorial positions!

Example #1: Is the following cyclohexane cis or trans? 

Example #2: Is the following cyclohexane cis or trans? 

Not too bad, right? It's as easy as it sounds! Let's move on.