DOC PREVIEW
UMass Amherst CHEM 261 - Cyclohexane Conformations, Disbustituted Cyclohexanes
Type Lecture Note
Pages 3

This preview shows page 1 out of 3 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 3 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 3 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

Lecture 11Outline of Last Lecture:I. Cyclohexane Conformation continuedOutline of Current Lecture:I. Chair Flip reviewII. Converting 2D to 3D images (or vice versa)III. Disubstituted CyclohexanesIV. Polycyclic MoleculesV. Stereochemistry and Tetrahedral Centers introChair Flip Review:-chair flip: not the whole molecule! The flip is INTERNAL1-3, diaxial interactions:-torsion: due to substituents on adjacent carbons (twist)-steric: due to substituents on non-adjacent carbons-When determining conformation of substituents, the bigger substituent “wins” axial vs. equatorial dilemma (want to be equatorialConverting 2D to 3D images (or vice versa): Chem 261 1st Edition-On the left hand of the above image, a cyclohexane with cis-face substituents is drawn in two different ways (2D on the top, 3D on the bottom). Note how the cis-methyl groups are drawn as substituents in the 3D image. -On the right hand side of the above image, a cyclohexane with trans-face substituents is drawn in two different ways, 2D on the top and 3D on the bottom. Note how the trans-methyl groups are oriented as substituents in the 3D image. Disubstituted Cyclohexanes:-Monosubstituted cyclohexanes are always most stable with their substituent in the equatorial position-But, disubstituted cyclohexanes are more complex than this; the steric effects of the substituents must be accounted for when determining the ideal conformation of the molecule.Book example: Compare the two isomer conformations of cis-1,2-dimethylcyclohexane and trans-1,2-dimethylcyclohexane -To determine the preferable conformation, the energy costs of the interactions (gauche, 1,3-diaxial, etc.) must be added together. Polycyclic Molecules:-Polycyclic molecules= less flexible. Flips and rotations are less frequent. Have a “fused ring” structure. Chem 261 1st EditionStereochemistry and Tetrahedral Centers Intro:Types of isomers…Constitutional isomer: same formula, different connectionsStereoisomers: same connections, different spatial arrangementsDiastereoisomers: non-mirror images, not super-imposableEnantiomer: mirror images, non-superimposable Chem 261 1st


View Full Document

UMass Amherst CHEM 261 - Cyclohexane Conformations, Disbustituted Cyclohexanes

Download Cyclohexane Conformations, Disbustituted Cyclohexanes
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Cyclohexane Conformations, Disbustituted Cyclohexanes and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Cyclohexane Conformations, Disbustituted Cyclohexanes 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?