Drawing Cyclohexane and Decalins. parallel bonds Drawing Cyclohexane.

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Presentation transcript:

Drawing Cyclohexane and Decalins

parallel bonds Drawing Cyclohexane

equatorial bonds

axial bonds

equatorial bonds axial bonds

Numbering Cyclohexane

Start anywhere and number consecutive carbons.

Tetrahedral Carbons in Cyclohexane

tetrahedral carbon 1

2

3

4

5

6

Disubstituted Isomers of Cyclohexane

trans-1,2-diequatorial 1 2

and...

trans-1,2-diaxial 1 2

are conformational isomers of one another, and...

cis-1,3-diequatorial 1 3

and...

cis-1,3-diaxial 1 3

are conformational isomers of one another, and...

trans-1,4-diequatorial 1 4

and...

trans-1,4-diaxial 1 4

are conformational isomers of one another.

Chair Conformations of Cyclohexane

flip this carbon above the plane flip the other carbon below the plane hold red bonds in a plane the other chair conformation you get

number carbons in this conformation number the same carbons in this conformation

given the plane formed by carbons 2, 3, 5, and 6 C 1 is below the plane and... C 4 is above the plane, while... C 1 is above the plane and... C 4 is below the plane.

equatorial bonds here become... axial bonds here, and... equatorial bonds here. axial bonds here become...

Equatorial bonds alternate being above and below the axial bonds on a given carbon atom above below above

and...

axial bonds alternate being above and below the equatorial bonds on a given carbon atom. above below above

Drawing Decalins

Add two vicinal equatorial bonds trans - Decalins Start with a chair cyclohexane Complete a second chair cyclohexane Axial fusion bonds are diaxial to rings A and B. AB

cis - Decalins Start with a chair cyclohexane Add two vicinal bonds: One equatorial; one axial Complete a 2nd chair cyclohexane Ring fusion substituents are cis to rings A and B. A B X Y Substituent X is equatorial to ring A and axial to ring B while substituent Y is equatorial to ring B and axial to ring A. cis-Decalin 1

cis - Decalins Start with a chair cyclohexane Add two vicinal bonds: One axial; one equatorial A B Ring fusion substituents are cis to rings A and B. Complete a 2nd chair cyclohexane Y X Substituent X is now axial to ring A and equatorial to ring B while substituent Y is now axial to ring B and equatorial to ring A. cis-Decalin Conformation 2

cis - Decalins X Y X Y cis - Decalin Conformation 1 Y X cis - Decalin Conformation 2 rotate clockwise 90 o Enantiomers but equal in energy

The End