newman to fischer

[arpitpatel86]

when you are converting the newman projection into a fischer do u alway switch the back two?

2. how do u go from a cyclohexane ring to chair conformation like if it shows that both substituent are cis how do u put that in teh chair?

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[PreDent2009]

This is kind of difficult to explain without a visual-aid, but to convert from a newman projection to the fischer, you just keep what the "Y" shaped is on the front carbon and put that onto the fischer. Then the back carbon you just switch the groups. This will retain the stereochemistry. As for interconverting between a planar depiction of a cyclohexane into its chair confirmation, you just keep the substituent numbers the same on the chair and make sure you keep the stereochemistry. For example if it is a cis, 1-2-cyclohexandiol on the flat structure, just put an OH group on the chair either axial or equatorial first, it is arbitrary where you put it. If you put the OH on the axial on lets say the top right tip of the chair, then the second OH would go on the carbon directly down from it, but that on is in the equatorial position. That would be cis. Or you could put the top OH on the tip equatorial first, then the carbon below that put it in the axial. That would also be cis. There is many ways you can do this and it does not matter which way you decide. Hope that helps.

 

[userah]

if you number the carbons on the cyclohexane and the chair projection, it will help you label any groups that might be on both and it'll make it easier for you. and cis/trans just means that both groups must either be facing up/down. i think the thing to remember is that any alkyl groups attached must be in the equitorial position. that's the most stable position for alkyl groups. as for halide groups, i believe they prefer the axial position.