Determining cis/trans for cyclohexane?

[kkentm]

Is there any concrete rule for this? I keep reading conflicting methods. I watched Chad's video on it and his method is to look/draw the planar diagram of the molecule where the substituents are represented by wedges/dashes. Then based on this diagram he draws out the chair conformation and converts the wedges/dashes to axial/equatorial. Is this method correct?

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[geeyouknit]

Is there any concrete rule for this? I keep reading conflicting methods. I watched Chad's video on it and his method is to look/draw the planar diagram of the molecule where the substituents are represented by wedges/dashes. Then based on this diagram he draws out the chair conformation and converts the wedges/dashes to axial/equatorial. Is this method correct?

I don't think so? It's not a matter of axial or equatorial since the molecule switches conformation rapidly, so the substituent will also switch between axial and equatorial. It's a matter of up and down. A substituent will always have an "up or down" axial and an "up or down" equatorial.

If you have 2 wedges or 2 dashes, they are cis (face same side). If you have 1 wedge and one dash, they are trans to each other. This means that one of subs faces "up", both when its axial (straight up) and equatorial (sideways 45 deg upwards) in chair conformation and the other faces "down" when its axial (straight down) and equatorial (sideways 45 deg downwards).

 

[kkentm]

I don't think so? It's not a matter of axial or equatorial since the molecule switches conformation rapidly, so the substituent will also switch between axial and equatorial. It's a matter of up and down. A substituent will always have an "up or down" axial and an "up or down" equatorial.

If you have 2 wedges or 2 dashes, they are cis (face same side). If you have 1 wedge and one dash, they are trans to each other. This means that one of subs faces "up", both when its axial (straight up) and equatorial (sideways 45 deg upwards) in chair conformation and the other faces "down" when its axial (straight down) and equatorial (sideways 45 deg downwards).

right, what you just said is what i meant. didnt mean that wedged/dashed correlates directly with either axial or equatorial but rather you can determine whether it is axial/equatorial by using the up/down method as you stated. just wanted to confirm that this method is indeed valid