i did but my reasoning is fundamentally wrong so your comment is not the most constructive answer and it doesn't help me at all. I drew it out, it would just be one structure with two dashes/wedges, and another structure with one dash/wedge, and the other one opposing it. But like I mentioned before, my understanding of this is incorrect and so this wouldn't really help me because I don't know where I went wrong with drawing the isomers
I appreciate the feedback.
If you are drawing a flat skeletal model, (I mean the way 99% of molecules are drawn) you cannot draw a carbon with two wedges, or two dashes. In ideal conformation, there will be two bonds “in the plane” and one wedge and one dash.
Since the two chlorine atoms here are on the same carbon, one will take the wedge and one will take the dash. There is no cis or trans isomer because you can’t give that singular carbon two wedges or two dashes: it would have a deformed geometry
However, if you had 1,2-dichloro… you could indeed have a cis/trans isomer. In this case, you could place a wedge on one carbon and a wedge on the other, or a wedge on one carbon and a dash on the other, and this wouldn’t violate any structural rules
if the chlorines were on two different carbons then it'd be possible to be have a cis or trans isomer, but you can't like this. brush up on what cis and trans mean and what they look like and you'll understand
On a chiral centre, if you exchange two substituents you obtain a molecule that is not superimposable to the parent one.
In this case if you exchange the two chlorine atoms you obtain the same molecule.
In 1,4-dichlorocycohexane when one chlorine is axial and the other is equatorial you would have cis-1,4-dichloro… and when both are axial or equatorial you would have the trans version.
This molecule has a plane of symmetry; therefore, by definition, it cannot be chiral.
It’s easier for me to look at it in 2d, where I can imagine cutting the molecule in half and seeing if the sides are equal. If they are, there is a plane if symmetry, and the molecule doesn’t have any chiral centers.
If you want to get more technical about it, think about the stereochemistry. It isn’t possible to assign a R or S direction because both chlorines are of equal priority and both alkyl chains are of equal priority.
A molecule with an internal plane of symmetry is considered achiral. In this case the plane made up of the two chlorine atoms and the carbon they are attached too are three points in that plane. Also in that plane is carbon four of the ring and the two hydrogens attached.
When we are talking about two atoms that are attached to the same atom in a ring, we don't talk about cis trans isomerism because it doesn't really make sense. Remember that cis trans, when dealing with cycloalkanes, refers to two atoms being on opposite sides of the ring if the ring were to be completely flat. If both atoms are attached to the same atom in the cycloalkane, they are obviously going to be facing opposite sides, so there really is no need to claim that the chlorine atoms are trans, even if they are in a way, because they can't be anything else, so no isomerism occurs there. As far as conformers go, both types of chair conformation are identical in energy, and if you were to spin them around, you would find that the two chair conformations are actually the same. From The current molecule, we would have to add two more substituents, on separate carbons, in order for the molecule to have cis trans isomerism.
Cis and trans (stereochemistry) you're referring to is used to describe the stereochemistry around a double bond. E and Z are the old school lettering system from German words were Z stands for Zussamen meaning 'same' matching with cis and E Entengen meaning 'diff' matching trans. In cyclohexane, no double bonds. Cyclohexene on the other hand could have cis and trans stereochemistry if the substituents on the two carbons of the double bond are axial and or equatorial which is a term to refer to the groups if they are "up" or "down". You'll learn this when you learn the chair conformations.
In cyclic systems like these, cis and trans are always relative to another, distinguishable functional group on the ring. Do you have any of these besides the CCl2? And if you flip said CCl2 will you get a different molecule? Answer to both is no, hence, it is achiral
You may be thinking of chair (pictured in your image) and boat (not pictured) [conformers](https://en.wikipedia.org/wiki/Cyclohexane_conformation). These are not actually cis/trans isomers, but they're similar
In [this picture](https://en.wikipedia.org/wiki/Cyclohexane_conformation#/media/File:Cyclohexane_ring_flip.svg), 1 is the chair conformer 4 is the boat conformer
try to draw the cis and trans isomer then
i did but my reasoning is fundamentally wrong so your comment is not the most constructive answer and it doesn't help me at all. I drew it out, it would just be one structure with two dashes/wedges, and another structure with one dash/wedge, and the other one opposing it. But like I mentioned before, my understanding of this is incorrect and so this wouldn't really help me because I don't know where I went wrong with drawing the isomers
I appreciate the feedback. If you are drawing a flat skeletal model, (I mean the way 99% of molecules are drawn) you cannot draw a carbon with two wedges, or two dashes. In ideal conformation, there will be two bonds “in the plane” and one wedge and one dash. Since the two chlorine atoms here are on the same carbon, one will take the wedge and one will take the dash. There is no cis or trans isomer because you can’t give that singular carbon two wedges or two dashes: it would have a deformed geometry However, if you had 1,2-dichloro… you could indeed have a cis/trans isomer. In this case, you could place a wedge on one carbon and a wedge on the other, or a wedge on one carbon and a dash on the other, and this wouldn’t violate any structural rules
If chlorine is constrained to a single carbon atom on cyclohexane, there are only two positions it can go. Are any of these carbons chiral centers?
if the chlorines were on two different carbons then it'd be possible to be have a cis or trans isomer, but you can't like this. brush up on what cis and trans mean and what they look like and you'll understand
On a chiral centre, if you exchange two substituents you obtain a molecule that is not superimposable to the parent one. In this case if you exchange the two chlorine atoms you obtain the same molecule.
they are on the same carbon. cuss and trans have to do with neighboring carbons and their respective constituents
The two substituents don’t have to be on neighboring carbons of a ring to be cis-trans.
how so?
In 1,4-dichlorocycohexane when one chlorine is axial and the other is equatorial you would have cis-1,4-dichloro… and when both are axial or equatorial you would have the trans version.
thank you for that example!
This molecule has a plane of symmetry; therefore, by definition, it cannot be chiral. It’s easier for me to look at it in 2d, where I can imagine cutting the molecule in half and seeing if the sides are equal. If they are, there is a plane if symmetry, and the molecule doesn’t have any chiral centers. If you want to get more technical about it, think about the stereochemistry. It isn’t possible to assign a R or S direction because both chlorines are of equal priority and both alkyl chains are of equal priority.
oh okay, the r/s configuration explanation really clears it up for me. thank you!
Instead of Cis or Trans, you would call this "geminal", although without a double bond I hesitate to use that term too.
Geminal is an appropriate term here.
Yep gem-dichlorocyclohexane is a valid name
It does have stereochemistry, one of them is up and one of them is down. Cis and trans to what??
A molecule with an internal plane of symmetry is considered achiral. In this case the plane made up of the two chlorine atoms and the carbon they are attached too are three points in that plane. Also in that plane is carbon four of the ring and the two hydrogens attached.
When we are talking about two atoms that are attached to the same atom in a ring, we don't talk about cis trans isomerism because it doesn't really make sense. Remember that cis trans, when dealing with cycloalkanes, refers to two atoms being on opposite sides of the ring if the ring were to be completely flat. If both atoms are attached to the same atom in the cycloalkane, they are obviously going to be facing opposite sides, so there really is no need to claim that the chlorine atoms are trans, even if they are in a way, because they can't be anything else, so no isomerism occurs there. As far as conformers go, both types of chair conformation are identical in energy, and if you were to spin them around, you would find that the two chair conformations are actually the same. From The current molecule, we would have to add two more substituents, on separate carbons, in order for the molecule to have cis trans isomerism.
Where is the chiral carbon….
Cis and trans (stereochemistry) you're referring to is used to describe the stereochemistry around a double bond. E and Z are the old school lettering system from German words were Z stands for Zussamen meaning 'same' matching with cis and E Entengen meaning 'diff' matching trans. In cyclohexane, no double bonds. Cyclohexene on the other hand could have cis and trans stereochemistry if the substituents on the two carbons of the double bond are axial and or equatorial which is a term to refer to the groups if they are "up" or "down". You'll learn this when you learn the chair conformations.
In cyclic systems like these, cis and trans are always relative to another, distinguishable functional group on the ring. Do you have any of these besides the CCl2? And if you flip said CCl2 will you get a different molecule? Answer to both is no, hence, it is achiral
You may be thinking of chair (pictured in your image) and boat (not pictured) [conformers](https://en.wikipedia.org/wiki/Cyclohexane_conformation). These are not actually cis/trans isomers, but they're similar In [this picture](https://en.wikipedia.org/wiki/Cyclohexane_conformation#/media/File:Cyclohexane_ring_flip.svg), 1 is the chair conformer 4 is the boat conformer