Tell the difference between cis and trans cyclodecene?

[uday28fb]

I know it's a randome question but it's bugging the hell out of me. Im looking at the picture in my text book and it tells which is which, but if it wasn't labeled I wouldn't be able to figure it out.

The trans has the double bond off of the middle carbon

It looks like this http://mits.nims.go.jp/matnavi/monomer/01/M0170105.png

the only reason I know that is the trans is because there is a similar picture in my textbook except the double bond is on the opposite side.

the cis has the double bond shifted over a carbon.

But how do you tell the difference if you were just given a picture?

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[uday28fb]

sorry i had to delete this this post, so im still curious.

 

[phospho]

I know it's a randome question but it's bugging the hell out of me. Im looking at the picture in my text book and it tells which is which, but if it wasn't labeled I wouldn't be able to figure it out.

The trans has the double bond off of the middle carbon

It looks like this http://mits.nims.go.jp/matnavi/monomer/01/M0170105.png

the only reason I know that is the trans is because there is a similar picture in my textbook except the double bond is on the opposite side.

the cis has the double bond shifted over a carbon.

But how do you tell the difference if you were just given a picture?

this is actually a very easy question if you can try to block out everything around the double bond for a second. think about the definition of a true E, and a true Z. The E will have the largest groups on opposite sides of the double bond. Isn't that what's happening in the picture you just put a link to? now think about the Z isomer...the two largest groups are supposed to be on the same side of the double bond. If we put the double bond on one of the sides of the decene, wouldn't that fulfill that requirement?
i hope this makes sense, if it doesn't, I can try to draw it out for you and scan it tomorrow...

 

[bkmonkey]

this is actually a very easy question if you can try to block out everything around the double bond for a second. think about the definition of a true E, and a true Z. The E will have the largest groups on opposite sides of the double bond. Isn't that what's happening in the picture you just put a link to? now think about the Z isomer...the two largest groups are supposed to be on the same side of the double bond. If we put the double bond on one of the sides of the decene, wouldn't that fulfill that requirement?
i hope this makes sense, if it doesn't, I can try to draw it out for you and scan it tomorrow...

Umm...I don't think these qualify as E/Z isomers, only cis/trans. To fall into the E/Z category, one of the carbons in the double bond needs to have two non-hydrogens attached to it. Using the cis/trans designation, if the hydrogens are on the same side of the double bond, it is cis, if they are on opposites, trans. The carbons actually involved in the bond are the same, it's just the relative postion of the substituents that changes.

 

[Isoprop]

the double bonds didn't really "shift." it's more like, if that double bond became trans, the other carbons need to be rearranged so that it looks like it shifted.

meh i can't really explain it in words.

 

[uday28fb]

this is actually a very easy question if you can try to block out everything around the double bond for a second. think about the definition of a true E, and a true Z. The E will have the largest groups on opposite sides of the double bond. Isn't that what's happening in the picture you just put a link to? now think about the Z isomer...the two largest groups are supposed to be on the same side of the double bond. If we put the double bond on one of the sides of the decene, wouldn't that fulfill that requirement?
i hope this makes sense, if it doesn't, I can try to draw it out for you and scan it tomorrow...

Wow, I'm really dumb, I can't believe I didn't see that. Basically all I did was look at it so the double bond was horizontal to me and saw that the largest groups went in opposit directions like you said, and thats pretty much an E or trans. Lol but don't worry Im still in orgo 1, dont think im taking the mcat right now lol.

 

[kronickm]

Imagine a line extending through the double bond.

For cis/trans, look where the carbon chain enters and exits the double bond. If it is on the same side, cis, opposite trans.

For E/Z, do the same thing but don't look at the carbon chain look at the largest (highest ranking) group on each side.