isomer (1 Viewer)

[Syd123123]

How many isomers does C2H4Cl2 have?
I count 3 when I draw it out but people say it only has 2?? https://au.answers.yahoo.com/question/index?qid=20070919183123AAnhlph

 

[rand_althor]

There are 2. You can either have both chlorine atoms on one carbon or one chlorine atom on each carbon.

 

[Syd123123]

But if I draw it out? There's 3??
......H H
Cl - C - C - Cl
......H H

......H H
Cl - C - C - H
......Cl H

......H H
Cl - C - C - H
......H Cl

3 and everything else is just a 'flip' or rotation??

 

[iforgotmyname]

^theres only 2 carbon atoms

 

[rand_althor]

Your first and last ones are both 1,2-dichloroethane. There is one chlorine atom per carbon for both.

 

[Drsoccerball]

As i've mentioned before its because its a 3D molecule therefore your 1st and last are the same

 

[Syd123123]

Wait so isomers are only if they're differently named? wtf my teacher said if they look different then it's an isomer thats why i thought 1st and 3rd are isomers??

 

[Drsoccerball]

wait so isomers are only if they're differently named? Wtf my teacher said if they look different then it's an isomer thats why i thought 1st and 3rd are isomers??

its a 3d molecule

 

[rand_althor]

It is when the molecules configuration of atoms is unique when viewed in 3D. For the last and third ones, you have one chlorine atom on each carbon. The following are all the same - they all have one chlorine atom bonded with each carbon atom:

......H H
Cl - C - C - H
......H Cl

......H Cl
Cl - C - C - H
......H H

......H H
Cl - C - C - Cl
......H H

 

[Syd123123]

It is when the molecules configuration of atoms is unique when viewed in 3D. For the last and third ones, you have one chlorine atom on each carbon. The following are all the same - they all have one chlorine atom bonded with each carbon atom:

......H H
Cl - C - C - H
......H Cl

......H Cl
Cl - C - C - H
......H H

......H H
Cl - C - C - Cl
......H H

Thanks. How would I use permuations/combinations to find how many isomers? It seems possible. And I know, it's much more work but Im curious

 

[iforgotmyname]

its just 2factorial

 

[iforgotmyname]

if there is 2 fluorines too then its 2fact x 2fact

 

[Fizzy_Cyst]

Wait so isomers are only if they're differently named? wtf my teacher said if they look different then it's an isomer thats why i thought 1st and 3rd are isomers??

Nope!

If there was a double bond between the two C's then they would be geometric isomers, but this is beyond the HSC course