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Streoisomerism. pass paper mistake or just me?

How many stereoisomers?

Mark scheme says 4. I only see 2.

one of the double bonds is surrounded by 3 H so you dont get an isomer?

Have I drawn it right?

thanks
Screenshot 2018-05-14 15.11.57.png56.8KB
Original post by flux capacitor
How many stereoisomers?

Mark scheme says 4. I only see 2.

one of the double bonds is surrounded by 3 H so you dont get an isomer?

Have I drawn it right?

thanks



2x E/Z isomers

2x Optical isomers (don't worry about this if you're currently on AS :smile: )
Original post by EdexcelAreIdiots
2x E/Z isomers

2x Optical isomers (don't worry about this if you're currently on AS :smile: )


wow! thanks for the reply. let me see if i can spot them now.
Nope cant see it.

Im looking at the first double bond, I see it surrounded by 3 different grps.
1) H
2) CH3
3) H
4) C4OH7

So we have 1 grp in common on the C atoms connected to the double bond (The H) so we can use cis/tran notation if we like.
That's all im seeing on the first double bond.

The second double bond
1) H
2) H
3) H
4) C5H9O

There are 3 groups the same - so we cant get any isomerism around that double bond?

Where am I going wrong?

for optical isomers we need 4 different grps no? OH i think i have seen my mistake now. it not to do with the double bond.

thanks
(edited 5 years ago)
ok the carbon connected to the OH is a chiral centre? is that what i was missing?
(edited 5 years ago)
Original post by flux capacitor
ok the carbon connected to the OH is a chiral centre? is that what i was missing?


Correct :smile:
Original post by EdexcelAreIdiots
Correct :smile:


Thanks, will look out for those in the future.
Original post by EdexcelAreIdiots
Correct :smile:


Your name is interesting. I had to switch from edexcel to OCR. I have not covered the whole syllabus of OCR yet but so far I have come across I think 2 things that seem to be easier on OCR. OCR don't bother with SN1/SN2. or half curly arrows. I wonder if they make up for it elsewhere?
Original post by flux capacitor
Your name is interesting. I had to switch from edexcel to OCR. I have not covered the whole syllabus of OCR yet but so far I have come across I think 2 things that seem to be easier on OCR. OCR don't bother with SN1/SN2. or half curly arrows. I wonder if they make up for it elsewhere?


I've had it since GCSEs lol. I actually do AQA, but from what my friends have told me OCR seems to be a bit harder than AQA.
Original post by EdexcelAreIdiots
I've had it since GCSEs lol. I actually do AQA, but from what my friends have told me OCR seems to be a bit harder than AQA.


OCR is easier than AQA in my opinion, not in terms of content (as I haven't seen what's different about both boards' specifications), but in terms of question wording. Their questions make a bit more sense to me. AQA seem to like asking 'strange' questions now and then...

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