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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: smghz on September 23, 2017, 04:49:46 PM

Title: Wrong Answer for a Meso Compound?
Post by: smghz on September 23, 2017, 04:49:46 PM: I stumbled upon this question that has a seemingly wrong answer.
(https://s.yimg.com/tr/i/3f811b57410744e6858422210b57f08e_A.png)

I mean, if you rotate either the right or left half of the structure, you get a trans structure that has no plane of symmetry. I proved it here with a molecular kit:
(https://ibin.co/3bPvVezi7V5H.jpg)
(https://ibin.co/3bPvNr3YYw3P.jpg)

I'm really confused, who is right and who is wrong??
Title: Re: Wrong Answer for a Meso Compound?
Post by: Borek on September 24, 2017, 03:36:23 AM: I am not sure what is what of what here. Can you elaborate on what the question is and what your pictures are?

I guess on the bw image top structure is the one you are asked to classify as either meso or not, but your model doesn't look like this structure. Perhaps that's the problem?
Title: Re: Wrong Answer for a Meso Compound?
Post by: smghz on September 24, 2017, 07:49:53 PM: Sorry for the confusion, the bottommost image is the answer they provided which says under it "Yes, meso compound." But, when I rotated their own answer's structure, I got the top molecular model structure, which is not the same as the question's structure.
Title: Re: Wrong Answer for a Meso Compound?
Post by: Borek on September 25, 2017, 04:06:01 AM: As I said earlier - I fail to see their structure in your model. On the upper picture of your model carbons are more or less in one plane, just like on the drawing marked "meso" - but both oxygens should go OVER the plane, that is, they both should stick in the direction of the viewer, yet one goes up and the other goes down..
Title: Re: Wrong Answer for a Meso Compound?
Post by: smghz on September 25, 2017, 08:25:22 AM: I apologize. My mistake. Here is the right structure:

(https://image.ibb.co/naHqM5/1ss.jpg)
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Ficonshow.me%2Fmedia%2Fimages%2Fui%2Fios7-icons%2Fpng%2F256%2Farrow-down-c.png&hash=62ded08c29e2272771f10c093645ce417e19b912)
(https://image.ibb.co/chvzEQ/IMG_20170925_081927_Edited.jpg)
Title: Re: Wrong Answer for a Meso Compound?
Post by: Babcock_Hall on September 25, 2017, 10:25:41 AM: Would you mind writing out the question for us?
Title: Re: Wrong Answer for a Meso Compound?
Post by: smghz on September 25, 2017, 02:51:18 PM: Here is the question!
(https://i.imgur.com/4G1CJZh.png)

I'm trying to ask if the structure in question is meso. I think it's not and that their answer is wrong.
Title: Re: Wrong Answer for a Meso Compound?
Post by: Babcock_Hall on September 25, 2017, 03:20:51 PM: If I have time, I will build a model later this evening myself, but I tend to agree with you. Wrong answers crop up all the time in homework problems.
Title: Re: Wrong Answer for a Meso Compound?
Post by: Vidya on September 25, 2017, 11:46:25 PM: Quote from: smghz on September 25, 2017, 02:51:18 PM
Here is the question!
(https://i.imgur.com/4G1CJZh.png)

I'm trying to ask if the structure in question is meso. I think it's not and that their answer is wrong.
There is one more way to check answer ...if structure is symmetrical and one chiral center is 'R' configuration and other one is 'S' then they are meso compounds.
Title: Re: Wrong Answer for a Meso Compound?
Post by: hypervalent_iodine on September 26, 2017, 12:16:08 AM: I would agree that it isn't meso. The structure they give in what I assume is the answer key (the structure with, 'yes, meso compound,' written underneath), isn't the same as the one given in e. The structure they give in the answer is a meso compound.