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Some chemistry (please help me convince the teacher and more importantly, myself)

akio123008
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Hello everyone, I need some chemistry related help, and I thought there might be some people who are able to provide that on this forum. I disagreed with my chemistry teacher, and the worst part is, my friends aren't even on my side on this one. But I'm not giving up so soon, I'm determined to get to the bottom of this, so here's what happened.

 

The teacher is explaining some IUPAC naming of organic molecules. At some point, he draws the structure of a molecule on the whiteboard, which looks like this:

cycl1.png.357800e5271795f3edf1686f82bb0596.png

He then asks the class to come up with the name of the molecule. Most people, including me, come up with the name "cyclohexane-1,2-dicarbonitrile". The teacher then proceeds to tell us with a big smile that this is in fact, the wrong answer, and that he's never heard anyone get it right. After which he shows the name should have been "cis-cyclohexane-1,2-dicarbonitrile" because both of the nitrile groups are on the same side of the ring (in 3D space)

 

Now here come's my argument why this question was impossible to answer: this 2 dimensional structure that he provided, doesn't tell a damned thing about the 3D space representation of this molecule. If he would have given us a structure like this:

cycl2.png.1ec189fbbdbe1b11ef10c9572ae54bc0.png

it's clear that the CN groups are both on the same side of the ring, because they both have solid wedged bond in the drawing, indicating they're pointing towards the viewer. (the natta projection method)

A Haworth projection (look on wikipedia if you don't know that name) would also make sense. 

 

In my opinion, the type of structural formula that the teacher used here doesn't tell on which side the groups are and therefore this question was a nasty and impossible to answer trick question.

 

I've seen some sources online specify that in the 2 dimensional formula used by my teacher, the side on which the groups are relative to the carbon atom tells you if they are in front or behind the ring, but that would strengthen my point, since it would mean the CN groups are on opposite sides of the ring, which would mean the name is actually "trans-cyclohexane-1,2-dicarbonitrile".

 

What I'm looking for is some sort of reliable source (an article or something) that confirms that I'm right so that I can demonstrate my point to the teacher, and more importantly, my classmates. (BTW I have a fine relationship with them and with the teacher too, there's no hate here) I hope someone on this forum can provide me either an explanation why the 2 dimensional structure *is* right and I'm wrong, or provide me with the evidence I need to convince my teacher that the reason nobody ever gets the right answer is because the question is impossible.

 

 

 

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3 minutes ago, akio123008 said:

Hello everyone, I need some chemistry related help, and I thought there might be some people who are able to provide that on this forum. I disagreed with my chemistry teacher, and the worst part is, my friends aren't even on my side on this one. But I'm not giving up so soon, I'm determined to get to the bottom of this, so here's what happened.

 

The teacher is explaining some IUPAC naming of organic molecules. At some point, he draws the structure of a molecule on the whiteboard, which looks like this:

cycl1.png.357800e5271795f3edf1686f82bb0596.png

He then asks the class to come up with the name of the molecule. Most people, including me, come up with the name "cyclohexane-1,2-dicarbonitrile". The teacher then proceeds to tell us with a big smile that this is in fact, the wrong answer, and that he's never heard anyone get it right. After which he shows the name should have been "cis-cyclohexane-1,2-dicarbonitrile" because both of the nitrile groups are on the same side of the ring (in 3D space)

 

Now here come's my argument why this question was impossible to answer: this 2 dimensional structure that he provided, doesn't tell a damned thing about the 3D space representation of this molecule. If he would have given us a structure like this:

cycl2.png.1ec189fbbdbe1b11ef10c9572ae54bc0.png

it's clear that the CN groups are both on the same side of the ring, because they both have solid wedged bond in the drawing, indicating they're pointing towards the viewer. (the natta projection method)

A Haworth projection (look on wikipedia if you don't know that name) would also make sense. 

 

In my opinion, the type of structural formula that the teacher used here doesn't tell on which side the groups are and therefore this question was a nasty and impossible to answer trick question.

 

I've seen some sources online specify that in the 2 dimensional formula used by my teacher, the side on which the groups are relative to the carbon atom tells you if they are in front or behind the ring, but that would strengthen my point, since it would mean the CN groups are on opposite sides of the ring, which would mean the name is actually "trans-cyclohexane-1,2-dicarbonitrile".

 

What I'm looking for is some sort of reliable source (an article or something) that confirms that I'm right so that I can demonstrate my point to the teacher, and more importantly, my classmates. (BTW I have a fine relationship with them and with the teacher too, there's no hate here) I hope someone on this forum can provide me either an explanation why the 2 dimensional structure *is* right and I'm wrong, or provide me with the evidence I need to convince my teacher that the reason nobody ever gets the right answer is because the question is impossible.

 

cycl3.png

Lighten up a bit dude, you're professor obviously has a sense of humour. Who cares if he tricked you with an unanswerable question.

 

Btw arguing with your professor and especially telling them they're wrong is a sure fire way to get in their bad books.

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Haha no, as I mentioned, my relationship with that teacher is just fine. He's great. But I can't stand this particular question. And yes he does have a sense of humor, which is also why I know he's fine with me disagreeing with him.

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7 minutes ago, akio123008 said:

Hello everyone, I need some chemistry related help, and I thought there might be some people who are able to provide that on this forum. I disagreed with my chemistry teacher, and the worst part is, my friends aren't even on my side on this one. But I'm not giving up so soon, I'm determined to get to the bottom of this, so here's what happened.

 

The teacher is explaining some IUPAC naming of organic molecules. At some point, he draws the structure of a molecule on the whiteboard, which looks like this:

cycl1.png.357800e5271795f3edf1686f82bb0596.png

He then asks the class to come up with the name of the molecule. Most people, including me, come up with the name "cyclohexane-1,2-dicarbonitrile". The teacher then proceeds to tell us with a big smile that this is in fact, the wrong answer, and that he's never heard anyone get it right. After which he shows the name should have been "cis-cyclohexane-1,2-dicarbonitrile" because both of the nitrile groups are on the same side of the ring (in 3D space)

 

Now here come's my argument why this question was impossible to answer: this 2 dimensional structure that he provided, doesn't tell a damned thing about the 3D space representation of this molecule. If he would have given us a structure like this:

cycl2.png.1ec189fbbdbe1b11ef10c9572ae54bc0.png

it's clear that the CN groups are both on the same side of the ring, because they both have solid wedged bond in the drawing, indicating they're pointing towards the viewer. (the natta projection method)

A Haworth projection (look on wikipedia if you don't know that name) would also make sense. 

 

In my opinion, the type of structural formula that the teacher used here doesn't tell on which side the groups are and therefore this question was a nasty and impossible to answer trick question.

 

I've seen some sources online specify that in the 2 dimensional formula used by my teacher, the side on which the groups are relative to the carbon atom tells you if they are in front or behind the ring, but that would strengthen my point, since it would mean the CN groups are on opposite sides of the ring, which would mean the name is actually "trans-cyclohexane-1,2-dicarbonitrile".

 

What I'm looking for is some sort of reliable source (an article or something) that confirms that I'm right so that I can demonstrate my point to the teacher, and more importantly, my classmates. (BTW I have a fine relationship with them and with the teacher too, there's no hate here) I hope someone on this forum can provide me either an explanation why the 2 dimensional structure *is* right and I'm wrong, or provide me with the evidence I need to convince my teacher that the reason nobody ever gets the right answer is because the question is impossible.

 

 

 

You are correct, but don't push it.

Your professor knows more than you in this subject and arguing doesn't solve anything in a case where everybody got it wrong.

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Just now, Kodiak. said:

You are correct, but don't push it.

Your professor knows more than you in this subject and arguing doesn't solve anything in a case where everybody got it wrong.

YES. That's always good to hear. Don't worry, I won't be annoying the crap out of the man, he's one of my favorite teachers in fact, wich is actually the reason I feel comfortable disagreeing with him. 

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It's a trick question. It's intended to have you answer incorrectly with the purpose of keeping your attention levels high. If the teacher had reprimanded you for answering incorrectly, you'd be right, but that's not the case.

 

It would still be possible to answer correctly given enough knowledge of chemistry though; if you already know the molecule, for example, or if you're expert enough to know that such a molecule can't take any other form.

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Technically you are correct (the best kind, but also the worst sometimes :P), but yeah don't push it too hard. Context may matter here though.

Does this class/chapter/whatever perhaps mark the start of the 3D structure of molecules being introduced? Maybe that's the whole point of asking this question, that molecules don't always exist in a single plane.

 

[Edit] or yeah, just a trick question to keep your attention

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5 minutes ago, Sauron said:

It's a trick question. It's intended to have you answer incorrectly with the purpose of keeping your attention levels high. If the teacher had reprimanded you for answering incorrectly, you'd be right, but that's not the case.

 

It would still be possible to answer correctly given enough knowledge of chemistry though; if you already know the molecule, for example, or if you're expert enough to know that such a molecule can't take any other form.

Yeah, that's true, I can understand it's just a trick question to keep people sharp, but when I asked him about that, he said it *was* solvable, which created made me doubt my own argument. Also, haha no way, I've never heard of this particular molecule.

5 minutes ago, tikker said:

Technically you are correct (the best kind, but also the worst sometimes :P), but yeah don't push it too hard. Context may matter here though.

Does this class/chapter/whatever perhaps mark the start of the 3D structure of molecules being introduced? Maybe that's the whole point of asking this question, that molecules don't always exist in a single plane.

There was no context, it was just a quick question. He was doing a whole series of molecules and made us come up with the names. This was one of them, the context was basically: "what's this called" followed by "no one's ever got the right answer". I guess that said enough though :)

 

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The main thing that frustrated me is that the teacher wouldn't admit that it was a trick question, which made me doubt whether I was right, but now I know better. Thanks a lot for your replies!

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You want honesty?

 

You sound like a condescending jerk right now. Your professor will have more knowledge than you in this field so don't push it. You might get on well with him, but if you keep doing this kinda thing you will tick people off very quickly. No-one likes being bluntly told they are wrong

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19 minutes ago, akio123008 said:

The main thing that frustrated me is that the teacher wouldn't admit that it was a trick question

They don't have to

20 minutes ago, akio123008 said:

which made me doubt whether I was right

The point of trick questions is to make you think and read the question carefully, instead of regurgitating everything you've learned

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Eh... The 'professor' didn't specify the stereochemistry when presenting the problem.  With the information you were given the correct answer would be cyclohexane-1,2-dicarbonitrile.  For the prof to say otherwise just seems like a strange 'gotcha' moment. 

 

Both isomers exist for this material. Have you studied stereoisomers? Was he trying to get you to ask about stereochemistry?

 

 

I'd only fight it if it was on a test.  

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1 hour ago, akio123008 said:

Now here come's my argument why this question was impossible to answer: this 2 dimensional structure that he provided, doesn't tell a damned thing about the 3D space representation of this molecule. If he would have given us a structure like this:

cycl2.png.1ec189fbbdbe1b11ef10c9572ae54bc0.png

You're actually right. I think either your teacher is giving you a trick question to test student comprehension or your teacher got it wrong. 

 

I highly recommend John McMurry's Org Chem book (2010, 7th ed).

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Well, i would approach this a little bit different.

 

Your professor says you are wrong, even tho you are not. Ask her why your answer is incorrect.

To make it a bigger challenge. Let her draw your answer (so ask her to draw a cyclohexane-1,2-dicarbonitrile or whatever it is called)

And you can of course keep pushing it by drawing them both and compare them.

 

People say that you should chill out, and i partially agree with them, but i also HATE people saying "you are wrong" and then refuse to explain why...

 

I don't know anything about chemistry (or like, stupidly little, i know h2o and the mendeljev stuff but that's it), it's just an idea.

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1 hour ago, akio123008 said:

trans

Outdated. better use e and z.

 

1 hour ago, akio123008 said:

cycl1.png.357800e5271795f3edf1686f82bb0596.png

this is not equal to: 

 

1 hour ago, akio123008 said:

cycl2.png.1ec189fbbdbe1b11ef10c9572ae54bc0.png

this. Just look at all the missing ch3.

 

And yes the first picture don't says anything about the stereochemistry. If he wanted to draw it like the second picture then culled line would be normal. It would then say there is stereochemistry but i don't care.

Don't know if iupac also specific the drawing but they have books like green, red, golden, etc. 

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1 hour ago, akio123008 said:

 

 

 

You are not correct.  Your prof is correct.  And it was a trick question.  If you had given the answer that your prof gave, he could still have said you were wrong.  This is the nature of trick questions.  Here's why:

 

The correct answer is: "As drawn there are two possibilities, __ and __."  Only then would you have been certain of being right.

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Let me address all of this:

FIrst of all, we have indeed discussed stereochemistry, so I am aware of how that works, but that wasn't mentioned in this particular situation; there was no clear evidence that stereochemistry played an important role in this particular challenge. E.g. he didn't mention it in the entire lesson, he did not sneak it into the question somehow, and on top of that, this type of 2 dimensional drawing implies that stereochemistry wasn't relevant in this case

 

Also, about the "being a jerk" part, that's not my intention. I just wanted to know whether I could have answered the question, that's all. As I've mentioned before, he's one of my favorite teachers. However, (probably because he knows I do understand the concept so it's fine anyway) he didn't take his time to explain it, so I just had to check if I was right, and I couldn't find any real answer online, so I decided to give this place a go. The fact that I'm posting all this, and thinking about it thoroughly just adds to my preparation for future tests, this afternoon I've been doing more research on the topic than I would normally ever do. The teacher could only appreciate that. Besides, I don't even have to convince him, I know what's going on now, and that's what matters to me.

 

Finally:

31 minutes ago, Blasteque said:

You are not correct.  Your prof is correct.  And it was a trick question.  If you had given the answer that your prof gave, he could still have said you were wrong.  This is the nature of trick questions.  Here's why:

 

The correct answer is: "As drawn there are two possibilities, __ and __."  Only then would you have been certain of being right.

I was told that when you have to provide the name of a molecule from a drawing, if the type of drawing doesn't allow you to perceive a certain property, you don't have to mention it in the name. Altough, naming all possibilities is also correct of course.

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39 minutes ago, James Evens said:

 

Outdated. better use e and z.

 

this is not equal to: 

 

this. Just look at all the missing ch3.

 

And yes the first picture don't says anything about the stereochemistry. If he wanted to draw it like the second picture then culled line would be normal. It would then say there is stereochemistry but i don't care.

Don't know if iupac also specific the drawing but they have books like green, red, golden, etc. 

The images are the same, the corners of the hexagon are equivalent to carbon atoms that each attach to a pair of hydrogen atoms.

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18 minutes ago, akio123008 said:

The images are the same, the corners of the hexagon are equivalent to carbon atoms that each attach to a pair of hydrogen atoms.

If you just make a line it is a carbon with the needed Hydrogen attached to it. In this case it would be methyl groups. If you want to draw a Hydrogen you have to letter the end of the line with a H.

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1 hour ago, James Evens said:

Outdated. better use e and z.

Why did the naming change exactly? Couldn't we just add an additional bullet point to cis/trans in case there was no clear pair of things?

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30 minutes ago, James Evens said:

If you just make a line it is a carbon with the needed Hydrogen attached to it. In this case it would be methyl groups. If you want to draw a Hydrogen you have to letter the end of the line with a H.

Look at the image of cyclohexane (C6H12) on this page https://en.wikipedia.org/wiki/Cyclohexane

 

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The simple truth is some professors make up a little to fill in the gaps and spark your interest. They're never going to be 100% right, but that doesn't matter because they mark the tests :) 

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Just now, RorzNZ said:

The simple truth is some professors make up a little to fill in the gaps and spark your interest. They're never going to be 100% right, but that doesn't matter because they mark the tests :) 

It's fine indeed, I just wanted to know for sure I couldn't have gotten it right.

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4 minutes ago, akio123008 said:

Look at the image of cyclohexane (C6H12) on this page https://en.wikipedia.org/wiki/Cyclohexane

 

Jehh nothing wrong with this. 

But this is his picture (part of it):

Capture.GIF.e24de6ff60ef1bbe96079c13537e7004.GIF

The red is from me. When you hast have a line it is a carbon. 

 

6 minutes ago, tikker said:

Why did the naming change exactly? Couldn't we just add an additional bullet point to cis/trans in case there was no clear pair of things?

Problems.  What is this?

IMG_20181107_190340.thumb.jpg.67e216e28ad69b1ca301e07268540d61.jpg

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Only in skeletal formulas (that's the second type of picture I created) ends and vertices (corners) indicate a carbon atom. But the first picture, the one created by the teacher isn't such a formula. In the "regular" 2 dimensional structural formula, since the carbon atoms are drawn using the letter C already, it's common (or a least where I live) to leave the hydrogen atoms and just draw the lines. So there are definitely no methyl groups here. Since this is agreed with by the teacher too, I know that he meant it that way too. I see where you're coming from though, it could have been clearer.

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