Which TWO of the following traits apply to Fischer's Conventio...

Question

Which TWO of the following traits apply to Fischer's Convention for naming stereoisomers?

a) Utilizes (+) and (-) designations.

b) Utilizes (D) and (L) designations.

c) Utilizes (R) and (S) designations.

d) Requires drawing the compound with aldehyde/ketone at the top.

e) Based on optical properties of the compound in solution.

f) Reflects stereochemistry at multiple centers.

Accepted Answer

So this practice problem is asking, which 2 of the following traits applied to Fisher's convention for naming stereo isomers, and we've got these 6 potential answer options down below. And so what we need to recall from our previous lesson videos is that Fisher's convention is referring to the d or l configurations. And really, it's the con ingold pre log system that refers to r and s configurations. And so what this means is that we can cross off option c, and we can actually highlight option b as one of the correct answers. But recall that we're looking for 2 correct answers. So, there is another correct answer amongst these options. And so, what we also need to realize is that, we can eliminate option a because it says that Fisher's convention utilizes plus and minus designations. However, this is not something that we mentioned in our previous lesson videos and this is not true. And so you might recall from way back in your old organic chemistry courses that the plus and the minus designations are indicating the optical activity of the molecule, but Fisher's convention does not convey the optical activity and so plus and minus is again not going to be correct. And this also means that we can eliminate option e because it suggests again that Fisher's convention is based on optical properties of the compound and solution, but we just mentioned that this is not the case when it comes to Fisher's convention. So, now, we're just left with either option D also being correct or also option F also being correct. Now, when we take a look at option f, notice that it says that Fisher's convention reflects stereochemistry at multiple centers or at multiple Chiral centers. But of course, we know from our previous lesson videos that this is not true. Fisher's convention will give a D or an L configuration, but that D or L configuration only reveals the stereo chemistry of 1 center, not multiple centers. And so as written, option f is incorrect. And so of course, this means that option D must be the correct answer here and it says that Fisher's convention requires drawing the compound with the aldehyde or ketone at the top. And so really, option D is just a reflection of making sure that the Fischer projection is in standard Fischer projection form. And so, this is definitely something that, must apply to Fisher's convention. We can only use Fisher's convention when the structure is in standard Fisher projection. So the two correct answers for this practice problem are options b and d. And so that concludes this practice problem and I'll see you guys in our next video.

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