November 26, 2024, 04:45:14 AM
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Topic: Drawing a Chiral Molecule - how to determine geometry of substituents  (Read 10441 times)

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Offline tiny101

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Hi there,

I am to draw a chiral molecule (R-3-iodo-2,3-dimethylpentane).

The first thing I did was draw a simple 5-Carbon chain that had the Iodine and one of the methyl groups in the 3-C position & the other methyl group in the 2-C position. I am confused however, about how to determine which substituents would be pointing out of the plane (solid wedges) and which would be pointing into the plane (hatched wedges).

I guessed that if it's labeled by an "R", then the Iodine should be pointing out of the page, and the CH3 on the 3-C would be pointing into the page. Then, the other CH3 (on 2-C) would be pointing out of the page.

Am I on the right track? Any help would be much appreciated.
Thanks in advance! =)

Offline Rabn

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you can try this method:  make the substituent with the lowest priority point into the plane of the page, the other three substituents would then be pointing out of the plane of the page.  Then arrange the three remaining substituents in a way to make it an R molecule.

Offline Vidya

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Okay let me help you
Here I is first priority grp -put it on the wedge
CH3 is the least priority grp--put it on the dash
Now rest of the groups R1 and R2 are in the plane of the paper.Now place R1 and R2 in such a manner that when you move your eye from first priority grp to second and than to third grp ,it should move in clockwise direction.

Offline tiny101

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I'm not quite sure of what you mean when you say "R1" and "R2". Would it be possible to further describe this? Also, there are two CH3 groups, so when you say, "CH3 is the least priority grp--put it on the dash", are you referring to the CH3 on the 3rd Carbon?

Thanks again =)

Offline Rabn

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try the method I suggested, you may find it easier to visualize than the two constituents in the plane of the page, one above, and one below.  with my method, only the chiral carbon atom is in the plane of the page.

Offline Vidya

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Chiral carbon has four different groups
-I   I priority
-CH(CH3)2  II priority
-C2H5       III priority
-CH3    IV priority
R1 and R2 I was referring to group II and III
Try to visualize it now.

Offline tiny101

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Thanks everyone! I've finally gotten it!  ;D

Offline song662309

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le me see

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