Identifying Possible Structural Isomers

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Discussion Overview

The discussion centers around identifying possible structural isomers for the compound C3H6Br2. Participants explore the implications of structural variations, including the arrangement of bromine atoms and the carbon skeleton, while considering the effects of molecular rotation and chirality.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant lists four potential structural isomers for C3H6Br2, including 2,2-dibromopropane, 1,2-dibromopropane, and 1,3-dibromopropane, but acknowledges potential confusion in naming.
  • Another participant questions the clarity of the isomer descriptions, particularly regarding the repeated mention of 1,2-dibromopropane.
  • A participant suggests that the "up" and "down" orientations of bromine atoms do not create distinct isomers, urging a focus on assigning bromine atoms to different carbon positions.
  • One participant admits to having given two structures the same IUPAC name and expresses intent to clarify their representations.
  • Another participant confirms the correct isomers as 1,1, 2,2, 1,2, and 1,3 dibromopropane.
  • A question is raised about the significance of which bond the bromine atoms attach to, leading to a discussion about chirality and its relation to isomerism.
  • One participant notes that including chirality results in five isomers and prompts others to identify which positional isomer has an enantiomer.
  • A later reply acknowledges the oversight of the chiral isomer in the initial discussion.

Areas of Agreement / Disagreement

Participants generally agree on the identification of certain structural isomers, but there is confusion regarding the naming and representation of some isomers. The discussion about chirality introduces additional complexity, indicating that multiple competing views and uncertainties remain.

Contextual Notes

There are unresolved issues regarding the naming conventions of isomers and the implications of molecular rotation on structural identity. The discussion also highlights the need for clarity in distinguishing between positional isomers and chiral isomers.

Who May Find This Useful

Individuals interested in organic chemistry, particularly those studying structural isomerism and chirality, may find this discussion beneficial.

Chem.Stud.
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C3H6Br2

There are 4 structural isomers possible to draw... which I'd like to do :)

The carbon skeleton isn't of much importance here, as we only have three carbon atoms. The two halides, however, are a pain, I've found.

The linear sigma bonds may rotate around its axis, meaning that several seemingly different structures basically are identical. Also, we can rotate the entire molecule, so we can that way also acknowledge several seemingly different structures as identical.


1) 2,2.dibromopropane

2) 1,2-dibromopropane (Br at the end no bonded at the end of the carbon chain, but either "up" or "down", if you get my point)

Br
C - C - C
###Br

3) 1,3-dibromopropane (each Br bonded to the ends of the carbon chain)

4) 1,2-dibromopropane (Br-CH2-C(Br)H-CH3)


Are these the correct structural isomers? Am I thinking correctly, here? I'm guessing that being able to efficiently identify isomers is a matter of practice and getting a "trained" eye, so to speak. I organic chemistry, they're telling us it's important to develop good 3D interpretations of 2D representations. A molecular building set is on the way from Evil-Bay

I appreciate any help :) I'll try to be a member of this community, and help where I'm able, and not just a user.

Regards,
Anders
 
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Chem.Stud. said:
2) 1,2-dibromopropane (Br at the end no bonded at the end of the carbon chain, but either "up" or "down", if you get my point)

Br
C - C - C
###Br

I'm not quite sure what you mean here (especially since you also list 1,2-dibromopropane for #4).
 
There will be no "ups" and "downs". Just try to assign Br atoms to carbons in four different ways.
 
That's what I thought I just had done :P

Yes, I've basically given two structures the same IUPAC name, which is a little off, perhaps. I'll give it another shot, and upload a picture of what I'm doing soon.

Thanks, folks!
 
Here's another go. Do you agree with this?

(don't mind the norwegian spelling of "structural isomers" on the top)
 

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1,1 and 2,2 and 1,2 and 1,3 - that's correct.
 
Okay, thanks!

One question:

In these structural isomers it doesn't matter which one of carbon's three available bonds the Br atoms are bonded to. What sort of isomers deal with that? The sigma bonds rotate around their axis, and so the "up" and "down" bonds practically are the same, but what about that bond on the end?

That was poorly formulated! Sorry.
 
Google chirality.
 
If you include chirality, there are 5 isomers. Can you determine which of your positional isomers has an enantiomer?
 
  • #10
How could I miss the chiral one?
 

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