IUPAC Names for Chlorinated Methylbenzenes: Analysis & Solutions

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Discussion Overview

The discussion revolves around the acceptable IUPAC names for chlorinated methylbenzenes, focusing on the naming conventions and priorities of substituents in organic chemistry. Participants analyze specific examples and seek clarity on the rules governing IUPAC nomenclature.

Discussion Character

  • Homework-related
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that the first option, "1-chloro-4-methylbenzene," is correct, questioning whether chlorine has higher priority than methyl in naming.
  • Others argue that "4-chlorotoluene" is accepted by IUPAC but is considered a common name rather than a systematic IUPAC name.
  • There is contention regarding "4-methylchlorobenzene," with some asserting it is correct while others later claim it is incorrect due to the definition of the parent chain.
  • Participants discuss the implications of alphabetical order in determining priority for naming, particularly in the case of "1-methyl-4-chlorobenzene."
  • Some participants express confusion over the classification of chlorobenzene and its implications for naming conventions.
  • References to external sources are provided to support claims about IUPAC naming conventions, though the reliability of these sources is questioned.
  • There is a discussion about the use of non-systematic common names and their acceptance in IUPAC nomenclature.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correctness of the names discussed, with multiple competing views remaining on the priority of substituents and the definitions of parent chains in IUPAC nomenclature.

Contextual Notes

Some participants highlight limitations in understanding the rules, particularly regarding the definition of the parent chain and the implications of using common names versus systematic names. There are unresolved questions about the application of IUPAC rules and their interpretations.

Who May Find This Useful

This discussion may be useful for students and professionals in chemistry, particularly those interested in organic chemistry nomenclature and IUPAC naming conventions.

Krushnaraj Pandya
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Homework Statement


among these, which are acceptable IUPAC names,
1-chloro-4-methylbenzene
4-chlorotoluene
4-methylchlorobenzene
1-methyl-4-chlorobenzene

2. The attempt at a solution
1)First option seems correct but is chlorine a higher priority group than methyl?? or does chlorine get a lower number due to alphabetical order?
2)toluene is accepted by IUPAC so correct
3)I see no reason as to why this should be incorrect
4)if methyl has higher priority then correct, if there is no such priority and alphabetical arrangement is followed in this case then incorrect- besides doesn't the name chlorobenzene imply chlorine is at position 1?

I'd be very grateful for some insight
 
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Krushnaraj Pandya said:

Homework Statement


among these, which are acceptable IUPAC names,
1-chloro-4-methylbenzene
4-chlorotoluene
4-methylchlorobenzene
1-methyl-4-chlorobenzene

2. The attempt at a solution
1)First option seems correct but is chlorine a higher priority group than methyl?? or does chlorine get a lower number due to alphabetical order?
2)toluene is accepted by IUPAC so correct
3)I see no reason as to why this should be incorrect
4)if methyl has higher priority then correct, if there is no such priority and alphabetical arrangement is followed in this case then incorrect- besides doesn't the name chlorobenzene imply chlorine is at position 1?

I'd be very grateful for some insight
1st is absolutely correct
2nd one is correct and accepted by IUPAC but it is a common name and is not IUPAC nomenclature.
3rd is correct
4th is incorrect because alphabet is given priority.
 
Victim said:
1st is absolutely correct
2nd one is correct and accepted by IUPAC but it is a common name and is not IUPAC nomenclature.
3rd is correct
4th is incorrect because alphabet is given priority.
I thought so, but here's the twist. 3rd is incorrect, I can't figure out how
 
Krushnaraj Pandya said:
I thought so, but here's the twist. 3rd is incorrect, I can't figure out how
Krushnaraj Pandya said:
I thought so, but here's the twist. 3rd is incorrect, I can't figure out how
4th is incorrect.The alkyl group is given least priority.
 
Victim said:
4th is incorrect.The alkyl group is given least priority.
you're right. 4th is incorrect and I understand that, but 3rd is incorrect too- why is that?
 
Victim said:
4th is incorrect.The alkyl group is given least priority.
even though chlorobenzene is accepted by IUPAC
 
Krushnaraj Pandya said:
even though chlorobenzene is accepted by IUPAC
yes chlorobenzene is accepted but 1methyl 4 chloro benzene is not accepted
 
Victim said:
yes chlorobenzene is accepted but 1methyl 4 chloro benzene is not accepted
I got that. My problem is regarding 4-methyl chlorobenzene now
 
anyone?
 
  • #12
3rd is incorrect because, by definition, the "parent chain" must be a pure hydrocarbon, and chlorobenzene isn't one.
 
  • #13
baldbrain said:
3rd is incorrect because, by definition, the "parent chain" must be a pure hydrocarbon, and chlorobenzene isn't one.
any link for reference to this rule??
 
  • #14
Krushnaraj Pandya said:
any link for reference to this rule??
I can give you one, but these are the very basics. If the parent hydrocarbon would compose something other than only C & H, there would remain no basis for classification.
 
  • #16
Last edited:
  • #17
baldbrain said:
Tell me, what is the 'parent chain' or stem of the name 2-chloropropanol?

Just because it is propane doesn't make your earlier statement correct (perhaps it is, I don't know for sure).

If memory serves me well (won't be the first time it fails if I am wrong) IUPAC rules allow usage of non-systematic common names as long as the result is unambiguous. so chances are it all depends on how orthodox you want to be about naming.
 
  • #18
baldbrain said:
This is absolutely correct. The '-oic acid' is a suffix (grammatically they would be 2 words, but relate it similar to -ol, -one, -amine etc. or any other suffix). The stem of this name is still toluene.
Tell me, what is the 'parent chain' or stem of the name 2-chloropropanol?
Edit: The stem of this name is still toluene.
 
  • #19
Borek said:
If memory serves me well (won't be the first time it fails if I am wrong) IUPAC rules allow usage of non-systematic common names as long as the result is unambiguous. so chances are it all depends on how orthodox you want to be about naming.
The question asked by @sjb-2812 was about preferred IUPAC names.
And as far as the aptitude of the OP and, in general, homework assignments are concerned, only the 'preferred IUPAC name' is really of interest.
Borek said:
Just because it is propane doesn't make your earlier statement correct (perhaps it is, I don't know for sure).
I gave them something easy to start with.
And as far as I know, it is correct. Look up any compound's 'preferred IUPAC name' on Wikipedia (I know it Wikipedia isn't fully reliable, nothing is, for that matter) and you'll find the 'parent chain' to be a pure hydrocarbon.
Do tell me if you find a compound that violates this rule.
 
  • #20
If you're thinking biomacromolecules, I agree that their rigorous IUPAC names are unnecessary.
 

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