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Correct IUPAC names

Krushnaraj Pandya

Gold Member
690
79
1. The problem statement, all variables and given/known data
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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1. The problem statement, all variables and given/known data
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.
 

Krushnaraj Pandya

Gold Member
690
79
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

Gold Member
690
79
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?
 

Krushnaraj Pandya

Gold Member
690
79
yes chlorobenzene is accepted but 1methyl 4 chloro benzene is not accepted
I got that. My problem is regarding 4-methyl chlorobenzene now
 

Krushnaraj Pandya

Gold Member
690
79
218
20
3rd is incorrect because, by definition, the "parent chain" must be a pure hydrocarbon, and chlorobenzene isn't one.
 

Krushnaraj Pandya

Gold Member
690
79
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??
 
218
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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.
 
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Last edited:

Borek

Mentor
27,963
2,470
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.
 
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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.
 
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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.
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.
 
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If you're thinking biomacromolecules, I agree that their rigorous IUPAC names are unnecessary.
 

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