• Support PF! Buy your school textbooks, materials and every day products Here!

Correct IUPAC names

  • #1
Krushnaraj Pandya
Gold Member
697
72

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
 

Answers and Replies

  • #2
22
1

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.
 
  • #3
Krushnaraj Pandya
Gold Member
697
72
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
 
  • #4
22
1
I thought so, but here's the twist. 3rd is incorrect, I can't figure out how
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.
 
  • #5
Krushnaraj Pandya
Gold Member
697
72
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?
 
  • #6
Krushnaraj Pandya
Gold Member
697
72
4th is incorrect.The alkyl group is given least priority.
even though chlorobenzene is accepted by IUPAC
 
  • #7
22
1
even though chlorobenzene is accepted by IUPAC
yes chlorobenzene is accepted but 1methyl 4 chloro benzene is not accepted
 
  • #8
Krushnaraj Pandya
Gold Member
697
72
yes chlorobenzene is accepted but 1methyl 4 chloro benzene is not accepted
I got that. My problem is regarding 4-methyl chlorobenzene now
 
  • #9
Krushnaraj Pandya
Gold Member
697
72
anyone?
 
  • #11
Krushnaraj Pandya
Gold Member
697
72
  • #12
232
20
3rd is incorrect because, by definition, the "parent chain" must be a pure hydrocarbon, and chlorobenzene isn't one.
 
  • #13
Krushnaraj Pandya
Gold Member
697
72
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
232
20
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
232
20
Last edited:
  • #17
Borek
Mentor
28,397
2,800
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
232
20
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
232
20
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.
 
  • #20
232
20
If you're thinking biomacromolecules, I agree that their rigorous IUPAC names are unnecessary.
 

Related Threads on Correct IUPAC names

  • Last Post
Replies
4
Views
728
  • Last Post
Replies
5
Views
5K
  • Last Post
Replies
2
Views
9K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
6
Views
967
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
9
Views
3K
  • Last Post
Replies
1
Views
15K
  • Last Post
Replies
1
Views
492
Replies
4
Views
4K
Top