There's an exercise that requires me to correct the names given to a set of molecules. Basically I should check for the longest Carbon chain. I bumped into 2,2,6,6,7- pentamethyl-octane. I first drew it as written and saw if the longest chain was indeed an octane or something else. I'm suspecting the name's actually correct. Can anyone confirm this hunch? Is there any other fault that has escaped my attention?


First we need to make the molecule with the help of the given name and then apply first point of difference rule.

I am assuming you know how to make the molecule.

I have numbered the structure according to the first point of difference rule. That's why i started the numbering from the right hand side and thus we have the IUPAC name i.e. 2,2,6,6,7-pentamethyl-octane

You can take the help of this link for some examples on this rule.


See,the numbering you had done is correct accoroding to point of difference rule .The same example is given there.You should avoid hyphen between methyl and octane.It should be 2,2,6,6,7-pentamethyloctane.

  • $\begingroup$ The rule says that The numbers and letters are separated by hyphens. $\endgroup$ – Sikander Nov 17 '15 at 11:35
  • $\begingroup$ So 2,2,6,6,7-pentamethyloctane is correct (I didn't copy the name correctly, it was without the second hyphen)? I can't access that link you gave. It takes me to the home page of the Dept. of Chem Uni Calgary, but I don't see the example you mentioned. $\endgroup$ – WobblyWindows Nov 17 '15 at 12:03
  • $\begingroup$ Yes it is correct.Search 'first point of difference rule-department of chemistry' in google.You will get website by Uni Calgary with the same as link.Go there ,you will be asked to go follow this link.There is this example. $\endgroup$ – Sikander Nov 17 '15 at 12:13

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