what molecule is this?

imported_guy

(A) 5-methyl-2-isopropylphenol
(B) 6-isopropyl-3-methylphenol
(C) 2-isopropyl-5-methylphenol
(D) 3-isopropyl-6-methylphenol

pretty sure its C, cant be A, hydroxy group takes priority so you start counting from there, and then the next biggest group is the isopropyl, in this case the methyl group is the lowest priority, or am i wrong?, i was informed the correct answer is A.... hows that??

DailyBlaa

I am pretty sure it is C also. I believe it is thymol

Marvinthefish

ChemDraw says (C)

Surely one would put the position numbers of the functional groups in numerical order, i.e., 2 and then 5, rather than 5 and then 2. (see Wikipedia entry below)

It's definitely not B or D because one always writes the name with the lowest numbers in it.

From wikipedia.org/IUPAC_nomenclature

Prefixed substituents are ordered alphabetically (excluding any modifiers such as di-, tri-, etc.), e.g. chlorofluoromethane, not fluorochloromethane. If there are multiple functional groups of the same type, either prefixed or suffixed, the position numbers are ordered numerically (thus ethane-1,2-diol, not ethane-2,1-diol.)

The functional groups in your compound are both of the same type (alkyl groups) so the position numbers will be ordered numerically.

SOL

It has to be 5,2 or 3,6 and the numbers are assigned to keep them the lowest possible... so I'm going to go for C

It is A. The content of A and C are the same, but A is the correct way to say it because methyl and isopropyl have to be in alphabetical order.

Edit: Hang on.. think I got confused there... Few too many drinks methinks.

Editing again!: yeah because iso doesn't count. But having done some looking up it seems it's actually called 5-methyl-2-(propan-2-yl)phenol. So I'm going back to saying A. If I change my mind again I'll keep it to myself!

hairyeggs

It goes something like this:

1. The base name is phenol, so the -OH gets priority, position 1.
2. For an aromatic ring, the substituents are listed in alphabetic order, so isopropyl-methyl-phenol.
3. You number the substituents so that you get the lowest possible set of numbers, 2-isopropyl-5-methyphenol, rather than 6-isopropyl-3-methylphenol (2+5 < 6+3).


@true-or-false: normally you don't count the modifier (e.g. di, tri, or tert-, sec-), but isopropyl is a single element under IUPAC rules i.e. iso is part of the name. So tert-butyl starts with 'b' but isopropyl starts with 'i'.

See 2.25
http://www.acdlabs.com/iupac/nomenclature/79/r79_36.htm

Marvinthefish

Say we had this molecule where the methyl group and isopropyl groups are switched, which rule takes precedent? Will the numbers be in order (2...5...phenol) or will the group names be in alphabetical order (...isopropyl...methylphenol)?

SOL

The alphabetical ordering is ONLY for writing out the name, i.e. methyl after ethyhl before phenyl, then numbers are always put in to give the lowest numbers...

5-isopropyl-2-methylphenol with the positions switched is 2-isopropyl-5-methylphenol

popsmar

The correct name for the above is Thymol it has Synonyms :
5-Methyl-2-isopropylphenol
5-Methyl-2-(1-methylethyl)phenol
2-Isopropyl-5-methylphenol

Formula : C10H14O
Molecular Weight : 150,22 g/mol
Name:ThymolIUPAC:thymolMF:C10H14OCAS #:89-83-8MW:150.22MDL #:MFCD00002309

The naming for IUPAC is Thymol.

For your question with those awnsers, yes the correct awnser is A.

For naming you take the bigest part possible to name and as you said "in this case the methyl group is the lowest priority" so ignore this.

The name is 2-isopropylphen-1-ol then you add the lower priority to the frunt not the back. then you have the awnser
5-Methyl-2-isopropylphen-1-ol then most people drop the 1
to get 5-Methyl-2-isopropylphenol

Mervinthefish

your compoind is called Carvacrol
IUPAC:5-isopropyl-2-methylphenolMF:C10H14OCAS #:499-75-2MW:150.22MDL #:MFCD00002236