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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: pinkphiloyd on August 06, 2008, 06:34:40 PM

Title: Distinguishing diacetylferrocene isomers?
Post by: pinkphiloyd on August 06, 2008, 06:34:40 PM
Anybody have any tips?  Color perhaps?  Our final product was dark red.  We're quite sure from NMR that it's not 1,1'.  But we're having trouble determining if it's 1,2 or 1,3.  We didn't realize until we were out of product that melting point would have been of use.
Title: Re: Distinguishing diacetylferrocene isomers?
Post by: Mitch on August 06, 2008, 07:17:16 PM
What do you mean by 1,1'
Title: Re: Distinguishing diacetylferrocene isomers?
Post by: pinkphiloyd on August 06, 2008, 08:15:49 PM
What do you mean by 1,1'

Ferrocene consists of an iron ion "sandwiched" between two 5 carbon rings.  When undergoing Friedel-Crafts acylation, if both of the acetyl groups wind up on one ring, they have two options for arrangement, 1,2 or 1,3.  If, however, one acetyl group goes to each 5 carbon ring, the acetyl substituents are said to be 1,1'.
Title: Re: Distinguishing diacetylferrocene isomers?
Post by: macman104 on August 06, 2008, 09:31:54 PM
If it's 1,2 you'll only have 2 different types of hydrogens on the carbon rings.  If it's 1,3 you should have 3 different types.
Title: Re: Distinguishing diacetylferrocene isomers?
Post by: sjb on August 07, 2008, 12:28:40 AM
What do you mean by 1,1'

1,1' means that there is an acetyl group on each of the Cp rings

S
Title: Re: Distinguishing diacetylferrocene isomers?
Post by: macman104 on August 07, 2008, 01:34:20 AM
If it's 1,2 you'll only have 2 different types of hydrogens on the carbon rings.  If it's 1,3 you should have 3 different types.
I wanted to add that I believe this to be true, but I'm not sure if there is any interaction between hydrogens between the two rings.
Title: Re: Distinguishing diacetylferrocene isomers?
Post by: pinkphiloyd on August 08, 2008, 12:41:44 AM
Thanks everybody.  I felt dumb as soon as the answer to this hit me.  We didn't wind up with 1,2 or 1,3.  Due to the deactivating tendency of the first acetyl group, the second always goes onto the other ring.  Thankfully, this hit me before my lab report was due!