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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: zerofantasym on November 11, 2008, 09:39:49 PM

Title: Reaction question - I or F
Post by: zerofantasym on November 11, 2008, 09:39:49 PM: So I have an exam tomorrow..and I have a practice exam. There is one question I just do not understand.

When 1:1:1 NaI, NaF, and reactant are mixed in DMSO. What is the most predominant product?

The answer for the product is heptane-F, not heptane-I. I don't get it. Why?

Oh and I don't know how to name the reactant.
It's a benzene ring with OsO₄-heptane attached.
Title: Re: Reaction question - I or F
Post by: enahs on November 11, 2008, 10:01:26 PM: Your question is all over the place.
I assume the reaction was done in heptane then?

And if you can react NaI, NaF with DMSO and heptane and make an osmium complex, you deserve 3 Nobel prizes.

Your question just confuses me....
Title: Re: Reaction question - I or F
Post by: zerofantasym on November 11, 2008, 10:04:33 PM: Well I did not make the question.

I made a screencap of it

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi48.photobucket.com%2Falbums%2Ff238%2FErisedW%2FUntitled-1-1.jpg&hash=03c547705268013220ef6ce4a89b949d26d5beb9)

I thought the answer was A but it's B and I just do not understand why.
Title: Re: Reaction question - I or F
Post by: Borek on November 12, 2008, 02:45:20 AM: So is it S or Os?
Title: Re: Reaction question - I or F
Post by: azmanam on November 12, 2008, 08:07:10 AM: Here's my take. The question probably reads as follows:

heptyl tosylate is reacted with 1 eq NaF and 1 eq NaI in DMSO in a competition experiment. Will the product be heptyl iodide or heptyl fluoride.

To answer this question you need to look at nucleophilicity trends of the halogens in polar aprotic solvents (DMSO is a polar aprotic solvent). The solvent solvates cations well but leaves anions relatively unsolvated. Which anion will be more nucleophilic in polar aprotic solvents?
Title: Re: Reaction question - I or F
Post by: nj_bartel on November 12, 2008, 11:07:11 AM: Didn't he say the answer was the fluoro compound? Thought reactivity increased going down a group.