NaI, acetone?

[dentista123]

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What does NaI, acetone do to 4-chloro-2-butanol?

Thank you.

 

[sfrice80]

It looks as though its testing your leaving groups maybe? Chloro would be a better leaving group, I dont think the -OH would leave when compared to chloro. My knee jerk response would be SN2 with only the chloro.

 

[pbure9]

What does NaI, acetone do to 4-chloro-2-butanol?

Thank you.

Its polar aprotic solvent, and a strong nucleophile I-... perfect scenario for SN2. The halogen on the primary carbon makes this a typical SN2 reaction. So you would form 4-iodo-2-butanol (with inversion of course)

 

[dentista123]

Thanks to you both. So the molecule at the chiral center (with the OH) would retain its stereochemistry?

I got this wrong on a Kaplan test because they were asking me what would happen to the chiral center. I saw acetone and thought...maybe it would so an SN2 on the chiral center. BUT I know better, it was a really dumb mistake. Thank you guys!

 

[notsowisetooth]

What's a good rule of thumb to determine if something is either a strong base or strong nucleophile?

 

[nze82]

What's a good rule of thumb to determine if something is either a strong base or strong nucleophile?

Anything with a negative charge is a strong Nucleophile, and most strong nucleophiles are also strong bases.

 

[pbure9]

What nze said is right. I think if you go from right to left and up the periodic table you increase basicity, and right to left and DOWN you increase nucleophilicity.

 

[Sublimation]

hmm....i see what the question is testing, however, im not to sure if the sn2 with chlorine is very favorable. Yes it may occur on a very small scale ( OH is def. not goin anywhere) however I is a better cleaving group then Cl- and is much more stable as an anion then Cl- so if u do substitute the Cl with I do kno that Cl will probably come back and take its place. I- is a happy camper the way he is. This isnt wat the question was testing. But i thought i might throw that out there.

 

[dentista123]

hmm....i see what the question is testing, however, im not to sure if the sn2 with chlorine is very favorable. Yes it may occur on a very small scale ( OH is def. not goin anywhere) however I is a better cleaving group then Cl- and is much more stable as an anion then Cl- so if u do substitute the Cl with I do kno that Cl will probably come back and take its place. I- is a happy camper the way he is. This isnt wat the question was testing. But i thought i might throw that out there.

Good point. But I- is also a better nucleophile than Cl because it's bigger.

 

[hunterpostbacst]

Good point. But I- is also a better nucleophile than Cl because it's bigger.

Then, both of you guys are right?
Then, we can come up with that the better leaving group is the better nucleophile? I got confused!! ;(

 

[dentista123]

Then, both of you guys are right?
Then, we can come up with that the better leaving group is the better nucleophile? I got confused!! ;(

I wish I had a copy of the original question for you. But the question was asking whether or not the sterochemistry of the molecule changed. Since the original chiral center was not the one that had SN2 reaction, it did not change.

So I hope on the real thing, they wouldn't give us something like this where the chiral carbon would be the one with the halide. In that case, we would likely be confused. I think it would be too specifiic, but who knows.

 

[hunterpostbacst]

I wish I had a copy of the original question for you. But the question was asking whether or not the sterochemistry of the molecule changed. Since the original chiral center was not the one that had SN2 reaction, it did not change.

So I hope on the real thing, they wouldn't give us something like this where the chiral carbon would be the one with the halide. In that case, we would likely be confused. I think it would be too specifiic, but who knows.

The stereochemistry of the molecule DOES change in this case, even though the nucleophile does not attack on the chiral carbon.

 

[teethmagnet]

What's a good rule of thumb to determine if something is either a strong base or strong nucleophile?

its a strong base or Nu if its has electron dots and it is negative, or if it is Nitrogen, its a good base
very good Nu/ bases: OCH3 (-), OC2H5(-), NH2(-), LDA

**only catch-- i think halogens are strong Nu but not good bases, or maybe its the reverse correct me if im wrong

 

[teethmagnet]

The stereochemistry of the molecule DOES change in this case, even though the nucleophile does not attack on the chiral carbon.

are you sure??? i feel that it wouldn't because you're not touching the chiral carbon so there should be retention, i highly doubt the sterochemical change.
i would assume this way from an ex i learned: hydrolsis of ester--when you cut the ester, there is retention on the chiral carbon, it is not changed,

also---(1R, 3S) 2 flouro-2-iodo reacts with NaCl, acetone----> the I will leave (rather than F bec better Leaving group) and the Cl will come in with alternate sterochem (making it an R), AND THE FLOURINE's STEREOCHEM IS NOT CHANGED