SN1 retention/inversion

[UW09]

Advertisement - Members don't see this ad

Which is true of an SN1 reaction?

(a) Equal amounts of retention and inversion
(b) Complete inversion of configuration
(c) Slightly more retention than inversion occurs
(d) Slightly more inversion than retention occurs
(e) Complete Racemization occurs

 

[joonkimdds]

SN1 is 2 step reaction so a is true.
I am not sure about e. If it's 50:50 retention and inversion, that's 50:50 R and S and doesn't it refer to racemization?

 

[nze82]

Which is true of an SN1 reaction?

(a) Equal amounts of retention and inversion
(b) Complete inversion of configuration>>>This happens in SN2 (false)
(c) Slightly more retention than inversion occurs>>>Either case will result in retention of optical activity (false)
(d) Slightly more inversion than retention occurs>>>Either case will result in retention of optical activity (false)
(e) Complete Racemization occurs

SN1 reactions result in loss of optical activity of the solution. Why?
E) is the exact reason why SN1 results in loss of optical activity. However, I'm confused, because (A) is kinda saying the same thing. But I'd go with (E).

 

[192LT192]

i would go with A not E bc what if youre doing SN1 on one chiral center and then you dont get complete racemization if the other chiral centers dont react and are kept. so you get equal amount retention and inversion. only racemization if your product is 2 enantiomers. but what if you have many chiral centers and so in your product you have diastereomers. i dont know if i explained this well.

 

[nze82]

i would go with A not E bc what if youre doing SN1 on one chiral center and then you dont get complete racemization if the other chiral centers dont react and are kept. so you get equal amount retention and inversion. only racemization if your product is 2 enantiomers. but what if you have many chiral centers and so in your product you have diastereomers. i dont know if i explained this well.

I don't think that's the correct definition of racemization. Even if you manage to prevent the 2nd chiral center from reacting, the chiral center that does react will still undergo complete racemization.
I don't know. You might be right though!

 

[UW09]

I also guessed E but the answer is D (from OChem Odyssey ch.8 #10)