[physstudent1]

http://www.webassign.net/userimages/kasandbe/CH221_ssii_02/CH221_exam2_ssii_02_7a.gif

I thought that the major product of B with ethanol as the solvent at 0 degrees Celsius would be a racemic mixture of the same compound except a OCH2CH3 would replace the OTs and there would be no wedges or dashes because its racemic but this is not correct?  Can anyone clear my confusion?

[macman104]

Depending on how your professor would want the question answered, it could either be the structure without the wedges and dashes, or maybe they wanted two molecules that were enantiomers of eachother (so, you would have two equal major products).  But yes, at 0C, an SN1 with Ethanol as the solvent would give the product you predicted.

[physstudent1]

ok thank you, it was driving me crazy I couldn't figure out what was wrong with it I don't think that webassign can take answers with two different molecules but I don't see any other option thanks a lot for the quick answer

[physstudent1]

I put both enationmers and just one product with wedges and they were both wrong I hate webassign... oh well at least I know the concept for the exam I guess

[azmanam]

carbocation rearrangement!

[macman104]

carbocation rearrangement!

Ah *headdesk* yea, you're doing an Sn1 on a 2° carbon.  You'll probably get some rearrangements products.

[physstudent1]

yea that is right, too bad we didn't learn about that till today and it isn't included until 4 chapters later in the book sigh

[spirochete]

One relatively minor point about SN1 reactions with a chiral molecule is that they technically do not produce racemic mixtures usually.  The ionized leaving group may create some steric congestion on the face of the carbocation from which it left.  So while your products might be enantiomers you don't necessarily get a perfect 50:50 mix. 

[sjb]

The question is then, if your reaction is really still describable as S_N1, or not. I see where you're coming from, and I agree totally, but is not the S_N1 mechanism one where the leaving group totally dissociates from the molecule?

S

[macman104]

Yes, I agree with sjb.  You completely form the cation in an SN1, and get a racemic mixture.