Sn2, E2

[dat_student]

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OR- + primary R-Br

isn't this SN2?

Based on my notes, a weirdo thinks it's E2 because he believes OR- is a strong base.

E2 or Sn2?!!

 

[Divineimpetus]

OR- is a big bulky base which is good for E2, and it doesn't matter if it is primary,secondary or tertiary for E2 reactions

 

[dat_student]

OR- is a big bulky base which is good for E2, and it doesn't matter if it is primary,secondary or tertiary for E2 reactions

which part of CH3O- is bulky???

(CH3)3CO- (tert-butoxide) is bulky and strong but methoxide isn't bulky, is it???!!!!

 

[mccarth2]

I would have put SN2 too. I looked up the pka for RO- & it has a pKa of 16-18 based on R group, which is higher than OH- (15.7). As pKa increases, basisity increases. Basisity starts at around a pKa of 9.

 

[Divineimpetus]

If the R group is just a methyl, yeah it isn't bulky...but usually when I see a R-group I think bulky carbon chain.. it dependns on what they mean by R

 

[ramona_k]

I would have put SN2 too. I looked up the pka for RO- & it has a pKa of 16-18 based on R group, which is higher than OH- (15.7). As pKa increases, basisity increases. Basisity starts at around a pKa of 9.

A compound that has more R group around is more basic. ==> 3>2>1> methyl. you can also look at it this way: R is more electronegative than H which means than it is more electron withdrawing and more stable and less basic. So since the [Nu] is not that basic I also think it would undergo SN2.

 

[mikester2]

OR- + primary R-Br

isn't this SN2?

Based on my notes, a weirdo thinks it's E2 because he believes OR- is a strong base.

E2 or Sn2?!!

Your notes are wrong. As one the other previous poster noted, it depends on what the R group is. If its tert-0. Then it would be a E2 reaction. However, if it a methyl group. It would be an Sn2.

 

[xxJuiceDxx]

Ether formations are Sn2, no?

 

[tRNA]

A compound that has more R group around is more basic. ==> 3>2>1> methyl. you can also look at it this way: R is more electronegative than H which means than it is more electron withdrawing and more stable and less basic. So since the [Nu] is not that basic I also think it would undergo SN2.

I thought R groups are electron donating not electron withdrawing???!!!

 

[mikester2]

I thought R groups are electron donating not electron withdrawing???!!!

R groups are electron donating.

 

[ramona_k]

R groups are electron donating.

You are correct. R are e- donating with respect to halides. And it also turns out they are electron donating in reference to Hydrogens. I used this source for clarification: http://www.mhhe.com/physsci/chemist...ics/carey04oc/ref/ch12substituenteffects.html

Thanks for pointing that out.