roadmap #2 question

[Jo07]

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The second row of reactions from the top, Ar-CH2Br with NaOC2H2 /DMSO..... why is it a Sn2 reaction instead of E2. I understand it is primary, but it also has a strong base, but polar aprotic. Can someone clear this up for me?

 

[issa]

The second row of reactions from the top, Ar-CH2Br with NaOC2H2 /DMSO..... why is it a Sn2 reaction instead of E2. I understand it is primary, but it also has a strong base, but polar aprotic. Can someone clear this up for me?

Sn2 favors a primary halide.

 

[Jo07]

even when there is a strong base?

 

[poc91nc]

http://en.wikipedia.org/wiki/SN2_reaction

 

[Jo07]

After reading that, my question still stands.

Anyone?

 

[sacjumpman]

After reading that, my question still stands.

Anyone?

Look at it REALLY close.

There is no H for the strong base to extract because it is a benzene ring.

Try to draw out the mechanism for an E2 and you will quickly see there is NO WAY for it to go E2.

HOWEVER, when you have primary halides with a strong, unhindered base the reaction will also go Sn2. This is the Williamson Ether Synthesis.

However, for this problem, E2 is not even a concern because of a benzene ring.

Thus, it will go Sn2.