Can anyone tell me why -NH2 acts as a base and not a nuc in destroyer #124?

[Jay0689]

We have CH3-CHBr-CH2Br react first with NaNH2 in NH3 and then with water in the second step. The product is an alkyne.

So this was a double elimination reaction with NH2- acting as a base (instead of acting as a nuc.) I thought it would be SN2 since the halide is a primary halide, at least for one of the Br's.

My question is how do you know if -OH, -OR, NH2-, -NHR, and other reagents that are both strong bases and strong nucs will do SN2 or E2?

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[rah08e]

I'm not sure if this answers your question but the Br's are being eliminated and not substituted for something else. The double elimination rxn with NaNH2 in NH3 is pretty common for dehydrohalogenation of dihalides.

http://www.google.com/imgres?imgurl...x=135&ty=55&page=1&ndsp=41&ved=1t:429,r:4,s:0