Is the following sequence of reactions correct?

$$\ce{CH2CH2 ->[][\ce{NH3},\,\ce{Na}] NaHC=CHNa}$$

$$\ce{NaCH=CHNa + 2CH3CH2Br-> CH3CH2CH=CHCH2CH3}$$

  • $\begingroup$ Have a look at the Birch reduction. $\endgroup$ – tschoppi Mar 1 '14 at 14:20
  • $\begingroup$ @tschoppi If it wasn't ethene but methylpropene and a branched hydrocarbon, I'd suggest sulfuric acid or hydrofluoric acid to achieve the alkylation. But the double bond would be gone then. $\endgroup$ – Klaus-Dieter Warzecha Mar 1 '14 at 15:16
  • $\begingroup$ @KlausWarzecha Well, after seeing ($\ce{NH3}$, $\ce{Na}$) I was thinking Birch and nothing happening afterwards... I didn't realize that the goal of this might be "alkylation of ethene" ;) $\endgroup$ – tschoppi Mar 1 '14 at 22:03
  • $\begingroup$ @tschoppi No problem! $\endgroup$ – Klaus-Dieter Warzecha Mar 1 '14 at 22:14

No, because for ethene, $\mathrm{p}K_\text{a} = 44$. You won't be able to abstract even one proton.

Maybe, you were thinking in ethyne ($\ce{HC#CH})$? In that case, you are right! The bis-alkylation would work with sodium amide as a base!

But is the simultaneous abstraction of both protons the most plausible reaction then?

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