[maakii]

hi, thanks to anyone who helps me answer these questions!

1) I was wondering if ethyne could be double deprotonated to give just 2 carbon atoms with a 2- charge?

2) Secondly, how can ethyne be both hydrogenated and deprotonated by Na/ liquid NH3?

3) If you deprotonate ethyne using Na/ NH3, to give a carbanion, then react it with aldehyde, will it only give a product that only goes though 1 round of addition (added only on 1 side)

or will it react further with 2 equivalents of aldehyde to give a product which has been added on both sides?

[english]

Once you deprotonate acetylene (ethyne) it becomes acetylide, a very strong base.  Using this understanding, do you think it would want to lose another proton?

[movies]

It can be done!  Calcium carbide is CaC₂.  True though, these dianions are petty rare.

[english]

It can be done!  Calcium carbide is CaC₂.  True though, these dianions are petty rare.

Why did I have a feeling you were going to say that.

 

[maakii]

ah i see thank you! so if i use a regular base (NaNH2) it would only deprotonate once, yes i got it!

any one knows the answers to the other 2 questions?

[movies]

For your second question, it's a matter of how you run the reaction.  In one case, you would dissolve the alkyne in NH₃ and add Na(0) to the pot.  As the Na dissolves, the alkyne would get reduced to the alkene.

In the other procedure, you first mix Na(0) and NH₃, which will eventually react to give NaNH₂ (note that this is a much slower pathway than the alkyne reduction described above).  Then, once the NaNH₂ has formed, you can add the alkyne and generate the sodium acetylide.

Of course, you can also just buy NaNH₂ to begin with, then it's easy!

[HP]

C2H2 + 2AgNO3--> C2Ag2 (precipitate)
Also with some Cu2+ salts giving Cu carbide...