Understanding Alkenes & Alkynes: Bromine Water Test

[Bladibla]

Hey all

How do you distinguish between and Alkene and Alkyne?

Bromine water is discoloured in both, so that rules out BW.

 

[gravenewworld]

you could try to take the compound and try to brominate the bond twice. excess Br2+alkyne---> tetrabromination excess Br2+alkene----->dibromination. So if your compound is an alkyne you can add on 4 bromines, if it is an alkene you can add on 2 bromines. After you are done reacting you can figure out how many bromines were added by finding mass or doing spectroscopy thus you can figure out if the compound is an alkyne or alkene

 

[movies]

How about just getting an IR spectrum? If the alkyne isn't symmetrical, that is.

The alkyne stretching frequency should be significantly different from the alkene stretching frequency.

 

[gravenewworld]

NMR would tell you what your compound is as well, you would just have to look for different splitting patters.