Hi,

 

I was wondering what chemical test you could perform to identify an unsaturated compound.

 

Thanks.

 

Jaydee

Bromine water. It goes colourless.

e.g.

Ethene

 

Put bromine water with ethene and it forms 1,1 dibromoethene

So, putting bromine water with any unsaturated compound, (any alkene,alkyne etc) will result in making it go colourless?

 

What I mean is, can this test for 'any' unsaturated compound, eg. if i mix say.. ethyne with bromine?

yup! It works!

Ok thanks, very cool.

 

Um, I know when a hydrocarbon is 'completely' combusted, it gives us CO2 and H2O, what if its 'incomplete', what does it give us?

It gives CO2, H2O, C (carbon) and CO (carbon monoxide)

a good way is to add a superacid like HF:SbF5 or HSO3-SbF5. it's hilarious; they can completely protonate alcohols and long chains of hydrocarbons.

what do you mean by "protonate"?

aommaster, in organic chemistry when you say "protonate" it means to throw on a proton (hydrogen atom).

 

If you protonate an alcohol, you go from R- OH to R- OH₂⁺

oh ok! Thanx alot Blike!

yeah, what's really disturbing is that a 50% solution of HF:SbF5 is 10^18x as acidic as conc H2SO4. if you drop a candle into it, the candle will cease to exist quite quickly. if you stick a hand in it, your hand will cease to exist quite quickly.

 

the most acidic substance i've ever worked with is a saturated solution of HCl, and that dissolved a small piece of styrofoam within seconds. imagine conc HF:SbF5

LOL! I read that in the guiness book of records! Antimony Pentafluoride must be a really scary substance! What do they store it in?

Antimony Pentafluoride must be a really scary substance!

 

^ only when mixed with a substance that ionizes to yield H+. i'm not sure what it's stored in, but i could imagine it would be some pretty strong glass.

I heard that it does not eat through specific plastics or something. I think that is what they store it in. Not sure though!

HAZARDOUS DECOMPOSITION PRODUCTS: Decomposes into antimony and hydrofluoric acid with heating or water contact. Decomposition products reactwith glass.

 

taken from: http://66.102.9.104/search?q=cache:8jb8Z_THpQkJ:www.boc.com/gases/pdf/msds/G121.pdf+%22Antimony+Pentafluoride%22&hl=en

ummmm... does that answer my question? If it does, could you please explain further?

sure, it can be stored in any plastic or metal (it mentioned weldable metal drums) that won`t react with Flourine

What metal wouldn't react with fluroine? And which plastic?

I`m fairly sure polyprop plastic doesn`t, as for the metals I`m not sure off the top of my head, but it`ll be something quite ordinary, just as Nitric Acid can and is safely stored in Aluminium containers

hmmmm.... would aluminium oxide reacti with fluorine? I don't think so because it is unreactive. This leads me to think that aluminium containers would be good to store the acid!

Antimony Pentafluoride attacks glass copper and lead, but other than that, if it`s kept perfectly dry, it`s quite safe

 

take a peek here too :http://www.inchem.org/documents/icsc/icsc/eics0220.htm

Thanx YT. Great link!

Hi! was just wondering about the unsaturates test with bromine water. what is the name of the chemical reaction that has taken place here??

xx:confused:

the reaction is an anti addition. the electrons from the pi bond of the ethene attack one atom of bromine in the diatomic molecule, causing the electrons from the sigma bond between Br and Br to go to the Br atom that was not attacked by the pi bond. simultaneously, the Br attacked by the pi bond puts a lone pair of electrons on the other carbon, making it bonded to two carbon atoms and positively charged. finally, the bromide anion performs an sN2 reaction, attacking one carbon, inverting the stereochemistry and causing the electrons from the C-Br+ bond to go to the bromine atom.

 

Step 1:

Br-Br

 

H2C=CH2

 

Step 2:

Br-

 

H2C(Br+)CH2

 

Step 3:

 

H2BrC-CBrH2

addition