[MrKukk]

How would you answer this question?

How can you see if there is a double bond in a molecule, you need to set up a "experiment" where you show a reaction that proves the double bond.

(sorry for any misspellings)

[LukeeeeBennett]

I believe one way of finding out is by adding a solution of bromine water to the compound that you're trying to investigate. If the normally brown bromine water colour turns colourless or obviously less of the brown colour then you've got yourself a double bond. This is because the Bromine jumps in to fill the gap and thus loses the colour.

Obviously if you're using a gas, then bubble it through the bromine water and look for the colour change.

[vmelkon]

Yes, bromine.
Also, HBr forms during the reaction, so you can do a pH test.

[Nobby]

If bromine is added to a double bond no HBr will be obtained. This is possible if you have substitution of H at an alkane.

[vmelkon]

If bromine is added to a double bond no HBr will be obtained. This is possible if you have substitution of H at an alkane.

My mistake.

[LukeeeeBennett]

Usually the Bromine will just take place with a carbon and prevent the double bond.


                                                                           H H

                                                                           |  |
For example, H₂-C=C-H₂ (Ethene) + Br₂ (Bromine) H-C-C-H   (1-2-Dibromoethane)
                                                                           |  |
                                                                           Br Br

Wow, that took a lot of work. Haha.