Will alkyne decolorise bromine water?

Question

Will alkyne decolorise bromine water?

Answer 1

Yes, it certainly will: and very rapidly indeed

(Though the product with four bromines in it (suggested by previous poster) is likely to be a minor product.

After attack by the first Br the most likely nucleophile to attach the carbocation is water (there's so much more of it in bromine water), which will introduce an -OH group.)

Answer 2

Yes, Br2 reacts with both alkynes (triple bond) and alkenes (double bond. The Br2 takes part in what is called an addition reaction. It adds across the triple or double bond. Breaking one pi bond and adding a Br to each side. For an alkyne, if there is enough Br2 then the addition can occur twice with Br2 adding across both pi bonds.

eg

Ethyne (HCCH) + Br2 -----> HBrC = CBrH (1,2 - dibromoethene)

HBrC = CBrH + Br2 --------> HBr2C - CBr2H (1,1,2,2 -tetrabromoethane)

The removal of the Br2 from the Bromine water (because it is reacting) is what causes the solution to lose it's colour.

Here is a great link for general reactions of organic compounds.

http://www.enter.net.au/~fairsci/chemist...