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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: davon806 on September 30, 2012, 10:50:28 AM

Title: cyclohexane and bromine water
Post by: davon806 on September 30, 2012, 10:50:28 AM

I have done an experiment several weeks ago.Cyclohexane was used to test the chemical properties of alkanes.
Under UV light,when cyclohexane is added to bromine water,the solution will not decolorize.
However,I remember some books said that when hexane is added to bromine water under the same condition,the red-orange colour of bromine is discharged.
Why?

Title: Re: cyclohexane and bromine water
Post by: discodermolide on September 30, 2012, 12:22:37 PM

Do you not find this strange? I mean cyclohexane and hexane are quite inert hydrocarbons. I don't think hexane will decolourise bromine water even under UV light.
Are you sure it is hexane could it be that the book said hexene? (I know books don't talk).

Title: Re: cyclohexane and bromine water
Post by: davon806 on September 30, 2012, 01:34:57 PM

yes.It is hexane,please see the attached.

Title: Re: cyclohexane and bromine water
Post by: discodermolide on September 30, 2012, 02:06:58 PM

Then the UV light is generating radicals, Br. and HO.
These the abstract a H radical from hexane, probably to give water, And a C₆H₁₃ radical which then reacts with the bromine radical to give C₆H₁₃Br.
But I would expect the same to happen with cyclohexane. This is somewhat puzzling.

Title: Re: cyclohexane and bromine water
Post by: curiouscat on September 30, 2012, 02:13:01 PM

Quote from: davon806 on September 30, 2012, 01:34:57 PM

yes.It is hexane,please see the attached.

Bromine is different from Bromine Water.

Title: Re: cyclohexane and bromine water
Post by: davon806 on September 30, 2012, 02:38:41 PM

Re curiouscat.
What is the difference?
Either water or organic solvent will not participate in the reaction.
I think we use bromine water just because of safety?And the final result should be the same as using pure bromine?