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Topic: Halogen + NaOH  (Read 22279 times)

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Offline Astrokel

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Halogen + NaOH
« on: September 29, 2008, 04:00:37 AM »
hey all,

in my A level syllabus we learnt about Chlorine reacting with cold and hot NaOH to hypochlorite and chlorate respectively, it is a disproportion reaction, so i can't tell is it because of chlorine strong oxidizing ability or weak reducing ability(relative to bromine and iodine) doing its effects. So i am wondering if other halogens including florine undergo this disproportion reaction with cold/hot NaOH, if no why?

i appreciate any helps, thank you!
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Offline Astrokel

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Re: Halogen + NaOH
« Reply #1 on: January 02, 2009, 09:35:04 AM »
Just to update this old post(sorry!) to those may have the same doubts as me because i found my answer. Other halogens will undergo the same situation as chlorine.

http://www.rod.beavon.clara.net/incat3.htm
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Offline cliverlong

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Re: Halogen + NaOH
« Reply #2 on: January 03, 2009, 05:46:07 PM »
hey all,

in my A level syllabus we learnt about Chlorine reacting with cold and hot NaOH to hypochlorite and chlorate respectively, it is a disproportion reaction, so i can't tell is it because of chlorine strong oxidizing ability or weak reducing ability(relative to bromine and iodine) doing its effects. So i am wondering if other halogens including florine undergo this disproportion reaction with cold/hot NaOH, if no why?

i appreciate any helps, thank you!
Hi Astrokel,

Coincidently, I have been editing the wikipedia pages on the chlorate (Hypochlorite, chlorite, chlorate, perchlorate) because they seemed a bit sketchy, inconsistent in style and poorly interlinked to me. I'm not claiming what is there is the final word but it makes more sense to me. If any feels they can improve, then wiki is wide open to edits.

I have started on hyopbromite and bromates. I will then move on to iodates.

The source I am using is Facts, Patterns and principles (Kneen Rogers and Simpson) which is a mega book, has loads of info and is woeful in the organisation of the material. Leaving that aside, from what I remember hypobromite (ox state +1) disproportionates directly to bromate (ox state +5). There is no (stable) bromite (ox state +3). I think the book stays there was evidence in the 1970's that the perbromates might exist fleetingly. I haven't got on to the iodate entries but I think again there are only the +1 and +5 oxidation states.

I need to check but I don't think there are any fluorooxide becasue fluroine is the strongest oxidizing agent.

Something I did find out about the disproprtionation of chlorate(I) and bromate(I) when in an alkali solution, is the second reaction rate is very temperature sensitive.

Clive

Offline cliverlong

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Re: Halogen + NaOH
« Reply #3 on: January 04, 2009, 09:13:16 AM »
<< snip lots >>

Something I did find out about the disproportionation of chlorate(I) and bromate(I) when in an alkali solution, is the second reaction rate is very temperature sensitive.

Clive
In response to a question about my statement above

In Facts, Patterns, Principles (Kneen, Rogers, Simpson) and referenced in http://en.wikipedia.org/wiki/Hypobromite

I found and quoted
Quote from: wikipedia hypobromite entry
Add bromine to an aqueous hydroxide (such as sodium or potassium hydroxide). At 20C the reaction is rapid.
(1) Br2(l) + 2OH-(aq) → Br-(aq) + BrO-(aq) + H2O(l)
In this reaction the bromine disproportionates (undergoes both reduction and oxidation) from oxidation state 0 (Br2) to oxidation state -1 (Br-) and oxidation state +1 (BrO-).

A secondary reaction, where hypobromite spontaneously disproportionates to bromide (bromine oxidation state -1) and bromate (bromine oxidation state +5) takes place rapidly at 20C and slowly at 0C.
(2) 3BrO-(aq) → 2Br-(aq) + BrO3-(aq)

Hence, in reaction 2, the formation and proportions of the -1, +1 and +5 bromine oxidation state products can be controlled by temperature.

These reactions are analogous to those forming hypochlorite, where the corresponding reaction 1 (to form ClO-) is fast at 20C and reaction 2 (to form ClO3-) is slow at 2OC and fast at 70C.
[\quote]

Offline Astrokel

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Re: Halogen + NaOH
« Reply #4 on: January 04, 2009, 02:01:18 PM »
Great, thanks alot!
No matters what results are waiting for us, it's nothing but the DESTINY!!!!!!!!!!!!

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