(Wizard Master)
10-26-02 05:38
No 372746
      HI from I2 + Ascorbic acid
(Rated as: excellent)

Ascorbic Acid  C6H8O6

Merck 11th Edition No. 855

Physical Properties

Molecular Weight 176.12 grams/mole
Mp 190-192 oC
pH = 3 (5mg/ml concentration)
pH = 2 (50mg/ml concentration)

Redox potential at first stage is pH 5.0 is E = +0.127 Volts.

One grams dissolves in 3 mls of water.

Possesses relatively strong reducing powers, decolourizes many dyes.

Aqueous solutions are rapidly oxidized by air. The reaction is accelerated by alkalies, iron and copper.

Making HI from I2 and Ascorbic Acid.


C6H8O6 Ascorbic acid.
C6H6O6 Dehydroascorbic acid.

Balanced Reaction:

C6H8O6  ==>> C6H6O6 + 2H(+) + 2e E = +0.127 Volts
I2 + 2e ==>> 2I(-) E = +0.540 Volts
C6H8O6 + I2 ==>> C6H6O6 + 2H(+) + 2I(-) E = +0.667 Volts

The above reaction is used in analytical chemistry to determine quantitatively the amount of ascorbic acid.

In basic form: C6H8O6 + I2 ==>> C6H6O6 + 2HI

Simple Experiment.

Control Flask.

In a 50 ml flask, fill with 50 mls of demineralised water and add an iodine crystal. Stopper with rubber stopper.
Iodine solubility in water is 0.0013 moles in 1Lt at 25 oC

Reaction Test Flask.

In a 50 ml flask, fill with 50 mls of 1M Ascorbic Acid solution (176.12 grams in 1 Lt of demineralised water) and add an iodine crystal of equal size as the Control. Stopper with rubber stopper.

Observe that happens.

57% HI SOLUTION (HYDRIODIC ACID) : B.p 125.5-126.5 oC/760mmHg
Density 1.70 gr/ml ;  55-57%  w/w HI is 0.936 to 0.99 grams of HI per ml.

If 57% w/w HI solution has a boiling point of 125.5-126.5 oC/760mmHg at which it form a azeotropic solution. Then lowering the pressure will lower the boiling point temperature and thus flash azeotropic distill the HI from the dehydroascorbic acid + HI solution.

At room temperature the reaction of HI with the hydroxy part of the glycol, -C(-OH)-C(-OH) functional group on the dehydrascorbic acid is very slow. Refluxing is required to iodinate or reduce to -CH2CH3

Therefore, by using flash azeotropic distillation (380-570mmHg) the reaction between the dehydrascorbic acid + HI can be minimized.

(Hive Addict)
10-26-02 07:46
No 372782
      DooBeeDoo...as eloquently put by The Chief...     

...a few posts back!
Ibee was reluctant to post a reply for fear of sounding stupid...But that's never stopped him before. Why Stop now???
They don't call it "The YellowBrick Road" for nothing!
Excellent is an understatement if this means what Ibee thinks it means!

Time to hit the Books!!!
Ibee may need a Nurse or TWO after this one!

Thanx WizardX...
Peace of the REaction

Everything Ibee says should be taken with a Large Grain of Sympathomimetic Amine Salt
(Hive Bee)
12-18-02 12:49
No 390492
      more than only interesting     

this is.

And it shows how easily valuable posts are overlooked by me.
Thanks WizardX! And also for the browser test, OPERA don┤t crashes wink
Quality matters....  smile


now or never
(Hive Bee)
01-06-03 22:54
No 395896
      vitamin c     

Shouldn't this be talked about more? Has anyone tried this? this seems very promising..and ascorbic acid is so easy to get.
(Hive Bee)
06-25-03 22:58
No 442520
      i feel obliged to revive this thread yet again     

i feel obliged to revive this thread yet again.   why won't a more knowledgable bee comment on this?

if i only had an education...

(Hive Bee)
06-26-03 00:10
No 442533
      because its like a lot of the other I2 + X...     

because its like a lot of the other I2 + X -> HI reactions..  it cannot be done in situ like hypo/phosphorous acid or red phosphorous.. it requires the HI to be distilled, or the HI(g) to be piped into some cool water
06-26-03 03:29
(Rated as: Completely uninformative)
11-14-03 21:44
No 470905
      Anybee have a writeup on this?     

This looks just too good to be true.  WizardX's homepage is down and SWIM would like more info on this.  SWIM may start experimenting with this method anyhow but would like some more input from bees with more wisdom than SWIM.
(Hive Bee)
11-16-03 23:38
No 471267
      water purification kit     

Ive seen kits that contain 2 bottles, one is iodine pills
the other is ascorbic acid pills. I wonder why?

11-17-03 00:06
No 471274
      U may have HI, but still need to P     

Now all you bees r flooding their labs with 'new' HI; lets not forget the necessity of a P based recyclant eg HypoP, RP, P acid.

Dont throw away your rp just yet...
(Hive Bee)
11-17-03 00:47
No 471278
      dude, I think that was the idea....     

Not that ning is the biggest expert on RP/I, but seems that the reaction goes:

blahblah-OH + HI --> blahblah-I + H2O
blahblah-I + HI --> blahblah-H + I2


H2O + I2 + P --> ??? + HI

So by using an excess of ascorbate, the HI is continuously regenerated from the I2. Just like RP...Of course, there is that little problem of the HI attacking the ascorbic acid's OH groups too...oh well...
11-17-03 02:16
No 471287
      P for reduction to meth     

I meant a P based recycler for the reduction of E to meth; where the HI is consumed and needs to be regenerated in real time and kept at [57%].  I think the distillation is to remove freshly made HI into another vessel so that it doesn't attack the remaining reagent ascorbic.  Or have i missed the boat again.... i hope so?!
(Wizard Master)
11-17-03 04:17
No 471301

HI from I2 + Ascorbic acid is a method for making HI only. Then use reduced pressure azeotropic distillation (1/3 less of B.p 125.5-126.5 degC @ 760mm Hg) to purify your HI.

Approx. B.p 84 degC @ 506mm Hg

Do not think you can use the Ascorbic acid like RP, to recycle the I2.

Login Page.
11-17-03 04:19
No 471302
      There are a number of previous posts ...     

There are a number of previous posts (including one from Rhodium)stating a recycler (some form of phosphorous)is not required if there is enough of an excess of HI
11-18-03 09:36
No 471542
      P less HI rxns are possible, but unfeasable...     

P less HI rxns are possible, but unfeasable on a clandestine level.  I know this because Swix has done them himself; however BOS has also made him aware of the possible avenues to sucess.

That said, the main problem with P-less HI reductions is that the HI decomposes.  This is caused in small part from the actual HI consumed by reaction; but mainly due to the decomposition of HI at reaction temp.  This lowers the HI concentration below the required 57%.  The nett effect being low yield, half reacted goods, and blackened solution due to the free Iodine.

Best bet is to make some quick and easy HI, then invest the rest of your time into a P-based recyclant.  However, i reinterate that HI-only rxns are possible; just 'not recommended' for easiest route to sucess.

<<insert P here>>
(Hive Addict)
11-19-03 03:58
No 471662
      the reason     

The reason that you need a recycler in the reaction is that you need a high concentration of HI for the reaction to work.  Without a recycler, after the HI reacts with pseudo to form iodometh then meth, you're left with I2 rather than HI. 

It's too bad that you cannot selectively boil off water from a water/HI solution.  That would then perhaps keep the concentration high enough to reduce the pseudo.
12-11-03 20:36
No 476206
      H2O selective distillation?     

SWIM is an amateur in every sense of the word. Yet he wonders why something similar to what feirceness mentioned cannot be effected.  SWIM admits he chuckled when he first read it, then on second thought, he wondered if something very polar may be able to hold the HI more so than the water and allow it to distill seperately from the HI. SWIM knows this can get tremendously complex when discussing and actual RxN, but for now he just wonders if the idea is plausible.
(Hive Bee)
12-12-03 10:49
No 476362
      may rid of iodo-m, but what about I2?     

From Wizard X
Ok! Lets look at "The reduction of Ephedrine with HI".

(1) HI + ephedrine => iodoephedrine + H2O
(2) iodoephedrine + HI => meth + I2

Do you mean boil off water (produced from reaction 1) to reduce the rxn volume and hence concentrate (or maintain 57%) HI in the remaining solution; to effect a complete reduction to meth.  This may satisfy reaction 1

Now reaction 2 - What about I2?  Without a P-based recycler; this would remain and leave u with a thick black sludge... primo for some nasty (inhibiting) side reactions and hardcore post reaction workup.

<<black gold - texas tea!!>>
(Wizard Master)
12-12-03 11:20
No 476365
      reduction mechanism     

By adding RP you remove the I2 & H2O

2P + 3I2 ==> 2PI3
PI3 + 3H2O ==>> 3HI + H3PO3

The fundamental reduction mechanism of ephedrine reduction goes through these steps.
(1) HI + ephedrine => iodoephedrine + H2O
(2) iodoephedrine + HI => meth + I2
01-20-04 12:58
No 483511
      Forgive me....     

Forgive me if I appear to be thicker than the offspring of a village idiot & a Tv weathergirl, but are we essentially looking at either an excess of HI, ie.2x the normal requirments? Or a two rxn process?
(Wizard Master)
01-20-04 13:34
No 483519
      Calculation of HI to Ephedrine Ratio     

Plague: Have a read of this. Calculation of HI to Ephedrine Ratio

../rhodium/chemistry /meth.hi-p.html

We are looking basically at a two step "insitu" reduction reaction.
01-21-04 01:42
No 483650
      Many Thanks     

Many Thanks
01-22-04 11:52
No 483981
      a possible means to use this more directly     

okay, to make it clear exactly what is occurring in this reaction, i think that the iodine is oxidising the ascorbic acid and in the process ionising - which then allows it to nab a hydrogen that the oxidising freed from the ascorbic acid. Have i grasped this correctly? The thing is, dehydroascorbic acid can be turned back into ascorbic acid, but the question is: does the hydriodic acid do this? Or in other words, is this an equilibrium reaction or does it only proceed in one direction. From everything i've looked at so far, it is one way, but i've not seen a lucid explanation of the reaction kinetics and i am not sure.

I thought about whether the hydriodic acid would react with the dehydroascorbic or ascorbic acids, and i can't see how that would happen, from what i understand of the HI reduction mechanism, it is more specific than some reaction mechanisms because the iodine's larger size. there is two hydroxyls on dehydroascorbic acid, but can they be reduced or not? likewise all those keto groups all over it.

if it were possible i imagine one would want to ensure that more than enough HI would form to bring the concentration up to 57%, perhaps do the reaction with 4 mol of I2 and 4 mol of ascorbic acid and 1 mol of ephedrine, and a neutral atmosphere to reduce the possibility of the ascorbic acid being oxidised by something other than the iodine. Or perhaps only the ascorbic acid needs to be in excess as it will regenerate any I2 that reforms. I thought about whether the ascorbic acid perhaps could be brought to melting point under a neutral atmosphere (that's 190 degrees) but that would be too high perhaps? also rhodium has been throwing around the idea of using anhydrous acetic acid as the reaction medium... Perhaps anhydrous acetic acid would be exactly the right environment to use ascorbic acid/I2 as an in situ source of HI...

edit: looking at rhodium's new idea's page... hypophosphorous/i2 reduction using anhydrous acetic acid... let's suggest another idea: could the HI azeotrope distillation be done so that one adds 5% acetic acid (vinegar) rather than dh20, and then fractionally distilling the water out first then bringing the HI across with the acetic acid. This might need to be dried further, maybe using a molecular polarity filter (molecular seive are they called?) or whatever...

and so then, you have HI dissolved in acetic acid sans water, if one uses an adequate excess of reagent, and gentle conditions, wouldn't this work?

Acetic acid would certainly make it easier to distill out the HI, and if acetic acid/HI could be used as is... you couldn't get much simpler and neater really...