Sciencemadness Discussion Board

HI reductions, no red P

Picric-A - 3-3-2010 at 03:37

I know this will look like a drug discussion but i do not want it to be one.
I am attempting the reduction of benzoquinone to hydroquinone with the HI/red P route. I know this is way ott as HI is alot stronger than is actually needed however i have never tryed this type of reduction but i dont want to make drugs with it.
Now as i try to seperate myself from drug materials such as red P i dont have any.
Research shows this is how HI is made industrially ;
2I2 + N2H4 --> 4HI + N2

So my question, is it possible to use hydrazine to replace red p in this proceudure. I intend to do the following;

Suspend 5g of I2 in a solution of 3g benzoquinone.
Slowly drip into the refluxing mixture 3ml of 100% hydrazine hydrate.
Add thiosulfate to remove exess I2, extract hydroquinone.

Jor - 3-3-2010 at 03:43

Excess I2? Hydrazine is in excess!

Picric-A - 3-3-2010 at 05:37

OK sorry i messed up on the stoichiometry, but the question still stands.
As far as i know the red p is only present to regenerate the HI and so surly N2H4 will work as well.

woelen - 3-3-2010 at 07:29

This is an interesting thing. I'm not sure that this works, because the N2H4 may be such a strong reductor that it directly reduces other materials besides the HI. Red P has the property that it is a solid which is not really reactive, except towards a few specific species, halogens being some of them. Hydrazine on the other hand is a very reactive species and I doubt that reaction of this chemical is confined to iodine only. It also may react with the organic compound in the reaction mix.

Please give it a try and let us know how it works. Also try it without adding iodine, this may also work.

Nicodem - 3-3-2010 at 12:14

References! Where are they?
Quote: Originally posted by Picric-A  
I am attempting the reduction of benzoquinone to hydroquinone with the HI/red P route.

Who says benzoquinone is reduced to hydroquinone with HI? What prevents the benzoquionone to instead react via the 1,4-nucleophilic conjugative addition to give 2-iodohydroquinone rather than hydroquinone and I2? In fact, benzoquinone reacts with solutions of HCl and HBr (in water, acetic acid or other solvents) to give 2-chlorohydroquinone and 2-bromohydroquinone respectively (Ann., 51 (1844) 146; Ber., 12 (1879) 1504; Ann., 209 (1881) 109; J. Chem. Soc., Perkin 2 (1983) 271-280). I would not know about HI, but according to the abstract of Zhurnal Obshchei Khimii, 24 (1954) 1433 it gives 2-iodohydroquinone. There are several referenceless claims that benzoquinone is reduced by iodides to give hydroquinone on internet pages (Wikipedia as usually gives no reference, neither do this and this or many other pages). I could find only references to analytical papers where the product of this reaction is identified, but no preparative method (and the reaction conditions were not those of a "HI/red P" type, but simple electron transfer based redox reactions - see bellow).

I know this is way ott as HI is alot stronger than is actually needed however i have never tryed this type of reduction but i dont want to make drugs with it.

Benzoquinone has no hydroxy groups to reduce, so the usual mechanism involved in HI based reductions does not apply. In principle the redox potential of the iodide ions in water is just low enough to give electrons to benzoquinone under appropriate concentrations and conditions, but this is a redox equilibrium, while the conjugative addition is irreversible. By rapid removal of I2 or in dilluted iodide solution it should be possible to drive the reaction toward hydroquinone (or hydroquinone/benzoquinone complex) as the redox reaction is way faster than the conjugative addition, but without I2 removal or in concentrated solutions of HI and with heating, I'm not so sure the reaction would stop at the hydroquinone stage. Do you now understand why we need references? The topic is much more complex than you think. The products are most likely reaction conditions dependent. Furthermore, the reduction reaction can be driven in the other direction and thus become an oxidation of hydroquinone with I2 (definitively see DOI: 10.1007/BF01204830 and the references cited therein). Also, the oxidation of hydroquinones with H2O2 by I2 catalysis is known: HI gets oxidized by H2O2 to I2 thus forcing the redox equilibrium in the oxidation direction via HI removal (see J. Org. Chem. 54 (1989) 728-731).

Research shows this is how HI is made industrially ;
2I2 + N2H4 --> 4HI + N2

Yes, hydrazine does reduce iodine, but please point us to the relevant patent or article so that we can read more about it.

So my question, is it possible to use hydrazine to replace red p in this proceudure. I intend to do the following;

Suspend 5g of I2 in a solution of 3g benzoquinone.
Slowly drip into the refluxing mixture 3ml of 100% hydrazine hydrate.
Add thiosulfate to remove exess I2, extract hydroquinone.

You first need to prepare a aqueous solution of HI by reducing I2 with stoichiometric amount of hydrazine or else benzoquinone reacts with hydrazine as well. Benzoquinone must be added only after all hydrazine is consumed. But what is the reaction product when applying reflux conditions still remains to be seen once you provide us all the literature sources you used. I would guess that if you want hydroquinone as a product you must certainly not heat the reaction mixture and quench it rapidly enough. This should give only the reduction product and no or nearly no product of nucleophilic addition.

Edit: Revised a lot.

[Edited on 3/3/2010 by Nicodem]

mr.crow - 8-3-2010 at 07:32

I hope you don't mind me asking, but how does the HI reduction actually work?

Lets say you have 2-iodopropane, would it react with conc HI to form I2 and the alkane? This isn't a regular substitution reaction.

Nicodem - 8-3-2010 at 08:43

Yes iodopropane should reduce with HI, though only at quite extreme conditions (which means closed vessel and so on).

I never saw any study of the mechanism and I don't think it was ever seriously studied.* By a first glance it appears as a simple aliphatic electrophilic substitution (S<sub>E</sub>2), but the problem is in that if the mechanism is based on a bimolecular process the activation energy would be high (due to I<sup>+</sup> as leaving group). So the electrophilic substitution could be assisted by a nucleophile capturing the leaving group (the I synchronously starting a bond with a nucleophile while the C-I bond is breaking; some time ago I posted a hypothesis based on this here) and if the assisting nucleophile is the iodide anion the activation energy is quite low. The problem is in that this would be a trimolecular process, meaning the reaction kinetics would be terribly slow even if the activation energy is low. With either mechanism the reaction requires high temperature and high HI concentration either due to high activation energy or lousy collision statistics. The other possibility is some kind of single electron transfer reduction which is not to exclude when iodide/iodine is involved.

* There are at these two papers that slightly ventured into the mechanism of reductions with HI (but unfortunately not the reduction of alcohols or their alkyl iodide intermediates): DOI:10.1016/S0040-4039(00)71715-1 and DOI: 10.1039/CT9242500710.

[Edited on 8/3/2010 by Nicodem]

Anders2 - 17-9-2010 at 13:36

Interestingly Hydrogen Iodide will react with Acetone, if the proportions are correct, to form 1-Iodopropane. This comes about if the elemental iodine that is formed from the inital reduction of the ketone is not absorbed by some other chemical, and is allowed to sit around in the solvent, eventually oxidizing a ketone. The rate of this oxidation is dependant on the acidity, the more concentrated the HI, and the less water, the faster the reaction.

I can inform you that bromine and a ketone will react with eachother in about 4-5 minutes. By using some 9% HNO3, the reaction was complete in 20 seconds.

madscientist - 17-9-2010 at 21:14

Halides react with ketones to form halo-alpha ketones.

majortom - 8-10-2010 at 12:52

The above posters are correct, although in either basic or acid conditions I have forgotten which, you get the full haloform reaction, which means acetic acid and platforms, under the full reaction ph the product is more reactive than the precursors, and the carbonyls-haloformyl bond breaks. in the other ph the products are less reactive and no cleavage occurs,

and for the record, hydrazine is just as suspicious as red p, at least with P you can get it from urine, opiates it matchbox strikers, hydrazine you have to buy, if you make it you need anhydrous ammonia and hydrogenperoxide, both are suspicious as anhydrous liquids, and very dangerous, plus the anhydous hydrazine you make is basically rocket fuel, that would be the last thing is want to reflux.

DJF90 - 8-10-2010 at 14:10

majortom needs to take some chemistry lessons. Haloform reaction occurs under basic conditions. A quick check on wikipedia would have confirmed that for you. Hydrazine can also be made in a variety of methods, and in most cases applicable to the amatuer, alot easier than getting phosporus from piss. If you think its that easy, how do you explain the lack of phosphorus production around here (we do have a little, and those members who have succeeded strived very hard to do so). Anhydrous hydrazine is hardly ever used in the lab; only for the most extreme of cases. More likely is the sulfate or hydrate (a 60% "solution"), and whilst Hydrazine is carcinogenic, it can be safely handled in these forms with little worry, providing the proper precautions are in place.

jon - 20-10-2010 at 12:32

another easy way to handle hydrazine is to use it in alcohol the sulfate is available anywhere fine chemical and supplements are sold.
add hydrazine sulfate to alcoholic alkoxide it is wise to chill the solution before adding the hydrazine portionwise this is all very hygroscopic so the room must be dehumidified.
the sulfate precips out which is then filtered and you have a relatively safe form of hydrazine (never think hydrazine is safe).
you don't want to reflux this shit it's better to do it in a bomb (pun intended) with an inert atmosphere blanket.

don't take my word when it comes to handling hydrazine

hydrazine handling and safety manual

[Edited on 21-10-2010 by jon]

[Edited on 21-10-2010 by jon]

majortom - 22-10-2010 at 19:23

Admittedly my post was pretty sad, mostly due to lack of sleep and a semi-functional laptop keyboard. (spellcheck butchered it even more) I really should have looked up the ph.

I was under the impression that you really had to push the equilibrium to the right by removing water, I am probably wrong though, Do you have any Idea on the reaction Kinetics.

jon - 22-10-2010 at 20:04

from my limited understanding terminal alkyl iodides reduce sluggishly and under *extreme* conditions.
but nicodem knows more about mechanisms than anyone else i know so i think he answered it best.

RiP057 - 28-10-2010 at 17:04

From what I see benzoquinone through tautemerization would protonate at the O leaving a positive carbocation at the 3 position. Iodine attack at the then 3 position gives the 3-iodohydroquinone product after another tautemerization. Calling it 3-iodohydroquinone does not follow IUPAC, but neither does calling it hydroquinone, but for neatness it is renumbered to 2-iodohydroquinone. Sorry for the confusing numeric system.

why not just use something like Fe/HCl I highly doubt that that system would reduce the hydroquinone, and it would certainly do something to the double ketone....

also wtf guy why use hydrazine.... if you are skilled enough to handle hydrazine there are a plethora of other options available to you along with just out right buying hydroquinone, however if you are doing research on various hydroquinones synthesized from benzoquinones I apologize.... if that is the case what is your synthetic route to benzoquinones???

peach - 29-10-2010 at 15:06

I have about a kilo of hydroquinone if you want some as a reference, or just need the quinone. I have no need for that much, it was just he minimum order I bought it in.

Bought it for making my own pinhole cameras, then got distracted tiling the kitchen and sanding the floors.

£5 or something like that should cover the cost for 100g, I dunno... it's Friday and I'm knackered from DIY'ing like crazy these last two or three weeks. To be honest, I forgot it was Friday until I checked the time on the computer.


[Edited on 29-10-2010 by peach]

RiP057 - 29-10-2010 at 15:51

Nicoderm has gotten on me for references, but that usually requires access

Huaxue Fanying Gongcheng Yu Gongyi (2006), 22(6), 544-548.

convert benzoquinone to hydroquinone with Fe powder in water thats all it says and I cant get that journal.... looks chinese

however this is all WAY off topic of initial post