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Sauron
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Why not use CCl4 with sulfur instead of S2Cl2 to moderate the rxn w/ Cl2O?
The Cl2O producing reaction over HgO is rather slow. Brauer says c.5 hours a acculate 15 g Cl2O in trap. Sounds like 3 g an hour. So this is a method
for making maybe 50 g a day SOCl2. If is a much better way of making HgCl2. Look at the stoichiometry in Brauer.
If this is too slow you had best consider another method. I have three suggestions.
Kyrides
Kyrides
Kyrides.
[Edited on 2-2-2009 by Sauron]
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Jor
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Yes Kyrides.
You need phthaloyl chloride, wich is expensive, but can be made from phthalic anhydride quite easily, using benzotrichloride.
So all materials you need are benzotrichloride, phthalic anhydride, a little ZnCl2 and SO2. The benzotrichloride is made by chlorination of toluene
as len1 has showed in republication. This seems this requires no hard to get chems.
However, I'd rather skip the chlorination of toluene and buy benzotrichloride.
But before buying the benzotrichloride in a month or two, does anyone know if I can prepare phthaloyl chloride from PCl5? I know it can be produced
from benzotrichloride and phosgene, so I'm pretty sure PCl5 should work as well, but confirmation would be great.
[Edited on 1-2-2009 by Jor]
[Edited on 1-2-2009 by Jor]
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panziandi
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Yes, PCl5 will chlorinate phthalic acid and you would distill off the POCl3 product which is easily doen since phthaloyl chloride boils much higher
than POCl3.
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DJF90
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Or use the PCl5 to make TCT, which can then be used to chlorinate phthalic acid with even less separation problems
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Jor
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Quote: | Originally posted by panziandi
Yes, PCl5 will chlorinate phthalic acid and you would distill off the POCl3 product which is easily doen since phthaloyl chloride boils much higher
than POCl3. |
Do you maybe have a reference for me? Does the reaction need a solvent or can I just mix the dry powders, and heat it, distilling of POCl3?
If I can go via PCl5, I will have my SOCl2 really soon!
Within 2 weeks, the required glasware for PCl5 synth. from red P arrives. I have phthalic anhydride at hand. So then I would be ready to set off.
I will make pictures when I have completed it.
If TCT would work, I would probably buy it, but TCT does not work, according to Sauron, be he's not sure.
[Edited on 1-2-2009 by Jor]
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panziandi
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Yes do take pictures it would be interesting to see this.
Well I don't have a ref at hand. If you look in Vogel in the forum library you will probably find some typical preparations of acid chlorides form
PCl5 follow one of those, there may even be one for phthaloyl chloride, I do not know since I can't download Vogel atm.
BAsically you would just mix phthalic acid and the PCl5 in a flask, the PCl5 will chlorinate the acid, forming the liquid products which will dissolve
the reactants and make the reaction go quicker! The reactions are usually quite exothermic (I once had a pyrex flask crack from reaction of PCl5 and
and acid within minutes of mixing!)
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Jor
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I don't think phthalic acid should be used! Phthalic anhydride!
First I think it is less reactive, second, if the method works, it will consume more PCl5!
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panziandi
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I'm not aware of phthalic anhydride going to phthaloyl chloride.
The acid would react like this:
C6H4-(COOH)2 + 2PCl5 → C6H4-(COCl)2 + 2POCl3 + 2HCl
I can't see the anhydride breaking open. You can get acid anhydrides to react with HCl to give acid chlorides...
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Sauron
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Read Kyrides. You do not need PCl5 to make phthaloyl chloride. You make it from phthalic anhydride and benzotrichloride at 200 C for 20 hrs. The
anhydride does open up and the byproduct is benzoyl chloride. See my thread A Twofur Reaction. Benzoyl chloride is very useful in its own right for
among other things, making acyl chlorides of more volatile carboxylic acid (See H.C.Brown. in JACS) They are formed almost quantitatively and are
seperated by fractionation. Hence thread name Twofur One. Two for One.
Phthaloyl chloride has some special properties and is good for making acid chlorides from 5 and 6 membered cyclic anhydrides. For monocarboxylic acids
other reagents (TCT, benzoyl chloride) are cheaper. For special cases see my thread on mild chlorinating agents.
SOCl2 is not my fave for most acyl chlorides, it however is the only one that works to make the dichloride of malonic acid. TCT fails at this. TCT
works for oxalic and succinic acids - go figure.
Here is Kyrides paper from JACS. There is also a petent he took out for Monsanto his employer.
[Edited on 2-2-2009 by Sauron]
Attachment: Kyrides_phthaloyl.pdf (318kB) This file has been downloaded 953 times
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Sauron
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And the matching US patents
I had a go round with Len1 about this. He was pushing the oxidation of sulfur chlorides with SO3, and criticized Kyrides procedure for allegedly low
yield. The yield was 60-something % which I regard as not bad, especially when one considers the following:
Kyrides was dripping liquid SO2 onto a melt at 200 C therefore residence time is very low.
Kyrides made no sttempt to cold trrap the off vapors and states that considerably SOCl2 may have been carried out that way.
So IMO simply adding a dry ice-acetone trap ought to improve the yield and injecting SO2 under pressure deeper into the melt ought to increase
residence time with same effect.
Did I forget to mention ZnCl2 is required catalyst? In small amount.
Len1 was justly pleased and proud of his SOCl2 prep but I thought and still think he gave Kyrides short shrift.
Jor, put your red P away for something where it is needed. This is not it. Making TCT from CA with PCl5 is possible, but buying it is also possible.
Using TCT to make phthaloyl chloride is possible but not supported in the lit. to best of my knowledge. And in light of Kyrides, unnecessary.Jor, put
your TCT away as well.
[Edited on 2-2-2009 by Sauron]
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garage chemist
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Jor, look at what Len1 has done regarding SOCl2 synthesis.
With benzotrichloride, there was no reaction at all:
http://www.sciencemadness.org/talk/viewthread.php?tid=10490
If you want to make phthaloyl chloride from PCl5, remember to cleanly separate the POCl3 before reacting it with SO2- the separation of POCl3 and
SOCl2 is surprisingly difficult, as I have already stated.
Phthalic anhydride would of course be the better choice, since only 1 mol PCl5 is needed for 1 mol of phthaloyl chloride, and no HCl is produced:
Ph(CO)2O + PCl5 ---> Ph(COCl)2 + POCl3
Using Cl2O would be beyond insane.
This substance is highly explosive and can detonate without apparent cause. This would be far, far more dangerous than working with SO3 could ever be!
I repeat my recommendation to use the SO3 + SCl2 method instead of the Kyrides method.
SO3 is dangerous, but completely manageable in a home lab.
In my many experiments involving it, I have never even worn gloves, to be honest.
I once got a drop on my finger- it immediately becomes black and hot, but the black color completely washes away with water, leaving no visible
injury!
If there is immediate washing upon skin contact, no visible harm is done.
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Sauron
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Len1's experiment with benzotrichloride was not supported by the literature. He did not employ any catalyst as required by the literature, and his
negative result is therefore unsurprising. The catalysts are not exotic nor are they expensive. FeCl3 (anhydrous)) is one of them.
PCl5 is a wasteful way to make phthaloyl chloride. The ZnCl2 catalyzed reaction of phthaloyl chloride with SO2 is fast and efficient and the huge
difference in bp's meakes purification easy. :en1 did not try this method and was unduly critical of it simply because it represented a viable
alternative to his pet method.
As to Cl2O I agree that the rxn with CS2 is hazardous, and I do not recommend it.
The generation of this gas as described in Brauer however, is quite slow, so that if the Cl2O is reacted with S in S2Cl2 in the cold and the generator
U-tube is also cooled as stated, the Cl2O does not accumulate but reacts in situ. If it were to accumulate the rate is c. 3 g/hour. Therefore the
amount of Cl2O present in the system at any time, when it is being consumed as fast as it is being made, is trivial. 3 grams per hour means 50 mg/min
being formed. What is the explosion hazard from say 1oo mg of this gas?
That does not sound like Krakatoa to me.
On the inlet side we have a cyl of dry air and a Cl2 generator and a drying train. These go to a U tuve submerged in an ice-brine bath at -12 C. The
U-tube contains HgO. The U-tube is connected to the reactor containing S in S2Cl2 also chilled to -12. The Cl2 forms in the U-tube and is reacted in
the solution of S. Both the U-tube and the reactor are under water and well chilled. So on this scale just what exactly is the explosion hazard?
The valid criticism of this method is that is slow.
If it were possible to scale it up your point would be well taken, but on the Brauer scale it looks safe enough to me.
Jor has never said how much SOCl2 he wants to make.
[Edited on 4-2-2009 by Sauron]
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panziandi
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I have to agree with Sauron, I see no real danger in the Cl2O method so long as the reaction is performed at a low temperature since the levels of
Cl2O generated at any one time is very low and immediately would be carried over in a current of air to react (I would imagine very rapidly) with the
sulphur.
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Sauron
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Also for those who prefer not to work with S2Cl2, CCl4 is a suitable replacement. I wonder whether other perchlorinated hydrocarbons are also inert
to Cl2O? Hexachloroethane?
If a larger quantity of SOCl2 is needed than 50 g a day I suggest the Kyrides method, or the SO3 oxidation of SCl2, or the HCMX/catalyst method.
I just ran a quick cost analysis for the SO3 method vs the Kyrides method, and also between buying phthaloyl chloride for the latter vs making it
from benzotrichloride. Surprisingly, all three methods come out roughly the same, hovering about 60 cents a gram for SOCl2 product.
The Cl2O method is a lot cheaper, since the air and chlorine cost about nothing, and the Hgo catalyst is regenerable, and S costs about nothing. Once
again its main drawback is that it is tediously slow.
[Edited on 4-2-2009 by Sauron]
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S.C. Wack
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I can't see how the method in Brauer can give a specific yield when the experimental is so vague; maybe it's easy to add the chlorine too fast or
slow. The related version in Inorg. Syn. gives some better guidance.
[Edited on 3-2-2009 by S.C. Wack]
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Jor
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I have decided that I am going to make one large batch of thionyl via Kyrides, when I have the money to buy the chemicals.
Phthalic anhydride is one of the cheapest chems I know. I already have 200g. Benzotrichloride is also very cheap, a liter from Acros at 25 EURO.
Even without a good collumn, seperation seems rather easy. Maybe I lose some phthaloyl chloride when I collect the benzoyl chloride fraction, but
that's not a real concern.
My largest flask is a 250mL 3-neck, so I can't do everything in one go. Well no problem, that I can trial and error the first time.
Zink chloride, I sealed old Merck bottle, so that's not a problem as well. And SO2, i will buy some more potassium metabisulphite (home brewers use
it, it is dead cheap). So basically, this is a very cheap synthesis of thionyl chloride, but the only problem is that you need quite some time to
perform the reaction, and I don't want to leave a reaction unattended.
I think the method of Cl2O is a very nice one, but indeed, you spend a lot of time, only getting 3g of Cl2O. I'd rather first hear other people's
experiences.
By the way, thanks Sauron for your last 2 PDFs. I will use that procedure.
And as a back-up method, I can go via PCl5, like garage chemist noted. This is precious, but I can buy red P, so I can make it via GC method,
substituting chloroform for DCM. Would distilling the phthaloyl chloride a second time without vigreux seperate it from most POCl3? I do not mind a
1-2% POCl3 contamination in SOCl2.
[Edited on 3-2-2009 by Jor]
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len1
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Quote: | Len1's experiment with benzotrichloride was not supported by the literature. He did not employ any catalyst as required by the literature, and his
negative result is therefore unsurprising. The catalysts are not exotic nor are they expensive. FeCl3 (anhydrous)) is one of them.
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My guide details the use of ZnCl2 catalyst.
It also details how phthaloyl chloride is obtained from PhCCl3 in good yield. I still have 120ml of it, but using this to get SOCl2 in low yield does
not excite me. I actually agree with GC, which I guess is not surprising because he does what he says.
This forum is an ancient hostory of posts of people promissing Ill do this, Ill do that, and then nothing. Its all on archive. Check. Wish you
better luck.
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Sauron
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You continue to obfuscate, Len1, ZnCl2 is not the succesful catalyst in the benzotrichloride or HCMX chlorination of SO2, and so it remains
unsurprising that your attempt with it failed. You continue to characterize a 66% yield as low, when in fact you are well aware, because I pointed
out to you months ago, that Kyrides himself stated that he made no attempt to analyze the contents of his cold trap and that a substantial amount of
SOCl2 was probably admixed with SO2 there. So a simple steo would have increased the already good 66% yield to yield perfectly comparable to those in
"your" SO3 method - a method that actually predates the Kyrides one by decades, dating from 19th century.
As to your continued little ad hominem tirades, my reply is NUTS. Since you rarely bother to put in any appearance here, no further rebuttal is
required. Go dream your dreamjs of making money publishing your handbook. It will be amusing to see how many copies get ripped off on the internet.
Jor, good decision. Acros price for phthaloyl chloride is $95 US/500 ml ehich is 750 g and 90%. Making it from benzotrichloride you get same weight
phthaloyl chloride as you put in, and you get benzoyl chloride as well so the effective cost plummets. The bp of phthaloyl chloride is almost 300 C so
you will have little trouble distilling off the benzoyl chloride. The phthaloyl chloride will stay in the pot. Kyrides says 94% pure, remainder is
phthalic anhydride. Same impurity in the commercial product.
S.C.Wack, the Brauer writeup clearly states that 15 g Cl2O collected as solid in the LN trap over 4-6 hours. If we take that to be 5 hours then 3 g/hr
is the mean. No the author did not detail exact rate of flow of Cl2 and air. Rather hard to do so reproducibly without a flowmeter or a mass flow
controller isn't it? However, I do not see how it matters. The amount of Cl2O in system, when it is being consumed in situ, will remain very low at
any given time with any reasonable rate of flow.
I will take your hint and have a look at Inorg.Syn. on this. It really is not a fast enough method for my purposes, but, it's good to have details.
Here is the citation you did not provide: Cody in vol 5 p 156. I have this and will post it shortly.
The attached file includes generation of neat Cl2O, and its solution in CCl4; its dissolution in water to produce HOCl, and the preparation of calcium
hypochlorite from that hypochlorous acid solution.
[Edited on 4-2-2009 by Sauron]
Attachment: Pages from IS-5.pdf (307kB) This file has been downloaded 1918 times
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Sauron
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It should be obvious to anyone reading the Inorg.Syn. article that the preparation of Cl2O in situ in CCl4 is easier and safer and faster than the
methods for making the neat gas or condensed Cl2O.
To briefly summarize, a solution of Cl2 in CCl4 is prepared of known Cl2 content, and dry yellow HgO is added 3.36 g per g Cl2, the mixture is
stirred, and the precipitate is removed by filtration. It is stated that initial yield 97% is reduced by losses in filtration. I would therefore
suggest a pressure filtration through a fritted glass filter. (Not vacuum filtration).
The regeneration of the HgO catalyst which is facile is also described.
The resulting solution of known amount of Cl2O in inert CCl4 can then be used to prepare SOCl2 by the slow addition of slifgt excess dry S at -12 C.
The SOCl2 can then be distilled from CCl4 and unreacted S.
UNFORTUNATELY SOCl2 and CCl4 have exactly the same boiling point 76 C.
Workaround: find an alternative inert solvent. Trichlorobromomethane would work. Hexachloroethane would work.
This makes one wonder about all those articles cited in Mellor about the use of CCl4 to moderate the rxn of CS2 and Cl2O. The SO2 will be impossible
to separate from the CCl4 at least by fractionation.
------------------
The attached JACS article from 1982 described the use of Cl2O as a powerful selective chlorinating reagent for organic substrates. If this is "beyond
insane" the please take it up with the ACS and the authors. Personally I find it very interesting that the alleged demon Cl2O has been tamed and put
to practical use on organic substrates without explosions.
The authors employed Cl2O c.1 M in CCl4 which they state can be safely handled and stoted < 0 C. The reagent gives 99% yields of benzotrichlorides
even with deactivated arenes such as p-nitrotoluene - these benzotrichlorides are otherwise very difficult to prepare and are useful in the synthesis
of the corresponding trifluoromethylbenzenes.
They went on to demonstrate the use of Cl2O in TFA to effect primary ortho ring chlorination of deactivated arenes.
All very interesti
[Edited on 4-2-2009 by Sauron]
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panziandi
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VERY interesting Sauron! I agree with you about the limited danger of Cl2O, sure if you generated bucket fulls in one go the explosion risk would be
real, but when you realise the catalyst bed is turning out 3g/hr diluted in a carrier gas, the danger isn't that real especially if the Cl2O is being
reacted in situ and not collected. And by operating at <0*C too...
If I have time when I next go home, perhaps I shall try a Cl2O chlorination of something...
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Sauron
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This ties in very nicely with the chlorination of CS2 to make CCl4.
Because that reaction produces first a mixture of Cl3CSCl and S2Cl2, then after distillation and refuction of the trichloromethyl sulfenyl chloride to
CCl4, the sulfur chloride is left over as a side product.
Now we have a USE for the side product, as solvent for the production of SOCl2 from S w/Cl2).
And yet another use for the CCl4, as solvent for in situ generation of Cl2O, for the preparation of benzotrichloride and HCMX. In both cases the
solvents are recoverable.
It is unfortunate that the S can't be reacted in CCl4 since the SOCl2 can't be separated from the carbon tetrachloride. I really want to find a higher
boiling alternative inert solvent compatible with Cl2O. Where I am I cannot buy CCl4. That's why I have to make it.
Upthread when I mentioned hexachloroethane I overlooked the fact that it is a solid.
The main two candidates therefore are Cl3CBr and tetrachloroethylene. But I am not sure the former will not halogen exchange with Cl2O, and I am
equally uncertain that the pi bond in the latter is inert to Cl2O. I know I can buy the bromotrichloromethane because I have a liter of it here. I
have not tried to buy the tetrachloroethylene ("perc") yet.
------------
Cl2O reacts with Cl2C=CCl2 to form a mixture of chlorinated and oxidation products. So this solvent is not inert. Lit. shortly.
[Edited on 4-2-2009 by Sauron]
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panziandi
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You could always attempt to make a solution of Cl2O in the Cl3CBr and then perhaps remove the Cl2O by addition of a reducing agent, then analyse the
Cl3CBr to see if there is any CCl4 present in it? If there is a halogen exchange then the Cl3CBr can not be used as a solvent, on the other hand if
there is an exchange you have another method of preparing CCl4! Just a note of reminder, HgF2 can replace halogens in trihalomethanes with F's, just a
proposal that HgCl2 may perform a similar reaction (and it is a by-product of the conversion of Cl2 > Cl2O)...
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Sauron
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Here's Chemical Review monograph on the chemistry of Cl2O from the 1970s. Cl2O is of industrial and technological importance, particularly in the
bleaching of wood pulp.
[Edited on 5-2-2009 by Sauron]
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S.C. Wack
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Quote: | Originally posted by Sauron
S.C.Wack, the Brauer writeup clearly states that 15 g Cl2O collected as solid in the LN trap over 4-6 hours. If we take that to be 5 hours then 3 g/hr
is the mean. No the author did not detail exact rate of flow of Cl2 and air. Rather hard to do so reproducibly without a flowmeter or a mass flow
controller isn't it? However, I do not see how it matters. |
So what? How are we supposed to figure out the amount of reactants based on yields, when we don't even know conversion %'s? How could a lack of detail
such as amount of reactants to obtain a specific yield, or at least the yield based on reactants, not matter? I'm supposed to build a flow rate based
on that, when I don't even know how much chlorine is converted with an amount of HgO that is not given other than "shallow layers"? I'm all for
experimentation, but vague, unreproducible experimentals are not quite so great as explicit ones, as I innocently, I thought, pointed out.
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Sauron
International Hazard
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S.C., don't get your knickers in a twist. You'll do yourself an injury.
Forget the prep of neat Cl2O,
These problems do not exist in the prepn of Cl2O soln in CCl4 where the Cl2 content of the CCl4 is quantifiable by iodimetry and for that matter by
weight. Knowing how many g Cl2, one adds dry yellow Hgo prerpared as advised, in the specified amount per g Cl2 (3.36 g if I remember) and stir. The
conversion is c.97%. Did you read the review from CR? Or the JACS article? Or for that matter the very Inorg Syn writeup you recommended? (Thanks.)
If so then your criticisma are all answered.
There is another JACS article on the analysis of mixtures of Cl2) and Cl2.
In the sole instance where in situ prepn in CCl4 is unsuitable, that of SOCl2, the Inorg.Syn. method is followed in preference to the one from Brauer,
the amount of ractants are specified, 5 L/hr Cl2 and 5 L/hr air, the amount of catalyst is specified, and the conversion is estimated. I'd simply run
it into the solution of excess S in S2Cl2 and based on weight gain, stop the Cl2 flow when done, flush the reaction tube with air only, then stir the
S2Cl2 mix some more before distilling off the SOCl2. No similarity in bp there. There's 60 degrees between the thionyl chloride and the solvent.
No Cl2O will remain in the system either in the generation tube or the reactor pot. The S2Cl2 can be reused (just add sulfur) and the HgO regenerated
by boiling with NaOH then drying as described in the texts.
Sic gorgeamus a los subjectatus nunc.
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