| Pages:
1
2
3
4 |
Damitwhy
Harmless
Posts: 8
Registered: 14-8-2011
Member Is Offline
Mood: No Mood
|
|
I've found myself with a spoilt Sulphur trioxide Oleum sample of 28.8grams which after all the hard work in making decided to go ahead and try to use
in making SOCl2 with SCl2 made previously...
I set up reflux condenser and dropping funnel on two neck adaptor attached to a 250ml flask, weighed and placed 30grams Sulphur Dichloride in flask
with magnetic stir bar, weighed and placed cold (suspect) Oleum in dropping funnel, flask was cooled in ice bath ontop of magnetic stirrer hotplate.
Began adding (suspect) Oleum dropwise with stirring at a slow rate, bubbles of gas could be seen flowing into a Sodium Hydroxide solution that was
attached to the gas out let from the drying tube on the condenser....
After all (suspect) Oleum was introduced I continued stirring changed ice bath then took a break...
Several hours later I returned to find ice had melted but slow bubbles in hydroxide outlet were still being produced so turned off magnetic stirrer
and let settle to find reaction mixture had two liquid phases one light yellow top layer and one dark brown lower layer.
I changed to oil bath and swapped out the dropping funnel for thermometer to measure refluxing temp and I began to reflux with Hotplate Temp at 80ºC
and found reflux temp to be 39ºC - 42ºC.... This is when I realized some thing was'nt quite right...
At this point I could only assume that I hadnt quite gotten all the Dichloromethane out from the production of the Sulphur Dichloride and it must be a
contaminant either that or something else with a lower Boiling Point had been made...
So I've refluxed for another hour then set up to distill what I can monitoring temp of distillate to be ranging from 25ºC right up to 55ºC before no
more distillate comes over...
Dark brown liquid still remained in flask and distillate has slight yellow colouration but still bubbles are visible in Hyroxide solution attached to
gas outlet on receiver flask...
I decided to change receiving flask and continue distilling with increased heat I found with each increase up to 130ºC a Yellow Distillate would be
seen creeping up the swan neck toward the condenser but this was slow in froming and not enough to collect in the receiver...
So After redistilling the distillate it turns slightly lighter yellow but still fumes in air and 5ml or so evaporating completely with strong acidic
sulphur smell within seconds when poored in a beaker in the fume hood... Is this my Thionyl Choride? will test later today...
Re tried all the above with Concentrated Sulphuric Acid inplace of (Suspect)Oleum and found all results nearly completely the same Just less residual
darkbrown liquid after distillation..
I found the Residue NOT so much the distillate reacts violently with water producing copious amounts of white gases/steam with lots of heat and the
strong acidic smell of Hydrogen Chloride and Sulphuric Acid..
Tell Me What Could be the Residue?
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
Would it be possible to safely perform the following based on the reaction of Sulfur with an organic solution of Cl2O from aqueous TCCA:
1. Add a small amount of water to TCCA to form a concentrated HOCl solution. Actually, due to a limited hydrolysis of TCCA in a neutral solution,
this reaction may proceed very slowly until Step 2 is performed to drive the reaction to the right .
2. Add CCl4 to capture Cl2O by shaking. Note, any Chlorine also formed from decomposition of HOCl to HCl reacting with TCCA, will also does dissolve
in CCl4, but HOCl itself is not soluble.
3. Keeping a low concentration of Cl2O in CCl4 (under 10%), slowly add small quantities of Sulfur (not finely powdered) to the mixture. This is
assuming the absence of an immediate detonation and a not overly vigorous reaction that cannot be controlled by cooling and/or working with a cooled
reaction mixture.
[Edited on 29-6-2012 by AJKOER]
|
|
|
Litmus
Harmless
Posts: 3
Registered: 28-2-2014
Member Is Offline
Mood: mad
|
|
All kinds of ideas come to mind for generating SOCl2. Many of the ideas proposed on this thread I'm not versed enough to give a useful reply. But I
get the general impression that making this stuff is tricky business, resulting in the thread's domination by a pitched battle between Len's ambitious
synthesis by the more or less industrial route, involving first the generation of S2Cl2/SCl2 and then subsequent oxidation by SO3, a nasty corrosive
sewer gas you don't want to get near to as pointed out by Sauron, while Sauron touts the Kyrides method, which involves an equilibrium reaction
between the more user-friendly SO2 and the chloric acid of Phthalic acid anhydride, TCL (more or less) pushed to the SOCl2 side and catalyzed by zinc
chloride(or the ZnCl2 helps push it to the left). Anyway, both methods have their pros and cons, involving yields, experimental difficulties, number
of reagents involved and their hazards, etc. As far as I can see.
Sulfur dichloride or disulfur dichloride is easy enough to make. A simple experiment is described here: http://lanthanumkchemistry.over-blog.com/160-index.html More or less Len's first step in his synthesis. I guess the question that comes to my
mind, is why can't S2Cl2/SCl2 be oxidized more simply, i.e. via hydrogen peroxide or some other easier oxidation route. Seems to me you're more than
half-way there with sulfur chlorides, but not.... Hmm.
Anyway, there's another method mentioned on the Wikipedia page on SOCl2 that uses SO2 and doesn't require phosphorus, done with phosgene. Note
phosgene is also a decomposition product of chloroform and perhaps methylene dichloride as well when exposed to UV light(why it's stored in brown
bottles), and a common byproduct of the haloform reaction( as in the well-known reaction between sodium hypochlorite solution(bleach) and acetone).
Okay, phosgene's no fun either, but nonetheless it sounds intriguing. I've been researching this up and down for awhile and found nothing so far. So
many on the forum seem much better at this. If someone can point me in the right direction, it would be a great help. The wikipedia page itself
gives no references for this particular reaction. Unless it's bogus  , however
the word "phosgene" is given expressly in the article regarding this reaction, which professes to produce thionyl chloride from phosgene and sulfur
dioxide.
George A Bell
|
|
|
AJKOER
Radically Dubious
Posts: 3026
Registered: 7-5-2011
Member Is Offline
Mood: No Mood
|
|
Here is a good Patent that discusses several catalysts for commercial paths to SOCl2. To quote from Patent US 3,419,353 (link to pdf viewer https://docs.google.com/viewer?url=patentimages.storage.goog... ):
"The SC12 is oxidized with oxygen, or an oxygen-containing gas, to thionyl chloride, for example, as taught by Evans et al., Faraday Society
Transactions, vol. 43, pp. 667-673 (1947), by passing the two over an activated carbon catalyst at a temperature of about 150 to 250 C. As an
exemplary activated carbon catalyst may be mentioned a calcium chloride-treated charcoal which may be prepared by soaking charcoal in an aqueous
solution of CaCl2, followed by filtering, washing with alcohol and then with ether and drying at about 100 C."
Also, a good review of the chemistry of employed commercial routes, to quote:
"Commercial processes for the preparation of thionyl chloride, SOCl2, are generally based on the oxidation of sulfur dichloride, SCl2, with sulfur
trioxide or oxygen or a combination of sulfur dioxide and chlorine. These reactions may be represented as follows:
(1) SCl2 + SO3 ---) SOCl2 + SO2 (see http://www.sciencemadness.org/talk/viewthread.php?tid=1439
(2) 2 SCl2 + O2 ---) SO2Cl2 + SCl2 = 2 SOCl2
(3) SCl2 + Cl2 + SO2 ---) 2 SOCl2 (200 C with a catalyst of activated carbon, see U.S. Patent 2,431,823)
The synthesis is often carried out in plural steps; for example, sulfur dichloride is usually first formed, or formed in situ, by the reaction of one
mole of sulfur monochloride, S2Cl2, with one mole of chlorine, as disclosed by Pechukas in U.S. Patent No. 2,431,823. Then the sulfur dichloride is
converted as indicated in the equations. "
This patent's suggested method is:
2 HCl + 1/2 O2 = H2O + Cl2 (Deacon catalyst)
Cl2 + S2Cl2 = 2 SCl2 (catalyst absorbent charcoal or antimony pentachloride, SbCl5)
SCl2 + 1/2 O2 = SOCl2 (catalyst charcoal treated with aqueous CaCl2, dried)
SCl2 + S = S2Cl2
For a net reaction of:
2 HCl + S + O2 ---) SOCl2 + H2O
where the water is removed prior to the formation of the thionyl chloride.
-------------------
If I dare to offer some substitutions for the home chemist, first conventiently prepare and dry Cl2 via another path than the author's requiring a
catalyst. Add SO2 to reaction mix (explained below) and lastly, especially if the preparation of a good Carbon catalyst presents an issue, replace O2
with freshly prepared and dried Singlet oxygen. The latter is a more reactive species of O2 albeit with a shorter life span (30 minutes) and more
costly (requires the action of dilute H2O2 on chlorine bleach, NaOCl), but I would hope for an improvement in yield.
Interestingly, to quote:
"Plasma-chemical oxidation of SO2 in air by pulsed electron beams ...
iopscience.iop.org/0022-3727/34/8/316
by YN Novoselov - 2001 - Cited by 8 - Related articles
The effects of the electron beam parameters, the external electric field and the ... are given as functions of the concentration of SO2, oxygen and
water vapour in the ... Analysis of the rates of the processes involving singlet oxygen molecules."
which suggests to me a small possibility that:
2 SO2 + 1O2 ---) 2 SO3 (with normal air, a catalyst based on V2O5/K2O/SiO2, at over 340 C, see Patent 8,323,610 )
Another source ("One conceivable mechanism of UV-light induced SO2 Oxidation to H2SO4", published in Atmos. Chem. Phys.,10,3141–3145,2010), link https://www.google.com/url?sa=t&source=web&rct=j&... , per page 3144 to quote:
"Nevertheless, the performed analysis shows readily the potential for the enhanced SO2 oxidation in air with O3 under UV irradiation via the chemistry
involving electron excited oxygen molecules.The most promising is likely the reaction of SO2 with O2(b1+g,υ). "
So with the possible formation of some SO3, we have per reaction (1) above:
2 SCl2 + 2 SO3 ---) 2 SOCl2 + 2 SO2
regenerating the SO2 for more Singlet oxygen consumption,....implying the net reaction in the presence of SO2:
2 SCl2 + 1O2 --SO2--) 2 SOCl2
which gives limited support for a small improvement with respect to substituting Singlet oxygen for O2 with a less than perfect constructed activated
Carbon catalyst. However, if employing both Singlet oxygen and a heated Carbon catalyst at 200 C in the presence of some Cl2 (from the creation of the
SCl2), there is a possible formation of phosgene. This issue may not be successfully addressed by allowing the reaction to proceed with an excess of
SO2, enabling yet another route, via COCl2 to SOCl2, as per the previously cited Mellor reference, to quote:
"at temp, above 200° with the formation of thionyl chloride and sulphur tetrachloride according to the equations: SO2+COCl2=SOCl2+CO2 and
SO2+2COCl2=SCl4+2CO2. The first reaction predominates at lower temp, and with excess of sulphur dioxide, and by suitable adjustment of conditions one
or other of the reactions may be almost entirely excluded. The reactions are carried out by passing the gases over a heated contact substance, such as
wood charcoal, and the carbonyl chloride may be partly or entirely replaced by a mixture of carbon monoxide and chloride, or carbon monoxide and
sulphuryl chloride may be employed. This mode of preparation gives good results. "
unless the reaction temperature exceeds 200 C in the presence of SO2. Note, Cl2 in the presence of SCl2 and SO2 also forms SOCl2 per reaction (3)
above.
[Edited on 4-7-2014 by AJKOER]
|
|
|
| Pages:
1
2
3
4 |
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
