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Author: Subject: CHCl3 and CCl4 Prep Overview
Sauron
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[*] posted on 3-4-2008 at 09:16
CHCl3 and CCl4 Prep Overview


Given an ample supply of materials for a reliable smooth chlorine generator, next we turn to what to do with it.

Chloroform and carbon tetrachloride are often needed, but often hard to get - essentially impossible where I am.

Conventional wisdom is, make CHCl3 via the haloform reaction, and make CCl4 by chlorination of CS2.

However, the haloform reaction of hypochlorite and acetone is IMO a rather laborious affair. A large volume of liquid reaction mixture has to be manipulated to obtain a miniscule yield of chloroform.

Similarly, carbon disulfide is flammable (very), rather costly, and its chlorination produces a large amount of stinking sulfur chloride byproducts that are unpleasant to handle, and difficult to separate from the CCl4. So unless one has a use for SCl2/S2Cl2, they are a nuisance.

I'd like to look at the alternatives.

CHCl3 can be made from CCl4 so let's focus on CCl4.

The main alternatives to chlorination of CS2 are twofold:

-- chlorination of methyl thiocyanate

-- preparation of trichloroacetyl chloride.

Methyl thiocyanate is rather expensive to buy but easy to make. Essentially one needs sodium or potassium thiocyanate and a methyl halide, 95% ethanol being the solvent.

A reaction I regard as overlooked and underappreciated is the second. H.C."Boron" Brown noted in a JACS article that benzoyl chloride is a general reagent for preparation of volatile acid chlorides. But in the cases of dichloro and trichloroacetic acids, the usual very high yields dropped sharply. The acyl chlorides of these acids fall apart readily to CCl4 and a little CHCl3.

I suggest that these acids are inexpensive enough (especially compared to CS2 and MeSCN) to buy them and go straight to Brown's procedure.

If more economy is desired, and an embarassment of Cl2 is at hand, then acetic acid (GAA) is dirt cheap and readily chlorinated beyond the monochloroacetic acid stage.

The fire hazards associated with CS2 are absent.

Another entry point to these acids is through chloral, from chlorination of anhydrous ethanol.

It is non-intuitive that ethanol and chlorine can get you to CCl4, or that acetic acid and chlorine can as well, but the chemistry is valid and the economics compelling.

The methyl thiocyanate route is the most interesting because it can be tweaked in a variety of directions, but the acid chloride route is apparently the most attractive for lab use and from cost effectiveness considerations.

The byproduct, dichloroacetyl chloride or trichloroacetyl chloride, are useful. Or they can be hydrolyzed back to the acids and reacted again. By this tactic, the per cent of conversion to CCl4 can be very high overall.

CCl4 by this method is entirely free from S-containing contaminants which is not the case when starting from CS2 or MeSCN.

I'd like to know if anyone else wants to explore this concept as well.




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[*] posted on 3-4-2008 at 09:43


Do you have a ref for the methyl thiocyanate chlorination? I suppose anhydrous conditions have to be used for CCl4, as I have read several articles that state that chlorination of alkyl thiocyanates in aqueous mixtures yields sulfonyl chlorides and CNCl...

CH3-S-CN --Cl2/H20--> CH3-SO2-CN --Cl2--> CH3-SO2Cl + ClCN

Could the carbon tetrachloride come from further chlorination of CNCl?
Or perhaps in absence of water the C-S bond is cleaved on the methyl side, leaving a chlorinated -SCN moiety, before or after replacing the hydrogens with chlorines...
I would be interested in reading any litterature you could have on hand on that subject.
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[*] posted on 3-4-2008 at 09:59


Here's the paper by James in J.Chem.Soc., on which my remarks are based.

One of the ways the reaction can be manipulated is to produce cyanuric chloride. Since that is the solid trimer of CNCl you are right. But anyway read on.

James isolates a variety of intermediate chlorination products but the ultimate product of continuede chlorination is mainly CCl4.

I would think that EU residents who can't readily obtain cyanuric chloride (TCT, CC) would be even more intrigued by the possibility of making this by this method, than making CCl4, which anyway can be done by other means.

Whereas the only other way to make TCT is from CNCl, no fun, or from chlorination of CA (cyanuric acid) with PCl5, also no joy.

3 CH3SCN + 11 Cl2 -> C3N3Cl3 + 2 CSCl4 + CSCl2 + 9 HCl

C3N3Cl3 is cyanuric acid.

CSCl4 is trichloromethyl sulfenyl chloride and this on further chlorination gives CCl4 and SCl2.

CSCl2 is thiophosgene and this on further chlorination also gives CCl4 and SCl2.

So, 3 mols methyl thiocyanate ultimately form a mol of TCT and 3 mols of CCl4 alog with 3 mols SCl2 and a pile of HCl.

I am suggesting that this is a very profitable series of reactions. TCT is very useful, so is CCl4. Thiophosgene is also useful, and is a pain to make. See the low yielding and rather cumbersome Sn/HCl reduction of CSCl4 as exemplified in the Thiophosgene monograph in Org.Syn.

SCl2 can be oxidized to SO2Cl2. S2Cl2 can be used in prep of acetic anhydride.

3 mols MeSCN is c.220 g.

From this we get about 70% of a mol of TCT (c.100 g); theoretically 3 mols CCl4 (c.450 g) and 3 mols SCl2 (306 g) and all that gained mass is due to the cheap and plentiful Cl2 from TCCA and HCl. 11 mols Cl2 are consumed in the chlorination of MeSCN (3 mols) and a further 8 mols in the chlorination of the thiophosgene and trichloromethyl sulfenyl chloride.

So this takes about 6 mols TCCA, that is roughly 1.5 Kg or about $6 US worth out of my 50 Kg drum.

Not bad.

[Edited on 4-4-2008 by Sauron]

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[*] posted on 3-4-2008 at 10:54


"So, 3 mols methyl thiocyanate ultimately form a mol of TCT and 3 mols of CCl4 alog with 3 mols SCl2 and a pile of HCl."

This is amazing! Never before have I seen such a variety of useful reagents produced from a single reaction. I have been looking for feasible routes to TCT and CCl4 for the longest time.

It's unfortunate, however, that methyl thiocyanate seems to be unavailable to me. This is just a preliminary observation, though.

Thanks for the paper, Sauron!




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[*] posted on 3-4-2008 at 11:25


Very interesting! Especially it seems very easy to seperate the TCT out of the reaction mixture.. But it would require large amounts of chlorine, and complete chlorination to CCl4 and SCl2 even more so!
I guess treating the distillate with water after complete chlorination and seperation of TCT would suffice to obtain SCl2-free CCl4, after fractionnation.

"The Action of Chlorine on Thiocyanates"
Treat B. Johnson and Irwin B. Douglass
JACS, (61)9, 2548 - 2550 (1939)

available at the ref thread thanks to Solo, middle of page 21, details the preparation of mesyl chloride from methyl thiocyanate. I think there is mention of the article you provided.
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[*] posted on 3-4-2008 at 11:35


Quote:

It's unfortunate, however, that methyl thiocyanate seems to be unavailable to me.


Not a problem. As Sauron mentioned above, it can be made from an alkali metal
thiocyanate and a methyl halide in ethanol. As I mentioned the other day in another
thread, the alkali metal thiocyanate can be made from sulphur, alkali metal
carbonate, and a ferrocyanide (or other source of cyanide). Looking further
back in the forum archives, methyl chloride can be made from methanol and
hydrochloric acid.

http://www.sciencemadness.org/talk/viewthread.php?tid=1509&a...

Hence, with a bit more work, one can instead start with
some quite common chemicals:

CH3OH
CH3CH2OH (as solvent)
S8
Na2CO3
Na4Fe(CN)6
HCl

[Edited on 3-4-2008 by microcosmicus]
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[*] posted on 3-4-2008 at 12:58


Sounds interesting, but how do you get your methyl halide. Thiocyanates are no problem for me, they are easy to obtain and very cheap (e.g. at photography raw chemical suppliers) and are not watched or suspicious in any way. Methyl chloride is another issue. I am not well educated in organics, how could this be made easily?

[Edited on 3-4-08 by woelen]




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[*] posted on 3-4-2008 at 13:47


I would much rather use methyl bromide (BP 3.5C) or methyl iodide (liquid at room temperature) than methyl chloride which is a semi-low BP gas. Unless it is easily soluble in EtOH and could be bubbled through it. Is it?

I should be able to obtain an alkali thiocyanate so that's not a problem. Bromomethane and iodomethane (I would probably go with MeBr because HBr is easier to make with more readily available materials than HI).

On wiki it says that one must use I2 and red phosphorus to make MeI from MeOH. I've noticed this method used on various iodo compounds. Is it just easier that way or is there a reason why HI can't be used?

I still can't believe I have to fear making something like HI though. I almost forgot about that crap. HBr + MeOH it is.




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[*] posted on 3-4-2008 at 13:48


Quote:

Methyl chloride is another issue. I am not well educated in organics, how could this be made easily?


What about the methyl chloride thread cited above? Doesn't that answer the question?

[Edited on 3-4-2008 by microcosmicus]
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[*] posted on 3-4-2008 at 13:52


The easiest way I know to prepare methyl chloride (gas) is to react TCT and methanol, liquifying the MeCL with a dry ice-acetone dewar condenser and storing it in a lecture bottle till needed.

That is of course rather circular if you are going to use the MeSCN to make TCT, but if your main target is the CCl4, and you can obtain TCT, it's the way to go.

Failing that, methyl iodide. Or methyl bromide.

Acros sells MeSCN for about $50/100 ml. So 3 mols is about$100. What price CCl4? It's banned here for "environmental" reasons, while CHCl3 is banned because of supposed drug-cookery. So buying MeSCN is not entirely out of the question economically.

I think making CCl4 from trichloroacetic acid is cheaper, that acid is cheap, also rather easy to make. Dichloroacetic acid also works, and can be made by chlorination of acetic acid or by starting with trichloroacetaldehyde (chloral), itself easily made by chlorinating anhydrous ethanol. The prep. of dichloroacetic acid from chloral is in Org.Syn.

I have not yet crunched the numbers but, I think these are the cheapest routes to CCl4, particularly if you are willing to start with GAA - another photographic chemical, I used to run a custom B&W darkroom -- and as I mentioned there are no smelly toxic sulfur compounds involved. Only corrosive chloroacetic acids and a little benzoyl chloride.

MJP, put not your faith in Wiki. There are other ways to make MeI than MeOH and red P and I2. Return to the light, read Org.Syn. instead. It has that procedure, but it also has one IIRC using KI and dimethyl sulfate. USE A HOOD! but the same is true for all the methyl halides. Brain tumors are nature's way of telling you to lie down and die.

[Edited on 4-4-2008 by Sauron]




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[*] posted on 3-4-2008 at 18:02


Might be interesting reading:

http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=117288...

The reaction of CNBr + methionine gives methyl thiocyanate, so the question then becomes, is this restricted to CNX?

Like for instance what would happen if TCCA was used to decarboxylate cysteine to the correspondent nitrile? You'd thereotically end up with an S and a CN attached to one carbon (same as you'd get from the dehydration of taurine - although with taurine you'd have a sulfonic acid group free at the end to bind to the CN of another degraded taurine unit). The question is, would this bond, and where would it cleave (C-S or C-N)? Someone should have a good reason why this wouldn't work...




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[*] posted on 3-4-2008 at 18:17


Quote:
Only corrosive chloroacetic acids and a little benzoyl chloride.


?? My understanding is that its at least stoichiometric. Using an expensive reactive precursor to make an inexpensive un-reactive non-precursor - albeit hard to purchase at times, although an interesting reaction is uninteresting economically. CCl4 was discovered by chlorinating CHCl3, so that reaction although old-hat and boring is at least on economically. Of course the more chlorinated the carbon, the harder it is to chlorinate further - but I dont think the yields for this process have been published anywhere.

[Edited on 4-4-2008 by len1]
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[*] posted on 3-4-2008 at 19:47


Where I am, I cannot buy CHCl3. And I cannot buy CCl4. But I need both. Who says CCl4 is unreactive? It is plenty reactive when properly motivated. Same with CHCl3.

Sure, I can get DCM, and maybe chlorinate that with some UV kicker to obtain the others. I believe this is done industrially all the way from methane and in the vapor phase all the way.

It is however, brute force and devoid of elegance.

Look at the three reactions I am contemplating:

CS2 -> CSCl4 + SCl2 Separate these, reflux w/Fe, and you have CCl4. The SCl2 is by product.

MeSCN -> TCT, separate (filter) Chlorinate the liquid mixture -> CCl4. Or fractionate it and you have CSCl2, and CSCl4

You can set the thiophosgene aside and purify it, and you can turn the trichloromethyl sulfenyl chloride into more thiophosgene if you want, or you can chlorinate it to CCl4. An embarassment of choices.

Acetic acid - > ClCH2COOH ->Cl2CHCOOH - > Cl3CCOOH (all one operation) then use Brown's method (PhCOCl) and you get roughly equal amounts of CCl4 and Cl3CCOCl.

Or chlorinate EtOH to Cl3CCHO and convert that to Cl2CHCOOH and enter the previous series in midpoint. Hint: chlorinating GAA requires UV, chlorinating ethanol does not.)

All of these get the job done. All pay bonuses in terms of side products. All are interesting. (Some would say, too interesting, if you are not eqipped to contain the "perchloromethyl mercaptan" and the thiophosgene.)

Looks good to me. I wouldn't mind chlorinating DCM, photolytically. But it has all the sex appeal of watching wet paint dry on a damp day.

LSD25's suggestion of cyanogen bromide and methionine on the other hand is definitely too interesting, particularly on a macro scale.



[Edited on 4-4-2008 by Sauron]




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[*] posted on 3-4-2008 at 20:18


Thiophosgene is about as toxic as phosgene - though has much lower vapour pressure, and with the lack of warning and latent phase, I dont think we should touch it at an amateur setting - unless looking for a painful way to commit suicide. The method is elegant I grant that.

PhCOCl method is relatively safe but is expensive unless you want to make the PhCOCl as its schedule II.

CS2 is method is cheap but you have the thiophosgene problem there again I believe.
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[*] posted on 3-4-2008 at 20:59


Very interesting, I didn't know that there is a method to make TCT that doesn't involve handling pure HCN or uses cyanuric acid and chlorinating agents.

DMS is indeed somewhat available to us, thanks to PainKilla's synthesis, and thiocyanates can be made from ferrocyanide.

I wonder why you still get both thiophosgene and perchloromethyl mercaptan from the MeSCN chlorination. If one would exhaustively chlorinate MeSCN, shouldn't the thiophosgene all be converted to to CCl3SCl, seeing that the CCl3SCl probably arises from chlorination of the thiophosgene in the reaction mix?
And isn't CCl3SCl eventually completely converted to CCl4 upon chlorination in the presence of anhydrous FeCl3, which is the way industry chlorinates CS2 when CCl4 is the sole desired product?

It seems like if CCl4 is the desired product besides TCT, one should chlorinate pure MeSCN first, separate the TCT by crystallization and then add FeCl3 or iron filings and continue chlorination until you have a mix of CCl4 and SCl2.
This way thiophosgene and the mercaptan are avoided as products.

len1, thiophosgene has very strong warning properties, making it a whole lot less dangerous than phosgene.
It's just like ketene, this one is immediately irritating as well.

[Edited on 4-4-2008 by garage chemist]




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[*] posted on 3-4-2008 at 21:14


Ketene, being a carcinogen, is a lot scarier.

If you exhaustively chlorinate MeSCN, you isolate no CSCl2 and no CSCl4 either. Fe or FeCl2 is not necessary to convert the latter to CCl4.

I suppose that the exhaustive chlorination can be carried out without removing the TCT, but, it would not be a big problem to use a transfer line to move the liquid mixture to another flask leaving TCT behind, without ever exposing the liquid to the lab environment. This in fact has to be repeated till no more TCT crystals are deposited.




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[*] posted on 3-4-2008 at 22:39


Quote:
Originally posted by microcosmicus
What about the methyl chloride thread cited above? Doesn't that answer the question?
Sorry about not being sufficiently clear. I read the thread, but the methods presented do not seem like easy methods. The method with CH3OH and HCl seems the easiest one, but there is the effect of back-reaction and I have bad experience with that kind of reactions (crappy yield, messy, hard to isolate). Probably my bad experience tells more about me and my organic chemistry skills, than about the reaction though :P

Would it be better to add CH3OH to concentrated sulphuric acid and adding some NaCl? Then there is dry HCl. Or does this result in formation of (extremely toxic) methyl sulfate?




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[*] posted on 4-4-2008 at 00:01


Quote:
Thiophosgene is NOT produced in the chlorination of CS2.


Quote:
CSCl2 is prepared in a two-step process from carbon disulfide. In the first step, carbon disulfide is chlorinated to give trichloromethanesulfenyl chloride, CCl3SCl:

CS2 + 3 Cl2 → CCl3SCl + S2Cl2
Reduction of trichloromethanesulfenyl chloride produces thiophosgene:

CCl3SCl + M → CSCl2 + MCl2
Typically, tin is used for the reducing agent M.


There is likely to be suffiecient reduction if this process is carried out in metal or with impurites such as are always present.

Yes CSCl2 smells as do most C-S compounds I did not mean to extend that aspect to it, but the effects are delayed as per COCl2, in that sense its just as insiduous. The warning is at much lower concentration, but what good is that if one decent whiff is enough to put you away?

These chlorinations are equilibrium reactions and never complete - there are always products at different stages of chlorination present - so I do not believe that just because no Cl2 is being absorbed theres no more thiophosgene.

[Edited on 4-4-2008 by len1]
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[*] posted on 4-4-2008 at 03:17


Sauron - HCN was a dismal failure in WWI - the French filled great quantities of gas shell with it and started its use at the Somme in 1916, however it produced few casualties and the French wasted 4000 tons - it has far too high volatility.

So can we use this to recommend 'one of the most virulent poisons known' to the amateur?

On the other side of the scale diphenylcyanarsine was the most toxic chemical of WWI - yet it was ineffective - the particle size wasnt right.

I take your point about Cl2 - but Cl2 is used by housewides to disinfect floors - it was used in WWI as a demonstration of principle - because it was on hand, what followed were much more potent gases and the fact that CSCl2 was one of them should make one think.

I know you are just theorising about these things, but there are people out there who take these ideas on board and actually do this as practical stuff. That is why I post these 'additions' to posts. Further on that CCl4 is carcinogenic

[Edited on 4-4-2008 by len1]
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[*] posted on 4-4-2008 at 03:58


Reaction of dichloro- and trichloroacetic acid with benzoyl chloride, giving chloroform and carbon tetrachloride you say? I bet it goes like this:

Cl3CCOOH + PhCOCl --> Cl3CCOCl + PhCOOH
Cl3CCOCl --> CCl4 + CO

Don't take chances with the carbon monoxide.
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[*] posted on 4-4-2008 at 04:16


That's interesting Sauron. Is HCl the second? I work and breath it almost everyday. How so? Can you give me the list or something og chemicals with most fatalities?
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[*] posted on 4-4-2008 at 06:25


I didn't bring up the subject of carbon monoxide because of lack of trust in your equipment or your confidence Sauron. I think it is important to actually mention possible toxic byproducts of a reaction so that one can be prepared. I checked the article by Herbert C. Brown, J. Am. Chem. Soc. 60(6) 1325-1328 (1938), where my suspicion is verified.

[Edited on 4/4/2008 by trilobite]
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[*] posted on 4-4-2008 at 13:23


Sauron,

The predominent reason cited that CW weapons were not used more extensively and/or operationally, in the PTO was due to volatility and the susceptibility of existing protective equipment to compromise through humidity/sweat transfer. The increased lethality of such agents (predominantly Mustard & Lewisite) also came as a shock to the volunteer's who participated in the trials (predominantly UK, US & Aust, conducted in Nth Queensland) as did the inneffectiveness of the protective equipment supplied for that purpose.

The overview of a book, 'Keen as Mustard' appears second in this link:

http://www.awm.gov.au/journal/j32/bookreviews.htm

Here is another look at the events:

http://www.opcw.org/synthesis/html/s7/p20.html

These show that playing with chemical weapons and the agents used therein, in tropical climates (which I'd imagine would include Thailand?) can have extremely different results and outcomes than would be expected in cooler climates.

PS Nitrates caused more deaths than any other chemical (although the actual cause of death probably could have been more directly attributable to Fe or Pb) during WWI. Germany did not use chemical weapons again in WWII as the prevailing winds were counterproductive (as they found in WWI). The only true chemical weapon used in quantity in WWII was WP (actually misnamed - called WP because the smoke is white, the actual phosphorus used in shells is RP, WP is far too difficult to store safely). Of side interest, the Geneva conventions prohibits the use of proximity (time) fuses on WP rounds, this despite the fact that the fuckers fit on the pointy end of the shell!!!:D This is because the shells are made to the standard pattern design and use the same case as the HE shells, on which the proximity fuse is designed to fit (interchangeable with the standard instant (HE-Q)/delay (HE-D) fuses normally found on shells straight out of the box).

As an addition (post-edit) is it possible to get this article:

http://www3.interscience.wiley.com/cgi-bin/summary/117873144...

It deals with, inter alia, thiocyanuric acid - as a derivative of cyanuric acid - I'd be interested to see how this occurs.

[Edited on 4-4-2008 by LSD25]




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[*] posted on 4-4-2008 at 16:45


My thread is not about benzyl chloride preparation but benzaldehyde and benzoic acid - benzyl chloride got made due to the irresponsible way in which some preparative manuals are written - as Ive outlined there. In fact I warn people about this compound and provide a procedure by which it is never isolated. I even have a section on health effects there - and Im proud of it - I think every practical prep dealing with dangerous substances should have one.

Having said that, I dont know why you like to pick problems. It was never my intention that you or others shouldnt follow your proposals (if you actually decide to do it). I think they are very interesting reactions, and you are one of the few who contribute to this forum constructively - I wish you continue that. My first two posts were just pointing the dangers - adding to rather than subtracting from what you had to say. After reading that, everyone is warned, and welcome to continue - same as on my BzCHO post. I myself would never isolate CSCl2, HCN, COCl2, exploding carcinogens, but thats just my preference. I have sufficient respect for others, and I wish my comments be taken in that light.

[Edited on 5-4-2008 by len1]
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len1
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[*] posted on 4-4-2008 at 18:49


If you dont want people responding to your pageful of unprovoked accusations at them then I suggest you mark your posts as such, I also suggest you dont use expletives when reasoning runs out. As a defence of that other guy, its you who introduced CWC to the thread, and wrote more about it than all other combined. Have a good day

[Edited on 5-4-2008 by len1]
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