Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: sjal on February 22, 2018, 06:17:42 PM
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Hi everyone
To a conical flask containing (0.01 mole) of dibenzylidenecyloalkanones 1a or 1b and (0.02 mole) of chloroacetylchloride, dissolved in 60 ml of carbon disulphide, and then anhydrous aluminum chloride (0.04 mole) was added in small portions. The reaction mixture was stirred in an ice bath for 6 h, the carbon disulphide was evaporated and the residue was poured into cold hydrochloric acid; the yellow precipitate was collected by filtration, washed with excess water, then dried, and recrystallized from appropriate solvent.
1- how I can evaporated carbon disulphide?
2- how I can pour the residue into cold hydrochloric acid?
THANK YOU :)
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Greetings, sjal:, I'd like to welcome you and everyone new to the Chemical Forums, but I want to ask you to review our Forum Rules{click} (http://www.chemicalforums.com/index.php?topic=65859.0). You already accepted the rules when you signed up for our forum, and you have to follow them, whether you agree with them or not, or even if you're unaware of them.
We're here to help you learn, and develop new skills. But this isn't a cookbook chemistry site. We don't do things just because they're cool.
Let's all work together with what you have, and look for what you need.
Hi everyone
To a conical flask containing (0.01 mole) of dibenzylidenecyloalkanones
I don't recognize this name, that's OK, different words are used in different countries. If you used the IUPAC name, everyone would understand it. Its an idea you could consider.
1a or 1b
So that somehow changes the definition of the past word? How can we know what you mean? Can you say it a different way? If you can't, then why can't you? Did you just copy this without understanding it? Are you ready for previous and future steps, to keep yourself from getting hurt? I have to wonder, I'm not sure.
and (0.02 mole) of chloroacetylchloride, dissolved in 60 ml of carbon disulphide, and then anhydrous aluminum chloride (0.04 mole) was added in small portions. The reaction mixture was stirred in an ice bath for 6 h, the carbon disulphide was evaporated and the residue was poured into cold hydrochloric acid; the yellow precipitate was collected by filtration, washed with excess water, then dried, and recrystallized from appropriate solvent.
1- how I can evaporated carbon disulphide?
What do you know about carbon disulfide's properties? There are a number of options, but they should include a good fume hood.
2- how I can pour the residue into cold hydrochloric acid?
What, exactly, would stop you? Can you take a guess, how you would set this up, and how you would do it, and let us tell you if its a good one? That's not a bad way to learn.
THANK YOU :)
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I've always felt like the boiling point of carbon disulfide was an anomaly. Its totally unexpected to me.
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[size=0px]Did you just copy this without understanding it? Are you ready for previous and future steps, to keep yourself from getting hurt? I have to wonder, I'm not sure.[/size][/size][/color]
i understand i will do the exprmental with diferant matrial... My Qustions was 1 and 2 which is again how i can evaporate the CS2.. and how i know its all evaporated?? and 2- how i pour the residue into cold HCl?
I know carbon disulfide evaporate at RT but i never evaporate it at lab so should i leave the conical in fume hood?? and for how long? how i know it evaporated all??
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2- how I can pour the residue into cold hydrochloric acid?
What, exactly, would stop you? Can you take a guess, how you would set this up, and how you would do it, and let us tell you if its a good one? That's not a bad way to learn.
i never did pouring in the lab so that why am asking here??
should i just pout the residue in flask with HCl and what the mount of HCl.
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sjal:, I've locked this thread, for now. It soesn't seem, to me, that you have the very basics of the organic chemistry laboratory skills you need to work safely. I'll defer to our organic chemistry experts, when they have a chance to review your raw materials and your process. In the meantime, you can do some more reading, confer with your instructors or other experts in your lab, or work on a different explanation of your process.
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sjal,
We discussed it among the experienced members of the forum and have decided you are not doing anything illicit, so we will try to help you.
The very first thing I would do is not use carbon disulfide. It is volatile, toxic, and has a low flashpoint. Dichloromethane is the typical solvent for this reaction (Freidel-Crafts acylation). It, and all your other reagents, should be thoroughly dried of water or else the reaction will likely fail or yield poorly. It should also be done under N2.
For adding HCl, I would do a liquid/liquid extraction of the reaction with something like 1M aqueous HCl solution. You can easily find examples of this technique on youtube. The dichloromethane can then be distilled off in a rotovap or a short-path distillation apparatus with vacuum or very mild heat.
Would you care to share with us your ultimate goal for this acylated dibenzylidene compound? The more info we have, the more we can help. Also if we know you're in an academic or industrial lab we can have a better concept of the resources and guidance available to you.
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Please, be aware that:
1). Alkylidene cylolakanones have a ketone group that is conjugated with a double bond, which is an electron attracting group and therefore, an aromatic deactivator that means: meta- Friedel-Craft acylation, long reaction times and moderate yields.
2). Additionally, you have a molecularly symmetrical bis-alkylidene cylolakanone, which means that you will probably get a mixture of monoacylated and bis-acylated alkylidene cylolakanone that might be difficult to separate.
3). Furthermore, AlCl3 may also catalyse an ortho- electrophilic attack of the benzene ring to the conjugated double bond and finally lead to expansion of the benzene ring, via intermolecular isomerization.
4). Thus, it is better to describe the final product that you want and so, we can help you to prepare it by a more convenient synthetic route.
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pgk, I think the goal is to diacylate it. 2 equivalents of chloroacetyl chloride are used. I also don't think this molecule is very deactivated, the ketone is several bonds away from the benzene ring even though its conjugated.
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Ok, sjal try the Friedel-Craft bis-acylation in dichloromethane and keep us informed about the obtained results.
Good luck.
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Can i use acetyl chloride instead of chloroacetyl chloride?
I want to Synthesis of diarylidenecycloalkanones monomers..
(0.01 mole) of dibenzylidenecyloalkanones 1a or 1b and (0.02 mole) of chloroacetylchloride, dissolved in 60 ml of carbon disulphide, and then ALCL3 (0.04 mole) was added in small portions then will get yellow precipitate which will be reacted with thiourea...
Can I use acetyl chloride instead of chloroacetylchloride?
I Attach pic of the reaction...
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You can but then you won't have a reactive handle for the thio urea.
Also it would be nice if you responded on your previous topic to some of our suggestions
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You can but then you won't have a reactive handle for the thio urea.
Also it would be nice if you responded on your previous topic to some of our suggestions
thank you...
is there any suggestions because i don't have the chloroacetyl chloride...
for the other topic i thought its locked ... i just see that it unlocked
thank you
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sjal,
We discussed it among the experienced members of the forum and have decided you are not doing anything illicit, so we will try to help you.
The very first thing I would do is not use carbon disulfide. It is volatile, toxic, and has a low flashpoint. Dichloromethane is the typical solvent for this reaction (Freidel-Crafts acylation). It, and all your other reagents, should be thoroughly dried of water or else the reaction will likely fail or yield poorly. It should also be done under N2.
For adding HCl, I would do a liquid/liquid extraction of the reaction with something like 1M aqueous HCl solution. You can easily find examples of this technique on youtube. The dichloromethane can then be distilled off in a rotovap or a short-path distillation apparatus with vacuum or very mild heat.
Would you care to share with us your ultimate goal for this acylated dibenzylidene compound? The more info we have, the more we can help. Also if we know you're in an academic or industrial lab we can have a better concept of the resources and guidance available to you.
I did it using DCM under N2 but never workd
Thank you for your suggestions
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Ok, sjal try the Friedel-Craft bis-acylation in dichloromethane and keep us informed about the obtained results.
Good luck.
did not work i got the starting again...
Thank you for your replay :)
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Could you chlorinate chloroacetic acid? It won't be fun, but you really do need a haloacetyl halide reagent. Halogenating at the acetyl spot on your diarylidenecycloalkanones seems like it would be difficult to do cleanly.
Perhaps make it by using chloroacetic acid and excess PCl5, then distill the product off.
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I would suggest trying a higher boiling solvent and doing it at a warmer temperature if there was not much conversion.
Before you do this though, do you feel that all the compounds and solvents you worked with were rigorously dried? Water will ruin this reaction. That means for every 1 g of chloroacetyl chloride, only 0.16 g of water will cause 0 conversion. Water is 0.16 g/100 mL soluble in DCM for instance, so if you had wet DCM, it would ruin the reaction. Wet air will quickly snuff it out as well.
Rigorous denial of water from a reaction is a really critical (and sometimes tough!) skill in organic chemistry.
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Hi there, sjal: I've merged your two threads, so all the work you've done is together, and you get the best answers. Sorry to everyone if this makes responses a little bit confusing, but having everything together will make future discussion better.
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Could you chlorinate chloroacetic acid? It won't be fun, but you really do need a haloacetyl halide reagent. Halogenating at the acetyl spot on your diarylidenecycloalkanones seems like it would be difficult to do cleanly.
Perhaps make it by using chloroacetic acid and excess PCl5, then distill the product off.
Thank you ... i will try it
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Please bear in mind that both chloroacetic acid and chloroacetyl chloride are pretty toxic. The chloroacetyl chloride is also a potent lachrymator (i.e. it irritates your eyes). You need to do a thorough safety assessment before you carry out these reactions, ensuring that you wear appropriate PPE, and ideally carry out all the work in a fume cupboard.
Any wildfyr's point about keeping everything dry is critical. When we say 'dry' we don't just mean that there arent visible drops of water, even a few tens of ppm of water in your solvent can be enough to ruin a reaction. If you don't have access to anhydrous solvents you can use activated molecular sieves to do it in an extremely safe and effective way:
https://pubs.acs.org/doi/full/10.1021/jo101589h?src=recsys
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Could you chlorinate chloroacetic acid? It won't be fun, but you really do need a haloacetyl halide reagent. Halogenating at the acetyl spot on your diarylidenecycloalkanones seems like it would be difficult to do cleanly.
Perhaps make it by using chloroacetic acid and excess PCl5, then distill the product off.
This would be my thought too. I know a person in my lab attempted it with thionyl chloride (before he realised we have buckets of the stuff) with little success, but PCl5 seems like a good alternative.
Otherwise, if you don’t have to worry about issues of sea freight to get it, I don’t think the acid chloride is overly expensive. I would buy it in if you can do so easily.
As mentioned, be mindful of your conditions. In my experience, adding the acid chloride to a chilled reaction can be very important as well as making sure it’s dry. Keeping it under inert atmosphere is crucial, and I would recommend a balloon with a wide gage needle for this part. I don’t know how your hood is set up, but I know I would be upset if HCl got into my manifold.
Also good to make sure you are careful with cleaning equipment and wearing / changing gloves. The stuff is deadly toxic, and you do not want to inhale it. I normally quench small amounts (ie. the amounts left over in used glassware, syringes, etc.) of the acid chloride with cold water and rinse with acetone into a waste container inside the hood.
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This would be my thought too. I know a person in my lab attempted it with thionyl chloride (before he realised we have buckets of the stuff) with little success, but PCl5 seems like a good alternative.
Under most circumstances I would go right for thionyl chloride because typically I'm making either A. a sulfonyl chloride which can handle aqueous workup for the most part or B. nonvolatile acid chloride, from which SOCl2 can be simple distilled off. In this case, though, chloroacetyl chloride only boils 20°C higher than SOCl2, and fractional distillation is hard so it makes sense to use a nonvolatile chlorinating agent and isolate with a quick simple distillation. Your lab buddy probably was making plenty of product, just couldnt separate it out.
Anyways, I would bet that water is the heart of OP's problem. It could be in the DCM or the AlCl3, or his acid chloride has mostly hydrolyzed before even getting into the reaction. Its hard to tell how far gone neat acid chloride bottles are because they all reek of HCl anyways, and the 13C looks almost identical.
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This would be my thought too. I know a person in my lab attempted it with thionyl chloride (before he realised we have buckets of the stuff) with little success, but PCl5 seems like a good alternative.
Under most circumstances I would go right for thionyl chloride because typically I'm making either A. a sulfonyl chloride which can handle aqueous workup for the most part or B. nonvolatile acid chloride, from which SOCl2 can be simple distilled off. In this case, though, chloroacetyl chloride only boils 20°C higher than SOCl2, and fractional distillation is hard so it makes sense to use a nonvolatile chlorinating agent and isolate with a quick simple distillation. Your lab buddy probably was making plenty of product, just couldnt separate it out.
Anyways, I would bet that water is the heart of OP's problem. It could be in the DCM or the AlCl3, or his acid chloride has mostly hydrolyzed before even getting into the reaction. Its hard to tell how far gone neat acid chloride bottles are because they all reek of HCl anyways, and the 13C looks almost identical.
Almost certainly the case, yes. I didn’t ask any more into his issues. I only saw his risk assessment and asked why he was making it when we have a litre in the corrosives cabinet (not his fault - someone removed it from the inventory).
I typically distill chloroacetyl chloride before using it. It is an annoying thing to distil, but just doing that I found boosted my yields by a good 20%. Maybe something to consider in addition to all of the suggestions around removing water.