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[*] posted on 27-2-2016 at 19:38
Green Synthesis of 3-methyl-heptan-3-ol from common materials


Hi guys! I did it! There has been a lot of interest in making tertiary alcohols, and after spending the day in my lab and doing some intense research, I picked up on a few tricks. Therefore, I am posting the first draft of my paper with the intent to make revisions and get it published here in the SM publication library! The yield is awful, but the purpose of this experiment is not to mass produce loads of tertiary alcohol, but rather to show that there are techniques for the home scientist to make tertiary alcohols via Grignard without having any ridiculously dry solvents or ether. PLEASE let me know what you think and if there are any ways I can make it better.

As far as the characterization of this compound, I do not think that it would be feasible to run an NMR on this compound. The best analytical instrument that I have everyday access to is a Waters LCMS, but this molecule is not heavy enough to get a good looking peak. If you have any other ideas, let me know and I may try them out sometime!

Attachment: Green synthesis of 3-methyl-heptan-3-ol.pdf (847kB)
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[*] posted on 27-2-2016 at 20:08


I am no expert on this so someone else will have to critique the technical aspects of your report. However...

1. This looks like a fantastic accomplishment. Well done. I hope you are really pleased.
2. Great to see original work being done and posted in prepub.
3. Positive identification of the compound is obviously critical. Are you able to do a melting point test? It will at least get you somewhere towards identification.




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[*] posted on 27-2-2016 at 20:19


Quote: Originally posted by j_sum1  
I am no expert on this so someone else will have to critique the technical aspects of your report. However...

1. This looks like a fantastic accomplishment. Well done. I hope you are really pleased.
2. Great to see original work being done and posted in prepub.
3. Positive identification of the compound is obviously critical. Are you able to do a melting point test? It will at least get you somewhere towards identification.


1) I am very pleased :)
2) Thanks, this technique is not widely known and I feel like it should be, because it is really practical especially for the home chemist.
3) CRC claims the m.p. is -83 or so. That means not even a dry ice/acetone bath will work. I would have to use liquid nitrogen, and unfortunately that might just freeze it regardless.




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[*] posted on 27-2-2016 at 21:27


I have only skimmed through it so far but you must actually post results and discussion after your experimental. Also, writing an equipment less procedure stream lines reading and presentation (also editing). The reason for this is that any competent chemist should be able to follow a basic procedure. You have done this in section 3.1 in this style (the right way imo, always write to your instructors specifications) then changed later. also, keep your significant figures consistent and make sure to add the molar quantities after the gram amounts. You could even say (as example) "Magnesium powder (x grams , y mmol) was added to 1- bromobutane (z, grams , u mmol)". so you don't need to say they were measured or anything. Good job, just needs to some adjusting to keep a consistent style throughout.

also, how would placing magnesium under vacuum dry it? surely you would need to heat it to dry it properly.

nice work and good effort!! :)

[Edited on 28-2-2016 by HeYBrO]
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[*] posted on 27-2-2016 at 22:17


Concentration of sulfuric acid in the synthesis in section 3.1? I would have assumed concentrated just because that is what most people have laying around but then during your wash of your organic layer you specify 80% concentration.

I like your procedure, sure the yields are the best but as you point out it is more accessible than a standard Grignard and that is the spirit of this forum. Glad to see this all documented. Excellent work, so much seems to be discussed in other threads with so few people actually experimenting.




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[*] posted on 28-3-2016 at 17:04
Final Draft?


HeYBrO and BromicAcid,

I took your advice and made the following changes.

  1. I specified 'concentrated' acid in experimental section x.1
  2. I switched the sections so that results and discussion comes after experimental
  3. I removed many lab equipment refs from the experiment
  4. I verified my sigfigs
  5. I posted grams and mmol in parentheses


You also asked about drying the magnesium, I just left it under vacuum for a couple hours... that's what we do in the lab I work in for most wet reagents. Yes, water doesn't come off in the vacuum as easily as DCM or acetone, but it is sufficient for this procedure. Remember that the sonication allows us to have small quantities of water without ruining our Grignard.

Who would I talk to about maybe getting this in the member pub's? This certainly won't be my last tertiary alcohol, and I really would like to collaborate with someone who can replicate these procedures and test with sodium and potassium reduction.

Attachment: Green synthesis of tert alcohol 2.pdf (849kB)
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[*] posted on 29-3-2016 at 05:29


you might be able to increase the yield if you used 2-methyl THF instead of THF
http://pubs.acs.org/doi/abs/10.1021/op060155c (73% yield)

[Edited on 29-3-2016 by CuReUS]
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[*] posted on 29-3-2016 at 06:11


@ScienceHideout:

Nice synthesis but why do you call it 'green'?




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[*] posted on 29-3-2016 at 08:35


CuReUs,

Thanks for the suggestion. At this time I don't have any methyl THF, but perhaps I could try that in the future.

Blogfast,

According to the American Chemical Society green synthesis utilizes careful approaches to limit exposure, hazardous byproducts, waste, and extreme conditions. I feel that I have made a careful effort to reduce these with my in situ bromination, lack of molecular sieves with THF, and regular air grignard formation.




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[*] posted on 29-3-2016 at 09:06


I think it is a good idea to synthesize as simply as possible, while still getting a decent yield. If the yield is poor then what is the point?

Your synthesis of n-butyl bromide looks standard to me. It is the same one that I use, which I took from Pavia, published in 1997. I performed this recently obtaining a 55% yield. So, I think your 31% yield here can be much improved.

I don't use an inert atmosphere with my Grignards but do use absolute ether. A smidgen of I2 gets it started OK. But If you can get a decent yield (>50%) with undried THF then this would be good. Right now your yield at 10% is poor. We'll have to see if this can be improved. Chemplayer... has a good YouTube out showing some good results in this effort.

You need to show some proof that you made the target compound. You could do this with a bp if you can get enough yield to do this.

If you want to publish this in Prepub I think the burden is on you to prove your claims instead of asking others to do this.

Please do not take these comments as anything other than constructive criticism. ;)




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[*] posted on 29-3-2016 at 15:41


Magpie, thanks for your input!

I am going to try again this weekend with both parts... I think that for part 1 my problem was that I added to much sulfuric acid and I made an ether. This time I will try it with just a slight excess.

I am also going to do the grignard again, four times. Once with Et2O off the shelf, once with Et2O over MgSO4, one with off the shelf THF, and one with THF over MgSO4. If the yields of all four are similar, that would verify my hypothesis by showing that normal, not super dry THF is a cost effective, efficient, safe and overall GREEN :D way to go.

As far as characterization, I can certainly purify and work on a BP, and I can prove it is a tert alcohol with an SN1 reaction... I was thinking though, perhaps I could react it with something that could put the mass over 200 so I can run an LCMS to characterize?




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[*] posted on 29-3-2016 at 16:28


Sorry I'm late to the party. I did actually see the original draft but was short on time and forgot to come back and comment.

Quote: Originally posted by HeYBrO  
I have only skimmed through it so far but you must actually post results and discussion after your experimental.


This is wrong. Results and discussion should always come first, and experimental details are usually tacked onto the end of the manuscript. Look at the articles in any reputable scientific journal and you'll see. Some journals don't even have an experimental section (eg. Tetrahedron Letters). Here's the general structure that I'd recommend:

Abstract/summary:
This should be a high level summary at the very start of the manuscript (after the title) detailing the key acheivements that will be detailed in the publication. You actually did a pretty good job of this! The bit I do have an issue with is this:
Quote:

The reaction produced few hazardous by-products, uses safe chemicals, and a very innovative approach to the Grignard reaction using ultrasounds to eliminate the need for argon-flushed glassware and anhydrous solvents.

Considering your overall yield was 10 %, you cannot tout this as "green" approach. It is far from it. More realistically, you can state that it uses relatively OTC chemicals and demonstrates the ultrasound assisted grignard reaction. Also note that the use of ultrasounic irradiation in the formation of grignard reagents is not innovative; there is plenty of existing literature on this and related chemistries, some of it relatively old (ca 1980's IIRC).

Introduction
This is where you set the scene to discuss your work. You should include what you aim to acheive, and others should be interested. Give a brief summary of relevant prior work, and use this to naturally lead onto your own work, commenting where appropriate as to the merits of your approach (eg. use of OTC precursors, specially dried solvents not required). You've done well with this section as well, although you need to add more references (and discuss why eg. t-BuOH is not satisfactory).

Results and discussion
This is where you detail and discuss your findings. Its probably best to to discuss each stage in sequence, stating what was tried and how it performed. You should be comparing and contrasting to existing work (if appropriate), and trying to rationalise your results. Again, you've made a good attempt at this, but it needs to be expanded upon; you're being too brief. One thing that baffles me is this statement:
Quote:

In an anhydrous, air-free Grignard reaction with similar reagents, it is reasonable to expect 67%.

Where did you pull that (arbitrary?) number from?

Experimental
This should be fairly straight forward. Remember to be consistent with significant figures.

Conclusion
This is where you summarise your acheivements, and tally them up against the objectives outlined in the introduction. If you did not acheive an intended aim, propose what could be done to improve chances of success on a subsequent attempt.


Quote: Originally posted by HeYBrO  

also, how would placing magnesium under vacuum dry it? surely you would need to heat it to dry it properly.

Given that the water content of the magnesium shreds will be significantly less than that of the THF, I wouldn't worry about this at all.

Quote: Originally posted by Magpie  
I think it is a good idea to synthesize as simply as possible, while still getting a decent yield. If the yield is poor then what is the point?

This is critical. A reaction cannot be considered "green" if you're losing the majority of your material at each stage.

Quote: Originally posted by Magpie  

Your synthesis of n-butyl bromide looks standard to me. It is the same one that I use, which I took from Pavia, published in 1997. I performed this recently obtaining a 55% yield. So, I think your 31% yield here can be much improved.

Digging through the ancient depths of OrgSyn, you shall find:
http://www.orgsyn.org/Content/pdfs/procedures/CV1P0025.pdf
The preparation of n-Butyl bromide is detailed using the NaBr/H2SO4 method, and a 90 %th yield is reported.

Quote: Originally posted by Magpie  

I don't use an inert atmosphere with my Grignards but do use absolute ether. A smidgen of I2 gets it started OK. But If you can get a decent yield (>50%) with undried THF then this would be good. Right now your yield at 10% is poor. We'll have to see if this can be improved.

Use of diethyl ether as solvent alleviates the need for inert atmosphere, due to the protective blanket of ether vapor. This was discussed recently elsewhere on the forum.

Quote: Originally posted by Magpie  

You need to show some proof that you made the target compound. You could do this with a bp if you can get enough yield to do this.

There are also crystalline derivatives you could prepare, and literature values for their melting points to compare to.

There are a few additional formatting issues to those mentioned above. The text of your publication should be "fully justified"; this will make it flush with both the left and right margins. Also try to get into the habit of using "non-breaking spaces" and "non-breaking hyphens" to ensure you don't get a line break between e.g. a value and its units. Putting them in as you go along is much easier than going through and adding them where needed.

Once again, this is meant to be constructive criticism.

[Edited on 30-3-2016 by DJF90]
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[*] posted on 29-3-2016 at 16:52


DJF90, you outdid yourself! :D

Your criticism was very valuable, and you definitely clarified a lot of things as well as stressed things that I should've caught onto myself.

Once again, I am going to try this again and see if I can't get a higher yield, so when I am writing part III I will most certainly take everything into account.




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[*] posted on 30-3-2016 at 06:52


Quote: Originally posted by ScienceHideout  

DJF90, you outdid yourself! :D
Your criticism was very valuable, and you definitely clarified a lot of things as well as stressed things that I should've caught onto myself.
Once again, I am going to try this again and see if I can't get a higher yield, so when I am writing part III I will most certainly take everything into account.


I'm glad my input was well received. There are a few other bits that I had failed to mention (it was late...):

> In the results and discussion section, I'd say that simple reaction schemes are sufficient, just as you have used in the introduction. Discuss each stage separately, and remember to include the RMM/MW under the starting/principal input material and the product. You do not need to provide mechanisms unless it is something that you believe to be worth discussing.

> You mention that the chemistry is suitable for preparing other tertiary alcohols. Perhaps you could take the time to exemplify this (once you've optimised the conditions at each step for the current substrates) as it would greatly improve your publication, especially if you're intending on doing so in future work anyway. You could vary either or both of the alkyl halide/ketone substrates, depending on how much time and effort you want to invest in this.

> You should perform a control experiment for the Grignard formation in the absence of ultrasonic irradiation. Maybe it would have worked satisfactory... did you test it? We'll come back to this in a bit...

>When describing wash procedures in the experimental, remember to include the volumes and (where appropriate) concentrations of each solution. I personally find the text to be more streamlined and readable with the following format (delete as appropriate):

"...was washed/extracted with [solvent/solution] ([conc.], [reps] x [volume] mL)". Note that the "x" should be a multiplication symbol and not the letter "x" as I have used. An applied example is shown below:

"The crude distillate was washed with water (10 mL) and sulfuric acid (80 %w/w, 0 to 5 *C, 10 mL). The organic phase was separated, dried over anhydrous magnesium sulfate and vacuum filtered. The filtrate was purified by distillation at atmospheric pressure, collecting the fraction boiling at 99 to 103 *C. The product was obtained as a colourless oil (4.67 g, 31 %th)."

> When giving concentrations as percentages, it is helpful to specify whether it is %w/w, %v/v or %w/v. Typically, percentage concentrations or purities are given as %w/w, but there are occasions where %v/v may be more appropriate (eg. chromatographic eluents). Being clear about what you're using saves any ambiguity.

Quote: Originally posted by ScienceHideout  

I think that for part 1 my problem was that I added to much sulfuric acid and I made an ether. This time I will try it with just a slight excess.

I'd really recommend using the OrgSyn procedure I linked to previously. I know you replied to Magpie before my post was made, so maybe this is your intention.

Quote: Originally posted by ScienceHideout  

I am also going to do the grignard again, four times. Once with Et2O off the shelf, once with Et2O over MgSO4, one with off the shelf THF, and one with THF over MgSO4. If the yields of all four are similar, that would verify my hypothesis by showing that normal, not super dry THF is a cost effective, efficient, safe and overall GREEN :D way to go.


Before embarking on this, perhaps it is worth considering the following... If your "off the shelf" solvents are already pretty dry (the bottles next to me specify <0.03% and <0.05% H2O for diethyl ether and THF respectively) then drying over MgSO4 is unlikely to remove any additional water and your "wet" and "dry" runs will be essentially identical. A more suitable approach may be to start with solvent as dry as you can get it, and spike it with a specified quantity of water (eg. 0.1 to 0.5 %w/w?) for the "wet" run. The problem with all of this work is that without access to a Karl Fisher titrator, its speculative and a bit meaningless.

Quote: Originally posted by ScienceHideout  

As far as characterization, I can certainly purify and work on a BP, and I can prove it is a tert alcohol with an SN1 reaction... I was thinking though, perhaps I could react it with something that could put the mass over 200 so I can run an LCMS to characterize?


Perhaps some qualitative analysis would be a nice addition to the characterisation. A test for 3* alcohol with Lucas' reagent should be easily performed. Formation of a crystalline derivative for melting point determination ought to be possible, but the required reagents may or may not be accessible.

[Edited on 30-3-2016 by DJF90]
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[*] posted on 30-3-2016 at 18:32


Hi guys,

DJ, just want to thank you again for all of the criticism, it is appreciated and I will take it all into account while writing my next version. Today I tried the orgo syn procedure on making the butyl bromide. I got a 57% yield at 1/10 scale... not the 90 that was reported. I am wondering if I am making too much dibutyl ether?

I will try one more time to make BuBr with awesome yield. This time, I will mix COLD sulfuric acid with the bromide salt, stoiciometric amounts in respect to each other, and let warm to room temperature before dripping in the limiting reagent BuOH and refluxing.




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[*] posted on 30-3-2016 at 20:50


Quote: Originally posted by DJF90  


Quote: Originally posted by HeYBrO  
I have only skimmed through it so far but you must actually post results and discussion after your experimental.


This is wrong. Results and discussion should always come first, and experimental details are usually tacked onto the end of the manuscript. Look at the articles in any reputable scientific journal and you'll see. Some journals don't even have an experimental section (eg. Tetrahedron Letters).



[Edited on 30-3-2016 by DJF90]



Indeed you are correct that tetrahedron letters presents their papers in such a format, but they also have papers without any formal structures that you mentioned, can you explain why this the case.

Generally universities teach the layout i suggested for lab reports and seeing how sciencemadnesss pre-pub papers normally follow this form i thought i might suggest this correction. Either layout works anyway; the information is still transferred across to the experimenter.
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[*] posted on 31-3-2016 at 03:59


Instead of using BuBr,why don't you try making BuCl, it can be easily made by the TCT/DMF method,and since you are using ultrasound to start the reaction,the slow reaction rate of RMgCl can be compensated
http://pubs.acs.org/doi/abs/10.1021/ol017168p

http://chemistry.mdma.ch/hiveboard/novel/000372508.html

BuBr can be obtained by adding NaBr to the TCT/DMF mixture
https://books.google.co.in/books?id=7oeQwEA_uVUC&pg=PA365&lp...
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[*] posted on 31-3-2016 at 05:09


Quote: Originally posted by ScienceHideout  

Today I tried the orgo syn procedure on making the butyl bromide. I got a 57% yield at 1/10 scale... not the 90 that was reported. I am wondering if I am making too much dibutyl ether?

You got a fairly decent yield for a first run through - Magpie stated upthread that he gets 55 %th using the method in Pavia (@Magpie - Any chance of providing a copy of the relevant pages?). There may be a couple of things that could get your yield up. I wonder if refluxing for 2 hrs is sufficient enough, considering the method using hydrobromic acid/sulfuric acid says:
Quote:

The flask is then attached to a reflux condenser and the mixture is refluxed during a period of five to six hours, during which time the formation of butyl bromide is carried practically to completion.

I'm not sure this is the right explanation though, as the procedure is checked independently (that's why OrgSyn preps are so great! You know they should work as described). It may be that the distillation is not driven to completion (how much does your crude distillate weigh?) although you say subsequent distillate is water miscible (almost certainly n-butanol-water azeotrope -which suggests the conversion is not complete and longer refluxing is required). I also cannot find any reference for the azeotrope of n-butyl bromide with water, except in a microscale organic chemistry textbook, which gives no data. I would not expect it to form an azeotrope, but that's just my gut feeling. If it does, then I would certainly be surprised if it wasn't heterogeneous, and you don't mention a biphasic distillate. Di-n-butyl ether boils too high for it to be a significant concern, and any that does pass over will be dealt with by the sulfuric acid wash (also note that the purpose of this wash dhould be discussed in the "results and discussion" section, not the experimental). I don't think a great amount will be formed in the first place, considering it results from butanol (which is likely protonated) acting as a nucleophile competitively with the bromide ions (which are present in excess). Another possible explanation for the moderate yield could be the use of excessive drying agent. OrgSyn has this to say on the matter:
Quote:

5. In many organic preparations too large a quantity of drying agent is usually employed, with the resulting loss of a considerable amount of material due to absorption by the drying agent. In the present experiments it is found that after a careful separation of the alkyl halide from the water layer as small a quantity as 15 g. of calcium chloride is sufficient for the drying of 1500 g. of alkyl halide.

Seeing how you're drying a neat liquid rather than an organic extract, the use of excessive drying agent should certainly be avoided as mechanical entrainment will destroy your yields (as you may well be experiencing).

Quote: Originally posted by ScienceHideout  

I will try one more time to make BuBr with awesome yield. This time, I will mix COLD sulfuric acid with the bromide salt, stoiciometric amounts in respect to each other, and let warm to room temperature before dripping in the limiting reagent BuOH and refluxing.

I'd follow the OrgSyn prep again using the pointers I've given above. I've not made n-butyl bromide before, although I've done similar preparations for ethyl bromide and isopropyl bromide, and both performed well.

Quote: Originally posted by HeYBrO  

Indeed you are correct that tetrahedron letters presents their papers in such a format, but they also have papers without any formal structures that you mentioned, can you explain why this the case.
Generally universities teach the layout i suggested for lab reports and seeing how sciencemadnesss pre-pub papers normally follow this form i thought i might suggest this correction. Either layout works anyway; the information is still transferred across to the experimenter.

I used Tet. Lett. as an example because it was the first one that came to mind that illustrated my point. The structure that I outlined was my personal preference based upon what I've seen in journals, and also seen/used for theses and project reports etc. Whilst articles may not explicitly have the headings that I mentioned, the text generally does follow that structure. A post-lab report is slightly different and many use that format when writing up experiments in the other sub-fora, but this is pre-publications and as such a higher standard should be required.

Quote: Originally posted by CuReUS  

Instead of using BuBr,why don't you try making BuCl, it can be easily made by the TCT/DMF method,and since you are using ultrasound to start the reaction,the slow reaction rate of RMgCl can be compensated...

...BuBr can be obtained by adding NaBr to the TCT/DMF mixture

This is simple case of economics and ease of acquisition. The yield of the Grignard stage is (currently) low enough with n-BuBr, so why make life even more difficult by using the chloride? n-Butanol is cheap, and its unlikely that TCT-DMF will afford any advantage over the currently employed method.

[Edited on 31-3-2016 by DJF90]
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[*] posted on 31-3-2016 at 09:16


Quote: Originally posted by DJF90  

You got a fairly decent yield for a first run through - Magpie stated upthread that he gets 55 %th using the method in Pavia (@Magpie - Any chance of providing a copy of the relevant pages?). There may be a couple of things that could get your yield up. I wonder if refluxing for 2 hrs is sufficient enough, considering the method using hydrobromic acid/sulfuric acid says:
Quote:

The flask is then attached to a reflux condenser and the mixture is refluxed during a period of five to six hours, during which time the formation of butyl bromide is carried practically to completion.



Yes, these school lab procedures often have to be rushed to meet a standard 3-hr lab period. Pavia specifies a reflux of 60-75 minutes.

I also think you are right about using too much CaCl2 for the drying step. Pavia specifies 1.0g CaCl2 for a charge of 10.0 ml of n-butyl alcohol.

I never worried too much about not meeting OrgSyn's %yields as their scale was usually 10X what I was doing. Therefore I expected my mechanical losses would be greater.

Here's the Pavia procedure:







[Edited on 31-3-2016 by Magpie]

[Edited on 31-3-2016 by Magpie]



Pavia n-butyl bromide procedure-1 (2).jpg - 109kB Pavia n-butyl bromide procedure-2.jpg - 103kB

[Edited on 31-3-2016 by Magpie]




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[*] posted on 31-3-2016 at 10:14


Thanks for the literature, Magpie!

Unfortunately the TCT/DMF prep is not practical for me, because I have yet to acquire either of those reagents. I have a fairly well stocked lab, so If I don't have those reagents I don't expect others to have them. The biggest purpose of this experiment is to show that tertiary alcohols can be made with OTC chemicals.

Anyways, I will keep experimenting!




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[*] posted on 31-3-2016 at 11:56


I thought I would throw in my experience with this reaction here as well. I too followed the OrgSyn prep at 1/10th scale and got a yield of 63.8% according to my lab notes. I do vaguely remember that I estimated the crude yield(distillate from the initial reaction mixture) at around 75%, so this 10% was likely lost due to mechanical losses during the washings, drying, and distillation, as well as dibutyl ether and butanol which were removed during the sulfuric acid wash. Unfortunately, running the reaction at the OrgSyn scale is not possible for most of the members here, myself included, due to both the cost of the reagents, and the cost of the apparatus necessary to run a reaction on that scale; so seeing if the yield can be improved this way is difficult. In addition, I doubt that many of us have a use for over a kg of nBuBr.



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[*] posted on 31-3-2016 at 12:25


Quote: Originally posted by ScienceHideout  
Thanks for the literature, Magpie!


You're welcome.

I looked back in my notes and see that I performed this prep at 4X and used a reflux time of 75 minutes. Next time I will follow the OrgSyn procedure as you and gdflp got better yields. ;)




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[*] posted on 31-3-2016 at 14:38


Quote: Originally posted by gdflp  
I thought I would throw in my experience with this reaction here as well. I too followed the OrgSyn prep at 1/10th scale and got a yield of 63.8% according to my lab notes. I do vaguely remember that I estimated the crude yield(distillate from the initial reaction mixture) at around 75%, so this 10% was likely lost due to mechanical losses during the washings, drying, and distillation, as well as dibutyl ether and butanol which were removed during the sulfuric acid wash. Unfortunately, running the reaction at the OrgSyn scale is not possible for most of the members here, myself included, due to both the cost of the reagents, and the cost of the apparatus necessary to run a reaction on that scale; so seeing if the yield can be improved this way is difficult. In addition, I doubt that many of us have a use for over a kg of nBuBr.


Thanks for sharing.

On 1/10th scale, I really wouldn't be so worried about mechanical losses. The theoretical yield is nearly 130 mL so its a non-issue (estimated losses = 5 mL, ca 4 %th). I suspect the drying step is where most of the material is lost, particularly if care is not taken to ensure a minimum of dessicant is used.

I do have the means to run the OrgSyn prep at the specified scale, but there is no reason to and I'd definately optimise the procedure on a smaller (eg. 0.5 mole) scale before commiting that that quantity of reagents (thats the process chemist in me talking...). If that were the case, I would seriously consider extending the reflux period prior to distillation if the losses are not accounted for by the use of excessive dessicant.

[Edited on 31-3-2016 by DJF90]
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[*] posted on 31-3-2016 at 19:19


Here is a link to a paper which provides some useful information regarding the preparation of alkyl bromides, especially reaction time vs yield.

Ref: J Chem Educ 1949, 26, 329.

The paper is 1 page long so can be read in its entirety at the ACS web site without any charge:

http://pubs.acs.org/doi/abs/10.1021/ed026p329?journalCode=jc...

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[*] posted on 1-4-2016 at 00:38


Thats a very insightful paper Av, thanks. Looks like the losses are associated with the isolation/workup and not the reaction itself.
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