| Pages:
1
2
3
4 |
Furboffle
Harmless
Posts: 46
Registered: 15-10-2012
Member Is Offline
Mood: No Mood
|
|
whats a typical experimental batch size?
I'm curious how much you guys run for experimental batches/first time experiments?
like grams or milligrams?
I've done experiments trying to make beta-carbolines, tryptamines, and various nitro-styrenes.
First time I made a nitro styrene I used the nitro-aldol reaction via 1g trimethoxybenzaldehyde. it proved extremely straight-forward and I was able
to then increase the quantity size successfully.
indoles and beta-carbolines on the otherhand were the first things I tried my hand at and had much difficulty. Due to loss of reagents and realizing
better equipment is necessary I ended up giving up on them after wasting a lot of time, money, and chemicals.
so I've come to realize its hit or miss on success depending on the nature of the target compounds being created. so I'd like to wise up with new
reactions I try my hand at.
whats a good rule of thumb for quantity in a first time experiment? how small is too small?
|
|
|
sargent1015
Hazard to Others
Posts: 315
Registered: 30-4-2012
Location: WI
Member Is Offline
Mood: Relaxed
|
|
Well, I guess it all depends. If you are following a paper from literature, it's never a bad idea to follow their scale, usually 1-10 mmol for my
research. My rule of thumb is to run a reaction with at least .1g (mainly due to losing yield in workups, which are much greater on small scale).
But, it really depends on the reaction you are running.
If you are "inventing" something new or trying a new reaction scheme, usually it's better to start smaller, especially if the
material you are working with is valuable. There are inherent problems with working with small scales, such as not having enough material for
analytics, a problem I run into sometimes when I am starting a scheme. If you ask one of our members, Kristof, he will tell you to run it on molar scales. 
In the end, I guess what I am dancing around here, is that there is no perfect amount of material to run with. Guessing, performing research,
and preparation are important not only for safety, but also for obtaining high yields. Remember, this is experimentalism, so you will run into
problems some of the times and your yields may not match literature, but repetition is key. That is what makes chemistry so exciting is that one
little variable (Temp, humidity, looking at it funny) will produce different results.
Keep on experimenting and don't get discouraged. Size doesn't matter 
(I don't work with energetic material, so the above statement DOES NOT APPLY when working with them )
|
|
|
kristofvagyok
National Hazard
Posts: 659
Registered: 6-4-2012
Location: Europe
Member Is Offline
Mood: No Mood
|
|
Oh, someone mentioned me, thanks!(:
Yesterday I started to work at a chemical company where they produce several N protected amino acids (BOC, Cbz, Fmoc) and related stuff. I work at the
research and development department and we design reactions from mmol scale to industrial size.
We usually start from 1-20g, depending on the value of the substance and if it works we do it on a nice 200-500g size, just before the industrial
synthesis (10-100kg).
I have a blog where I post my pictures from my work: http://labphoto.tumblr.com/
-Pictures from chemistry, check it out(:
"You can’t become a chemist and expect to live forever." |
|
|
Acidum
Harmless
Posts: 39
Registered: 2-5-2013
Location: Serbia
Member Is Offline
Mood: Sublimed
|
|
Depends on your lab setup.
Usually good starting point is around 100-500 mg.
During my graduation work (or however you call "diplomski rad") I did syntheses and experiments with starting amounts ranging from 10 mg to 50 g.
General considerations and "rules of thumb":
- You can not use amounts of chemicals that you cannot weight on your lab balance, either starting reagents or products - same goes for fluid
measurements, graduated cylinders, pipettes, burettes...
- adjust amount of reagents considering various apparatus for reactions and purifications - reaction vessels, destilation apparatus, separation
funnels, chromatography columns...
- Yield. Less you expect, more starting material you need. Or you will not be able to detect/isolate desired product. Also consider loses during
purifications.
- Number of steps. More steps, cumulative losses, more starting material.
- Price. More expensive chemicals you need, less you will use. You definitely do not want to throw gram of precious metal complex on a tryout... Or
half liter of some exotic solvent...
That should cover everything that crossed my mind for now...
...of course, these are guidelines for first time experiments. Production batches follow somewhat different rules, with desired amount of product
dictating starting amounts of reagents, not minimizing initial expenses...
...and then I disappeared in the mist...
|
|
|
sargent1015
Hazard to Others
Posts: 315
Registered: 30-4-2012
Location: WI
Member Is Offline
Mood: Relaxed
|
|
Oh, of course I had to mention you I feel like this similar topic was covered
quite some time ago. Plus, everyone needs to follow that Tumblr
|
|
|
bfesser
Resident Wikipedian
Posts: 2114
Registered: 29-1-2008
Member Is Offline
Mood: No Mood
|
|
<strong><a href="viewthread.php?tid=21684#pid271706">Real chemistry is dying out, why?</a></strong>
|
|
|
adamsium
Hazard to Others
Posts: 180
Registered: 9-4-2012
Location: \ƚooɿ\
Member Is Offline
Mood: uprooting
|
|
bfesser - I have never understood why some people like to perform every experiment at the Ymol <img src="../scipics/_wiki.png" /> scale (slight exaggeration there, perhaps - but only slight). I recall that thread and recall being
irked by it. Small scale work has many, many advantages - for anyone, but particularly for the amateur chemist. I, personally, also find it more
elegant than large scale work, which is often cumbersome and unwieldy (even more so in a home lab).
As for the original question; as small as is practicably reasonable is a good approach. This will, of course, mean different things according to the
requirements and the desired outcome (as others have pointed out).
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: Ymol made
me laugh; hard! You've earned a mystical <img src="../scipics/_wiki.png" />,]
[Edited on 7/10/13 by bfesser]
|
|
|
BromicAcid
International Hazard
Posts: 3253
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline
Mood: Rock n' Roll
|
|
Quote: Originally posted by kristofvagyok  | Oh, someone mentioned me, thanks!(:
Yesterday I started to work at a chemical company where they produce several N protected amino acids (BOC, Cbz, Fmoc) and related stuff. I work at the
research and development department and we design reactions from mmol scale to industrial size.
|
Neat! I've probably used your chemicals! When I was doing phosgene chemistry I was making all sorts of N-carboxyanhydrides from protected amino
acids on the large and small scale and we almost always bought from Europe 
Regarding the thread though, for me I've always been more concerned with the macroscopic properties of a reaction and find it intensely non-rewarding
to run at a scale of less than a hundred milliliters of solvent. I love seeing things thicken and thin and change colors and with the small scale
it's more like: Hummm... that's kind of dark, or is it getting thick?
It makes sense to run on the small scale, saves reagents, cheaper, less danger for unexplored reactions. But on the larger scale you combat loss of
yields, crummy reactions, and your devo run might turn out to be your final run.
|
|
|
bfesser
|
Threads Merged
9-7-2013 at 18:30 |
amazingchemistry
Hazard to Others
Posts: 104
Registered: 4-4-2013
Member Is Offline
Mood: Excited
|
|
I will put in my 2 cents here: Like many things in chemistry, it depends on what you are looking for. Multistep syntheses cannot be done entirely in
microscale unless you have sharpshooter-stable hands and an unnatural ability to prevent mechanical loss. Likewise, if your goal is to observe what's
going on (watch stuff changing color, boiling, or doing other interesting things) microscale can be unrewarding. However, I will say that I personally
like microscale and mini (meso) scale better than macroscale. Here's why:
-Less waste
-Less risk of exposure to toxic chemicals
-Less wait time (for heating, distilling and the like)
-Less setup and teardown time
-Literally forces you to think about what you're doing and to develop a plan for the most efficient way of doing things
-Increases (IMHO) your skill as a chemist, at least as far as dexterity goes.
-Allows you to use more expensive and exotic reagents.
The last point is in my opinion critical. My undergrad orgo lab was in micro/meso scale and I was able to use things like iodine monochloride,
currently priced at 2 dollars a gram. If you think about it, if we had to use say, 5g my school would not have been able to buy that reagent for all
of us (We were 100 in all) and the experiment may have been scrapped. My old lab manual even has a section on palladium on carbon hydrogenation. At 10
dollars a gram this experiment is out of reach for most of us if we want to do it macro. This is one of the biggest reasons for liking small scale. It
expands the chemist's range.
Always remember to check your pride at the door and ask that "stupid" question. Learning comes from having your "stupid" questions answered.
|
|
|
testimento
Hazard to Others
Posts: 351
Registered: 10-6-2013
Member Is Offline
Mood: No Mood
|
|
First you do the math and theory speculations and shit
Then you do it in mg-scale to prove that it works
Then you can scale it in oil drum an cook away for streets.
|
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by adamsium | | I have never understood why some people like to perform every experiment at the Ymol <img src="../scipics/_wiki.png" /> scale (slight exaggeration there, perhaps - but only slight). |
And there I was thinking that a yotta-molecule scale reaction is only about about 66% larger than a one-mole scale reaction. That
is a pretty slight exaggeration.
|
|
|
bfesser
Resident Wikipedian
Posts: 2114
Registered: 29-1-2008
Member Is Offline
Mood: No Mood
|
|
10<sup>24</sup> ( 6.022141 × 10<sup>23</sup> ) = 6.022141 × 10<sup>47</sup> = 602 214 100 000
000 000 000 000 000 000 000 000 000 000 000 000
That's a rather large number.
|
|
|
adamsium
Hazard to Others
Posts: 180
Registered: 9-4-2012
Location: \ƚooɿ\
Member Is Offline
Mood: uprooting
|
|
No, watson. 'mol' is the abbreviation for mole, not for molecule. A 'Ymol' would be 1024 moles, not
1024 molecules. bfesser showed the number of molecules above.
|
|
|
sonogashira
National Hazard
Posts: 555
Registered: 10-9-2006
Member Is Offline
Mood: No Mood
|
|
The reaction will work with 6.022x10^20 molecules but not with 6.022x10^23 molecules?!
|
|
|
Eddygp
National Hazard
Posts: 858
Registered: 31-3-2012
Location: University of York, UK
Member Is Offline
Mood: Organometallic
|
|
Well, I usually work with 0.4 moles or so in my reactions. Working with like 0.02 or less would be a bit hilarious and boring, because I don't think
anyone would be able to see something there except a spectroscope. The beauty of chemistry is not zurking with Ymol scales but not with zeptomol
scales either. I like to see the changes, to be able to use the product for other different reactions.
EDIT: I realised that one yoctomole contains no particles. Actually, it contains 0.6021 particles...
[Edited on 10-7-2013 by Eddygp]
there may be bugs in gfind
[ˌɛdidʒiˈpiː] IPA pronunciation for my Username |
|
|
watson.fawkes
International Hazard
Posts: 2793
Registered: 16-8-2008
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by adamsium | | No, watson. 'mol' is the abbreviation for mole, not for molecule. A 'Ymol' would be 1024 moles, not
1024 molecules. bfesser showed the number of molecules above. |
Oh, I know. My first reaction,
however, was "that's not an exaggeration; that's about a mole".
|
|
|
bfesser
Resident Wikipedian
Posts: 2114
Registered: 29-1-2008
Member Is Offline
Mood: No Mood
|
|
For a little perspective on that number, the <a href="https://en.wikipedia.org/wiki/Observable_universe" target="_blank">observable
universe</a> <img src="../scipics/_wiki.png" /> is calculated to contain about a tenth of a mole (6 ×
10<sup>22</sup> of stars, by one estimation. The approximate number of
atoms in the universe is calculated to be nearly 10<sup>80</sup> (again, estimates vary). Finally, by one estimate, the mass of the
observable universe has been calculated to be 8 × 10<sup>52</sup> kg.
10<sup>80</sup> atoms = 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10
× 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10
× 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10
× 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10
× 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10
× 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10
× 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10
× 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10
× 10 × 10 atoms
= 100 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 atoms
This image contains 1.25 × 10<sup>7</sup> pixels (scaled to 800px × 400px = 3.2 × 10<sup>5</sup>
pixels for display, click for full resolution) and ~ 3.994 × 10<sup>7</sup> bits of data:
<a href="https://upload.wikimedia.org/wikipedia/commons/0/0f/Earth%27s_Location_in_the_Universe_SMALLER_%28JPEG%29.jpg" target="_blank"><img
src="https://upload.wikimedia.org/wikipedia/commons/0/0f/Earth%27s_Location_in_the_Universe_SMALLER_%28JPEG%29.jpg" width="800" /></a><img
src="../scipics/_wiki.png" />
Do you feel <a href="http://www.worldometers.info/world-population/" target="_blank">insignificant</a> <img src="../scipics/_ext.png"
/> yet?
[Edited on 7/10/13 by bfesser]
|
|
|
GreenD
National Hazard
Posts: 623
Registered: 30-3-2011
Member Is Offline
Mood: Not really high anymore
|
|
uh - on this note I came from a lab that used 'brute force chemistry'
It was really old techniques, and basically if we couldn't do it for under 300 bucks and get 10+g of our final product, we didn't want to even look
into it.
Now, I work with herbicides. You know the active dose of some of these? 1uM.
So, we order 500mg for THE ENTIRE YEAR.
Needless to say, coming from a bruteforce lab, and now I'm synthesizing things on the <100mg scale, I really, REALLY hate forgetting to close my
stoppers on my funnels >
ʃ Ψ*Ψ
Keepin' it real.
Check out my new collaborated site: MNMLimpact.com
|
|
|
Random
International Hazard
Posts: 1120
Registered: 7-5-2010
Location: In ur closet
Member Is Offline
Mood: Energetic
|
|
I like doing experiments in few mL test tube scale because it is a lot safer. Especially if I put on the gloves I can handle pretty toxic stuff and
not be worried.
On another side handling a half a jam jar of toxic stuff would get hard. Especially if the reaction goes out of control. Lately I love to do a very
small reaction in a test tube just to see how it goes. And if the reaction gets out of hand, on a small scale I can just throw the stuff in a bucket
of water and forget about it. Doing this with 200-500g of something is not so viable.
|
|
|
Fantasma4500
International Hazard
Posts: 1681
Registered: 12-12-2012
Location: Dysrope (aka europe)
Member Is Offline
Mood: dangerously practical
|
|
i would like to second that, but this is mainly if you have something you know youre gonna do several times...
take this site as a really good examble..
http://www.artsuppliesonweb.com/restauratie-chemie/chemicali...
as you see 100g copper nitrate is 6.25 euro
now if we go up to 1000g, 10 times as much we get it for 25
by advanced math we can say that if we buy 1 kg, each 100g in that would have a price of 2.5 euro, whereof buying 10 x 100g would cost 62.5 euro
in chemistry where you need to filter and such, yes there is waste when you filter it etc. so some processes might not be anywhere near worth it to do
in small scale..
CuCl2 + Al + HCl > CuCl + AlCl3 + H2
the CuCl can be precipitated by being dumped in water, this is a nice little reaction for demonstration, however if you want this to have any use you
might want to scale it up, otherwise very likely the precipitated CuCl will be clogged in the filter
the costs are relative, if you can only see whats in front of you at the moment then yes it will be very costly per kg
but if you have a company and you can buy home 50kg of reagent or perhaps tonnes, then it can be taken as an investment, its not that hard to figure
out guys, come on, how can you not agree on a such simple thing?
|
|
|
adamsium
Hazard to Others
Posts: 180
Registered: 9-4-2012
Location: \ƚooɿ\
Member Is Offline
Mood: uprooting
|
|
Antiswat:
No, no and no!
Just because it might be cheaper, per unit of weight, to buy in bulk, one does not have to scale up their experiments to be 'saving', even if
they do buy in bulk. We're not talking about the scale at which we purchase reagents, but the scale at which we perform experiments. These are not
the same thing!
The fact is that, when doing amateur chemistry, many of the procedures we do are purely for the enjoyment of it. It's our hobby; we do it because we
like it. We are not generally doing it because we need large quantities of the end product.
We are not Sigma-Aldrich who can say "we can make 10 kg of this compound for $80/kg or 1000 kg for $20/kg" and, if they know that they can sell the
1000 kg, this is obviously in their best interests. However, for a home chemist, using these figures, 10 kg @ $80/kg = $800; 1000 kg @ $20/kg =
$20,000. It really doesn't matter what the exact figures are, even if buying more starting material is cheaper per kilogram, buying more will
still cost more and one does not have to use it all right away just because they have it.
The important point is that it still costs more to make more. There is no point in making more product than you need; it is still
going to cost more, be more risky and be more of a disposal hassle.
Also, for amateur chemists who do work on a small scale, there is more to be gained in buying smaller quantities of different reagents rather than a
large quantity of a single reagent. For the example you cite, you could buy 4 x 100g of different reagents (of that same price) OR you could buy 1 x
1000 g of that one reagent. The former will allow you to do a range of experiments with just those reagents and nothing else (save for perhaps water),
while the latter will likely allow you to do.... not much.
How can you not agree on such a simple thing?
<hr>
[edit:] removed quoted text
[Edited on 12-7-2013 by adamsium]
|
|
|
amazingchemistry
Hazard to Others
Posts: 104
Registered: 4-4-2013
Member Is Offline
Mood: Excited
|
|
I would like to add that given that a lot of us work out of our homes, I don't see how the so-called 'economy of scale' benefits us when you consider
the logistical problem that arises from trying to store kilogram and liter amounts of potentially dangerous reagents as opposed to gram and milliliter
amounts. On another thread, I suggested that flammable organics be stored in a modified fireproof safe (these can be found even at walmart for
relatively cheap). However, if you are storing 2 liter bottles of stuff like acetone or diethyl ether you are going to need a dedicated cabinet if you
want to have some measure of safety for yourself and your family, and those can run you in the hundreds or even thousands of dollars. Ditto for other
nasty stuff. To me, having the amount of chemicals in stock required to do macroscale chemistry is a major logistical problem for the home chemist and
not worth the money you're supposedly saving by buying reagents in bulk
Always remember to check your pride at the door and ask that "stupid" question. Learning comes from having your "stupid" questions answered.
|
|
|
ElizabethGreene
Hazard to Others
Posts: 141
Registered: 15-10-2012
Member Is Offline
Mood: No Mood
|
|
Large scale chemistry is certainly not dead. It's only wounded.
On How it's made yesterday I saw this beautiful copper smelting operation. The ore was contained in these massive ponds and leached with thousands of
gallons of sulfuric acid. The runoff went to a mindbogglingly massive settling tank to concentrate and then they plated it out on thousands of
starter copper sheets. It was beautiful.
I love to see big chemistry. That said, I read about this "slightly pyrophoric" pentabromide compound in Max Gegel's biography. His was near the
end of a very long list of companies that refused to synthesize it. To put it in perspective, this refusal came from a person that repeatedly
described retrieving reaction products from the ceiling, floor, and faces near the work area. If I get --suicidal-- ambitious enough to synthesize
it, "tiny" amounts might be best.
In the youtube "PeriodicElements" video on Plutonium, the professor describes accidentally losing the UK's entire supply of plutonium (in Mg) one
evening. He recovered most of it by sawing out the spilled section of the workbench, burning it, and leaching the salt from the ashes. Fun?
Certainly!
|
|
|
bfesser
Resident Wikipedian
Posts: 2114
Registered: 29-1-2008
Member Is Offline
Mood: No Mood
|
|
Wow, a megagram of plutonium‽ That's a metric ton!
<iframe sandbox width="420" height="315" src="//www.youtube.com/embed/XLufmakbiU0?rel=0" frameborder="0" allowfullscreen></iframe>
[Edited on 7/14/13 by bfesser]
|
|
|
Pickardjr
Harmless
Posts: 45
Registered: 27-5-2013
Member Is Offline
Mood: vapor state
|
|
I used to be able to buy my stock cheap, then the economy took a dump and cost went up.All the reactions I used to do on a one mole maximum are now
scaled down to mmol. scale and it sucks. aside from that the usa schooling isnt what it used to be and when I went to school, and I was a chem major
the chemistry was just for demonstration and theory, bullshit stuff. All the skills I have now I learned from books on my own and own expense, very
costly. my 2 cents.
|
|
|
| Pages:
1
2
3
4 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
