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Hexavalent
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Esterification Reaction
I have recently begun a personal research project on esters - the standard process of making esters is heating an acid and an alcohol under reflux
with a catalyst of H2SO4, but, if the materials react with this catalytic acid, can you substitue another catalyst? Is it just the H+ or hydronium
ions that are needed, or is the entire molecule mandatory?? If it is only the H+ ions that are needed, I assume you could use any other strong acid,
or, if the acid you are using for the synthesis is strong, I assume you could just use a small stoichiometric excess.
Any ideas?
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Adas
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Just try to remove the reaction water using anhydrous salts (MgSO4, CaCl2...) - water removal is most important.
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Hexavalent
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Ah, so water inhibits the reaction and the sulfuric acid, due to its hygroscopy, would absorb it. I get it. But I guess you'd have to be careful that
whatever drying agent you use wouldn't interfere with the reaction.
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Adas
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These salts are pretty unreactive. Nothing to be worry about 
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kavu
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Quote: Originally posted by Adas  | | Just try to remove the reaction water using anhydrous salts (MgSO4, CaCl2...) - water removal is most important. |
This is not the entire truth, Fischer esterification relies on acid catalyzed nucleophilic addition. Protonation of carbonyl oxygen is needed to make
carbonyl carbon electrophilic enough for alcohol to attack. You can look it up on o-chem portal: http://www.organic-chemistry.org/namedreactions/fischer-este.... A common misconception presented by school chemistry is that H2SO4 would catalyze
the reaction by removing water, as a purely catalytic amount of acid is needed this most surely is not the case. Any acid acidic enough to protonate
carbonyl oxygen is good enough. Commonly used are p-TsOH and H2SO4, more exotic reagents are applied when reacting compounds have fragile functional
groups.
[Edited on 31-12-2011 by kavu]
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Hexavalent
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Thanks for your input.
As long as you have correct stoichiometry, can you use any alcohol with any acid? Like go Nitric acid + Methanol ---> Methyl Nitrate, or Benzyl
alcohol + Oxalic Acid ---> Benzoyl oxalate?? Or are you limited to certain categories for these reactions, such as only using primary, secondary
tertiary alcohols etc.? (as long as you are careful as you say and bear in mind other functional groups etc.) Also, is it possible to produce double
esters, something like methyl ethyl acetate?
Thanks for your help
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kavu
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Inorganic esters are a slightly different story. Using Fischer esterification you can synthesize most of the simple esters. There are many good books
on these kinds of preparations, such as Vogel's textbook. You can find books on preparative organic chemistry from the sciencemadness library at http://library.sciencemadness.org/library/index.html. Methyl ethyl acetate is not an valid name for a compound. I would advise you to go through
some basic organic chemistry from chemguide at http://www.chemguide.co.uk/organicprops/alcohols/esterificat.... Also the videos in Khan academy are really helpful. I know it's a tough thing to
go through such websites, but in the end you need to understand the theory to get most out of your chemistry experiments.
[Edited on 31-12-2011 by kavu]
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Hexavalent
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Yeah, I know it wouldn't be a proper name but I wrote it as that to highlight what I meant (I assume the longest alkyl chain would no longer actually
be an ethyl).
Also, without being rude, I knew most of the stuff on the chemguide link you included. I do understand a reasonable amount of organic chemistry, just
not in this particular area.
[Edited on 31-12-2011 by Hexavalent]
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kavu
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That's good, I would advise you to get familiar with the electron pushing formalism ("the arrows") and basics of MO-theory. These will reveal a new
way to look at chemistry. Using these methods reactivities, thermodynamics and much more can be reasoned with just a pen and paper. Apply these
methods to stuff in the lab and you can enhance your skills further.
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Hexavalent
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OK, great - thanks for the suggestion!
Somewhat off topic, if I were to prepare benzene in small (30ml) quantities, what precautions would you advise me to take other than working in a
fumehood, splash goggles, nitrile gloves, lab coat, shoes and (maybe) face shield)?
I've read the MSDS sheet from a few companies but it doesn't represent the information in a quantifiable way in my opinion. Any ideas?
I was thinking of doing a dry distillation of calcium oxide and benzoic acid.
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peach
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| Quote: Originally posted by Hexavalent | | what precautions would you advise me to take other than working in a fumehood, splash goggles, nitrile gloves, lab coat, shoes and (maybe) face
shield)? |
There is an effort here to keep all the information related to preparing things in one or two threads. This is to avoid having to search thirteen
different threads.
E.g. If the mods see this reply, they'll likely merge it to one of the benzene ones. Always use the thread to which it's most related.
Preparation of benzene
Benzene synthesis
<iframe sandbox width="640" height="480" src="http://www.youtube.com/embed/sYyw_hrXrZ8" frameborder="0" allowfullscreen></iframe>
<iframe sandbox width="640" height="360" src="http://www.youtube.com/embed/S8rtyRnZZMU" frameborder="0" allowfullscreen></iframe>
Do it outside due to the serious fire risk (there is an open butane burner sat under a sealed can full of benzene vapour, and half a pint of hot,
liquid benzene sat next to that). Setting the still up the way I've done here allows the vapour to cool prior to hitting a vertical coil condenser it
also has to climb to escape. The white 'vapour' is particulate from the can, not benzene.
<a href="http://img196.imageshack.us/i/dscf8171.jpg/" target="_blank"><img src="http://img196.imageshack.us/img196/4007/dscf8171.jpg"
alt="Free Image Hosting at www.ImageShack.us" border="0"/></a><br>
Stay away from it whilst it runs, have a fire extinguisher
<a href="http://img805.imageshack.us/i/dscf8158.jpg/" target="_blank"><img src="http://img805.imageshack.us/img805/1721/dscf8158.jpg"
alt="Free Image Hosting at www.ImageShack.us" border="0"/></a><br>
You need some form of breathing protection
<a href="http://img10.imageshack.us/i/dscf8394u.jpg/" target="_blank"><img src="http://img10.imageshack.us/img10/2976/dscf8394u.jpg"
alt="Free Image Hosting at www.ImageShack.us" border="0"/></a><br>
Because you'll have to clean that mess up, which will be full of carcinogenic dust. Gloves.
<a href="http://img809.imageshack.us/i/dscf8498p.jpg/" target="_blank"><img src="http://img809.imageshack.us/img809/8669/dscf8498p.jpg"
alt="Free Image Hosting at www.ImageShack.us" border="0"/></a><br>
May as well redistil it outside as well
<a href="http://img833.imageshack.us/i/dscf8546th.jpg/" target="_blank"><img src="http://img833.imageshack.us/img833/3985/dscf8546th.jpg"
alt="Free Image Hosting at www.ImageShack.us" border="0"/></a><br>
I made enough of it with this method I gave a liter away
<a href="http://img839.imageshack.us/i/dscf8625m.jpg/" target="_blank"><img src="http://img839.imageshack.us/img839/1646/dscf8625m.jpg"
alt="Free Image Hosting at www.ImageShack.us" border="0"/></a>
[Edited on 1-1-2012 by peach]
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Lambda-Eyde
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It's a good idea to look at the mechanism for a reaction before asking such questions. Studying the mechanism helps you understand what happens during
the reaction, and if you had known that the first step in a Fischer esterification was protonation of the acid by a strong acid, you wouldn't have
asked that question in the first place.
| Quote: Originally posted by Hexavalent |
Somewhat off topic, if I were to prepare benzene in small (30ml) quantities, what precautions would you advise me to take other than working in a
fumehood, splash goggles, nitrile gloves, lab coat, shoes and (maybe) face shield)?
|
That's more than enough for handling benzene. Just don't sniff it - although the smell is fantastic.
We have several threads on the subject here. Check out "Extract of benzene thread" in the Prepublications section.
Also, I'll beat Nicodem to it - threads without any references belong in the beginnings section.
Edit: Peach, I love you 
[Edited on 1-1-2012 by Lambda-Eyde]
This just in: 95,5 % of the world population lives outside the USA
Please drop by our IRC channel: #sciencemadness @ irc.efnet.org
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entropy51
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| Quote: Originally posted by Hexavalent | OK, great - thanks for the suggestion!
Somewhat off topic, if I were to prepare benzene in small (30ml) quantities, what precautions would you advise me to take other than working in a
fumehood, splash goggles, nitrile gloves, lab coat, shoes and (maybe) face shield)?
I've read the MSDS sheet from a few companies but it doesn't represent the information in a quantifiable way in my opinion. Any ideas?
I was thinking of doing a dry distillation of calcium oxide and benzoic acid. |
It's benzene, not Sarin. For
making 30 mL I probably wouldn't even do it in my hood. Just make several small runs to minimize the fire hazard.
I recommend using NaOH instead of CaO. At least it's worked well for me. Mix the two in enough water to dissolve the sodium benzoate and then
evaporate the water.
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Adas
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NaOH can easily eat through your glassware, I wouldn't do it.
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Vogelzang
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How about anhydrous copper sulfate?
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peach
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| Quote: | | NaOH can easily eat through your glassware, I wouldn't do it. |
That's why we're all doing it in empty paint cans and propane tanks, if by it you mean making benzene.
I believe entropy did it in glass but used flasks that he wouldn't mind getting damaged.
I have made a copper pipe condenser myself. Doubt I'll bother with that again anytime soon. By the time I'd added up the cost of the plumbing parts,
soldering it all together, it worked out about the same as buying a glass condenser. The glass is much more useful.
| Quote: | | although the smell is fantastic. |
It does smell nice. Although I put a trap on any experiment I'm doing that involves warming it up or blowing gases into or over it, so I can't smell
it, since smelling it means I'm breathing it, and it is one of the few proven carcinogens; "Group 1, Carcinogenic to humans, 107 agents" - IARC.
A 20 a day smoker inhales about 1mg of benzene per day. Even small experiments can involve ten thousand times that.
| Quote: | | Peach, I love you |
XxX 
[Edited on 1-1-2012 by peach]
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entropy51
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| Quote: Originally posted by peach | | Quote: | | NaOH can easily eat through your glassware, I wouldn't do it. |
That's why we're all doing it in empty paint cans and propane tanks, if by it you mean making benzene.
I believe entropy did it in glass but used flasks that he wouldn't mind getting damaged.
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That's correct. I once scavenged several dozen round bottoms that were headed to the trash. They are old
fashioned thick Pyrex. I used the same flask for several benzene runs. It became etched, but was still intact. I think the paint cans are a good
idea.
Apropos the toxicity of benzene, my organic professor used to laugh about how many times he had washed tar off his hands using benzene. He died last
year. At age 92. He did not have cancer.
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hissingnoise
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| Quote: |
Apropos the toxicity of benzene, my organic professor used to laugh about how many times he had washed tar off his hands using benzene. He died last
year. At age 92. He did not have cancer. |
OK, toluene isn't nearly as toxic as benzene, allegedly, but in the early sixties, being the newbie, I was given the task of cleaning a spill of a
gallon of 'high-grade' toluene ─ intoxicated!!! Hell, I was sick as a dog for three fucking days!
But a large area of flooring was so squeaky clean, everyone complimented me on my efforts and the sodden newspaper was simply burned round the back!
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bahamuth
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Regarding benzene toxicity IIRC the consumption of ethanol shortly before or after mulitiplied the toxicity by several fold, though I may be mixing
benzene with carbontetrachloride which I know has that effect with alcohol consumption...
Any sufficiently advanced technology is indistinguishable from magic.
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Hexavalent
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I've never heard of that, but I have read that if exposed to a dichromate salt, drinking a solution of ascorbic acid immediately after will help
reduce the toxicity danger because of metabolism or something . . .hell, I'm a chemist, not a biologist.
Also, for the same reason, I believe that consuming some ethanol if you are exposed to the toxin methanol can help.
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peach
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I think the World Health Organisation mentioned that drinking alcohol and simultaneously smoking multiplied the carcinogenic effect by an order of
magnitude. I'm not sure if that is an actual interaction between the two or due to the fact that the ethanal produced by the metabolism of the alcohol
is it's self carcinogenic. That could also be influenced by other lifestyle factors, as the two combined are indicators that the person may not be
living too healthily in other aspects.
Regarding getting drunk to save lives, an extreme example is given by antifreeze (ethylene glycol). Because it's brightly coloured and tastes nice,
kids will drink it.
The program of treatment involves getting the patient well cooked, the ethanol blocking the pathway shared with the glycol, slowing down the rate at
which it's converted to other toxic metabolites.
In an amusing example, a hospital resorted to running out to buy creates of vodka after receiving a poisoned patient.
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entropy51
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Yes indeed. Administration of ethanol is part of the standard medical treatment for methanol intoxication.
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Panache
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Ha!
Most gasoline is 1-5% benzene. Try doning a full face aspirator when filling your car and see the reception you get. Lol. I want to try it just to
see.
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Hexavalent
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*Respirator.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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Panache
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The aspirator is the Masquerader as the respirator
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