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Author: Subject: Cou's esters megathread
arkoma
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[*] posted on 16-6-2020 at 06:31


Don't particularly like4 doing doing business with The Bezos Empire, but cinnamic acid is available on Amazon, and not on ebay *sigh*.

torn between 50g and 500g sizes........




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Cou
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[*] posted on 20-6-2020 at 00:39


Synthesis of isopentyl formate: https://www.youtube.com/watch?v=BkQwunQxl8g (my first chemistry video)

Edit: i was informed that i made a safety mistake by using an open flame to distill the ester. I got into that habit because I had a really hard time distilling esters with boiling points above 200 C, even sand baths cranked up to 10 were not working. and i dislike messing around with vacuum distillation Next time I do this I would touch the RBF to the hot plate and use an aluminum foil skirt to hold in heat.


it doesn't smell like banana. it's cherry, tart, delicious, reminds me of cherry airheads.

Updated list of esters:
Formate esters
Ethyl formate (ethereal rum)
Isopentyl formate (cherry tart blackcurrant candy)

Acetate esters
methyl acetate (ethereal sweet fruity)
ethyl acetate (ethereal fruity sweet)
propyl acetate (pear)
isopropyl acetate (pear)
butyl acetate (apple)
isobutyl acetate (cherry)
(RS)-sec-butyl acetate (grape)
pentyl acetate (banana)
isopentyl acetate (banana candy)
hexyl acetate (green floral pear)
heptyl acetate (rum woody)
octyl acetate (orange mushroomy)
nonyl acetate (green herbal mushroomy)

Propionate esters
ethyl propionate (pineapple)
isopentyl propionate (real banana fruit)

Butyrate esters
Octyl butyrate (faint waxy pink slightly sweet)

Isobutyrate esters
(none)

Salicylate esters
methyl salicylate (rootbeer minty fresh wintergreen)
isopropyl salicylate (green leather floral)

I am mailing 1 mL samples of esters to anyone who wants to smell them for themselves. Cost is shipping and than 50 cents for each ester. I can also synthesize a custom ester from any combination of alcohol/acid not yet listed. U2U

[Edited on 20-6-2020 by Cou]




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[*] posted on 25-6-2020 at 20:40


Been lazy and recuperating from traveling, but my esters were waiting for me when I got home.

Isopentyl Propionate--most DEFINITELY banana.

Isobutyl Acetate--smells sorta like ethyl acetate, with a sort of nitrite ester undertone. Not cherries to me.

Octyl Butyrate--waxy indeed. Like the scent of a hard wax candle burning.

Cou, good job. Stuff was packed well, labeled and shipped quickly. I too like stuff that smells good and esters ain't breaking any new ground, but so what? I too enjoy making them, and by gosh, running a reaction is like working on a car. It CAN be done first go round with a book, but nothing beats practice to iron out the humps (like violent bumping, they really mean it when it says :"only fill flask MAXIMUM halfway) and org chem is notoriously finicky and needs practical lab experience to get any good at all. Guess what I am rambling on is that before you can contribute to the field Young Scientist, ya need some skills and these esters are dang sure doing that, and amateurs with good basic skills have indeed made some pretty hefty contributions.

Now if I would quit practicing how to make nitrite esters......LOL




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[*] posted on 27-6-2020 at 22:22


Butyl salicylate:



faint floral blackberry smell

I only got 3 mL, a 24% yield. This was my first time making an ester of salicylic acid and an expensive alcohol, so there were some hiccups that I learned from.

When making methyl salicylate, you use a large excess of methanol as the solvent, because methanol is cheap and readily available [1]. but larger alcohols, such as 1-butanol, are specialty chemicals that should be conserved. salicylic acid is very cheap and readily available (I have a 1 kilogram bag from amazon that cost $35) so it should be used in excess to fully react all the 1-butanol.

Ideally benzene could be used for dean-stark technique, but benzene is expensive (for non-industrial sale), and carcinogenic.

I used a 3 molar excess of salicylic acid to 1-butanol. Xylene was used as the solvent (no dean-stark trap, just reflux). I added too much xylene than what was needed to dissolve all the salicylic acid. One day maybe I'll determine the solubility of salicylic acid in boiling xylene, but you could add a little xylene, heat to boiling, then drip it in with an addition funnel until everything is dissolved. Salicylic acid is much more soluble in boiling xylene than room temp xylene. Less is better

After refluxing for several hours, then allowing to cool, you should gravity filter to remove the unreacted salicylic acid, and wash funnel w/ xylene. Then proceed to typical fischer esterification workup: water, sodium carbonate, water. A simple distillation removes xylene first, then the salicylate ester comes out much later (this one boiled at 271 C)

[1] https://www.youtube.com/watch?v=lJLP2bcXDqY

EDIT: I found that salicylic acid is actually more expensive per mole than 1-butanol. It might be better to just use 1-butanol as the solvent. Ideally you should use benzene as the solvent and use the dean-stark technique, but I'm not sure if I want to mess around with benzene. Once you get to making salicylate esters of high boiling alcohols, such as 1-pentanol, toluene works as a dean-stark solvent. 1-butanol and 1-propanol are relatively inexpensive, so you can invest in larger amounts of those to use as excess solvents. I have a huge amount of salicylic acid so I chose to use it in excess with xylene solvent.

[Edited on 6-28-2020 by Cou]




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[*] posted on 28-6-2020 at 01:48


When doing fischer esterification, the decision on which reactant to use in excess (or whether you should use equimolar amounts of both with the dean stark technique) is based on many factors.

Cost: the cheaper one per mole should be used in excess.

Current availability: if you have a lot more of one reactant than the other in your inventory

Ease of extraction in workup: If one is easier to remove from the organic layer in workup, it should be used in excess. Carboxylic acids are easier to remove because they are either solids that cam be removed by filtration, or they can be ionized with a base and extracted with water. Low MW alcohols can be extracted easily with water. Long chain alcohols are insoluble in water and must be extracted with a deep eutectic solvent. It's better to use the long chain alcohol as the limiting reagent.

Boiling points and azeotropes: if both reactants are expensive, the dean stark technique can react an equimolar amount of both to completion. The dean stark solvent should have a lower boiling point than any reactants or azeottopes. Use "azeotropic data" to search for azeotropes between any 2 compounds in the reaction mixture. Benzene is best for dean stark solvent, but scary and expensive. Toluene has a BP of 110 c. If all of the reactants boil above 110 C, and there are no low boiling azeottopes, then good to go. This means no propyl or butyl alcohol with toluene. But they're inexpensive anyway, and easy to extract if used in excess, so things work out conveniently.


The decision is made on a case by case basis. For example, butyl salicylate... if I had benzene I could use the dean stark trap, but I prefer to avoid benzene. The boiling point of butyl alcohol is too low to be used with toluene. If I had a big jug of butyl alcohol in stock, I would use an equimolar amount of butyl alcohol and salicylic acid, since they are both about the same price per mole. But at the moment I have about 100 mL of butyl alcohol and 1 kilogram of salicylic acid. So until i receive large bottles of butyl alcohol and propyl alcohol in the mail, I use salicylic acid in excess because I have way too much of it.




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[*] posted on 28-6-2020 at 04:24


Cou, 1-butanol drives out a lot of water as it boils as an azeotrope with 55% of water, but very likely it could be some ternary azeotrope due to the ester present. It separates into 2 layers where upper contains 80% wt. butanol, lower layer water with little of butanol (7,7% wt. butanol). If you have Dean-Stark trap adapter you could allow the upper layer to return back and drain out only the lower layer so the loses of butanol would be very small. Yes it is quite cheap so use it in some excess, perhaps 1,5 x more than the acid (calculate the amount according the loses of butanol boiling with water in azeotrope and add then add some extra amount of the butanol to be sure, it is easy to distill it out. And perhaps no need to use xylene at all - just my thoughts. Ester with such high b.p. requires vacuum distillation. I expected salicylic acid could be well soluble in the ester, but apparently it isn't, strange...
Butanol should be well available, there were attempts to use it as a fuel into cars (produced by fermentation process). Here in my country I can buy from chem supplier analytical grade 1-butanol at a price 12 EUR per 1 liter. So less pure should be even cheaper.




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[*] posted on 28-6-2020 at 13:35


the BP of butyl salicylate is 271 C. I did a normal simple distillation with heat alone, but any hotter and I would worry about the flask breaking.




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[*] posted on 29-6-2020 at 01:00


Cou, wow you are very brave chemist! I wouldn't distill any chemical with such high b.p. without vacuum... another choice is steam distillation if there is no risk of hydrolysis...



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[*] posted on 29-6-2020 at 11:55


Again I forgot to check EVERY azeotrope before doing the dean-stark technique. 1-pentanol and water form a low boiling azeotrope which is great if you're using 1-pentanol as the solvent, but screws it up when using toluene.

You're right, you can use the alcohol alone as the solvent and water still separates in the dean-stark trap. It's more effective for higher MW alcohols. I didn't need to be messing around with toluene, but it was worth a try.

if you don't have enough solvent to fill the trap, you can use a 3 neck flask and periodically empty the upper layer of the trap back into the flask.

edit: what source did you use to find that the water layer contains 7.7% butanol? I need a good book of solubilities.

[Edited on 6-29-2020 by Cou]




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[*] posted on 30-6-2020 at 05:02


https://en.wikipedia.org/wiki/Azeotrope_tables
https://cpb-us-e1.wpmucdn.com/blogs.uoregon.edu/dist/1/8309/...




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[*] posted on 5-7-2020 at 18:51


Need help removing water from a small scale (0.06 mole) fischer esterification reaction. anhydrous magnesium sulfate?

it doesn't work with toluene b/c 1-pentanol and water form an azeotrope that screws up separation of water in the trap.

the volume of the reaction mixture is 16 mL

It's too small for a dean-stark apparatus if i don't use a solvent like toluene.

Molecular sieves are not compatible with fischer esterifications.

Can I use anhydrous magnesium sulfate powder to drive fischer esterification to products side?


EDIT
i found that i can use a pressure equalizing addition funnel as a substitute for a soxhlet extractor if i don't have enough volume

[Edited on 7-6-2020 by Cou]

unknown.png - 66kB




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[*] posted on 6-7-2020 at 19:06


I'm just going to hitch my wagon to your train here, and report the successful synthesis of methyl pivalate and isoamyl benzoate. Pivalic acid, to me, smells a lot like gummy candies, and so does the ester- my colleagues thought the acid smelled like shit or rancid socks, but the ester smells like watermelon or blue raspberry gum. The isoamyl benzoate needs to be purified more before I can smell anything but isoamyl alcohol.



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[*] posted on 7-7-2020 at 00:02


Quote: Originally posted by Cou  
Need help removing water from a small scale (0.06 mole) fischer esterification reaction. anhydrous magnesium sulfate?

it doesn't work with toluene b/c 1-pentanol and water form an azeotrope that screws up separation of water in the trap.

[Edited on 7-6-2020 by Cou]


Magnesium sulfate should be fine, it only loses water at 150 degrees. Maybe you can put it in your PE funnel, it is so course it shouldn't pass the tap.

Edit: or if you aim for the monohydrate of MgSO4 you only need about 7 grams for a 0.06 mol reaction. The monohydrate only loses water at 200 degrees.

[Edited on 7-7-2020 by Tsjerk]
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[*] posted on 10-7-2020 at 13:10


Very concerned after finding out that coronavirus can destroy your sense of smell.

It can't be completely gone, right? Just means you have to bury your nose deeper in the ester flask. Surely if the air in your nose is a very high ester concentration, it will still work.




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[*] posted on 10-7-2020 at 13:54


Dallas is damn sure a Covid-19 hot spot right now.



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[*] posted on 10-7-2020 at 14:06


Even in the unlikely case a young person like you would contract that and get serious symptoms like the anosmia you fear, that can still be treated successful using some cortisone derivatives.
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[*] posted on 10-7-2020 at 18:02


I read that the anosmia is rarely permanent.



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[*] posted on 10-7-2020 at 18:26


A note on loss of taste and smell.

I was in Italy last May and June when I cam down with a horrible virus infection / flu. Chills, fever, horrible congestion and and terrible cough. Shortly after I got this I lost ALL sense of taste and smell. Ironically, I was supposed to be attending an intensive food and wine class just after I became sick. My doctor said that the loss is caused by the virus infecting the nerves for taste and smell and nerve damage can be permanent. These nerves can be used as pathways for subsequent brain infection. The nerves became infected because they pass near the sinus cavities which were heavily infected in my case. He said loss of taste and smell is common with serious viral infections. Doc said that recovery of taste and smell could take a year or more and might never fully recover. After one year taste and smell have still not fully returned.

The flu-like symptoms recurred on my second trip to Italy in September of last year although at a much milder level. This probably affected my recovery of taste and smell. Interestingly, on both trips my wife did not get visibly sick.

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[*] posted on 10-7-2020 at 20:53


my sense of smell is already very weak to begin with (could be the reason why i like esters so much), maybe it can't get much worse.



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