Sciencemadness Discussion Board

Easy to make aromatic esters

VestriDeus - 4-2-2010 at 20:07

Does anyone know any reactions for some safe, easy to make (nice-smelling) aromatic esters?

Especially notable ones like such as Ethyl formate, or other things like that?
Like making notably known smells such as certain distinct fruit/flower smells (berries, cinnamon, vanilla, etc.)

User - 5-2-2010 at 03:14

Benzoic acid is sometimes used for esters and its easy to obtain.
You could try the ethyl/methyl or more complex alcohols.
I dont remember how they smell must have been a couple of years ago.
I do remember that they have a very "new" smell like seeing something for the first time, kinda nice.

Also take a look at salicylic acid.
(search for aromatic carboxylic acids, there are plenty of those :) )

Nicodem - 5-2-2010 at 05:10

Ethyl formate is not an aromatic ester. Please read some basic organic chemistry book to understand the basics.

Methyl salicylate is the only aromatic ester that I know of as having a pleasant smell (http://en.wikipedia.org/wiki/Methyl_salicylate). Methyl benzoate and other benzoates do not smell much of anything to me. Methyl vanillate is listed as having a vanilla odor. para-Anisyl acetate and some others are also supposed to have some odor. Search
this list for other aromatic esters used in flavouring and/or having pleasant odor. There are structural formulas added, but still, you will first need to learn which structures are aromatic and which not.

> Moving to Beginnings section.

DJF90 - 5-2-2010 at 06:37

I think the OP means aromatic as in "aroma"...

Nicodem - 5-2-2010 at 11:07

Ups, sorry, that other meaning completely escaped my mind. :D
The spectrum of pleasant smelling esters widens quite a bit in if aromaticity is not an requirement.

bahamuth - 5-2-2010 at 11:50

Last year we had a class with new curriculum and one of the labs involved was making esters, but those in the book was boring and not very distinct, so I, another lab tech and an apprentice sat down and made about 50-60 different esters. Not in any large scale, just test tube trials...

Can you imagine three people sitting in the opening of the fume hood sniffing esters and trying to decide what they smell..., the way we did that was soaking a piece of paper tissue and passing it along; back & fourth, deciding the overwhelming smells.

After about half a work day with this, the laughter and the bad jokes was running loosely...

Rest of the day was ruined for all of us, major headaches...



The ting is, before we set out upon this ester journey, we made a chart of the different esters we would make, to keep track; and as we sniffed our way through these wondrous smells we made notes of their character.

Will post them on Monday when i get to work, if I remember....

Some smelled really good, like the one, pear in low conc. and something quite different in high conc. Ethyl pentanoate I think it was. And isoamyl acetate; banana smell.



Now when I come to think of it my memory is...., ehh, esters yes, my memory is a little off...that is, esters.....mmm..

VestriDeus - 5-2-2010 at 15:04

Quote: Originally posted by Nicodem  
Ups, sorry, that other meaning completely escaped my mind. :D
The spectrum of pleasant smelling esters widens quite a bit in if aromaticity is not an requirement.


Ya, i kinda wasnt thinking of the technical definition when i posted, but more of smells. It doesnt need to have benzenes or anything; it just needs to smell good.

Sandmeyer - 5-2-2010 at 15:27

Quote: Originally posted by VestriDeus  
Quote: Originally posted by Nicodem  
Ups, sorry, that other meaning completely escaped my mind. :D
The spectrum of pleasant smelling esters widens quite a bit in if aromaticity is not an requirement.


Ya, i kinda wasnt thinking of the technical definition when i posted, but more of smells. It doesnt need to have benzenes or anything; it just needs to smell good.



actually it does not have to smell good or pleasant either...

entropy51 - 5-2-2010 at 15:42

Quote: Originally posted by Sandmeyer  
actually it does not have to smell good or pleasant either...
Original post:
Quote: Originally posted by VestriDeus  
Does anyone know any reactions for some safe, easy to make (nice-smelling) aromatic esters?

some esters

mnick12 - 5-2-2010 at 15:53

Well I have worked quite a bit with esters in the last few months and I have mad quite a few. Most of the esters I made were esters of benzoic acid, and since you may be interested I will describe the aroma as best as I can. The first two I made were ethyl and methyl benzoate, made from 5gr of the carboxylic acid and 20ml of the alcohol along with 3ml of sulfuric acid, then reflux for 2 hrs pour into water and separate the ester from the unreacted benzoic acid. Both the ethyl and methyl ester smelled strongly of mints, but the ethyl ester smelled a little bit fruity.

The other ones I made were propyl, isopropyl, and n-butyl benzoate. They were made the same way and all of them smelled nice, the propyl smelled like cherries at a low concentration but at a higher one like gross cough syrup(Yuck!. The butyl ester smelled similar to pears but also kinda cherrish. And finally the isopropyl ester this was by far my favorite one, it smelled alot like pears and very sweet also it didnt really have that chemical-ish smell that some of the others had.

So I hope this helps you out, and sorry for any gramattical errors I am in a huge hurry

VestriDeus - 6-2-2010 at 16:44

Quote: Originally posted by mnick12  
Well I have worked quite a bit with esters in the last few months and I have mad quite a few. Most of the esters I made were esters of benzoic acid, and since you may be interested I will describe the aroma as best as I can. The first two I made were ethyl and methyl benzoate, made from 5gr of the carboxylic acid and 20ml of the alcohol along with 3ml of sulfuric acid, then reflux for 2 hrs pour into water and separate the ester from the unreacted benzoic acid. Both the ethyl and methyl ester smelled strongly of mints, but the ethyl ester smelled a little bit fruity.

The other ones I made were propyl, isopropyl, and n-butyl benzoate. They were made the same way and all of them smelled nice, the propyl smelled like cherries at a low concentration but at a higher one like gross cough syrup(Yuck!. The butyl ester smelled similar to pears but also kinda cherrish. And finally the isopropyl ester this was by far my favorite one, it smelled alot like pears and very sweet also it didnt really have that chemical-ish smell that some of the others had.


Thank you very much!:). Is there a temperature i should heat it at (cause i'm afraid of the alcohols catching on fire), or is there any chemical that i can use as a catalyst?

(Still looking for more recipes though:D)

mnick12 - 6-2-2010 at 18:34

Ah well now that I have some time I will try do a little better explanation, and answer your questions. Allow me to elaborate on how I made these esters. For the reflux I used a 250ml rbf, a 200cm condensor, and a teflon stopper( glass works to). The reflux setup was put in an oil bath on a hotplate, then heated until the alcohol boiled ( depends which one you use) no tempurature was taken I simply made sure the alcohol was boiling well. After two hours I let the mix cool and poured it into a beaker with around 150ml of tap water, once you do this two things will happen first the ester will form as a pale yellow liquid, and any unreacted benzoic acid will precipitate out of the solution. So after this happens you simply need to separate the two I find doing a vaccum filtration and washing the filtrate a few times helps to separate the benzoic acid from your ester. After that I just separate the ester using a seperatory funnel.

To answer your question about catalysts:
There a seriously hundreds of catalysts that have been used in some of the more obscure esterifications, but for a simple esterification like the ones I described you need nothing more than a few % of conc sulfuric acid. But if you do not want to use H2SO4 I hear p-toluenesulfonic acid is sometimes used, but thats a little harder to get and besides sulfuric acid is dirt cheap.

So I hope my explanation helped a little, and If you have any more questions feel free to ask. Also if I get the chance, and if your interested, next weekend I will do an esterification and take some pictures.
Have fun!

bahamuth - 6-2-2010 at 18:59

Sulfuric acid is for me the best "catalyst" for estrification of simple esters.

But remember to have an excess of the alcohol, since it usually smells the least and you get a better picture of the ester without doing some purification...

If you want a pure ester you have to have an excess of acid, reflux for a long time, and wash it with a bicarbonate to make the acid go with the water phase(separatory funnel), dry it with MgSO4 or similar and distill it...

This is just as i find it convenient if I wat to make some Ethyl pentanoate e.g.


Different separation methods exists so just google it, alot of howtos is out there.

ester synth

mnick12 - 13-2-2010 at 17:16

Ah as promised I did an ester synthesis with pics.

The ester I chose to make was n-propyl benzoate, I made it using the procedure I explained in my other two posts except instead of 20ml of alcohol I used 15ml, but they are essentialy the same in every other way. The propanol was 98%, the benzoic acid lab grade, and the sulfuric acid technical grade.
One more thing normally I like to reflux for at least 1 or 2 hrs, but I was in a pinch so I had to do 50min.



reflux setup.jpg - 35kB
This is everything in the flask ready to reflux.



finished reflux.jpg - 35kB
This is the mix after 55mins of refluxing, notice the yellowish color.



ester.jpg - 31kB
And here is the ester separating from the first wash with tap water, you can see some of the benzoic acid clouding the ester.

I am unsure of what the final yield was, but if I had to guess I would say around 5 grams of cherry-peary smelling liquid. I am sorry I do not have any pictures of the washed and dried product, I just don't have that kind of time!
Anyway I hope you all enjoy these pictures, and if you have any questions feel free to ask me.

Jor - 13-2-2010 at 17:35

How did you purify the ester? I would think you should wash the organic layer with sat. NaHCO3-solution, until no more CO2 evolves. Then dry the organic layer with MgSO4, filter, and distill the propyl alcohol, leaving the ester (wich you can purify even more by vaccuum distillation if you want).

mnick12 - 13-2-2010 at 22:34

I did not make any real attempt to purify the ester. I simply washed it twice with tap water then once more with distilled water. I am not to concerned with the purity as I simply made this for fun, and at the moment have no further use for the ester other than its nice smell. Also I have not neutralized the solution yet so I will do that when I get the chance. Oh I like the idea of distilling the propanol off since I could then use it again or in other reactions.
Thanks for the ideas.

bahamuth - 14-2-2010 at 07:53

Here, as promised, a chart of the different esters we made and smelled on.

Far from complete, as I aim someday to have all the simpler esters smelled on and described.
This list was only limited by only having a few alcohols and carboxylic acids.



Attachment: Esters and their smells.xlsx (10kB)
This file has been downloaded 2549 times

chemrox - 15-2-2010 at 00:09

I'm confused by the photo showing the condenser with what appears to a teflon stopcock part or teflon stoper. Surely you didn't run the reax with the condenser plugged up like that. It could be misleading to someone learning the basics.