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Texium
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Esters!
Hello everyone, I decided to start a general thread about esters, because they are lovely things, and so simple to make.
First off, my favorite infographic on the subject:
I've made a few esters at home before (methyl salicylate, ethyl salicylate, ethyl acetate, isopropyl acetate), although I'm rather limited by my
reagents. Today in AP Chemistry class though, we had an ester party, where we spent all class making a ton of different esters. We had methanol,
ethanol, 1-propanol, isopropanol, 1-butanol, 1-pentanol, benzyl alcohol, and 1-octanol available for alcohols, and formic, acetic, propanoic, butyric,
and salicylic acids available for carboxylic acids. I was so excited! As such, I tried making a lot of the more interesting looking esters from the
table that I could access today. A review of them follows...
n-propyl salicylate: Sort of minty but muddled
n-butyl salicylate: The !STRONG! blackberry smell noted in the table was very disappointing. It emulated the smell of Expo marker almost perfectly.
Benzyl salicylate: Something weird happened: an orange precipitate formed in the test tube, and there was no perceived smell after heating for a while
Benzyl propanoate: Floral, fruity, not unpleasant
Benzyl butyrate: subtle and fruity, very nice
n-octyl formate: Hints of grapefruit, but kind of detergenty, like a grapefruit scented soap or other cleaning product.
n-pentyl acetate: The classic super intense banana laffy-taffy smell.
n-pentyl propanoate: Very pleasant peach smell with notes of banana
I may be able to try a few more over the next couple of weeks, but I'm not sure. Anyway though, just thought I'd share that and open up the
discussion.
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aga
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Cool ! Nice table.
My next forray into OC will definitely be another esterification, simply because the change of smell is a good sign that something happened.
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papaya
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Could you describe how did you isolate pure esters ? You mention synthesis being "easy" however without proper equipment all you can isolate is the
smell, not bulk product.
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diddi
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you only need basic o-chem glassware for most.
Beginning construction of periodic table display
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Texium
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Quote: Originally posted by papaya  | | Could you describe how did you isolate pure esters ? You mention synthesis being "easy" however without proper equipment all you can isolate is the
smell, not bulk product. |
I just said that the synthesis is easy, not the isolation. For the ones that we did
at school, we did not isolate the pure esters. It was just a qualitative lab where we made test-tube scale amounts of a lot of different esters to
smell. If I was making them at home, I'd do it larger scale with a nice reflux apparatus and either do a distillation or a solvent extraction to try
and isolate the pure ester, like I did when I made methyl salicylate at home.
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Amos
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| Quote: Originally posted by papaya | | Could you describe how did you isolate pure esters ? You mention synthesis being "easy" however without proper equipment all you can isolate is the
smell, not bulk product. |
It's not really all that difficult to isolate them, generally. Generally, the procedure is, once you've boiled off most of the alcohol you've used as
a solvent, the mixture can be dumped into water, where the ester forms a separate layer. It can then be washed with base and with saturated sodium
chloride to remove acid and excess water, respectively, and distilled. So all that's really needed is distillation equipment and a separatory funnel.
[Edited on 5-9-2015 by Amos]
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Texium
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As long as your yield of the ester is high enough that is. If you don't do it on a large enough scale, you won't get a cohesive layer in the
separatory funnel, just a bunch of little bubbles.
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blargish
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Really neat chart! I've only really made made methyl salicylate myself and didn't bother to isolate the product...
Definitely an area of chemistry that I want to delve into in the future!
BLaRgISH
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DraconicAcid
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We do a similar lab at our college, where we make iso-amyl acetate and methyl salicylate (along with aspirin and nylon). The iso-amyl acetate
(3-methylbutyl acetate) smells strongly of artificial banana.
I've tried to do my own "ester party" and make a whole bunch of random esters the same way, but nothing ever works. Now I've got a condenser, I can
do it right and isolate them (like I did with the methyl cinnamate). Just need to find the time.
[Edited on 9-5-2015 by DraconicAcid]
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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blogfast25
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Very nice chart, zts16! (any chance of formatting it a bit better?)
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gdflp
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One thing though, it's missing isopropyl esters! Other than that, nice chart.
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Pumukli
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And now I lost another illusion. Until looking at the chart above I tought that a given ester has a fairly unique smell. But look at those apples and
green leaves and bottles! Seemingly unrelated esters share the same smell! I thought that if I smelled something like e.g. banana then I could
identify the compound as a fairly pure isopentyl-acetate. Now it seems I can't save on a gas chromatographe. :-) (Which would otherwise be a handy
item in my shed.)
Shouldn't "benzanoate" be benzoate?
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Texium
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Thanks! Although I must say, I did not make that chart, it's just something that I found upon looking up "ester smells table." It came from here. The creator of the site made some other nice infographics also. I suppose it would be possible to create a modified, expanded version that
is more detailed, with his permission. I don't see any copyright stuff anywhere, though I think it would still be polite to ask him first.
The lack of isopropyl esters is definitely the first thing that jumps out.
| Quote: Originally posted by Pumukli | And now I lost another illusion. Until looking at the chart above I tought that a given ester has a fairly unique smell. But look at those apples and
green leaves and bottles! Seemingly unrelated esters share the same smell! I thought that if I smelled something like e.g. banana then I could
identify the compound as a fairly pure isopentyl-acetate. Now it seems I can't save on a gas chromatographe. :-) (Which would otherwise be a handy
item in my shed.)
Shouldn't "benzanoate" be benzoate?
|
Many of the esters that have the same picture on the chart actually smell rather different from one
another. The chart simplifies it, to give you a rather vague idea of what the esters smell like, but they're still quite unique. And yes, it should be
benzoate. 
[Edited on 5-10-2015 by zts16]
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Etaoin Shrdlu
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Okay guys, does ethyl formate really smell like rum? People keep insisting that to me and on the occasions I've smelled it I always without fail got a
strong impression of apple. (Maybe I should start drinking?)
Also, propyl acetate. Pear or not pear? I know it's supposed to be pear. It's supposed to be quintessential pear. But it just smells horrid
to me, even in small quantities. Horrid in a way that makes me understand what people mean when they say they can't stand organic solvents.
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Texium
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| Quote: Originally posted by Etaoin Shrdlu | | Also, propyl acetate. Pear or not pear? I know it's supposed to be pear. It's supposed to be quintessential pear. But it just smells horrid
to me, even in small quantities. Horrid in a way that makes me understand what people mean when they say they can't stand organic solvents.
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I agree. It's pretty terrible. When diluted a lot, it smells a bit more like pear, but still really harsh
and fake smelling. The least offensive fruity ones that I smelled the other day were benzyl butyrate and pentyl propanoate.
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DraconicAcid
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I can't even tell what some of those pictures are supposed to be. What kind of flower is that? Is that some sort of spice?
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Etaoin Shrdlu
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| Quote: Originally posted by DraconicAcid | | I've tried to do my own "ester party" and make a whole bunch of random esters the same way, but nothing ever works. Now I've got a condenser, I can
do it right and isolate them (like I did with the methyl cinnamate). Just need to find the time. |
If you just want to smell them, mix approximately equimolar amounts of the alcohol and acid in a small test tube, add a few drops of concentrated
sulfuric acid, then stuff the top with paper towel or otherwise loosely cover it to prevent rapid evaporation and let sit in a water bath at ~80C for
~30 minutes. Dump the contents of the test tube into a beaker with 10-20 times the volume of saturated bicarbonate solution. This will neutralize
leftover carboxylic acid so it doesn't contribute to the smell. The alcohol is usually much less strongly scented than the ester, and some gets mopped
up by the water so you can get a good idea of the smell by wafting over the beaker. It's a good way to try a whole bunch of different ones at once,
and works especially well for the stronger ones.
zts, if you're interested in berry smells, isobutyl formate is a great raspberry.
EDIT: The ambiguous flower is jasmine. The kind of flowery kind of seedy looking thing is star anise.
[Edited on 5-10-2015 by Etaoin Shrdlu]
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Texium
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Really the 30 minutes aren't even necessary. When we did it at school it took maybe 10 minutes max to be able to clearly distinguish the smell of the
ester. I hadn't thought about doing the bicarbonate wash before smelling them, that's a good idea. (Especially with butyrates!)
And I would have made isobutyl formate, but we don't have isobutanol at school  I
love raspberries.
Edit: Wait a minute, it's n-butyl formate that has the raspberries according to the chart. I think I will try making some of that at school when I get
a chance.
[Edited on 5-10-2015 by zts16]
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DraconicAcid
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That's pretty much what I did, and I never managed to get it to work with the combinations I tried. No idea why it didn't go, when the methyl
salicylate and isoamyl acetate work perfectly that way for the students. Maybe my lack of a green thumb applies to floral scents in addition to
flowers.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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DraconicAcid
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I did manage to make (but not isolate) methyl vanillate (my students oxidized vanillin to vanillic acid a few years ago, and I still had some kicking
around). Smelled a lot like nutmeg.
I've tried two esters this week, and adding ice-cold sodium carbonate gives a homogeneous mixture. I didn't think the ester would hydrolyze that
quickly when cold.
ETA: Stupid! I needed to use sodium BIcarbonate!
[Edited on 12-5-2015 by DraconicAcid]
[Edited on 12-5-2015 by DraconicAcid]
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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smaerd
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Ooo fun esters . I have some nice alcohols which could be turned into carboxylic
acids if I felt like dealing with dichromate. Hmmmm hmm hmm. Maybe I'll join in on some of the fun. Put my dean stark and molecular sieves to use.
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Etaoin Shrdlu
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Basic permanganate can take primary alcohols to carboxylic acids, if you don't feel like dealing with dichromate.
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DraconicAcid
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Methyl benzoate smells rather minty.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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blogfast25
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| Quote: Originally posted by DraconicAcid |
ETA: Stupid! I needed to use sodium BIcarbonate!
[Edited on 12-5-2015 by DraconicAcid]
[Edited on 12-5-2015 by DraconicAcid] |
Methinks you merely used too much carbonate. Calculate how much is needed and add it more slowly and alkaline de-esterification should not occur, I
think. Bicar is fine too, of course.
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Firmware21
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Has anyone tried to synthetize Isopropyl Salicylate ? I tried it recently, but couldn't isolate the product (Using wet solvent and overshooting either
Sulfuric acid and sodium carbonate didn't help very much I guess).
it still had a very uncommon "green-scent" which now perfumes my leibig condenser. I might try it again if I manage to get my hands on anhydrous IPA.
[Edited on 28-8-2015 by Firmware21]
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