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Ester Experiments :)

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here`s a thread for any Curious Chemists that want to try a little bit of Organic chem, the idea is to make and share recipes for Esters and TRY to describe the smells if you can.

 

I`ve just had a go myself and made Ethyl Benzoate, it smells almost good enough to eat!

 

simply 5ml of 100% Ethanol (it should work with the 95% too), added to Benzoic Acid (I added roughly half a T`spoon (or 2 spatulas) and then 4 drops of Conc Sulphuric acid.

interestingly the benzoic acid dissolves in the ethanol 100%, but when you add the sulphuric (esp in one spot) a white solid forms but then dissolves again? :)

 

next gently heat it, when the vapor starts to rise and condense half way up the test tube, Stop and let it cool, you can do this a few times if you like, I find it gets a little stronger each time.

 

when cool, get a bowl of cold water, and dump the test tube contents into it, then have a sniff.

this particular Ester smells a bit like some sort of wild Mint plant with perhaps and underscore of Liquorice?

 

try it yourselves as let me know what you think, and also add your own "recipe" in this thread too :)

 

Let`s make a HUGE collection of them, I recon this should be alot of fun!

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I'm curious on whether esters are dangerous if consumed directly ?

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some are, some are not.

many of the "artificial" flavorings and scents are Ester based, they occur naturaly in plants also, Cherry Cola or soda will probably contain a man made Ester for instance, and have Nothing at all to do with a REAL Cherry ever ! :)

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Most easy ester to synthesise is probably ethyl acetate. If smell is all that is desired one can use almost any acetic acid (including 6%), some drops of sulfuric acid (battery acid is ok) and some vodka instead of ethanol. If mixture is heated there will soon be smell of ethyl acetate. Be cautious though - never bend over hot liquid. Sudden boiling may occur and you may get all this onto your face.

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Synthesis of Methyl salicylate (oil of wintergreen) from aspirin and methanol:

 

Step 1: Saponification of acetylsalicylic acid

Extract acetylsalicylic acid from a ground up aspirin tablet using acetone. Prepare a strong solution of NaOH and disolve the acetylsalicylic acid in it. Heat to a boil for about 2 minutes, then cool to room temperature. This will saponify the acetylsalicylic acid (an ester itself) to produce salicylate and acetate.

 

Add an ice-cold solution of dilute HCl to protonate the salicylate and precipitate it from solution. Collect the solid (salicylic acid) and dry well.

 

Step 2: Fischer esterification of salicylic acid and methanol

Disolve the salicylic acid from part 1 in methanol, then add a catalytic amount of conc. sulfuric acid. Heat to produce methyl salicylate. If you want to isolate the methyl salicylate, remove the salicylic acid by extracting with cold aqueous base (so the base does not promote hydrolysis of the ester), dry with a drying agent, then distill off the methanol (bp =64.6C) from the methyl salicylate (bp = 220 - 224C). What remains should be colorless, yellowish or reddish oily liquid.

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wat do u mean by saponification in this instance and fischer reaction?

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btw ehtyl aceatte smells kinda like pear. if u really concentrate can smell a relation ship. smeel a pear, then the ethyal aceate. but ya. itr smells just like nail polish remover. anyone kno any other fruity esters? liek grape or soemtin i can make that woodent be too hard?

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Both terms are just names of reaction mechanisms:

 

A saponification is the base-catalyzed hydrolysis of an ester, forming a carboxylate (deprotonated carboxylic acid) and an alcohol.

 

A Fischer esterification is the acid-catalyzed condensation reaction between a carboxylic acid and an alcohol which produces an ester.

 

Here's a list of some different esters and their smells:

 

Isoamyl acetate - banana oil

Ethyl butyrate - pineapple

Isobutyl propionate - rum

Octyl acetate - orange

Methyl anthranilate - grape

Isopentenyl acetate - "Juicy Fruit"

benzyl acetate - peach

n-propyl acetate - pear

methyl butyrate - apple

ethly phenylacetate - honey

methyl salicylate - oil of wintergreen

2-phenyl ethyl propionate - lily flower

 

Note that isoamyl acetate (IUPAC: 3-methylbutyl ethanoate) is also the alarm pheromone for honey bees.

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I`m glad you added that last bit of info! I don`t think I`ll bee making any of That in a Hurry :)

 

I`m going to try and see if Glycerine (Glycerol) and Benzoic acid forms anything interesting, I`ve no idea what it would be called though? 1-2-3 propan triol + benzoic?

it Is an alcohol, so it Should work :)

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Another easy to make (and isolate) ester is the "inorganic" ester methyl nitrite.

 

Mix 1 part of methanol with 5 parts of dilute acid (e.g. 10% HCl or H2SO4) and add some solid NaNO2 or KNO2. You'll get a lot of bubbles of a colorless gas. This is mainly methyl nitrite, CH3-O-NO

 

Do not breathe the gas mix too much. As a side reaction there may be some NO-gas and that it VERY toxic, you also will breathe some methanol vapors, which are not good as well. If you light the ester-gas, then it burns with a green/gray flame, really nice to see that. If you have a mix of the gas and air (I did not determine the precise ratio), then you can see the green/gray flame move slowly into the test tube, until it reaches the surface of the liquid. Really cool to see this.

 

Higher nitrite esters can also be made in this way easily (e.g. from butyl- or allyl alcohol). These are liquids, which can be extracted with ether and then purified by letting the ether evaporate.

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so not all the acids have to be COOH (organic) to make an ester then?

 

well I tried the Glycerol and benzoic, it`s a problem at 1`st to get the benzoic to dissolve in the glycerol, but heating sees to that, there was a Faint smell, but not enough to identify, I think I`ll reflux it next time.

I did the Ethyl Acetate synth, I quite like the smell, buy the wife said it made her want to be sick and she Doesn`t like it, the Ethyl Benzoate she does like, but recons it smells "Medical", funny how people interpret these smells differently :)

 

I can see I need to stock up on OLs and ATEs as I`m running out of ideas, I`ll try some Citrates when I get a little more time :)

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so not all the acids have to be COOH (organic) to make an ester then?

No, not at all. A very well known ester is nitroglycerin. The name of this compound is very confusing, because it is not a nitro-compound (with -NO2 attached directly at a carbon atom), but a nitrate-ester.

 

So a better name would be glycerine-trinitrate. The formula of this triple ester is CH2(ONO2)CH(ONO2)CH2(ONO2). It can be produced by an esterification reaction between glycerin and HNO3, with H2SO4 as added compound to take away any water formed in this reaction.

 

well I tried the Glycerol and benzoic, it`s a problem at 1`st to get the benzoic to dissolve in the glycerol, but heating sees to that, there was a Faint smell, but not enough to identify, I think I`ll reflux it next time.

I did the Ethyl Acetate synth, I quite like the smell, buy the wife said it made her want to be sick and she Doesn`t like it, the Ethyl Benzoate she does like, but recons it smells "Medical", funny how people interpret these smells differently :)

To my opinion the smell of most esters is not that pleasant at all. They all have a very "chemical" smell. What makes natural flavors so attractive is the subtle mix. Pure ethylacetate does not smell fruity to me, it is the mix of ethylacetate with lots of other compounds, which make it fruity.

 

I can see I need to stock up on OLs and ATEs as I`m running out of ideas, I`ll try some Citrates when I get a little more time :)

You can have endless variations....

Citrates may work, but do not expect much smell from these. The molecule is so large that it is not sufficiently volatile anymore to perceive any smell.

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aha! I never considered NG to be an ester, but now you present it THAT way, of course it is! :)

and would certainly explain the lovely Lemony smell it has (if you can ignore the headache afterwards).

so adopting the same naming convention the glycerol and benzoic acid, would become Glycerine tribenzoate then?

 

and bTw, I actualy like the smell of all the esters produced so far :)

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Another very easy ester.

 

I droped into test tube one tablet of nonfizzing aspirin, some milliliters of 80% ethanol and some milliliters of battery acid. After heating during twenty minutes on hot water bath mixture developed strong smell. It smells even now rather good and not like ethyl acetate.

 

After standing some hours on cool place there appeared nice needlelike crystal on bottom of test tube. I do not know what it was. Maybe unreacted aspirin. And ester... I do not know. Probably ethyl salicylate.

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sounds like you have a good combo of 2 different esters there, undoubtedly it`ll smell pleasant (well it prolly would to me anyway).

I rem seeing similar Crystals form in an erlinmeyer flask some time ago when using aspirin pure (the buffer agent was removed in methanol and filtered).

these needle like crystals would form on the inside of the flask towards the neck area and would sometimes "Reach" across this void and connect to the other side, I used to get rid of them as they were just "Junk" and not part of that particular Synth, I always assumed they were Acetic Acid crystals, I`ll stand corrected if someone says/shows otherwise though :)

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how would you go about making Isoamyl acetate?

 

What would be the organic molecules with a carboxylic functional group that yields isoamyl acetate?

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no, that would be acetic acid

 

he asked "carboxylic functional group " and that would be COOH

 

What are you saying "NO" to?

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"What would be the organic molecules with a carboxylic functional group that yields isoamyl acetate?"

 

is the quote. he's basically asking what the acid is that reacts to form isoamyl acetate. he wasnt asking what the carboxyl group is

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so any esters to make other than the ones already said? how bout orange or banana?

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how would you go about making Isoamyl acetate?

 

What would be the organic molecules with a carboxylic functional group that yields isoamyl acetate?

 

React isoamyl alcohol (a.k.a. isopentyl alcohol or 3-methylbutan-1-ol) with acetic acid (a.k.a ethanoic acid).

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