Sciencemadness Discussion Board

Ester hydrolysis

Priest - 24-1-2008 at 22:55

Hi!
SWIM got some Phenylacetic acid ethyl ester this week and asked me if he could break the ester up with a strong lye...

vulture - 25-1-2008 at 13:59

How about UTFSE and typing "ester hydrolysis" into google?

chemrox - 26-1-2008 at 00:00

@vulture et al., what is "UTFSE?" I've always wanted to know (for six months or so anyway).

12AX7 - 26-1-2008 at 00:19

Dur, UTFSE!!!! :rolleyes:

http://www.google.com/search?q=utfse

A tip: www.acronymfinder.com and www.urbandictionary.com are your two most important language resources on the 'net.

Tim

chemrox - 1-2-2008 at 19:27

Indeed! Thanks.

solo - 7-6-2008 at 16:23

I have a question ...on the hydrolysis of phenyl ethyl acetate....the product would be an acid and an alcohol....as in all hydrolysis of esters, some claim that it would yield phenylacetic acid and an alcohol.....how can that be.....once the salt is treated with the acid ...

C6H5CH2-CH2-O-C(O)-CH3 +NaOH------> CH3-C(O)-ONa + C6H5-CH2-CH2-OH---->RX--H2SO4----->

CH3-C(O)-OH + C6H5-CH2-CH2-OH

.............I see no Phenylacetic acid....what did I miss? (puzzled)....solo

MagicJigPipe - 7-6-2008 at 17:09

Because I think they mean the following:

C6H5-CH2-C(O)-O-CH2-CH2 + NaOH

That should technically be called "ethyl 2-phenylacetate".

Yours would be called "2-phenylethyl acetate" which, as you stated, should produce 2-phenylethanol and sodium acetate.

Technically, only one of these should be of much use to a certain group of individuals. Guess which one...

I woudn't mind having some phenylacetic acid to mess around with, though, if it weren't so damn risky to possess.

[Edited on 6-7-2008 by MagicJigPipe]

solo - 7-6-2008 at 17:22

Ok right, I missed the CH3...so it should read not as you suggest,


C6H5CH2-CH2-O-C(O)-CH2-CH3 +NaOH------> CH3-C(O)-ONa + C6H5-CH2-CH2-OH---->RX--H2SO4----->

CH3-C(O)-OH + C6H5-CH2-CH2-OH

........let's deal with the question at hand, not with your intuitive insights of precursors....solo

Klute - 7-6-2008 at 17:44

You've still got sodium acetate and 2-phenylethanol there..

C6H5-CH2-C(O)-O-CH2CH3 --NaOH--> C6H5-CH2-COO-Na+ + CH3-CH2-OH

I think a hour or two reflux with 10% excess base in ethanol/H2O mixture would be just fine... The recation could be folowed by TLC, and the formed phenylacetate should be too sensitive to excess base, even with heating.

Is phenylaectic acid a solid? If it isn't too soluble in water, you could even distill off EtOH/water until reaching H2O's bp, and then cool and acidify with conc. acid to precipiatte the phenylacetic acid..
If your ester is pur enough, there wiouldn't much needed is recrystallizing the phneylacetate,a s any trapped abse would be neutralized by the acid, and even after acidifying a recrysatllized phenylacetate, you will still have sodium/potassium sulfate/chloride to remove, so you would better be off purifying the acid if it is more practical (distn?).

I guess the ester must smell nice, I'ev heard the acid itself is pretty bad smelling!

solo - 7-6-2008 at 18:22

---Is phenylaectic acid a solid?

.........yes

my bad...I read it wrong ....the ester is Ethyl 2-phenylacetate (ethyl phenyl acetate) not phenylethylacetate no wonder it didn't make sense......thanks Klute, Edit and MagicJigPipe I thought I was loosing it....and it seems after being exposed to the NaOH in excess, to make sure all the ester is used up, it does make the the phenylacetic salt which later RX with H2SO4 will precipitate the phenylacetic acid , which is then filtered and washed several times with clean water and put to dry.....yields are usually in the high 90%, I think the sulfate and potassium salts remain in the water , so no need to purify, is there any concern about moisture and the sensitivity of the carbonium in the phenylacetic acid when RX with the other elements in the Dakin West Reaction (i.e. acetic anhydride, sodium acetate) ? so that the phenylacetic acid should be completely dry before using?.......solo





[Edited on 7-6-2008 by solo]

MagicJigPipe - 7-6-2008 at 18:27

The issue at hand is which chemical someone is more likely to be talking about. It is relative to note that it would be the ethyl ester of phenylacetic acid.

Actually, you are incorrect. "C6H5CH2-CH2-O-C(O)-CH2-CH3" would be 2-phenylethyl propanoate which would yield sodium propanoate and PhEtOH. THIS IS IN RESPONSE TO YOUR RESPONSE TO ME. YOU (ACCIDENTLY?) PUT AN ESTER OF PROPIONIC ACID.
EDIT
This was to be posted 2 posts up. Apparently 2 people posted before I was done typing this. Solo, I basically said the same thing yet you say, "Thanks Klute". That is very disrespectful. Is there a problem?
....
Okay, I was wondering what solo's problem was (I tried to settle this through PM but for some reason he has me blocked) but I figured it out. Damn, these Willy Daisies hold on to anger and grudges as long as women...

[Edited on 6-7-2008 by MagicJigPipe]

solo - 7-6-2008 at 18:30

As stated in my last post , I was wrong, ....so let's move on.....solo

Edit


"........let's deal with the question at hand, not with your intuitive insights of precursors"

Sounds sarcastic to me. Anyway, I'm going to have to assume that to be the case if/until I get an answer.


........no you're right it is sarcasm.....solo

[Edited on 7-6-2008 by solo]

solo - 4-8-2008 at 13:01

Quote:
Originally posted by Klute
You've still got sodium acetate and 2-phenylethanol there..

C6H5-CH2-C(O)-O-CH2CH3 --NaOH--> C6H5-CH2-COO-Na+ + CH3-CH2-OH

I think a hour or two reflux with 10% excess base in ethanol/H2O mixture would be just fine... The recation could be folowed by TLC, and the formed phenylacetate should be too sensitive to excess base, even with heating.

Is phenylaectic acid a solid? If it isn't too soluble in water, you could even distill off EtOH/water until reaching H2O's bp, and then cool and acidify with conc. acid to precipiatte the phenylacetic acid..
If your ester is pur enough, there wiouldn't much needed is recrystallizing the phneylacetate,a s any trapped abse would be neutralized by the acid, and even after acidifying a recrysatllized phenylacetate, you will still have sodium/potassium sulfate/chloride to remove, so you would better be off purifying the acid if it is more practical (distn?).

I guess the ester must smell nice, I'ev heard the acid itself is pretty bad smelling!



Actually the phenylacetic acid will precipitate out and the other salts will stay in solution ..... sodium sulfate will be washed off y soaking the phenylacetic acid in water a couple of times then allowing it to dry well before use.

Note: As a point of interest ...all the esters of acetate , the methyl , ethyl propyl and many more will produce the phenylacetic acid via hydrolysis and the respective alcohol, be it methyl ethyl propyl....etc.

kmno4 - 4-8-2008 at 15:04

Ethyl phenylacetate hydrolyses quickly (2-3 hours) in excess of 20% NaOH under reflux. No TLC is needed, just layer of ester disappears completely in the end of reaction.
To reduce time of reaction, small (10%) amount of any alcohol can be added - it increases solubility of ester.
Interesting - isopropyl phenylacetate reacts much slower with NaOH.
Both: ethyl and isopropyl ester possesses honey like smell. Personally, I feel associations of this smell with some kind of candies :)