Sciencemadness Discussion Board

preparation of ethyl formate

antibody - 10-7-2011 at 12:03

I need to prepare a batch of ethyl formate for an experiment I'm planning. I am thinking of using the preparation cited in vogels;

Ethyl formate. Reflux a mixture of 61 g. (50 ml.) of A.R. formic
acid (98/100 per cent.) and 31 g. (39-5 ml.) of absolute ethyl alcohol for 24 hours. Transfer to a Claisen flask with fractionating side arm (or attach a fractionating column to the flask), distil and collect the liquid passing over below 62°. Wash the distillate with saturated sodium bicarbonate solution and saturate with salt before removing the ester layer. Dry with anhydrous sodium or magnesium sulphate, filter, and distil. The ethyl formate passes over at 53-54°. The yield is 36 g.

But coming up with anhydrous formic is going to be a challenge. None of my suppliers carry it. Can 88% formic be dehydrated to 98/100% with 3A seives?

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Another route that looks interesting is from A treatise on chemistry, Volume 3, Part 1 By Henry Enfield Roscoe, Carl Schorlemmer

A still more simple method is to heat anhydrous glycerin with equal molecules of alcohol and oxalic acid, connecting the flask with a reversed condenser until complete decomposition has occurred ; the oxalic acid then requires to be warmed and the ether distils over. The distillate obtained according to one or other of these methods is shaken up with milk of lime in order to remove free acid, and then dried over chloride of calcium and rectified.

According to Dittmar the product thus obtained is, however, not quite pure. In order to remove the impurities it must be warmed for some time with anhydrous copper sulphate and then distilled.

Oxalic acid and glycerine are easier for me to acquire, except there isn't much detail given about temperatures etc. and I'm not sure what exactly they mean by a "reverse" condenser. Any ideas?

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Another route I've looked is via Fisher esterification. It appears to be faster with the use of H2SO4. I've attached the ref. In it they don't specifically give a proceedure for ethyl formate, so I'm left with the question about whether the formic acid used needs to be anhydrous, but I suspect it does.

Could one get away with using 88% formic with lots of molecular seives or would the H2SO4 be sufficient to dehydrate the Rxn.

Any advise, experience or preferable proceedures would be greatly welcomed

Thanks
Ab2



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[Edited on 10-7-2011 by antibody]

turd - 10-7-2011 at 12:51

Ethyl formate is one of the easiest simple esters to make, because it does not form an azeotrope with water, has a low boiling point and doesn't need a catalyst. Unfortunately it does not have a decent smell. :(

Check out: E. C. Wagner, Journal of Chemical Education, 27, 245-247 (1950)
Quote:
Preparation of Ethyl Formate. B. p. 54°; sp. gr. 0.906 (20°/4°); solubility in water 11 per 100 at 18°. No azeotrope including this ester can be involved, and the azeotropes of ethanol-water and formic acid-water boil too high (78.1° and 107.3°, respectively) to interfere.

Use as reactants 12.5 g. of U.S. P. ethanol (15.4 ml.; 11.5 g. actual ethanol; 0.25 mole) and 17.8 g. of 88-90 per cent formic acid (14.9 ml.; 16.1 g. actual formic acid; 0.35 mole). As ethyl formate is volatile pack the space between the condenser outlet and the neck of the receiver with cotton, and throughout the experiment try to prevent undue-evaporation losses. Distillation begins at about 54°, and the entire yield of ester should boil in the narrow range 54-56°. When the temperature of distillation just exceeds 56° allow several additional drops of distillate to collect (drainage in the condenser) and then replace the first receiver by a 50-ml. Erlenmeyer flask (not weighed) and continue the distillation. The temperature rises steadily and finally reaches 106° or 107°, indicating that the liquid distilling is the azeotrope of formic acid and water (77.5:22.5; b. p. 107.3°; h. p. of anhydrous formic acid 100.8°). Compare the odors of the two distillates.

The 54-56° distillate is probably nearly pure ethyl formate, and if weighed it may prove to be over 90 per cent of the theoretical amount. Wash the ester with
two separate 2.5-ml. portions of saturated sodium chloride solution, drawing off and discarding the aqueous layers, and dry the ester using 2 to 2.5 g. of granular anhydrous magnesium sulfate. Distill the dried ester from a 50-ml. side-arm flask as a 1° fraction (54-55° corr.). The yield should be 11-13 g. (60-70 per cent).

I made ~250 ml of ethyl formate this way using 85% formic acid, absolute EtOH and a 20 cm Vigreux - it took a few hours since reaction is quite slow, but wasn't much work, just checking temperature from time to time. Dried over K2CO3 and fractionated from P2O5.

Thx

antibody - 11-7-2011 at 04:07

Thanks Turd! I'll give it a try with 88% formic.

simba - 11-7-2011 at 17:50

Quote: Originally posted by turd  
Ethyl formate is one of the easiest simple esters to make, because it does not form an azeotrope with water, has a low boiling point and doesn't need a catalyst. Unfortunately it does not have a decent smell. :(

Check out: E. C. Wagner, Journal of Chemical Education, 27, 245-247 (1950)
Quote:
Preparation of Ethyl Formate. B. p. 54°; sp. gr. 0.906 (20°/4°); solubility in water 11 per 100 at 18°. No azeotrope including this ester can be involved, and the azeotropes of ethanol-water and formic acid-water boil too high (78.1° and 107.3°, respectively) to interfere.

Use as reactants 12.5 g. of U.S. P. ethanol (15.4 ml.; 11.5 g. actual ethanol; 0.25 mole) and 17.8 g. of 88-90 per cent formic acid (14.9 ml.; 16.1 g. actual formic acid; 0.35 mole). As ethyl formate is volatile pack the space between the condenser outlet and the neck of the receiver with cotton, and throughout the experiment try to prevent undue-evaporation losses. Distillation begins at about 54°, and the entire yield of ester should boil in the narrow range 54-56°. When the temperature of distillation just exceeds 56° allow several additional drops of distillate to collect (drainage in the condenser) and then replace the first receiver by a 50-ml. Erlenmeyer flask (not weighed) and continue the distillation. The temperature rises steadily and finally reaches 106° or 107°, indicating that the liquid distilling is the azeotrope of formic acid and water (77.5:22.5; b. p. 107.3°; h. p. of anhydrous formic acid 100.8°). Compare the odors of the two distillates.

The 54-56° distillate is probably nearly pure ethyl formate, and if weighed it may prove to be over 90 per cent of the theoretical amount. Wash the ester with
two separate 2.5-ml. portions of saturated sodium chloride solution, drawing off and discarding the aqueous layers, and dry the ester using 2 to 2.5 g. of granular anhydrous magnesium sulfate. Distill the dried ester from a 50-ml. side-arm flask as a 1° fraction (54-55° corr.). The yield should be 11-13 g. (60-70 per cent).

I made ~250 ml of ethyl formate this way using 85% formic acid, absolute EtOH and a 20 cm Vigreux - it took a few hours since reaction is quite slow, but wasn't much work, just checking temperature from time to time. Dried over K2CO3 and fractionated from P2O5.


I'm not quite familiar with ethyl formate, but wiki says it has the smell of rum or raspberries...so how come these is not decent?

turd - 12-7-2011 at 11:20

Maybe a professional perfumist will recognize that ethyl formate is a contributor to the smell of rum and raspberries, but to my untrained nose it just smells like a run of the mill solvent. Maybe if you dilute it - apparently even skatole smells nicely after sufficient dilution. I wouldn't even have realized that the smells of rum and raspberries have something in common.

simba - 12-7-2011 at 17:31

From wikipedia:

Ethyl formate has the characteristic smell of rum and is also partially responsible for the flavor of raspberries.

And the source of the citation in wikipedia brings an even more unexpected fact than the relationship between rum and raspberry...

http://www.guardian.co.uk/science/2009/apr/21/space-raspberries-amino-acids-astrobiology

[Edited on 13-7-2011 by shivas]

Panache - 12-7-2011 at 19:37

Apparently the journalist hacked the phones of the scientists in involved to leak the crucial information.