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Author: Subject: Preparation of Diethyl Sulfate
Magpie
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[*] posted on 7-12-2017 at 08:28
Preparation of Diethyl Sulfate


December 7, 2017

A. Introduction

This preparation follows the method of Lynn and Shoemaker (ref1).

2C2H5OH + H2SO4 --→ (C2H5)2SO4 + 2H2O

Na2SO4 is added to the pot as a dehydrating agent.

B. Reagents
90g anhydrous Na2SO4
50g 95% ethanol
104.5g conc sulfuric acid
Na2CO3

C. Equipment

2-neck 1-L rbf (the “pot”)
distillation tapered glassware
hotplate
thermocouple (or suitable thermometer)
vacuum pump (or aspirator)
p-e funnel
oil bath
separatory funnel

D. Procedure

a. Reaction/Distillation

Caution: Diethyl sulfate is reputed to be poisonous when vapors are inhaled or the liquid is absorbed through the skin. Provide adequate ventilation and wear gloves.

1. Setup the equipment for simple distillation using the 1-L rbf as pot.
2. Add 90g anhydrous Na2SO4 to the pot.
3. Pour 50g of the 95% ethanol in a beaker and cool in an ice bath.
4. Slowly add 104.5g of conc H2SO4 to the ethanol while cooling in the ice bath.
5. To the side neck of the pot attach the p-e funnel.
6. Pour the ethanol/acid mix into the p-e funnel.
7. In the center neck of the pot affix the thermocouple, or thermometer (See Note 1 below.)
8. Place the apparatus under full vacuum (≤ 45 mmHg).
9. Heat the oil bath to about 180°C. The goal is to bring the pot to 155°-165°C. (See Note 2 below.)
10. Add the ethanol/acid mix at 120-150 drops/minute. Distillate will collect at 2-3 drops/s.
11. Add all of the ethanol/acid dropwise. Distill until no more distillate accumulates.

diethyl sulfate preparation.JPG - 149kB
Photo 1: equipment set-up

utilities for diethyl sulfate preparation.JPG - 193kB
Photo 2: utilities

b. Separating, Washing, & Drying
1. Separate the distillate using a separatory funnel into diethyl sulfate and ethanol. The density of diethyl sulfate is 1.17 so it will be the bottom layer.
2. Wash the diethyl sulfate with dilute Na2CO3.
3. Separate and wash the diethyl sulfate twice with water.
4. Separate, saving the diethyl sulfate and discarding the wash water. See note 3.
5. Place the ~30 mL of diethyl sulfate in a flask and add a scoop of anhydrous Na2SO4. Cap and set aside to dry.
6. Filter the diethyl sulfate and weigh for yield.

E. Results

My yield was 32.7g. Lynn & Shoemaker obtained 32.6g. %yield on ethanol is 41.1%.

F. Discussion

My first attempt to make diethyl sulfate was a miserable failure (see above, in a separate thread) due to inadequate equipment. More importantly, I may have mixed up the diethyl sulfate layer with the dilute Na2CO3 layer during the washing step.

G. References
1. “The Laboratory Preparation of Diethyl Sulfate,” by EV Lynn & HA Shoemaker, January 3, 1924,
[Contribution from the Research Laboratory, Eastman Kodak Co, No. 199], Seattle, WA. See photos of paper here:






Notes
1. If a thermometer is used assure that it can be read in the 155°-165°C range.
2. My pot temperature never came up to 155°C until the very end of the distillation. This was due to clumping of the Na2SO4.
3. Distinguishing the diethyl sulfate layer from the dilute Na2CO3 layer can be tricky. Use the drop sink/float test. Density of diethyl sulfate is 1.17.

Comments, questions, and suggestions are welcomed.



[Edited on 7-12-2017 by Magpie]

[Edited on 7-12-2017 by Magpie]

Lynn & Shoemaker diethyl sulfate paper.JPG - 159kB Lynn & Shoemaker diethyl sulfate paper, p.2.JPG - 126kB

[Edited on 7-12-2017 by Magpie]

[Edited on 7-12-2017 by Magpie]




The single most important condition for a successful synthesis is good mixing - Nicodem
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DJF90
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[*] posted on 7-12-2017 at 11:40


Nice work Magpie. If you have the paper perhaps you could attach it to your post for convenience (although I think I am familiar with it). What is your %th yield?
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Magpie
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[*] posted on 7-12-2017 at 13:09


Quote: Originally posted by DJF90  
Nice work Magpie. If you have the paper perhaps you could attach it to your post for convenience (although I think I am familiar with it). What is your %th yield?


Thanks, Dan. I added the paper and the %yield to the original post on edit. I don't have a scanner. Hope you can read the paper.




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[*] posted on 8-12-2017 at 03:17


Magpie, the reference for the paper is JACS 1924 46 (4) pp. 999 to 1001. I've attached it as a .pdf for convenience.

Attachment: ja01669a023.pdf (65kB)
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[*] posted on 8-12-2017 at 14:11


Nice write up and very important for OTC preparation of sulfuric ether (diethyl ether) :):D

Just some side notes...
Side products coud be:
==> CH3-CH2-O-SO2-OH thus a partial sulfuric ester
==> CH2=CH2 (ethene) and H2SO4/H2O if the heating is slightly too high.

[Edited on 8-12-2017 by PHILOU Zrealone]




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Magpie
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[*] posted on 10-12-2017 at 08:28


Quote: Originally posted by PHILOU Zrealone  
Nice write up and very important for OTC preparation of sulfuric ether (diethyl ether) :):D

Just some side notes...
Side products coud be:
==> CH3-CH2-O-SO2-OH thus a partial sulfuric ester
==> CH2=CH2 (ethene) and H2SO4/H2O if the heating is slightly too high.

[Edited on 8-12-2017 by PHILOU Zrealone]


Thank you PHILOU. In review I feel that I did not know my true temperature because the Na2SO4 clumped around the thermometer bulb. When I get my stepper motor mixer operating I will repeat this synthesis. I have Ba(OH)2 on order and will also do an assay of the product. I urge caution to others who may wish to repeat this synthesis until I can report my assay results.

Do you happen to know the temperature range in which CH3-CH2-O-SO2-OH is produced?




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[*] posted on 23-12-2017 at 13:40


Quote:
Na2SO4 is added to the pot as a dehydrating agent.

Of course, Na2SO4 cannot serve as dehydrating agent in this case, because all its hydrates are stable only below 40 C.
It must be a component in this reaction, generating (in situ) some salts.
This procedure works, but not because Na2SO4 can dehydrate anything under given conditions.

Edit:
Literature reseach gives interesting information about given reaction, it is said that hydrogen ethyl sulfate reacts with Na2SO4 under vacuum and heating, giving diethyl sulfate and double salt Na2SO4•NaHSO4.
So indeed, it has nothing to do with dehydration :P

[Edited on 27-12-2017 by kmno4]




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[*] posted on 12-1-2018 at 21:02


On December 7, 2017 I attempted to make phenetol using the procedure in Brewster. This method uses phenol and diethyl sulfate. The synthesis was a failure, casting doubt on whether or not I had actually made diethyl sulfate.

I was hoping I could find the error and make a correction in my procedure for diethyl sulfate but I have not had a chance to get to this in the alloted time of one month.

Therefore, I will pursue this further when I get my overhead stirrer repaired, soon I hope.




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[*] posted on 12-1-2018 at 21:10


The smell is pretty tell-tale... Some say peppermint, I say candy shop... But it is hard to mistake. You didn't re-distill it, did you?

Edit: I know it's a known occupational carcinogen and one shouldn't go around breathing large amounts of it, but does one occasionally produce small amounts of it when making other things, such as ether for example. I don't imagine it is as bad a thing as some people fear, like benzene in my opinion. I try to breathe as little as possible, but somewhat enjoy it.

[Edited on 1-13-2018 by happyfooddance]
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[*] posted on 13-1-2018 at 06:27


I did not redistill it. I have an excellent sense of smell and smelled only a trace of peppermint.

The synthesis of phenetole was a failure. I will try to make the DS again.




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[*] posted on 13-1-2018 at 11:15


I'm thinking addition of a Dean-Stark type apparatus here could improve yield, by returning the unreacted ethanol to the boiling flask, and allowing continuous removal of the product as it condenses.



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[*] posted on 13-1-2018 at 11:19


Quote: Originally posted by PirateDocBrown  
I'm thinking addition of a Dean-Stark type apparatus here could improve yield, by returning the unreacted ethanol to the boiling flask, and allowing continuous removal of the product as it condenses.


It would be hard or maybe impossible to keep the ethanol condensing and not the product, as the b.p. of ethanol is about 120°C below that of diethyl sulfate.
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