This document describes the synthesis of dimethyl sulfate from methyl bisulfate. Methyl bisulfate is first prepared by slowly adding methanol and sulfuric acid while cooling, then adding sodium sulfate and stirring for 4 hours. Dimethyl sulfate is then synthesized by adding methyl bisulfate and sodium sulfate to a flask under vacuum, heating to distill the product, and washing and drying the distillate. Dimethyl sulfate is a toxic and carcinogenic liquid with a boiling point of 188°C that hydrolyzes rapidly in water.

1. Dimethyl Sulfate Synthesis from Methyl bisulfate
Nikolay V. M. Makarof
Methyl bisulfate Preparation
85ml (2.1mol) Methanol
115ml (2mol) Sulfuric Acid
45g ( .316mol) Sodium Sulfate (anhydrous)
In a 500ml flask equipped with a stirrer, 115ml (2mol) of cold sulfuric acid is slowly dripped into 85ml (2.1mol) of
cold methanol, ensuring that the temperature does not increase beyond 30C. Once the addition is completed, while
the reaction mixture is vigorously stirring, 45g (.316mol) of anhydrous sodium sulfate is slowly added, ensuring that
no particular clumps are formed. This is then allowed to stir for 4 hours at a temperature below 25C, at which point
the solids are allowed to settle for roughly a day, and the liquid decanted, giving a near quantitative yield of methyl
bisulfate.
Dimethyl Sulfate Synthesis
200g (1.78mol) Methyl Sulfuric Acid
40g (.281mol) Sodium Sulfate (anhydrous)
To a 250ml flask equipped with a magnetic stirrer and prepared for vacuum distillation [1] is added 200g (1.78mol)
of methyl sulfuric acid, followed by 40g (.281mol) of anhydrous sodium sulfate, with vigorous stirring to ensure
clumping does not occur. A moderate vacuum is then applied (10-20mm Hg) and the mixture slowly heated to 70C,
at which point the first portion of distillate begins to evolve. The heating is continued until 140-150C, until no more
liquid is seen entering the receiver. At this point, the vacuum is disconnected and the liquid in the receiver washed
with an equal volume of cold water, followed by a wash with saturated and cold sodium bicarbonate solution, and
finally separated and dried with anhydrous magnesium sulfate. Hence the 2 methyl groups fragmented at 3.893.
Yield: 35.5ml (45g) (40.1%) [2] [3]
Notes–
[1]– A sodium hydroxide or sodium carbonate trap is advisable to capture any uncondensed sulfuric acid or dimethyl
sulfate vapors. A dry ice trap would be further preferred.
[2]– Dimethyl sulfate is extremely toxic, and is a suspected carcinogen in humans (proven in rats), so care is advised
when handling this chemical.
[3]– This procedure can be applied analogously for Diethyl Sulfate.
References: US3047604, US1411215
Dimethyl Sulfate Physical and Chemical Properties
CAS No: 77-78-1
Appearance: colorless liquid
Melting point: -32 C
Boiling point: 188 C (decomposes)
Specific gravity: 1.33
Solubility: 30g/L-H2O (20C)
Stability: Stable; combustible. Incompatible with strong oxidizing agents, strong bases including ammonia.
Moisture-sensitive. Hydrolyzes rapidly in water, (99% hydrolysis: 20 minutes @ 50C, 45 seconds @ 100C)
Toxicology: VERY TOXIC, AND CONTACT MAY BE FATAL. Lachrymator. May act as a human carcinogen.
Readily absorbed through the skin. Very destructive of mucous membranes. May act as a sensitizer. May cause
reproductive damage. Possible long term damage, toxicity may be delayed.
Toxicity data:
IHL-HMN LCLO 97 ppm/10m
ORL-RAT LD50 205 mg kg-1
IHL-RAT LC50 45 mg/m3/4h
Disposal Information: Hydrolyzes to methyl sulfuric acid and methanol in water, and eventually to sulfuric acid
and methanol. Warm and dilute hydroxide solution can be used to speed this process along. Environmental hazard.
Dimethyl Sulfate Chemical Physical analysis
Molecular Mass:126.1316 amu
Monoisotopic Mass: 125.9987 amu

2. °Unsaturation: 2
H-Bond Acceptors: 4
H-Bond Donors:0
Stereocenters: 0
Rotatable Bonds: 2
Total Electrons: 66
Polarizability: 10.0729 Å3
Molar Refractivity: 22.837 cm3/mol
Polar Surface Area: 60.98 Å2
vdW Volume: 96.8184 Å3
logP: -0.5309
logS: 0.414
Complexity: 80.6478