Dimethyl sulfoxide (DMSO) is a dipolar aprotic solvent widely used in chemical industry and academic research. It is inherently less toxic and can be oxidized to dimethyl sulfone or reduced to dimethyl sulfide in the human body and is metabolized and excreted in urine and feces. However, in some cases, DMSO poses a safety risk, may explode or cause damage to the human body, and special attention should be paid to assessment in the following cases:
Thermal decomposition of pure DMSO: Pure DMSO is stable at room temperature, but it will decompose at high temperatures and may explode. Differential scanning calorimetry (DSC) evaluation showed that the decomposition of pure DMSO was detected at about 278°C when tested in a nitrogen atmosphere. Accelerated calorimetry (ARC) shows that thermal decomposition can occur near the boiling point of 189°C.
Acidic conditions: The presence of acidic substances will cause DMSO to decompose at lower temperatures, which may trigger autocatalytic decomposition, resulting in uncontrolled or even explosive.
Under alkaline conditions: Strong bases can convert DMSO into effective methylating agent dimethyl ions, which may be violently exothermic and have the risk of explosion. For example, an explosion accident occurred when DMSO was processed with NaH to prepare dimethyl ions.
In the presence of halides: Halides will reduce the initial temperature of DMSO decomposition, increasing potential safety hazards. Such as alkyl bromide, KBr, NaBr, KF, FeCl3, hexachlorocyclotriphosphazine, Br2/HBr, cesium fluorosulfate, symmetrical dichlorobenzyl (2,4, 6-trichlorophenyl) urea, halomethyl ketone and DMSO contact may be dangerous.
In the presence of metals and metal salts: Metals and metal salts may catalyze the thermal decomposition of DMSO, raising safety concerns.
In the presence of electrophilic reagents: electrophilic substances can activate DMSO for various oxidation transformations, and it reacts violently with electrophilic reagents, such as cyanuryl chloride, acetyl chloride, benzoyl chloride, benzene sulfonyl chloride, thionyl chloride, phosphoryl chloride and phosphorus trichloride. The chloride ions formed during the reaction may also catalyze the thermal decomposition of DMSO, leading to uncontrolled reaction or even explosion.
When oxidizing agents are present: DMSO reacts violently with oxidizing agents such as periodic acid and perchloric acid, which may lead to explosion. Other oxidants such as nitrogen dioxide, metal chlorate, metal permanganate, etc., will also react violently with DMSO, bringing safety risks.
In the presence of reducing agents: the reduction of DMSO to dimethyl sulfide by some reducing agents may be violently exothermic, and if the heat release rate exceeds the heat removal rate, there is a safety risk.
When using DMSO, safe operation procedures should be followed to avoid the danger caused by its decomposition. For example, it is necessary to control the temperature, avoid contact with the above-mentioned substances that can promote its decomposition, and operate in a well-ventilated environment. In case of DMSO leakage, personnel in the contaminated area should be evacuated to the safety zone, isolated, cut off the fire source, and treated in accordance with emergency treatment methods.
