Dimethyl sulfoxide, caution

A mixture of the epoxide ca. 5 mmol), sodium azide (6 g, activated by the method of Smith) and 0.25 ml of concentrated sulfuric acid in 70 ml of dimethyl sulfoxide is heated in a flask fitted with a reflux condenser and a drierite tube on a steam bath for 30-40 hr. (Caution carry out reaction in a hood.) The dark reaction mixture is poured into 500 ml of ice water and the product may be filtered, if solid, and washed well with water or extracted with ether and washed with sodium bicarbonate and the water. The crude azido alcohols are usually recrystallized from methanol. 

Liimsyl anion3 was prepared from 10.2 g. (0.24 mole) (Note 10 of 56.8% sodium hydride, which was washed with pentane and vacuurr dried, and 200 ml. of anhydrous dimethyl sulfoxide. The mixture was heated at 65-70° for about 50 minutes, until hydrogen evolution ceased. Caution This mixture should not be heated above 80°, because of the possibility of explosive decomposition. 

Dimethyl Sulfoxide [DMSO] (Rimso-50) [GU Agent] Uses Interstitial cystitis Action Unknown Dose Intravesical, 50 mL, retain for 15 min repeat q2wk until relief Caution [C, ] Contra Component sensitivity Disp Soln SE Cystitis, eosinophilia, GI, taste disturbance Interactions -1-Effects OF sulindac EMS May cause garlic/onion taste in mouth OD Acute effects unlikely... 

Caution. Concentrated hydrobromic acid is corrosive, volatile (fumes in air), and toxic. Diethyl ether, diglyme, dimethyl formamide, and dimethyl sulfoxide are flammable and toxic. Triphenylphosphine oxide is toxic. Use safety gloves and goggles, avoid inhalations of vapors and dust, and conduct all operations in a well-ventilated hood far from ignition sources. 

Dimethyl sulfoxide decomposes violently when in contact with a wide range of acyl halides and related compounds, such as cyanuric, acetyl, benzoyl, benzenesulfonyl, thionyl, and phosphoryl chlorides and PC13- DMS should be used with caution as a solvent in exploratory reactions... 

Caution Dimethyl sulfoxide is raidly absorbed through the skin. Wash off spills with water. Wear disposable gloves when shaking the apparatus. 

C. 9-Thiabicyclo[3.3.1]nonane-2,6-dione (3). (Caution Oxalyl chloride and dimethyl sulfoxide are reported to react explosively at room temperature. Preparation C should be carried out in a well-ventilated hood since a co-product of the reaction is dimethyl sulfide). To a 1-L, three-necked flask equipped with a magnetic stirring bar, low temperature thermometer, dropping funnel protected from moisture by a drying... 

We may even have access to an NMR tube washer, a device available from vendors of chemical laboratory equipment. If possible, we use high-performance liquid chromatography (HPLC) or spectroscopy ("Spec") grade water or acetone for the final rinse. We never use dimethyl sulfoxide (DMSO) for the final rinse unless we are immediately going to reconstitute our sample in DMSO, because the low vapor pressure of DMSO prevents its evaporation. Caution we always wear gloves when working with DMSO. If our solute/DMSO solution comes in contact with our skin, the DMSO will transport our solute direcdy through our skin into our bloodstream. 

CAUTION Although no difficulties have been experienced in our laboratory, care must be taken when heating sodium hydride in dry dimethyl sulfoxide, as there have been rejjorts of violent explosions when the anion was prepared on a large scale [28,29]. The amounts of the base and of the halide should be in more than 50% excess over the number of equivalents of replaceable hydrogen atoms. 

A note on partial molar properties In case you are beginning to wonder why there are so many questions and problems about concentrations I will answer by telling you that you need concentrations in about four out of every five problems in physical chemistry. The matter of fact is that a lot of chemistry and all of biochemistry takes place in solutions. Then there are problems inherent to solutions. Solutions are considered simple physical mixtures of two or more different kinds of molecules, with no chemical bonds made or broken. For a really well-behaved solution physical chemists have a name, by analogy with the gas laws an ideal solution. Yet solutions are actually complicated systems whose molecular nature we are only now beginning to understand [1, 2, 3, 4]. Two solvents, when mixed, often release heat (or absorb heat) and undergo change in volume. Think of a water sulfuric acid (caution]) mixture or a water DMSO (dimethyl sulfoxide) mixture. After the solvent mixture equilibrates you will find that its volume is not equal to the sum of the volumes of the pure solvents (it is usually smaller). In physical chemistry we treat these problems by using the concept of molar volume, V. Molar volumes are empirical numbers - they are determined by experimental measurements for different solvent compositions. Read the next problem. 

Dimethyl sulfoxide (DMSO) has a high dielectric constant and is an excellent aptotic solvent for nucleophilic substimtion reactions. DMSO readily penetrates the skin, and any compound dissolved in DMSO is carried with it across the skin. Hence, great caution is required when this compound is used as a solvent. 

I CAUTION See notes at the beginning of this chapter on the hazards in handling sodium cyanide. Dimethyl sulfoxide should also be handled with caution. This solvent is readily absorbed through the skin, carrying with it some impurities which may be present on the skin (e.g., residual soap), leading to physiological reactions. The solvent is also said to reduce the sensation of pain. Test animals have exhibited reactions in their eyes upon treatment with DMSO. 

CAUTION Dimethyl sulfoxide has been reported to be easily absorbed through the skin and to then pass into the blood stream. Others have given some indication that skin irritation or bums and eye injuries may result from prolonged exposure to sulfoxides. Therefore, great caution should be exercised in handling and preparing sulfoxides since these compounds possess this great tendency of skin penetration. 

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