Diazomethane cautions

Diazomethane. CAUTION. Diazomethane is very toxic its preparation should be carried out only in a fume cupboard (hood) provided with a powerful exhaust system. The use of a screen of safety glass is recommended. 

Procedure Pass 10 ml of urine through a cation-exchange resin column (Dowex 60-W-X4, 20-50 mesh, in the hydrogen form) and wash the column with 30 ml of distilled water. Elute the amino acids with 20 ml of concentrated ammonia solution. Evaporate this eluate to dryness in vacuo. To the residue add 1 ml of trifluoroacetic anhydride and 0.5 ml of trifluoroacetic acid, and allow the mixture to stand at room temperature for 20 minutes. Remove excess reagents with a stream of air and treat the oily residue with an ethereal solution of distilled diazomethane (DANGER Poisonous-explosive) for 15 minutes. Remove excess diazomethane (CAUTION ) with a stream of air. Dissolve the residue in methanol and inject a suitable aliquot part into the gas chromatograph. Figures 25 and 26 show results obtained by this procedure. 

Methylation of carboxylic and phenolic hydroxyl groups with diazomethane. Preparation of an ethereal solution of diazomethane. Caution Diazomethane is extremely toxic and explosive, and all operations should be conducted in a well-ventilated hood behind a safety screen. 

CAUTION Carry out the preparation in an efficient fume cupboard (hood) since diazomethane is very toxic. 

Cyclic hydroxamic acids and V-hydroxyimides are sufficiently acidic to be (9-methylated with diazomethane, although caution is necessary because complex secondary reactions may occur. N-Hydroxyisatin (105) reacted with diazomethane in acetone to give the products of ring expansion and further methylation (131, R = H or CH3). The benzalphthalimidine system (132) could not be methylated satisfactorily with diazomethane, but the V-methoxy compound was readil3 obtained by alkylation with methyl iodide and potassium carbonate in acetone. In the pyridine series, 1-benzyl-oxy and l-allyloxy-2-pyridones were formed by thermal isomeriza-tion of the corresponding 2-alkyloxypyridine V-oxides at 100°. 

Reaction with alcohols is general for diazo compounds, but it is most often performed with diazomethane to produce methyl ethers or with diazo ketones to produce ot-keto ethers, since these kinds of diazo compounds are most readily available. With diazomethane the method is expensive and requires great caution. It is used chiefly to methylate alcohols and phenols that are expensive or available in small amounts, since the conditions are mild and high yields are obtained. Hydroxy compounds react better as their acidity increases ordinary alcohols do not react at... 

Diazomethane In a distillation flask equipped with an distillation funnel and a cooler, place a solution of 5 g of potassium hydroxide in 8mL of water and 25 mL of ethanol. Warm the distillation flask to 65 °C in a water-bath. Add a solution of 21.5g (0.1 mol) of A-methyl-lV-nitroso-p-toluenesulfamide in 130 mL of diethyl ether through the instillation funnel in 5 min. If the distillation funnel becomes empty, pour 20 mL of diethyl ether into the funnel, and distill it gradually. Continue distillation until the distilled ether solution becomes colorless. About 3 g of diazomethane is contained in the whole resultant ether distillate. Caution these procedures should be conducted in a laboratory hood Orbencarb, methyl 2-chlorobenzylsulfone (I), 2-chlorobenzoic acid (II), methyl 2-chlorobenzoate analytical standard materials (Ihara Chemical Industries Co., Ltd) Orbencarb and I standard solution for gas chromatography 1.0 qgmL in acetone Methyl 2-chlorobenzoate standard solution for gas chromatography 0.1 qgmL" in n-hexane... 

Caution Diazomethane is both explosive and poisonous, and all operations involving its preparation and use must be carried out in a hood. Follow the directions for its handling given in earlier volumes.2,3... 

CAUTION Diazomethane is explosive (sharp edges trigger it) and poisonous, so avoid ground glass joints, chipped glassware, etc. 

Caution Diazomethane shouid be handled in an efficient fume hood behind a protection shield because of its toxicity and the possibility of explosions. 

Caution Diazomethane is very toxic therefore the operations must be carried out in a well-ventilated hood. 

Caution Diazomethane is toxic and explosive. The operation must be carried out in a good hood with an adequate shield (.see Note 1) ... 

Caution It is extremely important that the flask contents be cooled to at least 0°. The reaction is rapid and a considerable amount of diazomethane is generated at this temperature. 

Phenyldiazomethane, 1, 834. A new method for preparation of this (and other aryl-diazomethanes) involves a vacuum pyrolysis of the sodium salt of benzaldehyde tosylhydrazone, a method introduced for carrying out the Bamford-Stevens reaction. The yield is 80%, the highest yield yet reported. Another advantage is that the reagent is obtained free from solvents. The pyrolysis can also be coitducted in ethylene glycol at 80° with extraction of the aryldiazomethane into hexane.1 Caution All diazo compounds arc highly toxic and potentially explosive. 

B. Diazomethane. Sodium isopropoxide method (Note 9). CAUTION... 

CAUTION Diazomethane is highly toxic and irritating. It is also a detonator and appropriate safety precautions and procedures should be used when handling this reagent (e.g., special glassware, blast shield, well-ventilated fiime hood, etc.). 

CAUTION Diazomethane is a detonator and is highly toxic. Appropriate safety precautions should be taken when using this reagent. 

CAUTION Diazomethane is a very toxic gas keep under a fume hood. 

Caution Diazotnelkane is hazardous. Follow the directions Jor safe handling of diazomethane given in earlier volumes. 3 All operations are carried out in a hood. 

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