Page 243 - Demo

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Disposal Procedures
#1a OrganicAcidHalidesand Acid Anhydrides
Chemical Disposal Procedures
241
FLINN METHOD
3
Slowly add a few milliliters or grams of the acid halide or anhydride to the container while constantly stirring. You can tell the decomposition reaction is occurring when the material begins to dissolve. The evolu- tion of gaseous carbon dioxide should also be evident.
4
If a noticeable temperature rise is observed, place the container in an ice-water bath.
5
Continue slow addition of the acid derivative while stirring until all the compound has been consumed.
Products in this class readily react with water, amines, and alcohols. They are also generally corrosive and their vapors are lachrymators. Acid halides and acid anhydrides may be RCRA listed and/or charac- teristic wastes due to their reactivity or flammability. Leftover organic acid derivatives remaining in an experiment may be hydrolyzed to water-soluble products of low toxicity that can be flushed down the drain. The reactions are exothermic; immerse the reaction vessel in ice water to control the heat.
Examples
Adipoyl chloride and acetic anhydride
Materials Required
Large glass or polyethylene container
Saturated solution of sodium carbonate (200 g Na2CO3/L) Stirring rod
Hydrochloric acid, HCl, 3 M
pH paper
Ice-water bath (optional)
Overview
Acid halides and acid anhydrides are reacitve derivatives of carboxylic acids. These substances react with water to form the original organic acid or its conjugate base in basic solution. Excess acid halide or acid anhydride remaining in a reaciton mixture may be decomposed with saturated sodium carbonate solution. The acid anhydride or acid halide reacts with water, and the products of that reaction, which are acidic, immediately react with sodium carbonate to form a salt of the acid. Most carboxylic acid salts are innocuous and may be flushed down the drain. Gaseous carbon dioxide is also produced, also forms, which will produce a fizzing as the reaction proceeds. The reaction of acetic anhydride proceeds as follows:
(CH3CO)2O + H2O → 2CH3COOH
2CH3COOH + Na2CO3 → 2NaCH3COO + CO2 + H2O
Note that one mole of sodium carbonate is required to fully neutral- ize one mole of the original acid halide or acid anhydride. To push the reaction to completion, a twofold molar excess of sodium carbonate is recommended. At 25 °C, a saturated sodium carbonate solution contains about 2 moles of sodium carbonate per liter of solution. Sodium hydroxide solution (2 M) may be substituted for saturated sodium carbonate in this procedure.
Both adipoyl chloride and sebacoyl chloride contain two chlorine atoms per molecule. Use a fourfold molar excess of sodium carbonate solution to hydrolyze these compounds.
Procedure
1
Perform this procedure in a fume hood. Wear chemical splash goggles, chemicals-resistant gloves, and a lab coat or chemical-resistant apron.
2
Place a saturated solution of sodium carbonate in a large glass or plastic container.
pH Paper
6
When a clear solution has been obtained, cool it to room temperature and neutralize to pH 7 with 3 M hydrochloric acid.
7
3M HCl
Flush the neutral mixture down the drain with a 20-fold excess of water.
Please...Read the Narratives
Important narratives precede these specific chemical disposal methods! Please read each narrative carefully! Do not use these procedures if you are not comfortable with the chemistry. Do not use these procedures without first consulting with your local government regulatory officials. These procedures may not be used in some jurisdictions. All procedures involve some hazards and risks. Once again...read the narratives that precede these specific chemical disposal methods.
Ice and Water