TEGDN

     TEGDN, an acronym for triethylene glycol dinitrate, is a nitrated ester chemically similar to nitroglycerin, although far more stable. Other names include 2,2'-[1,2-ethanediylbis(oxy)]bis-ethanol dinitrate; 2,2-ethylenedioxydiethyldinitrate; triglykoldinitrat; dinitrate de triethyleneglycol; and TEGN. It is commonly used in rocket propellants as an energetic plasticizer to increase burning rates and to keep solid propellant formulations plastic and flexible at varying temperatures and to prevent cracking and shrinking. It is also used in explosive compositions for the same reasons and to improve the safety of such compositions. TEGDN is a liquid at room temperature, and while it can be detonated by itself, it is only used in admixture with other explosives because it is so insensitive. In fact TEGDN does not detonate unless strongly confined. TEGDN is stable at room temperature and can be stored for extended periods. It is very toxic and can be absorbed through the skin or inhaled as vapors. Toxic symptoms are similar to nitroglycerin, i.e. bad headaches.

CHEMICALS	APPARATUS
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     Synthesis 1: Prepare a mixture of 66 g of 98% sulfuric acid and 37.8 g of 66.6% nitric acid in 120 mL of dichloromethane; cool this mixture to 0 C in an ice bath. Slowly add, with vigorous stirring, 15 g of triethylene glycol at such a rate as to keep the temperature between 0 C and 2 C. Continue stirring for 15 minutes after the addition, and then stop stirring to allow the layers to separate. Decant off the top layer of product and add it to a separatory funnel. Wash the solvent solution by shaking with three 20 mL portions of water followed by one 50 mL portion of water. There should be no trace of acid, but if there is wash the product layer by shaking with a portion of 10% sodium carbonate solution. The solvent can be removed on a rotary evaporator, or by gently warming on a water bath at 60 C. Final yield of TEGDN is a little over 23 g or 97%. The remaining acid layer (primarily sulfuric acid) can be quite unstable, but with cautious heating the sulfuric acid may be recovered. Heat the acid very slowly to boiling over a period of several hours to decompose any remaining product and unreacted reagent, which boils off along with water. Synthesis 2: Prepare a mixture of 150 g of 98% sulfuric acid and 257 g of 98% nitric acid in 1000 mL of dichloromethane; cool this mixture to 0 C in an ice bath. Prepare a second mixture of 150 g of triethylene glycol in 300 mL of dichloromethane. Slowly add, with vigorous stirring, the glycol mixture to the acid mixture at such a rate as to keep the temperature between 0 C and 2 C. Continue stirring for 15 minutes after the addition, and then add 24.5 mL of water. Stop stirring to allow the layers to separate. Decant off the top layer of product and add it to a separatory funnel. Wash the solvent solution by shaking with three 100 mL portion of water, and then a fourth portion of 100 mL of aqueous ammonium hydroxide solution. The solvent can be removed on a rotary evaporator, or by gently warming on a water bath at 60 C. Final yield of TEGDN is around 98-99%. The remaining acid layer (primarily sulfuric acid) can be quite unstable, but with cautious heating the sulfuric acid may be recovered. Heat the acid very slowly to boiling over a period of several hours to decompose any remaining product and unreacted reagent, which boils off along with water. Synthesis 3: In a 100-mL beaker prepare a nitrating acid mixture consisting of, by weight, 60 parts nitric acid, 40 parts sulfuric acid, and 5 parts water. Pour 30 parts of the mixed acid in a separate beaker along with 60 parts of dichlorofluoromethane*. In yet another beaker prepare a mixture of 13 parts of triethylene glycol and 50 parts of dichlorofluoromethane*. Cool the contents of both of the beakers containing the solvent to 8 C in a salt-ice bath. Carefully pour one of the beakers into the other with considerable stirring. After all the chemicals have been mixed the reaction only needs a few minutes to go to completion. A reaction temperature no higher than 11 C should be maintained because the solvent will evaporate off. Stop stirring a let the reactants settle. Two layers will separate consisting of an upper solvent layer containing TEGDN and a lower spent acid layer. Place the mixture in a separatory funnel and drain off the lower acid layer. The solvent layer should be placed in another beaker and the acid added to the separatory funnel. Extract any remaining TEGDN from the acid by drowning with an excess of water; a small amount of TEGDN should separate. The solvent portion should be washed by shaking with a 20 parts of water, 20 parts of 4% sodium carbonate solution, and another 20 parts of water. The solvent is now allowed to evaporate, either by gently heating or aspiration, and only TEGDN remains. Final yield of TEGDN is about 15 parts, or 74%. * The particular choice of solvent for this reaction does not have to be dichlorofluoromethane. A suitable alternative solvent must be a hydrocarbon with at least half of the hydrogens replaced by halogens, and at least one halogen must be fluorine. The solvent must have a low boiling point, typically between 10 and 30 C. Such solvents are available OTC as refrigerant at stores that sell automotive supplies. Synthesis 4: Since TEGDN is often mixed with other explosive materials this particular synthesis involves a way of conitrating an additional material, trimethylolethane, to make trimethylolethane trinitrate (TMETN). Prepare a mixture of 258 g of trimethylolethane, 104 g of triethylene glycol, and 117 mL of water; the mixture should be warmed to 51 C. Prepare a second mixture of (by weight) 50% nitric acid and 50% sulfuric acid totaling 1733 g. The acid should be 98-100% concentration and should be cooled to 0 C in an ice bath. Mix the acid very slowly and with cooling as it will produce substantial heat. With vigorous stirring slowly add the glycol mixture to the acid at such a rate as to keep the temperature between 0 C and 20 C. It is important to keep the temperature below 20 C, if it rises above 25 C the explosive products will decompose. Continue stirring for 10 minutes after the addition is complete, and then stop stirring to allow the layers to separate. The oily (top) layer of product can be decanted from the (lower) acid layer and added to a beaker. Wash the product by stirring with 500 mL of water for 30 minutes followed by removal of the water, and then stir the product with 500 mL of 10% sodium carbonate solution for 1 hour. Again remove the aqueous layer to obtain an acid free mixture of TEGDN and TMETN. Final yield is a little over 600 g. It is possible to recycle the spend acids by distilling off the nitric acid at low pressure, and then heating the sulfuric acid at a high temperature to drive off the water. Only a small amount of final product remains in the acid mixture which is decomposed upon heating and the byproducts are removed when the sulfuric acid is boiled.

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