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• • • GEORGIA INSTITUTE OF.TECHNOL OFFICE.OF RESEARCH ADMINISTRATION Complex Metal rides, High Energy Fuel Components for Solid - Project Title: Propellant Rocket Motors Project B-1520 (9_ Project Director: Dr.; R. C• Ashby* Officirof.Naral Research, Department:of the Na 28 February.- Agreement Period: From h. 1968" Type Agreement: Contract No Amount: - , - Scientific Mminietrator Pover- Brandh-' Material Scienceti,:rd.vision Office of NavaIliesearch Department -Of theijiavy. Washington, Contract an& Property Administrator Mr. R. J. Whitcomb Office of Naval. Research Resident Representative 103-104. Elactronics Research Building 0,2orgia InAituta of Technology- Ationta G,:rgia. 30332 School of Chemistry Assigned to: COPIES TO: n Project Director En Library -.-;- ri School Director EA1 Rich Electronic Computer Center- Dean of the College 11 Photographic Laboratory F-1 Administrator of Research EES Machine Shop n Associate Controller (2) EES AecounLaI, g ACC: ►onitcasb, ONE ER . Security-Reports-Property Office Mr. R. A.,-Martin fl Patent Coordinator RA-3 4/55) GEORGIA INSTITUTE OF TECHNOLOGY OFFICE OF RESEARCH ADMINISTRATION RESEARCH PROJECT TERMINATION Date: Une 4, 1)73 Project Title: Co;apla.x .:iyei:^1,.'-raf 3 •-o. J. Co onea LQ1.1:1 21-0,11:",--vrzt 4riotur°3 Project No: . G-33—LU3 rromerl„y — 15 20) Printipal Investigator: Dr. L.; Ptol'Iziy Sponsor: 'Ofric of Naval 2eaearch; Arlington, VA 2 2217 Effective Termination Date: 3 7/ /7 e e("vrr, neseim periogt Clearance of Accounting Charges: by 12/31/74 C, vant/Con ract Clo3aout Actiona Final Involae 11 1 3. ?inal 301';ort or Invantionu .7roprt:,7 Invvltory/ Cert. 4 3'..ontraat Jod. 11 deltato,i final r,”ovt; rfyluiremem; (t -o be part or re2ortil-4! arti:!,)r Jroject therey t4e Contract 27.-,721ratiQn ',late 12/31/Y ,nd r perfor= AZISIL':.i.i:1) '147501 A4 . COPIES TO: Principal Investigator Library, Technical Reports Section School Director Rich Electronic Computer Center Dean of the College Photographic Laboratory Director of Research. Administration Terminated Project File No. Associate Controller (2) Other Security-Reports-Property Office r•-- Patent_ and Inventions Coordinator RA-4 (51701 Annual Report to the Office of Naval Research March 1, 1968 to February 28, 1969 Complex Metal Hydrides. High Energy Fuel Components for Solid Propellant Rocket Motors from E. C. Ashby, Principal Investigator Georgia Institute of Technology, Atlanta, Georgia 30332 This Research was sponsored by the Office of Naval Research under Contract No. NO0014-67-A-0159-005 and ONR Contract Authority No. NR 093-050/12-5-67...429. Reproduction in whole or in part is permitted for any purpose of the United States Government. CONCERNING THE REACTION OF LITHIUM ALUMINUM HYDRIDE WITH DIETHYLMAGNESIUM IN DIETHYL ETHER E. C. Ashbyl and R. G. Beach School of Chemistry Georgia Institute of Technology, Atlanta, Georgia 30332 Abstract The reaction of lithium aluminum hydride with diethylmagnesium in diethyl ether has been studied in detail. The reaction was found to proceed according to the following equations: LiAlH) + 2(C2H5 ) 2Mg 2 MgH2 + LiAl(C2H5 ) ) 2 LiA1H 2H5 ) 2Mg - 3 MgH + 2 LiAl(C2H5 ) H + 3(C 2 3 LiA1HL + (C mg -+MgH + LiAl(C H ) H 4 2 H5 ) 2 2 2 5 2 2 2 LiA1HL + (C mg — MgH + 2 LiAl(C2H5 )H 3 4 2 H5 ) 2 2 The identity of the aluminum containing products was established by com- parison with the authentic compounds prepared by the redistribution of LiA1H4 and LiAl(C2H5 ) 4 . Attempts to prepare C2H5MgH and HNgA1H4 by the reaction of LiA1H 4 and (c2115 ) 2Ng are discussed. 2 Introduction In a paper on the preparation of group II hydrides Schlesinger, 2 et al., reported that magnesium hydride could be prepared from lithium aluminum hydride and diethylmagnesium in diethyl ether only under very special conditions. It was reported that lithium aluminum hydride in diethyl ether must be added slowly to a 0.5 M solution of diethylmag- nesium in diethyl ether until the ratio of lithium aluminum hydride to diethylmagnesium is 0.3:1. It was emphasized that unless this procedure was followed exactly, either no magnesium hydride was formed, or if magnesium hydride were formed, it contained excessive aluminum. Under ideal conditions the magnesium hydride product contained 0.1 mole of aluminum per mole of magnesium. The Schlesinger group uncovered a further interesting aspect concerning this reaction. They found that if diethylmagnesium in diethyl ether was added to a large excess of lithium aluminum hydride solution, a clear solution resulted, from which a compound analyzing for HMgAlH4 precipitated on addition of benzene. The precipitate was not further characterized. These workers further reported that when lithium aluminum hydride in diethyl ether was added to diethyl- magnesium solution, a precipitate occurred, but on continued addition of lithium aluminum hydride solution, the precipitate redissolved. On long standing a gelatinous precipitate formed which analyzed similar to the above. In view of these interesting features, the report of the possible preparation of HMgA1H4 , and the fundamental nature of this reac- tion, a more detailed study seemed appropriate. It was our intention to study the reaction of lithium aluminum hydride with diethylmagnesium in diethyl ether solvent varying the mode of addition and stoichiometry of 3 the reaction in an attempt to describe the products of the reaction with stoichiometry. It was also of great interest to us to attempt to isolate and characterize two possible intermediates in this reaction, HMgA1H4 and C 2H5MgH. Experimental Apparatus - Reactions were performed under dry nitrogen at the bench. Filtrations and other manipulations were carried out in a glove box equipped with a manganese oxide recirculating system to remove oxygen. Infrared spectra were obtained on a Perkin Elmer 621 Spectrophotometer using either KBr or CsI liquid or mull cells. Infrared spectra of the solids were obtained in Nujol mulls. Analytical - Total gas analysis was accomplished by hydrolysis of solid or solution samples and measuring the resultant liberated gas. No separation of gases was made although diethyl ether was trapped with a dry ice-acetone trap. Magnesium was determined by titration with EDTA at pH 11 using Eriochrome Black T as an indicator. When aluminum was present, it was masked by complexation with triethanolamine. Aluminum was determined by adding excess EDTA and back titrating with standard zinc acetate at pH 4 in 50% ethanol with dithizone as an indicator. Halide was determined by the Volhard procedure, and lithium by flame photometry. Materials - All solvents were distilled immediately before use from lithium aluminum hydride or sodium aluminum hydride depending on the 4 boiling point of the solvent. Diethylmagnesium ((C2H5 ) 2Mg) was prepared by the dioxane precipi- tation of MgBr from ethylmagnesium bromide. 3 Triply sublimed magnesium 2 was obtained from Dow Chemical Corporation and ethyl bromide from Fisher Scientific Company. Ethyl bromide was dried over anhydrous MgSO24 and distilled prior to use. Ethylmagnesium bromide was prepared in diethyl ether in the usual manner. The (C 2H5 )2Mg solution was standardized by magnesium analysis. Bromide analysis was negative. Lithium aluminum hydride (LiA1H 4 ) was obtained from Ventron, Metal Hydride Division. A solution was prepared by stirring a slurry of LiA1H4 in diethyl ether overnight. The solution was filtered through a glass fritted funnel using dried Celite filter aid. The clear solution was standardized by aluminum analysis. Lithium tetraethylalanate (LiAl(C 2H5 )4 ) was prepared by a modification of the procedure of Zakharkin. 4 Lithium metal was obtained from Foote Minerals. A lithium dispersion was prepared by heating lithium metal in mineral oil to approximately 200 ° and stirring with a high speed stirrer in a creased flask. The mineral oil was removed from the dispersion by washing with benzene. The dispersion was allowed to react with triethylaluminum (obtained from Texas Alkyls) at the temperature of refluxing benzene. After allowing the reaction mixture to reflux for 2 hours the solution was filtered, and the product crystallized from the filtrate on cooling. ), was recrystallized from a benzene-hexane mixture. After The LiAl(C2 H 54 drying in vacuo diethyl ether was distilled onto the solid, and the solution standardized by aluminum analysis. Infrared spectra of the solid and solution agreed with the reported spectra. 5 5 Infrared Study of the Reaction of LiA1H 4 with (C2H5 ) 2Mt: in Diethyl Ether - A 0.10 M solution of (c05 )2Ng in diethyl ether was placed in a 3-neck round bottom flask fitted with a condensor, an addition funnel, and a a- way stopcock to enable samples to be removed by syringe for infrared analysis. A 1.32 M solution of LiA1H 4 was placed in the addition funnel. Increments of the LiA1H 4 solution were added to the magnetically stirred ) Ng solution. After each addition the solution was stirred for 15 (C2H5 2 minutes. Then the stirring was stopped to allow the precipitate to settle. A sample of the supernatant was withdrawn by syringe under ni- trogen for infrared analysis. The addition was continued until LiA1H4 was in large excess. The entire experiment was repeated using a 0.582 M ) Ng solution. In a like manner a 0.883 M solution of (C2H5)2mg in (C2H5 2 diethyl ether was added in increments to solutions of LiA1H4 of the follow- ing concentrations: 0.100, 0.500, and 1.00 M. In Figure 1 a typical set of infrared spectra is shown. ), - Reaction between LiA1H and Redistribution of LiA1H4 and LiAl(C2 H54 4 LiAl(C2H5 )4 was performed by mixing the reactants in appropriate ratio from standard solutions. After thoroughly mixing the solutions, infrared spectra were obtained. Preparation of MgH2 from (C2H5 )2Mg and LiA1H4 - A reaction, using the exact conditions reported by Schlesinger, et al., was carried out. A diethyl ether solution of LiA1H4 (1.24 M) was added slowly from an addi- tion funnel to a 0.5 M solution of (C H ) mg.
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