Solutions of di-t-butylmagnesium have been prepared by the dioxan precipitation method, and from them several dibutylmagnesium complexes have been obtained. These include But,Mg-dioxan, which is insoluble in toluene and soluble in ether, the bistetrahydrofuran complex which is partly dissociated in benzene, and the tetramethylethylenediamine complex. Reaction between trimethylethylenediamine and Pr' ,Mg and But,Mg gives (Pr'MgNMeC,H,NMe,), and (ButMgNMeC,H,NMe,),, the latter being slightly dissociated in benzene. Pyrolysis of these compounds leads to alkane, not alkene, evolution.Reactions between diethylmagnesium and alkali-metal hydrides either do not take place or result in attack on the solvent. Butyl-lithium gives LiBu"Me,Mg,OEt, on reaction with dimethylmagnesium in ether, but pyrolysis of this gives dimethylmagnesium and lithium hydride. Exchange reactions between sodium trialkylborohydrides and some alkylmagnesium compounds result in the precipitation of magnesium hydride containing occluded alkyl groups.The solid Grignard reagent, (ButMgCIOEt,),, is dimeric in benzene, and is believed to contain chlorine bridges.WHEREAS t-butylmagnesium chloride is a well known and much used Grignard reagent, nothing has been reported concerning di-t-butylmagnesium or its derivatives. The application of the dioxan precipitation method to the preparation of solvent-free di-isopropylmagnesium has been described by Strohmeier and Seifert who pointed out that a temperature of 115" must not be exceeded in the process of separating dioxan in vacuo (this being a lower temperature than some other magnesiumalkyls tolerate), and that they were unable to prepare di-isobutylmagnesium by this method on account of pyrolysis of the product. Though we did not obtain solvent-free di-t-butylmagnesium, on account of the ease with which it loses isobutene when heated, we were able to prepare solutions of it which served as a suitable source for several derivatives. The dioxan precipitation method suffers from two complications when applied to solutions of t-butylmagnesium chloride. Unlike the precipitated dioxan-magnesium bromide complex obtained from, for example, dioxan and methyl-or ethyl-magnesium bromide, the dioxanmagnesium chloride complex from Bu'MgCl does not settle readily and is difficult to remove by filtration, though it could be separated with a centrifuge. Secondly, we found that chloride and dioxan could both be present in solution at the same time, though in low concentration. This is in contrast to the precipitation of dioxan-magnesium bromide, which is virtually complete when the dioxan : total halide ratio exceeds unity. Though chloride can be removed from solution by addition of an excess of dioxan, this was undesirable for our purposes since the presence of dioxan in the resulting solution of di-t-butylmagnesium would have complicated the preparation of several of the other coordination complexes. We therefore added only one mole of dioxan for each mole of chloride, and used, for preparative purposes, ether solutions o...

Several alkylmagnesium alkoxides have been prepared by alcoholysis of the dialkyls in diethyl ether, and can be obtained free from ether. In benzene, EtMgOPr", Pr'MgOMe, and Pr'MgOEt are oligomers (degrees of association ca. 8). but those alkoxides we have studied in which there is chain-branching a to oxygen are tetramers, (EtMgO'Pr'),, (EtMgOBd),, and (Pr'MgOPr'),.The 3-ethyl-pentan-3-01 derivative, from Et,Mg + Et,COor Et,Mg + Et,COH, crystallises as an ether complex (EtMgOCEt,.Et,O) which loses ether very readily: the tetrahydrofuran adduct is dimeric in benzene (EtMgOCEt,,TH F),.Some alkylmagnesium alkoxides are tetramers in diethyl ether, (EtMgOEt),, (MeMgOBd),, and (EtMgOBut),, but two are dimers, (EtMgOCMeEt,), and (EtMgOCEt,),.Methylmagnesium t-butoxide disproportionates in dilute solution in benzene. Both dimethylmagnesium and ethylmagnesium ethoxide crystallise from diethyl ether at room temperature without solvent of crystal I isat ion.The diethyl ether complex of t-butoxymagnesium bromide crystallises from the solution obtained when acetone is added to methylmagnesium bromide in ether. It is a dimer, (ButOMgBr,Et,O),, both in benzene and in ether and in the crystalline state. Several analogous products have been obtained by other similar reactions, and all those whose molecular weights were measured were also dimeric (solvent given) examples are ( ButOMgBr,THF), (benzene), (Et,CO M g Br,TH F) , (benzene), ( Et,M eCO M g Br.Et,O) , (ether), (Et,MeCO M g I, Et,O) , (ether), ( Me,PrnCOMgl,Et,O), (ether). t-Butoxymagnesium bromide-diethyl ether complex has also been prepared from magnesium bromideand both Mg(OBut),and MeMgOBut. The 'H n.m.r. spectra of several of the compounds described are anomalous in unexplained ways.South Road, Durham ALKYLMAGNESIUM alkoxides have been mentioned in various connections, and are discussed in a review.l Two of them have been found to be trimeric, (EtMgOEt), in ðyl ether,2 and (BunMgOPri), in b e n ~e n e . ~ Recently,* inethylmagnesium 3-methyl-pentyl-3-oxide has been found to have an apparent degree of association of 2-8 in 0 . 1 1 2 M (calculated as monomer) solution in diethyl ether at 40".

Free-piston engine generators (FPEGs) have huge potential to be the principal energy conversion device for generating electricity from fuel as part of a hybrid-electric vehicle (EV) powertrain system. The principal advantages lay in the fact that they are theoretically more efficient, more compact, and more lightweight compared to other competing EV hybrid and range-extender solutions (internal combustion engines, rotary engines, fuel cells, etc.). However, this potential has yet to be realized. This article details a novel dual-piston FPEG configuration and presents the full layout of a system and provides technical evidence of a commercial FPEG system’s likely size and weight. The work also presents the first results obtained from a project which set-out to realize an operational FPEG system in hardware through the development and testing of a flexible prototype test platform. The work presents the performance and control system characteristics, for a first of a kind system; these show great technical potential with stable and repeatable combustion events achieved with around 700 W per cylinder and 26% indicated efficiency.

No abstract

The use of short-lived isotopes in the determination of trace amounts of impurities in gallium arsenide is deslxibed. Methods are presented for determining silicon, zinc and magnesium. The effect of thermal neutron self -shielding in the determination of silicon and magnesium has been investigated and shown to be insignificant.