Characterization and Hydrogen Storage Capacity Analysis of Dip Coated Lithium Aluminium Hydride Thin Films

Complex metal hydrides are one of the most effective hydrogen storage materials due to their unique property to absorb and desorb hydrogen with the hydrogen storage capacity of about 5-7 wt%. In this study, lithium aluminium hydride (LiAlH4) was coated on glass substrate using dip coating method. The coating conditions investigated were LiAlH4 concentrations of 6 g/l, 10 g/l and 20 g/l and post-annealing time from 0 to 60 min. Phase and grain size of the deposited LiAlH4 were analyzed using X-ray powder diffraction (XRD). Scanning electron microscope (SEM) was used for surface morphology analysis. The hydrogen storage capacity of the deposited thin films was analyzed using thermogravimetric analysis (TGA). The experimental results revealed that the phase of the deposited LiAlH4 thin films on glass substrate were mixed with lithium aluminium hydroxide hydrate (LiAl2(OH)7·2H2O) and lithium hexahydroaluminate (Li3AlH6). The intensity of the LiAl2(OH)7·2H2O and LiAlH4 peaks tends to decrease with increasing LiAlH4 concentration and post-annealing time while the intensity of the Li3AlH6 peaks increased with increasing LiAlH4 concentration and post-annealing time. The grain size was decreased with increasing LiAlH4 concentration and post-annealing time. The smaller grain size the better the hydrogen storage capacity. The hydrogen storage capacity of the deposited LiAlH4 thin film was increased from 0.124 wt % using LiAlH4 concentration of 6 g/l without post-annealing to 1.675 wt % using LiAlH4 concentration of 20 g/l with 60 min post-annealing time.

Stereospecific Synthesis of (4E,10Z)- 4,10-Tetradecadienyl Acetate, the Major Sex Pheromone of Apple Leaf Miner Moth, Phyllonorycter ringoniella

: The main component of the sex pheromone of many lepidopteran pests, (4E,10Z)-4,10-tetradecadienyl acetate (1) has been synthesized stereoselectively by using a simple route with 4-pentynol as a starting material. The stereoselective formation of the 4E double bond is based on the stereospecific reduction of internal alkyne with lithium aluminium hydride (LAH) while Wittig reaction was used to achieve 10Z double bond in the target pheromone component. The GC purity of the final acetate was achieved 97.87% while isomeric purities are more than 99%. The green chemistry principle shows a new concept towards for the multistep pheromone synthesis via green metrics calculations.

Convenient Synthesis of (Z)-7- and (E)-9-dodecene-1-yl Acetate, Components of Some Lepidoptera Insect Sex Pheromone

Were developed new and practical synthesis of (Z)-7-dodecene-1-yl acetate and (E)-9-dodecene-1-yl acetate. The routes involve, as the key step, the use of the mercury derivative of the terminal-alkyne w-functionalised as intermediate. The synthesis of (Z)-7-dodecene-1-yl acetate was based on a C6+C2=C8 and C8+C4=C12 coupling scheme, starting from 1,6-hexane-diol. The first coupling reaction took place between 1-tert-butoxy-6-bromo-hexane and lithium acetylide-ethylendiamine complex obtaining 1-tert-butoxy-oct-7-yne, which is transformed in di[tert-butoxy-oct-7-yne]mercury. The mercury derivative was directly lithiated and then alkylated with 1-bromobutane obtaining 1-tert-butoxy-dodec-7-yne. After acetylation and reduction with lithium aluminium hydride of 7-dodecyne-1-yl acetate gave (Z)-7-dodecene-1-yl acetate with 96 % purity. The synthesis of (E)-9-dodecene-1-yl acetate was based on a C8+C2=C10 and C10+C2=C12 coupling scheme, starting from 1,8-octane-diol. The first coupling reaction took place between 1-tert-butoxy-8-bromo-octane and lithium acetylide-ethylendiamine complex obtaining 1-tert-butoxy-dec-9-yne, which is transformed in di[tert-butoxy-dec-9-yne]mercury. The mercury derivative was directly lithiated and then alkylated with 1-bromoethane obtaining 1-tert-butoxy-dodec-9-yne. After reduction with lithium aluminium hydride of 1-tert-butoxy-(E)-9-dodecene and acetylation was obtained (E)-9-dodecene-1-yl acetate with 97 % purity.

Study of lithium aluminium hydride reduction of 5-acetyl-1,6-dimethyl-4-phenyl-3,4-dihydropyrimidin-2(1h)-one

In this paper, we investigated the LiAlH4-reduction of 5-acetyl-1,6-dimethyl- 4-phenyl-3,4-dihydropyrimidin-2(1H)-one (N-methylated Biginelli compound). Following the reduction and SiO2-promoted dehydration, (Z)-5-ethylidene-1-methyl-6- methylene-4-phenyltetrahydropyrimidin-2(1H)-one was isolated as the major product (33% yield). Chromatographic separation of the reaction products also allowed us to isolate (yield in parentheses) and fully spectrally characterize: 1,6-dimethyl-4-phenyl- 5-vinyl-3,4-dihydropyrimidin-2(1H)-one (20%), 5-ethyl-1,6-dimethyl-4-phenyl-3,4- dihydro-pyrimidin-2(1H)-one (9%), 5-(1-hydroxyethyl)-1,6-dimethyl-4-phenyl-3,4- dihydropyrimidin-2(1H)-one (5%). A possible mechanism explaining the formation of these products is proposed.

Improved microwave synthesis of unsymmetrical N,N'-diaryl-1,2-aminoethane and imidazolidinium salts as precursors of N-heterocyclic carbenes

Microwave facilitates the difficult to accomplish lithium aluminium hydride reduction of bis-unsymmetric-diaryloxamides 3 especially for the sterically hindered mesityl derivatives.