LiAlH solubility

LiAlH is soluble in ethers, 35-40 g/100 g diethyl ether at 25°C. Solubihty in THF, the other common solvent for LiAlH, is 13 g/100 g at 25°C. Polyethylene glycol diaLkyl ethers are also good solvents. 

The reactions of NaAlH are the same as those of LiAlH. However, it is much less soluble THF is the only good solvent. Heterogeneous reductions in good yield with NaAlH in hydrocarbon media have been reported (49). 

To remove water, the benzene was azeotroped and distilled over CaH2. The n-pentane was stored over LiAlH and distilled over CaH2. Toluene was distilled over CaH2. Toluene from Burdick Jackson, Muskegon, MI could also be used for dilute solution characterization without any adverse effects on polymer solubility. Tetrahydrofuran (THF) was dried over molecular sieves and doubly distilled over CaH2. The solvents were blanketed with nitrogen to maintain dryness. 

Preliminary structural characterization was carried out on the soluble products of treatment with BF3/CH3OH (or LiAlH (8), in order to verify the similarity of our samples to materials studied previously (8-11). Gas chromatography-mass spectrometry (GC-MS) (Finnigan 3300 spectrometer) was used to establish the molecular ion and fragmentation patterns solution-state 13C NMR (IBM Instruments WP-200 spectrometer) was employed for quantitation of CH2, CH2OH, and CHOH moieties. 

While ether is the common solvent for LiAlH, in which it is soluble, hydroxylic solvents like water, methanol and ethanol are preferred for NaBH, It is more soluble in methanol than in ethanol, but since it reacts with the former at an appreciable rate than the latter, hence ethanol is the preferred solvent. Isopropanol, in which NaBH4 is stable, is used for kinetic studies of the reduction of aldehydes and ketones. 

Ref 93). Extreme caution should be used in reducing any fluorinated compound with LiAlH. Violent reactions have been observed with two different fluoro compounds (Refs 76 St 95). Excess trimethylamine, NMe, reacts with an ethereal - solution of LiAlH in vacuo at -50SC to form a white addition compound which js slightly soluble in ether, insoluble in benzene, and spontaneously flammable in air (Ref 98a) Magnesium perchlorate may be used as a drying... 

Lithium aluminum hydride, LiAlH, is another reducing agent often used for reduction of ketones and aldehydes. A grayish powder soluble in ether and tetrahydrofuran, LiAlH4 is much more reactive than NaBH4 but also more dangerous. It reacts violently with water and decomposes explosively when heated above 120°C. 

Lithium tri-t-butoxyaluminum hydride, LiAlH[OC(CHj)3]3. Mol. wt. 254.30, sublimes at 280° under vacuum, solubility at 25° in g./lOO g. diglyme, 41 tetrahydrofurane 36, ether, 2 1,2-dimethoxyethane, 4 t-BuOH, 0. Supplier Ventron Corp. The reagent currently costs 1.5 as much as LiAlH and the active hydrogen per gram is only 3.7% that for LiAlHa. 

---