Amides, Imides and Mixtures

As early as 1910, Dafert and Miklauz [1] reported that the reaction between lithium nitride (U3N) and hydrogen (H2) generated Li3NH4. However, the product was proved by Ruff and Goeres [2] to be a mixture of lithium amide (IINH2) and lithium hydride (LiH)  

The chemistry of alkali amides was well investigated in the early twentieth century [3, 4], especially, sodium amide (NaNH2) has been used as a reagent in synthetic organic chemistry because of its ability to promote condensation reactions, to introduce amino groups into a molecule, and to remove the elements of water or of a hydrohalide acid. Lithium nitride has also been investigated for more than 50 years [5]. 

Hydrogen Storage Properties of Amide and Imide Systems 

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Figure 4. (a) Ti MAS spectra for amide, imide, and LiH phases that include a sample made from a mixture of Li2NH and A1 metal reacted at U. Utah with hydrogen gas to form LiNHi and LisAlHe phases [26], (b) Ti H CPMAS spectrum of LiH and LiNHi, where the amide was enriched with the isotope by reacting NHs gas with LiH. Ti CPMAS NMR spectrum of the natural L1NH2 purchased from Aldrich is displaced together for comparison. Note the Ti triplet peaks of the LiNH2 phase are consistent with the three distinct site locations in its crystal structure [28]. 

The water solubilities of M(OH)2 (M = Mg, Ca, Sr, Ba) increase down the group, as do their thermal stabilities with respect to decomposition into MO and H2O. Magnesium hydroxide acts as a weak base, whereas Ca(OH)2, Sr(OH)2 and Ba(OH)2 are strong bases. Soda lime is a mixture of NaOH and Ca(OH)2 and is manufactured from CaO and aqueous NaOH. Soda lime is easier to handle than NaOH and is commercially available, being used, for example, as an absorbent for CO2, and in qualitative tests for [NUi] salts, amides, imides and related compounds which evolve NH3 when heated with soda lime. 

All three amides are evidently mixtures of tautomers. It should be noted that the nitrogen atom in the imide form is sterically unhindered and sufficiently basic to provoke deprotonation of silylated AN... 

Claisen rearrangement of ally l imidates.1 This Pd(II) catalyst effects exclusive [3, 3] rearrangement of allylic imidates at 25° to allylic amides. Rearrangement of the chiral (E)-allylic imidate 1 results in a mixture of two chiral allyl amides 2 and 3. Thermal rearrangement of 1 results only in 2. 

This chiral column has been shown successfully to resolve enantiomeric mixtures (or racemates) of aromatic alcohols including l,l -bi-2-naphthol and its analogues (p. 836), aromatic hydroxy (or alkoxy) carboxylic esters and amides, amino acid derivatives, sulphoxides, cyclic imides and amides, lactones, etc. Even this list should not be regarded as limiting. The potential of this method, coupled with the simplicity of operation will undoubtedly be extensively developed and explored in the coming years. 

Blaschke et al. [54—56] synthesized polyacrylamide and polymethacrylamide containing chiral side chains. In order to make CSPs, these polymers were bonded to silica gel chemically [54-56]. The CSP obtained by /V-acrylol-(.S)-phenylalanine ethyl ester was commercialized by Merck Chemical Company by the trade name ChiraSpher. The racemic compounds resolved are those capable of forming hydrogen-bondings (i.e., amides, imides, carboxylic acids, and alcohols). It has been reported that nonpolar solvents like benzene and toluene individually or their mixtures were the best mobile phases. In addition to these CSPs, other amide CSPs were prepared and tested for the chiral resolution [57,58]. 

A-Haloamides and imides are a most versatile group of halogenating reagents. They are normally prepared in an aqueous solution by reaction of the parent amide/imide with the corresponding hypohalite. An improved method for the synthesis of A-bromo amides/imides has recently been published, in which the parent compounds are oxy-brominated in aqueous solution by a mixture of HBr/NaBr03 or NaBr/NaBr03/H2S04 (equation 95)700. 

Within the past year, a few papers have been published describing MAS-NMR experiments to evaluate transitions between the amide/imide phases [18] and also for amide-alanate mixtures [16, 17, 26]. Nearly aU of these studies have used either the Li isotopes or A1 when the alanates were involved. As shown in Figure 4, the Li MAS and CPMAS specda are especially useful to discriminate... 

For the triimides, it is expedient to increase the scale of the preparation, and then to effect a preliminary concentration of the triimides from the other imides so that the chromatography can be done on a much smaller column. The crude imide mixture is made as just described, but uang 3 1. of dimethylfonn-amide and 420 ml. (5.2 moles) of disulfur dichloride. After grinding finely once or twice as before, it is extracted with successive portions of dry, peroxide-free ethyl ether, totaling 3 1. The combined ether extracts are left to evaporate spontaneously until 150-300 ml. of cold liquid is left. Evaporation is continued until it is judged that more than half of the solute has crystallized. The solution is decanted away from the mass of crystals of heptasulfur imide and hexasulfur diimides, and allowed to evaporate to dryness, leaving 30-40 g. of solid, which consists... 

Additional polymer blends comprising PAEK s offering property combinations of potential utility include PSF [Robeson and Harris, 1986 Harris and Robeson, 1989] structurally different poly(aryl ketones) [Harris and Robeson, 1986], PAr [Robeson and Harris, 1992], poly(amide-imide) PAI [Harris and Gavula, 1992], PPS [Robeson, 1987], and other PI [Harris et al., 1992]. Mixtures of structurally different PAEK s were noted to be isomorphic within specific limits of ether/ketone ratios [Harris and Robeson, 1987]. Blends of polybenzimidazole, PBI and several commercial PI (Ultem 1000 and Matrimid 5218) have been studied in depth at the University of Massachusetts and found to be miscible. FTIR studies [Guerra et al., 1988 Kim et al., 1993], NMR studies [Grobelny et al., 1990], thermal, dielectric, and mechanical... 

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