Ammonium ions, synthesis

Structure Modification. Several types of stmctural defects or variants can occur which figure in adsorption and catalysis (/) surface defects due to termination of the crystal surface and hydrolysis of surface cations (2) stmctural defects due to imperfect stacking of the secondary units, which may result in blocked channels (J) ionic species, eg, OH , AIO 2, Na", SiO , may be left stranded in the stmcture during synthesis (4) the cation form, acting as the salt of a weak acid, hydrolyzes in aqueous suspension to produce free hydroxide and cations in solution and (5) hydroxyl groups in place of metal cations may be introduced by ammonium ion exchange, followed by thermal deammoniation. 

Synthesis of 1 mol of urea requires 3 mol of ATP plus 1 mol each of ammonium ion and of the a-amino nitrogen of aspartate. Five enzymes catalyze the numbered... 

Most of the permeases which are insensitive to NCR are synthesized in cells grown on minimal medium containing ammonium ions, without addition of any inducer. However, a few of them do appear to be inducible. For instance, addition to the medium of methionine, leucine valine, isoleucine and alanine, which are taken up by several distinct NCR-insensitive permeases, increases the rate of synthesis of the corresponding permeases [54]. This process involves amplification of a basal rate of permease synthesis rather than all-or-none induction. It has not been studied further at the molecular level. 

Nitrogen-catabolite repression of GAPl synthesis has been studied in mutant strains containing mutations such as npil or npi2 which destroy the permease inactivation mechanism. With the help of these mutants, it could be clearly demonstrated that GAPl synthesis is repressed in cells grown in the presence of ammonium ions. 

If ammonium thiocyanate is used, the ammonium ion can itself provide a nitrogen atom for heterocyclic ring construction. Such nitrogen and sulfur transfer is the basis of an elegant synthesis of isothiazoles (15) from 3-chloropropenals (16).18... 

Figure B. Pictorial representation of the self-assembly of pseudorotaxa-nes based on (a) charge-transfer and C-H—O hydrogen-bonding interactions between 1,1 -diben-zyl-4,4 -bipyridinium dication and 1,5-dinaphtho[38] crown-10 (1/5DN38C10), and (b) hydrogen-bonding interactions between dibenzyl ammonium ion and dibenzo[24]crown-8 (DB24C8). A possible route towards the synthesis of rotaxanes and catenanes is also schematized.

Chiral active pharmaceutical ingredients, 18 725-726. See also Enantio- entries Chiral additives, 6 75—79 Chiral alcohols, synthesis of, 13 667-668 P-Chiral alcohols, synthesis of, 13 669 Chiral alkanes, synthesis of, 13 668-669 Chiral alkenes, synthesis of, 13 668—669 Chiral alkoxides, 26 929 Chiral alkynes, synthesis of, 13 668-669 Chiral ammonium ions, enantiomer recognition properties for, 16 790 Chiral ansa-metallocenes, 16 90 Chiral auxiliaries, in oxazolidinone formation, 17 738—739... 

A mixture of an industrial blend of di-nonylphenolethoxy carboxylates (di-NPECs (CnH2n+1)2-C6H3-0-(CH2-CH2-0)x-CH2-C00 (Fig. 2.11.15(1) R = (C9H19)2), which contained nonylphenolethoxylates (NPEO) as impurities from synthesis, was first analysed by APCI-FIA-MS(+/—) followed by a separation on a RP-Cig column in the presence of ammonium ions for ion-pairing purposes and for ionisation support. 

Uses Organic synthesis photographic agent manufacture of pesticides, herbicides, explosives, and wood preservatives yellow dyes preparation of picric acid and diaminophenol (photographic developer) indicator analytical reagent for potassium and ammonium ions insecticide. 

I. Hasegawa and S. Sakka, Silicate Species with Cagelike Structure in Solutions and Rapid Solidification with Organic Quaternary Ammonium Ions, Zeolite Synthesis (ACS Symposium Series 398) Am, Chem. Soc., Washington, DC 1989, p.140/51... 

The formation of novel silicon-rich synthetic zeolites has been facilitated by the use of templates, such as large quaternary ammonium cations instead of Na+. For instance, the tetramethylammonium cation, [(CH3)4N], is used in the synthesis of ZK-4. The aluminosilicate framework condenses around this large cation, which can subsequently be removed by chemical or thermal decomposition. ZSM-5 is produced in a similar way using the tetra-.n-propyl ammonium ion. Only a limited number of large cations can fit into the zeolite framework, and this severely reduces the number of [AIO4] tetrahedra that can be present, producing a silicon-rich structure. 

Furthermore, investigations of template decomposition in zeolites upon calcination of the as-synthesized materials have received much attention by researchers (248-250). However, the decomposition mechanisms of quaternary ammonium salts, which are commonly used as templates for zeolite synthesis, are still not well understood. Thus, MAS NMR investigations of the decomposition of quaternary ammonium ions in zeolites bear the potential of significantly improving the understanding of these processes (243,251). For this purpose, a general method was developed for the synthesis of... 

C. Synthesis and Immobilization of Quarternary Ammonium Ions in Zeolites... 

The above-mentioned route to the preparation of quarternary ammonium ions in acidic zeolites is remarkable for the following reasons an immobilization of quaternary ammonium ions in a well-controlled concentration is an approach to modification of zeolite catalysts. Furthermore, the synthesis of isotopically labeled compounds is of importance in organic, pharmaceutical, and agricultural chemistry. This method is an approach to the synthesis of C-labeled (or C, N-labeled) tertiary amines via a thermal decomposition (243,251) of the corresponding quaternary ammonium ions in zeolites. 

Synthesis of Quaternary Ammonium Ions (Column 1) on Acidic Zeolites (Column 2) by a Methylation of the Corresponding Tertiary Amines (Column 3) with C-Enriched Methanol at the Reaction Temperatures Given in Column 4 (251)... 

A study is presented of the synthesis and properties of the novel synthetic zeolite omega. The synthesis variables and kinetics of formation are discussed, as well as the ion exchange, sorption, and thermal properties. By decomposition of imbibed tetra-methylammonium ions and exhaustive treatments of the zeolite with ammonium ions, a pure hydrogen form can be obtained which is a suitable substrate for the preparation of hydrocarbon conversion catalysts. Several catalysts were prepared and utilized to isomerize n-hexane, and to hydrocrack a heavy gas oil. 

A new catalyst salt (20) that consists of an achiral ammonium ion and a chiral phosphate anion and which catalyses highly enantioselective transfer hydrogenations of ,/J-unsaturated aldehydes to the corresponding saturated derivatives has been developed. The underlying principle, namely asymmetric counteranion-directed catalysis, is claimed to be a new strategy for highly enantioselective synthesis.357... 

---