Potassium anion

One case of n—5 —n delocalization was demonstrated by Stevenson et al. (2006). The potassinm anion-radical salt of l-(9-methyl-9H-fluoren-9-yl)-4-methyl benzyl is characterized by the delocalization of an nnpaired electron within the fluorenyl moiety only. Its ESR spectrnm completely coincides with the spectrnm of the potassium anion-radical salt of the 9,9-dimethyl fluorene anion-radical in THE However, the cesium anion-radical salt of the fluorenyl methylbenzyl derivative produces the ESR spectrum corresponding to the placement of this cation between the fluorenyl and methylbenzyl moiety. The conditions of n—s—n delocalization appear An unpaired electron spends its time within both fluorenyl and methylbenzyl fragments. The situation is explained in Scheme 3.54. 

Reductive cleavage of the potassium anions (3) of (methylthio)pentadienes with Li in NH, followed by methylation gives 4 with retention of configuration of the Ci — ( bond, but the C3—C4 bond is always (Z) regardless of the configuration in 3. 

The intermediate p-hydroxyphosphine oxide is isolated only if lithium is used to deprotonate the phosphine oxide. Sodium or potassium anions eliminate in situ to form the alkene direedy. Eliminations of... 

According to this mechanism, the potassium anion attacks the 3 lactone ring to cleave the CH2-CH2 bond and form a carbanlon. This anion, which can exist in a tautomeric equilibrium with its enolate form, reacts with the next 6-lactone monomer by the opening of the alkyl-oxygen bond. The propagation reaction, therefore, proceeds by reaction of the carboxylate anion active centers. Experimental data, to be reported later, provides evidence for this unusual C-C bond-breaking reaction in the monomer and for two types of active species, which are responsible for the course of the lactone initiation and polymerization reactions that occur. 

Asymmetric alkylations of anions of chiral allylamines 5.6 have been performed at -78°C by Ahlbrecht and Enders [1012], These reactions form 2-en-amines with high regio- and stereoselectivities. These enamines are hydrolyzed to generate 3-phenylalkanals 5.7 with a good enantioselectivity (Figure 5.4). The same types of nonracemic aldehydes 5.7 were already obtained with a similar enantioselectivity by Mukaiyama and coworkers [148] via selective alkylation of potassium anions of chiral allyl ethers 5.8 (Figure 5.4). 

The p/fa of carbon acids can depend greatly on the solvent (15.8 for phenylacetylene in diethyl ether, 26.5 in DMSO).22 This effect is explained by the extent of ion-pairing or ion aggregation. The equilibrium for the deprotonation of phenylacetylene is shifted to the right when the solvent is changed from cyclohexylamine (pA a = 20.5) to diethyl ether due to increased stability of the ion pair (for the potassium anion, PhCsC K+) or the ion aggregate (PhCsC K+) . 

Such alkali metal ion pairs are capable of two electron transfer from the potassium anion towards a suitable substrate, e.g. p-butyrolactone with formation of a respective carbanion. The strong tendency to two electrons transfer is due to the unusual oxidation state of potassium anion bearing on its outer s orbital a labile electron doublet shielded from the positive potassium nucleus by inner orbitals. Using 5 -enantiometr of P-butyrolactone as a monomer and potassium supramolecular complex as catalyst, enolate carbanion is formed as the first reactive intermediate which induces polymerization, yielding poly-(R)-3-hydroxybutanoate. The resulting biomimetic polyester has the structure similar to native PHB produced in nature, except for acetoxy-end-groups, which are formed instead of the hydroxyl ones typical for natural PHB. 

Initiation of heterocyclic carbon-carbon bond fission by potassium anions Generation of carboxylic acid ester dianions from p-lactones... 

A potassium mirror contacted with a soln. of 18-crown-6 in THF at —20°, after exactly 15 min the blue mixture filtered into a connected reactor, an equimolar amount of 2-oxetanone added, and the dianion quenched with methyl iodide - ethyl propionate. Y 70%. The unusual C-C bond fission is initiated by attack of potassium anions. F.e. and quenching with HCl s. Z. Jedlinski et al., J. Chem. Soc. Chem. Commun. 1988, 1261-2 details and apparatus s. J. Org. Chem. 54, 1500-1 (1989). 

The electrolytes sodium, potassium, calcium, and magnesium occur in the body fluids (aqueous solutions) as cations, partly bound to proteins or other organic components, and they are in equilibrium with the anions. In relation to the water balance the main function of the ions is to maintain osmotic pressure. In the extracellular space the most important cation is sodium (anion chloride), in the intracellular space the main cation is potassium (anion bicarbonate). The regulation... 

These curious chemical entities led us to study the reactivity of potassium anion (K ) generated from K/crown ether/diglyme (or Et20, THF) system and toluene radical anion from K/crown ether/toluene system. The effectiveness of the former system for reductive cleavage of sulfonamide was reported elsewhere- -. In the present paper, reductive defluorination with the latter system is reported- -. ... 

Edwards PP, Ellaboudy AS and Holton DM (1985) NMR spectrum of the potassium anion K , Nature (London) 317 242-244. 

Ferrate(VI) has powerful oxidising properties, for example ammonia is oxidised to nitrogen. Potassium ferratefVI) is isomorphous with potassium chromatefVI), and both anions are tetrahedral. 

If nickel(II) cyanide, Ni(CN)2, is dissolved in excess potassium cyanide, the orange-red complex salt K2Ni(CN)4. HjO can be crystallised out this contains the stable square-planar [Ni(CN)4] anion. 

Silver chloride is readily soluble in ammonia, the bromide less readily and the iodide only slightly, forming the complex cation [Ag(NH3)2]. These halides also dissolve in potassium cyanide, forming the linear complex anion [AglCN) ] and in sodium thiosulphate forming another complex anion, [Ag(S203)2] ... 

The "zip-reaction (U. Kramer, 1978, 1979) leads to giant macrocycles. Potassium 3- ami-nopropyl)amide = KAPA ( superbase ) in 1,3-diaminopropane is used to deprotonate amines. The amide anions are highly nucleophilic and may, for example, be used to transam-idate carboxylic amides. If N- 39-atnino-4,8,12,16,20,24,28,32,36-nonaazanonatriacontyl)do-decanolactam is treated with KAPA, the amino groups may be deprotonated and react with the macrocyclic lactam. The most probable reaction is the intramolecular formation of the six-membered ring intermediate indicated below. This intermediate opens spontaneously to produce the azalactam with seventeen atoms in the cycle. This reaction is repeated nine times in the presence of excess KAPA, and the 53-membered macrocycle is formed in reasonable yield. 

The conjugate bases listed m Table 1 7 that are anions are commonly encountered as their sodium or potassium salts Thus sodium methoxide (NaOCH3) for example is a source of methoxide ion (CH30 ) which is the conjugate base of methanol... 

The most frequently encountered nucleophiles in functional group transformations are anions which are used as their lithium sodium or potassium salts If we use M to represent lithium sodium or potassium some representative nucleophilic reagents are... 

Table 8 1 illustrates an application of each of these to a functional group transfer matron The anionic portion of the salt substitutes for the halogen of an alkyl halide The metal cation portion becomes a lithium sodium or potassium halide... 

Dihalocarbenes are formed when trihalomethanes are treated with a strong base such as potassium tert butoxide The trihalomethyl anion produced on proton abstraction dissociates to a dihalocarbene and a halide anion... 

In media such as water and alcohols fluoride ion is strongly solvated by hydro gen bonding and is neither very basic nor very nucleophilic On the other hand the poorly solvated or naked fluoride 10ns that are present when potassium fluoride dis solves m benzene m the presence of a crown ether are better able to express their anionic reactivity Thus alkyl halides react with potassium fluoride m benzene containing 18 crown 6 thereby providing a method for the preparation of otherwise difficultly acces sible alkyl fluorides... 

Multiplicative Prefixes. The multiplicative prefixes bis, tris, etc., are used with certain anions for indicating stoichiometric proportions when di, tri, etc., have been preempted to designate condensed anions for example, A1K(S04)2 I2H2O, aluminum potassium bis(sulfate) 12-water (recall that disulfate refers to the anion S20jfi. 

The macrocychc hexaimine stmcture of Figure 19a forms a homodinuclear cryptate with Cu(I) (122), whereas crown ether boron receptors (Fig. 19b) have been appHed for the simultaneous and selective recognition of complementary cation—anion species such as potassium and fluoride (123) or ammonium and alkoxide ions (124) to yield a heterodinuclear complex (120). 

Continuous processes have been developed for the alcohols, operating under pressure with Hquid ammonia as solvent. Potassium hydroxide (206) or anion exchange resins (207) are suitable catalysts. However, the relatively small manufacturing volumes militate against continuous production. For a while a continuous catalytic plant operated in Raveima, Italy, designed to produce about 40,000 t/yr of methylbutynol for conversion to isoprene (208,209). 

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