Potassium bonding

It has a carbon-potassium bond and thus is an organometallic compound. 

Two potassium atoms transfer an electron each to butadiene forming a dianion transmetallation with o-xylene then gives the potassium-bonded carbanion, which inserts butadiene. A second transmetallation with o-xylene liberates the potassium-stabilized benzylcarbanion, which is the actual catalytic species and generates o-pentenyltoluene. This can then be cyclized to 1,5-dimethyltetralin, which, after dehydrogenation to the corresponding naphthalene and isomerization to the 2,6-isomer, affords 2,6-naphthalenedicarboxylic acid by oxidation. 

The crystal structure shows the expected E geometry of the double bond. The length of the silicon-potassium bond (3.45 A) lies within the range observed for similar anionic compounds [3]. The length of the carbon-carbon olefinic bond is not significantly affected by the adjacent anionic silicon atom, in contrast to the spectroscopic behavior of this bond (see below). 

The structure of 1 reveals a trigonal bipyratnidal coordination around the potassium atom. N(l) and N(4), occupying the axial positions, exhibit elongated nitrogen-potassium bond distances. The length of the silicon-potassium bond (3.394 A) is slightly shorter than that of the related crown ether adducts (about 3.50 A) [4c]. 

Table 2.1.8 Sn NMR parameters of compounds with tin-silicon, -germanium, -tin, -lead, -boron, -lithium and -potassium bonds ...

Table 1.5 Differences between the sodium and potassium bond distances for the metal halides...

The nature of the carbon-metal bond varies widely, ranging from bonds that are essentially ionic to those that are primarily covalent. Whereas the structure of the organic portion of the organometaiiic compound has some effect on the nature of the carbon-metal bond, the identity of the metal itself is of far greater importance. Carbon—sodium and carbon-potassium bonds are largely ionic in character carbon—lead, carbon—tin, carbon—thallium, and carbon—mercury bonds are essentially covalent. Carbon—lithium and carbon—magnesium bonds lie between these extremes. 

If the ester enolate reaction involves reversible addition while the cyclisation remains irreversible, it should be possible to use weaker bases than the generally used lithium amides for the condensation reaction. A situation of this type results when potassium enolates are used. In this case, the highly ionized oxygen-potassium bond renders the addition of the enolate to the imine reversible. As a result, we were able to prepare P-lactams via ester enolate imine condensation using potassium r-butoxide that has a pK of 16.5 (Scheme 16). ... 

Hydrogencarbonates of sodium, potassium and ammonium are known in the solid state and show hydrogen bonding in the crystal ... 

The ability to form hydrogen bonds explains the formation of complex ions such as HFJ and HjFj when a fluoride salt, for example potassium fluoride, is dissolved in aqueous hydrofluoric acid ... 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

Test the solution so obtained for unsaturation by adding cold 1 per cent, potassium permanganate solution a drop at a time. The immediate disappearance of the purple colour and the formation of a brown turbidity indicates the presence of a double bond Baeyer a test). It must be noted that many substances, not unsaturated, decolourise warm acid or neutral potassium permanganate solution. 

The position of the triple bond is established by oxidation of the latter by means of alkaline potassium permanganate solution to sebacic acid, H02C(CH2)gC0jH, m.p. 133°. 

The formation of ethyl isopropylidene cyanoacetate is an example of the Knoevenagel reaction (see Discussion before Section IV,123). With higher ketones a mixture of ammonium acetate and acetic acid is an effective catalyst the water formed is removed by azeotropic distillation with benzene. The essential step in the reaction with aqueous potassium cyanide is the addition of the cyanide ion to the p-end of the ap-double bond ... 

The last isomerization is remarkable in that the triple bond can shift through a long carbon chain to the terminus, where it is fixed as the (kinetically) stable acetylide. The reagent is a solution of potassium diami no-propyl amide in 1,3-di-aminopropane. In some cases alkali metal amides in liquid ammonia car also bring about "contra-thermodynamic" isomerizations the reactions are successful only if the triple bond is in the 2-position. 

Triethylammonium formate is another reducing agent for q, /3-unsaturated carbonyl compounds. Pd on carbon is better catalyst than Pd-phosphine complex, and citral (49) is reduced to citronellal (50) smoothly[55]. However, the trisubstituted butenolide 60 is reduced to the saturated lactone with potassium formate using Pd(OAc)2. Triethylammonium formate is not effective. Enones are also reduced with potassium formate[56]. Sodium hypophosphite (61) is used for the reduction of double bonds catalyzed by Pd on charcoal[57]. 

Use curved arrows to show the bonding changes in the reaction of CIS 4 tert butylcyclohexyl bromide with potassium tert butoxide Be sure your drawing correctly represents the spatial relationship between the leaving group and the proton that is lost... 

Solvent Effects on the Rate of Substitution by the S 2 Mechanism Polar solvents are required m typical bimolecular substitutions because ionic substances such as the sodium and potassium salts cited earlier m Table 8 1 are not sufficiently soluble m nonpolar solvents to give a high enough concentration of the nucleophile to allow the reaction to occur at a rapid rate Other than the requirement that the solvent be polar enough to dis solve ionic compounds however the effect of solvent polarity on the rate of 8 2 reactions IS small What is most important is whether or not the polar solvent is protic or aprotic Water (HOH) alcohols (ROH) and carboxylic acids (RCO2H) are classified as polar protic solvents they all have OH groups that allow them to form hydrogen bonds... 

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... 

Gabriel synthesis (Section 22 8) Method for the synthesis of primary alkylamines in which a key step is the formation of a carbon-nitrogen bond by alkylation of the potassium salt of phthalimide... 

Propellants cast into rockets are commonly case-bonded to the motors to achieve maximum volumetric loading density. The interior of the motor is thoroughly cleaned, coated using an insulating material, and then lined with a composition to which the propellant binder adheres under the environmental stresses of the system. The insulation material is generally a mbber-type composition, filled with siUca, titanium dioxide, or potassium titanate. SiUca-filled nitrate mbber and vulcanizable ethylene—propylene mbber have been used. The liner generally consists of the same base polymer as is used in the propellant. It is usually appHed in a thin layer, and may be partially or fully cured before the propellant is poured into the rocket. 

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