Potassium structures

In contrast, the (111) surface of iron exhibits an ordered potassium structure only at low potassium coverages where a (3 x 3) structure is observed. At higher coverages of potassium, the diffraction pattern corresponding to the (3x3) structure deteriorates and a (1x1) structure results, with a high background that indicates the presence of disordered potassium. 

Fig. XVni-8. (a) Work function change for Pt(lU) as a function of oxygen adatom coverage. From Ref. 82. b) Same, for potassium. The corresponding sequence of LEED structures is indicated. [Reprinted with permission from R. G. Windham, M. E. Bartram, and B. E. Koel, J. Phys. Chem., 92, 2862 (1988) (Ref. 83). Copyright 1988, American Chemical Society.]...

Is 2s 2p 3s 3p 3d 4s. If the 3d states were truly core states, then one might expect copper to resemble potassium as its atomic configuration is ls 2s 2p 3s 3p 4s The strong differences between copper and potassium in temis of their chemical properties suggest that the 3d states interact strongly with the valence electrons. This is reflected in the energy band structure of copper (figure Al.3.27). 

Why is potassium aluminium sulphate not soluble in benzene A compound M has the composition C = 50.0% H=12.5%o A1 = 37.5%. 0.360 g of M reacts with an excess of water to evolve 0.336 1 of gas N and leave a white gelatinous precipitate R. R dissolves in aqueous sodium hydroxide and in hydrochloric acid. 20 cm of N require 40 cm of oxygen for complete combustion, carbon dioxide and water being the only products. Identify compounds N and R, suggest a structural formula for M, and write an equation for the reaction of M with water. (All gas volumes were measured at s.t.p.)... 

Decomposition of potassium ferratefVI) at 1000 K gives a ferrate V), K3Fe04, and several types of ferrate(IV), for example FeOj", Fe04 are known these ferrates(IV) have no solution chemistry and are probably best regarded as mixed oxides, since the FeOl" ion has no identifiable structure. 

When an aqueous solution of benzenediazonium chloride is added to a cold concentrated solution of potassium hydroxide, the unstable potassium diazo-tate, C(HjN NOK, is formed, and this when heated with alkali to 130° changes to the isomeric but far more stable potassium isodiazotate it is probable that these copipounds have the structures (A) and (B) respectively. 

It is frequently advisable in the routine examination of an ester, and before any derivatives are considered, to determine the saponification equivalent of the ester. In order to ensure that complete hydrolysis takes place in a comparatively short time, the quantitative saponi fication is conducted with a standardised alcoholic solution of caustic alkali—preferably potassium hydroxide since the potassium salts of organic acids are usuaUy more soluble than the sodium salts. A knowledge of the b.p. and the saponification equivalent of the unknown ester would provide the basis for a fairly accurate approximation of the size of the ester molecule. It must, however, be borne in mind that certain structures may effect the values of the equivalent thus aliphatic halo genated esters may consume alkali because of hydrolysis of part of the halogen during the determination, nitro esters may be reduced by the alkaline hydrolysis medium, etc. 

It may be pointed out that dehydration of p hydroxy esters with fused potassium hydrogen sulphate, acetic anhydride, phosphoric oxide or with tliionyl chloride in benzeue solution leads to ap unsiiturated esters containing some PY-unsaturated ester the proportion of the latter depends not only upon the structure of the ester but also upon the dehydrating agent used. Elehydration occasionally occurs during the reaction itself or upon attempted distillation. 

Compound A (C4H10) gives two different monochlondes on photochemical chlorination Treatment of either of these monochlondes with potassium tert butoxide in dimethyl sulfoxide gives the same alkene B (CaHg) as the only product What are the structures of compound A the two monochlondes and alkene B2... 

Compounds A and B are isomers of molecular formula C9Hi9Br Both yield the same alkene C as the exclusive product of elimination on being treated with potassium tert butoxide in dimethyl sulfoxide Hydrogenation of alkene C gives 2 3 3 4 tetramethylpentane What are the structures of compounds A and B and alkene C2... 

A compound was obtained from a natural product and had the molecular formula C14H20O3 It contained three methoxy (—OCH3) groups and a —CH2CH=C(CH3)2 substituent Oxidation with either chromic acid or potassium permanganate gave 2 3 5 trimethoxybenzoic acid What is the structure of the compound" ... 

Pellagra is a disease caused by a deficiency of niacm (C6FI5NO2) in the diet Niacin can be synthesized in the laboratory by the side chain oxidation of 3 methylpyndine with chromic acid or potassium permanganate Suggest a reasonable structure for niacin... 

Each of the following dihaloalkanes gives an N (haloalkyl)phthahmide on reaction with one equivalent of the potassium salt of phthalimide Write the structure of the phthahmide denvative formed m each case and explain the basis for your answer... 

Phlonzm is obtained from the root bark of apple pear cherry and plum trees It has the molecular formula C21H24O10 and yields a compound A and D glucose on hydrolysis in the pres ence of emulsin When phlorizin is treated with excess methyl iodide in the presence of potassium carbonate and then subjected to acid catalyzed hydrolysis a compound B is obtained Deduce the structure of phlorizin from this information... 

In 1959 a new non-protein L-a-amino acid was isolated from the seeds of Acacia willardiana and later from other species of Acacia-, it proved to be l-/3-amino-/3-carboxyethyluracil (977) (59ZPC(316)164). The structure was confirmed by at least four syntheses in the next few years. The most important involves a Shaw synthesis (Section 2.13.3.1.2e) of the acetal (975) and hydrolysis to the aldyhyde (976) followed by a Strecker reaction (potassium cyanide, ammonia and ammonium chloride) to give DL-willardiine (977) after resolution, the L-isomer was identical with natural material (62JCS583). Although not unambiguous, a Principal Synthesis from the ureido acid (978) and ethyl formylacetate is the most direct route (64ZOB407). 

Again, as with pyridopyrimidines, the main reaction is oxidation of di- or poly-hydro derivatives to fully aromatic structures, often merely by air or oxygen. In some cases the reagent of choice is mercury(II) oxide, whilst other reagents used include sulfur, bromine, chloranil, chromium trioxide-acetic acid, hydrogen peroxide, and potassium ferricyanide, which also caused oxidative removal of a benzyl group in the transformation (306) (307)... 

Pyrazoles can be prepared by ring opening reactions of fused systems already containing the pyrazole nucleus. Thus several [5.5], [5.6] and [5.7] fused heterocycles have been opened to substituted pyrazoles, usually in basic medium. In general, the method has little preparative interest since another pyrazole derivative has usually been used to build the ring-fused system. However, due to the unexpected structures obtained, two publications are worthy of notice. 6//-Cyclopropa[5a,6a]pyrazolo[l,5-a]pyrimidine (638) was readily obtained from the corresponding pyrazolopyrimidine by the action of diazomethane at room temperature (Scheme 59) (81H(15)265). When (638) was treated with potassium hydroxide, the pyrazole (640) was formed, probably via the diazepine (639). 

An X-ray structure of 5yn-triepoxide (38) (74AG(E)539) shows that the cyclohexane ring is planar, with the three oxygens and sbt hydrogens lying in parallel planes 1.19 and 0.42 A respectively from the carbon plane. With all oxygens on one face , (38) forms a crystalline 2 1 complex with potassium iodide. 

Consider a lake with a smaU watershed in a forest ecosystem. The forest and vegetation can be considered as an acid concentrator. SO2, NO2, and acid aerosol are deposited on vegetation surfaces during dry periods and rainfalls they are washed to the soil floor by low-pH rainwater. Much of the acidity is neutralized by dissolving and mobilizing minerals in the soil. Aluminum, calcium, magnesium, sodium, and potassium are leached from the soil into surface waters. The ability of soils to tolerate acidic deposition is very dependent on the alkalinity of the soil. The soil structure in the... 

Doyle, D.A., et al. The structure of the potassium channel molecular basis of K+ conduction and selectivity. Science 280 69-77, 1998. 

MacKinnon, R., et al. Structural conservation in prokaryotic and eukaryotic potassium channels. Science 280 106-109, 1998. 

The improved method herein described is adapted from the procedure of Runti and Deghenghi. Hydroxyurea has been prepared from potassium cyanate and hydroxylamine hydrochloride. A lower melting isomeric substance, m.p. 71°, has been described." " The structure NH2CO2NH2 has been proposed for this low-melting substance. 

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