Appearance , xxiv

In neutral and alkaline media, the rate of exchange at the 3 and 6 position of 4-aminopyridazine is independent of acidity but decreases markedly when the media become more acidic. This was interpreted in terms of a rate-determining removal of the 6-proton by deuteroxide ion to give the ylid (XXIV), which reacts with deuterium oxide in a fast step. A similar result for the 3 and 6 positions of py-ridazin-4-one suggests the same mechanism. For reaction at the 5 position, the rate-acidity profile indicated reaction on the free base as did that for the 5 position of pyridazin-3-one, though the appearance of a maximum in the rate at — HQ = 0.8 was anomalous and suggested incursion of a further mechanism. 

Considerably less is known about the chemistry of palladium and platinum 1,1-dithio complexes. Of late, there has been only one report that dealt with the synthesis of a large number of palladium dithiocar-bamates 392). Twenty-five yellow palladium dithiocarbamate complexes were obtained by reaction of PdCla with NaR2dtc in methanol solution. Several other reports have appeared in which a few dithiocarbamate complexes of palladium were synthesized. Thus, the novel [Pd (OH)2dtc 2], which is soluble in water, was isolated 393). The synthesis of optically active palladium(II) complexes of AT-alkyl-a-phen-ethyldithiocarbamates, similar to (XXIV), via the reaction between the optically active amine, CS2, and PdCl2, has been described. From ORD and CD spectra, it has been established that the vicinal contribution of a remote, asymmetric carbon center could give rise to optical activity of the d—d transitions of palladium 394). Carbon disulfide has been shown to insert into the Pt-F bond of [PtF(PPh3)3]HF2, and X-ray studies indicated the structure (XXIX). 

Electrochemistry. The cyclic voltammogram of Compound 87a was measured and is compared to octa. S -benzyl porphyrazine, Ni[pz(A4)] A = difS -benzyl), 60a (from Section IV.B.l) in Table XXIV. Compound 87a has two reversible ring reductions, which are more positive than those measured for H2 pc and more negative than those measured for Ni[pz(.V-benzyl)8], 60a, suggesting that the conformational influences of the peripheral seven-membered ring make this pz harder to reduce than the pz with unconstrained peripheral thioethers. Because these compounds are of limited solubility and cannot be oxidized or reduced readily, they appear to be unsuitable for use as building blocks for molecular conductors. 

Although thiophene derivatives, e.g., tetraphenylthiophene XXI and XXII70 do not appear to form photoperoxides sulfurated 9,10-diphenyl-anthracenes XXIII and cerothiene XXIV derivatives have been reported to form transannular peroxides of the type A on irradiation in the presence of oxygen.209,210... 

The first applications of NMR to the study of dynamic systems of the platinum group metals appear to have been studies on the rotation about the metal-olefin bond of coordinated olefins, and this process has been investigated by many workers. There are two reasonable orientations of an olefin with respect to the rest of a square planar complex, XXIV and XXV. 

This result was confirmed by cleavage of the double bond in XXIV to give the aldehyde XXV, in which the aldehydic hydrogen atom shows a 1 2 1 triplet at 9.83 S and therefore lies adjacent to a methylene group in position 6. Furthermore, isomerization of the methine XXIV with hydrochloric acid moves the double bond to the 6,7 position (XXVI) as shown by the appearance of an allylic methyl group in the NMR-spectrum (1.68 S, doublet, J = 2.6 c/sec), and in this compound (XXVI) there are two vinyl protons (multiplet at 5.47 S). The transformation of XXIV to XXVI does not involve rearrangement because both compounds on reduction yield the same dihydro derivative, XXVII. 

The Hydrolysis of cis and trans Cyclohexene Chlorohydrin. When trans cyclohexene chlorohydrin is treated with strong alkali, trans cyclohcxene glycol is obtained. Thus inversion does not appear to have occurred during the displacement. When the reaction is carried out with the cis isomer, cyclohexanone is formed.27 These facts can be explained if it is assumed that the first step in the reaction is the removal of a proton from the hydroxyl group (XXI to XXIII and XXII to XXIV), followed by the displacement of chloride ion by the alkoxide ion of the trans form (XXII1 to XXV) and by a hydride ion in the cis form (XXIV to XXVII). Displacement by alkoxide leads to cyclohexene oxide (XXV), and this intermediate can be further attacked by hydroxide ion to give the dl trans glycol (XXVI). Cyclohexanone is produced by the hydride displacement (XXIV to XXVII) ... 

An important feature of coordinatively unsaturated alkyls, such as those just noted or those of Mg, Zn, etc., is the moderately rapid exchange of alkyl groups.46 The exchanges can be readily studied by nmr methods and it appears that bridged transition states, or intermediates of the type (10-XXIV) and the like, provide the means for exchange. The rates of exchange reactions are... 

XXIV-IA. A similar number assigmnent [see Table 7A in (3266)] was made in the case of individual components used as tobacco ingredients by cigarette manufactures outside of the United States. That numerical listing appears in Table... 

The iron catalyst can also be assembled in situ. The Na+ form of fluorotetrasilicic mica was ion exchanged with Fe +, then the iron-modified clay was treated with a solution of a bis(imino)pyridine ligand in l-butanol.i Formation of the intercalated metal complexes was inferred by the appearance of the characteristic u(C = N) mode at 1588cm i and an increase in the basal spacing of the clay from 1.0 to 1.6nm for XXIII and XXIV. The bulkier XXII apparently did not form due to the inability of the ligand to penetrate the interlayer space. 

The syntheses and some pharmacological properties of mono- (XXIIIb) and diacetyldapsone (XXIIIc) were reported . Investigation of repository dapsone polymers resulted in the preparation of XXIV, which was found to have a more intense but less prolonged effect than XXIIIb and to be safer than dapsone XXIIIa. This was manifested by the appearance of only a low order of methemoglobin, a major problem with prolonged dapsone therapy. 

Additional reports have appeared on pharmacological and clinical investigations with azapropazone (xxi) (Apazone 0 Benzpiperylon (xxil) and LH-150 (xxill) are reported clinically effective. Trl-methazone (xxiv) is reported as effective as phenylbutazone clinically and claimed to cause less gastric irritation or water retention. ... 

The molecular weights of Vertebrate haemoglobins are situated around 65,000-68,000. The molecules are apparently made up of two systems of three peptide chains. The N-terminal amino acid sequence of a number of haemoglobins is given in Table XXIV. There would appear to be a common basic chain in all cases. 

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