Spectra anions

Figure 9 Anion photoelectron spectroscopy. Its unique features are (I) Intrinsic mass selectivity and (ii) neutrals as final states. Here, as an example the results for compounds of iron, carbon and hydrogen are shown which exist in catalytic processes, high-temperature terrestrial or low-temperature astrophysical chemistry. Bottom spectrum a primary anion mass spectrum containing anions of the complexes of interest. Top spectra anion photoelectron spectra obtained by electron kinetic energy analysis after laser-induced photodetachment. They reveal the change of molecular structure and electronic energies for increasing numbers of hydrogen atoms in the complex.

The transition-state spectroscopy experiment based on negative-ion photodetachment described above is well suited to the study of the F + FI2 reaction. The experiment is carried out tln-ough measurement of the photoelectron spectrum of the anion FH,. This species is calculated to be stable with a binding energy of... 

The ESR spectrum of the pyridazine radical anion, generated by the action of sodium or potassium, has been reported, and oxidation of 6-hydroxypyridazin-3(2//)-one with cerium(IV) sulfate in sulfuric acid results in an intense ESR spectrum (79TL2821). The self-diffusion coefficient and activation energy, the half-wave potential (-2.16 eV) magnetic susceptibility and room temperature fluorescence in-solution (Amax = 23 800cm life time 2.6 X 10 s) are reported. 

A measurement of the ratio [RH] [R ] at a known H yields the pK. If, as is frequently the case, the electronic spectrum of the hydrocarbon and its anion are not sufficiently different, one of the indicators is used and its spectrum is monitored. The equilibriuih established between the indicator and hydrocarbon in the basic mediiun... 

An isomeric form of the anion that is initially formed is converted to the aU-cis system rapidly at room temperature.Data on the equilibrium acidity of the parent hydrocarbon are not available, so the stability of the anion cannot be judged quantitatively. The NMR spectrum of the anion, however, is indicative of aromatic character. 

The NMR spectrum indicates a planar aromatic structure. It has been demonstrated that the dianion is more stable than the radical anion formed by one-electron reduction, since the radical anion disproportionates to cyclooctatetraene and the dianion ... 

Fig. 12.2. EPR spectra of small organic free radicals, (a) Spectrum of the benzene radical anion. [From J. R. Bolton, Mol. Phys. 6 219 (1963). Reproduced by permission of Taylor and Francis, Ltd.] (b) Spectrum of the ethyl radical. [From R. W. Fessenden and R. H. Schuler, J. Chem. Phys. 33 935 (1960) J. Chem. Phys. 39 2147 (1963). Reproduced by permission of the American Institute of Physics.]...

Analyze the hyperfine coupling in the spectrum of the butadiene radical anion given in Fig. 12.PI I. What is the spin density at each carbon atom according to the McConnell equation ... 

The combination of electrochemical and EPR studies can provide valuable information about unstable S-N radical species. A classic early experiment involved the electrochemical reduction of S4N4 to the anion radical [S4N4] , which was characterized by a nine-line EPR spectrum. The decay of the radical anion was shown by a combination of EPR and... 

The tetramethylammonium salt [Me4N][NSO] is obtained by cation exchange between M[NSO] (M = Rb, Cs) and tetramethylammonium chloride in liquid ammonia. An X-ray structural determination reveals approximately equal bond lengths of 1.43 and 1.44 A for the S-N and S-O bonds, respectively, and a bond angle characteristic bands in the IR spectrum at ca. 1270-1280, 985-1000 and 505-530 cm , corresponding to o(S-N), o(S-O) and (5(NSO), respectively. Ab initio molecular orbital calculations, including a correlation energy correction, indicate that the [NSO] anion is more stable than the isomer [SNO] by at least 9.1 kcal mol . ... 

This shift in the infrared spectrum is practically independent of the anion properties. 

The absorption spectrum of this nonstoichiometric phase forms the basis for the formerly much-used qualitative test for zinc oxide yellow when hot, white when cold . Alternatively, anion sites can be left vacant, e.g. ... 

Trimethyl-4-pteridinone is an acid of pZ 9.5 and is therefore hydrated in the anion. The hydroxyl group is thought to be attached to C-7 and the negative charge to resonate between N-1 and N-3. The neutral species cannot be appreciably hydrated because its ultraviolet spectrum is very different from that of the anion. 

For reasons discussed in Section VI, a survey of the purine series (29) is being made in this Department, but so far no example (including 2-hydroxy- and 8-trifluoromethyl-2-hydroxy-purine) of covalent hydration has come to light. An examination of ionization constants disclosed no apparent anomalies, although the interpretation is made more difficult by the ease of anion formation in the 9-position, which often competes with that from other anionic substituents. The only abnormal spectrum seems to be that of the anion of 2-mercaptopurine which is being further examined. 

Hydroxy-8-azapurine was shown by rapid-reaction techniques (see Section II, E) to be anhydrous in the anion and hydrated in the neutral species. The hydration reaction has a half-time of about 0.5 second, which is too rapid for exact measurements with existing apparatus. The cation of 2-amino-8-azapurine was shown to have an anomalous value and ultraviolet spectrum, although its 6-methyl derivative is quite normal. Hydration in this case proved to be too fast to register in the rapid-reaction apparatus. 

Tile low-temperature ESR spectrum of the anion radical of purine disclosed that about 45% of the spin density is localized at position 6 (80BCJ1252), although a single very broad signal for N(7) and N(9) did not allow discussion of the tautomerism. 

The Apomorphine-derived alkaloid PO-3 (129) was isolated as violet needles after crystallization from acetone and ether from Papaver orientale (66MI2), but was not found in the green solutions of autoxidized apomorhine hydrochloride (62M941, 68HCA683) (Scheme 51). No anion was detected by elemental analysis. The pA"a of PO-3 is 3.88 0.02 in 50% ethanol. The IR spectrum displays no carbonyl absorption between 1650 and 1700 cm (69MI2). The UV absorption maxima of PO-3 are in agreement with the formulation of a mesomeric betaine [T-max (EtOH) = 310... 

A criterion for the position of the extent of the mesomerism of type 9 is given by the bond order of the CO bond, a first approximation to W hich can be obtained from the infrared spectrum (v C=0). Unfortunately, relatively little is known of the infrared spectra of amide anions. How-ever, it can be assumed that the mesomeric relationships in the anions 9 can also be deduced from the infrared spectra of the free amides (4), although, of course, the absolute participation of the canonical forms a and b in structures 4 and 9 is different. If Table I is considered from this point of view, the intimate relationship betw-een the position of the amide band 1 (v C=0) and the orientation (0 or N) of methylation of lactams by diazomethane is unmistakeable. Thus the behavior of a lactam tow ard diazomethane can be deduced from the acidity (velocity of reaction) and the C=0 stretching frequency (orientation of methylation). Three major regions can be differentiated (1) 1620-1680 cm h 0-methylation (2) 1680-1720 cm i, O- and A -methylation, w ith kinetic dependence and (3) 1730-1800 em , A -methylation, The factual material in Table I is... 

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