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White dwarfs, with masses just above the Chandrasekhar limit (1.4 solar masses), can violently collapse into small (104 km radius) and very dense (ρ = 1017 kg/m3) magnetars that can produce B-field...

Pasteur was the first to realize Earth's homochirality. Consequently, he attempted to design experiments revealing a mechanism that would expose life's chiral preference. Some of these experiments involved the application of magnetic fields to chemical reactions. His experiments failed, in part, because B-fields are pseudo-vectors and cannot couple preferentially to one handedness. However, extremely large magnetic fields cause the Maxwell equations to break down. This allows the motions of spin and charge densities in paramagnetic anion radicals to produce polarized axial B-fields that can undergo preferential coupling to one handedness. Hence, when a racemic mixture of paramagnetic organic molecules passes by an extremely large external gradated magnetic field, the enantiomers experience different torque forces and acquire different translational directions. B-fields of the required magnitude are unknown on this planet. In fact, they would be lethal, thereby eliminating any chance of Pasteur's success. On the other hand, Duncan and co-workers have recently discovered and garnered physical understanding of magnetars in interstellar space. Some of these neutron star systems produce B-fields greater than the quantum electrodynamic field strength, which is more than enough to generate the required torque for the interstellar enantiomeric separation. In space, chiralitically enriched materials can be deposited on planetesimals and result in homochiral "islands" on the planets. The formation of magnetars is a consequence of weak force events. We assert that, in interstellar space, a plethora of enantiomerically enriched dust clouds resulted from inter-magnetar-paramagnetic molecule force fields.

A mechanism is presented concerning electrolysis of deuteriated water with a palladium cathode that is infused with deuterium (palladium deuteride) resulting in the formation of small amounts of radioactive tritium, excess energy (more than allowed by EMF chemistry alone) and the concomitant liberation of 4He. These net electron catalyzed nuclear chemical reactions (2H + 2H + e− → 4He + e− + heat) and (2H + 1H + e− → 3H + e−) appear to be a result of respectively four and three isotope effects acting in combination with each other in a non-linear (chaotic) fashion to produce a metastable nuclear isomer of hydrogen-4 or hydrogen-3. The four isotope effects begin with the influx of electrons into the –Pd D Pd D Bravais lattice conduction band and consequent preferred rupture of individual weak Pd-D bonds (over those of Pd H) in the cathode liberating D2. This is followed by the newly freed deuterium capturing an electron yielding a di-neutron (onon). The onon then reacts with a deuterium or hydrogen (from protic impurity in the lattice) via phonon enforced quantum tunneling resulting in 4mH or 3H respectively. The 4mH quickly undergoes nuclear internal conversion to form 4He. These reactions involve the weak force (Feynman Diagrams are shown), but they take place in simple electrochemical systems that are normally thought of in terms of the electromagnetic forces only. The combined influence of the four isotope effects explains thousands of, what were considered, anomalous observations by top electrochemical researchers. The newly described mechanistic effects involve a very important and almost forgotten intermediate (the di-neutron) and may even involve unique safety concerns.

Benzophenone, a material that is common in biomass and coal, resists pyrolysis up to 400 °C. However, when the compound is reduced with potassium metal in tetrahydrofuran (THF) followed by solvent removal, the C−H bonds, as well as the CO bond, are activated, and the solid K+C12H10CO•–·THF salt begins to gasify at less than 250 °C. The noncondensable (at liquid nitrogen temperature) gases consist of hydrogen and methane. Condensable pyrolysis products include the following: benzene, toluene, biphenyl, xylenes, diphenylmethane, and ethylbenzene. When the temperature is raised to 380 °C and held there for several hours, CO is also liberated. Isotopic labeling studies suggest that the CH4 comes from a carbene intermediate, and the CO does not originate from the carbonyl moiety of the ketyl.

EPR studies in tetrahydrofuran, reveal that the one electron reduction of 1-(9-methyl-9H-fluoren-9-yl)-4-methylbenzene via electron transfer from cesium metal produces an anion radical that has a large affinity for the cesium cation. The affinity of this anion radical for Cs+ is so great that it will actually "suck" the Cs+ (but not Na+ or K+) right out of the grasp of 18-crown-6, leading to a cation-assisted pi-stacked complex, where the s-orbital of the metal cation is simultaneously overlapped with the pi-clouds of the phenyl and fluorenyl moieties. At ambient temperature, proton- and cesium-electron coupling constants are rapidly (on the EPR time scale) modulated as a result of the simultaneous existence of two interconverting conformers having an averaged cesium splitting (a(Cs)) of about 1.6 G. The pi-s-pi-electronic coupling can be turned on or off via the addition or removal of cesium cations. Analogous pi-s-pi-electronic coupling is observed in the 1,4-bis(9-methyl-9H-fluoren-9-yl)benzene-cesium system.

[reaction: see text] Reaction of 1,4-dibromo-[8]annulene (C(8)H(6)Br(2)) with potassium tert-butoxide in THF followed by exposure to potassium metal leads to the formation of the anion radical of sym-[8]annuldiyne. The rapid interchange of Jahn-Teller-induced alternating bond angle conformers of sym-[8]annuldiyne is halted by ion association with a metal-crown ether complex forming the cyclooctadienyne-eta(2)-ynyl potassium zwitterionic radical, rendering all four protons nonequivalent. Neutral sym-[8]annuldiyne can form the [2 + 2] polymer, which is not soluble in the THF solution.

The room temperature potassium reduction of 1,2,3-triscyclooctatetraeneoxypropane, in hexamethylphosphoramide (HMPA), yields an anion radical, which disproportionates so strongly to the dianion diradical that the anion radical cannot be observed via EPR. The dianion diradical has one unpaired electron in a primary and one in a secondary ring system, and it can be readily reduced to the corresponding trianion triradical. An analogous reduction of 1,2,3,4-tetrakiscyclooctatetraeneoxybutane does produce an observable anion radical, but it also is readily reduced to the system corresponding to one electron per eight-membered ring (the tetraanion tetraradical). These results and those obtained from systems containing two cyclooctatetraene (COT) moieties are explained in terms of the geometry changes COT undergoes upon one-electron reduction, the interactions between reduced and adjacent unreduced ring systems, and the electron- electron repulsion present in the polyanion polyradicals.

The anion radical of mono-bromo-[8]annulene was generated in the absence of ion association, and the EPR-measured spin densities can be explained in terms of the odd electron occupying MOs: Ψ4‘ = [2√(n2 + 1)]-1(ψ1 + nψ2 − ψ3 − nψ4 + ψ5 + nψ6 − ψ7 − nψ8) and Ψ5‘ = [2√(n2 + 1)]-1(ψ1 − nψ2 − ψ3 + nψ4 + ψ5 − nψ6 − ψ7 + nψ8) where n > 1. This anion radical subsequently disproportionates to its corresponding dianion and neutral molecule. The dianion then undergoes a loss of Br-, leaving the [8]annulenyl carbanion, which can abstract a proton from either HMPA or liquid ammonia. The pseudo-ortho-bromo-[8]annulenyl carbanion also loses Br- to give [8]annulyne, which can be stabilized in the form of its anion radical. The g value of the anion radical of [8]annulyne indicates that the extra strain energy due to the presence of the triple bond causes the two highest occupied MOs (degenerate in the anion radical of [8]annulene) to be slightly split.

The low-temperature (-100 degrees C) dehydrohalogenation of bromocyclooctatetraene followed by immediate electron-transfer yields a stable solution of the [8]annulyne anion radical. If the unstable [8]annulyne is reacted with itself, cyclobutadiene, or benzyne, the respective bi-[8]annulenylene, [6]annuleno[8]annulene, or [6]-[8]annulenylene can be trapped as their anion radicals via one-electron transfer. These condensation products were all obtained from simple [2 + 2] cycloaddition reactions. B3LYP/6-31G geometry optimizations were carried out, and the calculated spin densities were compared to the EPR spectral results obtained for the anion radicals of [6]annuleno[8]annulene, [8]annulyne, bi[8]annulenylene, and [6]-[8]annulenylene, and excellent agreement has been realized. This simple "one-pot" approach should be applicable to a wide range of such systems.

[reaction: see text] The room-temperature potassium reduction of 1,2-bis-cyclooctatetraeneoxypropane yields two different regio-spin isomer anion radicals in equilibrium (COT-O-C(Me)HCH(2)CH(2)-O-COT(*)(-) = (*)(-)COT-O-C(Me)HCH(2)CH(2)-O-COT) that is shifted far to the right. The presence of the unreduced ring perturbs the spin density on the reduced ring. Addition of more electrons generates the diradical dianion ((*)(-)COT-O-C(Me)HCH(2)CH(2)-O-COT(*)(-)), and the anion radical on the secondary side splits the degeneracy of the psuedo-ortho protons of the anion radical on the primary side.

C60 can be reduced to its trianion anion radical in hexamethylphosphoramide with potassium or cesium metal. The addition of water to these solutions, followed by toluene extraction, yields materials that exhibit the expected mass spectral peaks for the Birch reduction products of C 60 *3- (C60Hn). However, when cyclooctatetraene (COT) is present in the solution, the mass spectral signature for the Birch reduction products of M+@C60-COT*3- and C60-COT*3- are also found. The trianion radical of C60 reacts with COT in HMPA to yield a [2 + 2] cycloaddition product, and subsequent ring opening provides a passageway for the Cs+ or K+ counterion to the interior of the fullerene. Analogous results are not observed when the smaller metals (Na and Li) are used as the reducing agents. Only the larger alkali metal cations form tight ion pairs with the trianion of C60-COT. The tight ion association is necessary to bring the cation into a sufficiently close proximity to the trianion for the cation to proceed to the interior.

Both freshly sublimed C 6 0 and "off-the-shelf' C 6 0 were reduced with the alkali metals in hexamethylphosphoramide (HMPA). When pure C 6 0 is reduced to its trianion radical, it condenses with a molecule of HMPA to yield C 6 0 3-(HMPA)_, which exhibits a typical EPR pattern for a system with a doublet multiplicity and hyperfine splitting from the 3 1 P (a 3 1 P = 0.93 G). When Rb or Cs serves as the reducing metal, hyperfine is observed from the metal cation (a 1 3 3 Cs = 0.78 G, a 8 7 Rb = 1.393 G), which is involved in tight ion association with the P=O moiety (C 6 0 3-(HMPA)_,M + ). The small cations do not form intimate ion pairs, and both C 6 0 3-(HMPA)_ and C 6 0 3-(HMPA) 2 are present in solution when M = Na or Li. The latter species exhibits an EPR splitting from two 3 1 Ps. The "off-the-shelf" C 6 0 contains C 1 2 0 O as an impurity. Extensive reduction of this impurity results in a charged multianionic state where very large splittings from three 3 1 Ps are observed.

Electron paramagnetic resonance (EPR) studies have revealed that the steric interaction between the methyl hydrogens on a tert-butoxy substituent and the cyclooctatetraene (COT) ring system sterically induces a puckering of the eight-membered ring in the anion radical of tert-butoxy-COT. The induced nonplanarity of the COT ring system causes a large attenuation of the EPR coupling constants. Since the C-D bond length is slightly shorter than is the C-H bond length, replacement of the tert-butyl group with a tert-butyl-d(9) group results in less steric interaction and measurably larger electron proton coupling constants. The oscillation between the two close to planar alternating bond length (ABL) D(2d) conformers of the COT moiety was found to be extremely rapid (k10(12) s(-1)) and quantum mechanical tunneling is proposed to be involved.

The anion radicals of [18]annulene and of [6]annulene undergo Jahn-Teller distortions from the D 6 h conformations of their respective neutral molecules. The conformation of lowest energy for the anion radical of benzene has a C 2 e symmetry, and that for the anion radical of [18]annulene is D 2 h . The very rapid pseudo-rotation of the benzene C 2 r system causes the six protons of the benzene anion radical to appear as if they were equivalent in the EPR experiment. Fast pseudo-rotation rendering the uniform distribution of spin density in the [18]annulene anion radical system is prevented by the nonplanarity of the radical. Hence, the EPR spectrum of the [18]annulene anion radical must be interpreted in terms of a static (on the EPR time scale) D 2 h conformation, which pseudo-rotates over a C 2 h transition state. B3LYP calculations support these conclusions.

In contrast to the thermolysis of p-benzoquinone, which does not decompose until the temperature is over 800 degrees C, and then primarily yields vinylacetylene, the corresponding anion radical, precipitated from liquid ammonia [Na(+)(NH(3))C(6)H(4)O(2)(*-)], decomposes at 380 degrees C and fragments primarily into phenol, hydroquinone, ammonia, methane, carbon monoxide, hydrogen, and minor amounts of other simple compounds. When the benzoquinone is replaced with perdeuteriobenzoquinone, deuterium and hydrogen are randomly scrambled into the products, and both ND(3) and CH(4) are formed. When the hot pyrolysis container is completely sealed, preventing the escape of volatile materials, p-aminophenol, as opposed to phenol, is the major liquid product.

The anion radical of cyclooctatetraene (COT) must undergo a Jahn−Teller distortion from its ideal D8h symmetry. Both B3LYP/6-31+G* calculations and EPR observation have shown that the COT moiety in the anion radical of 1,2-dicarbo-tert-butoxycyclooctatetraene exists in a pair of degenerate D4h alternating bond angle conformations (a b1g distortion). The rapid (k = 3 × 107 s-1) interconversion between the two identical conformations leads to specifically predicted line width alternation effects in the EPR spectrum. The COT ring system in the 1,2-dicarbomethoxycyclooctatetraene anion radical [(CH3OOC)2COT-•], on the other hand, has a ground state with alternating bond lengths. Since this b2g distorted (COT-•) system has a plane of symmetry that can be drawn through the molecule and between the two substituents, no line width alternation effects can take place. However, in this system, the B3LYP/6-31+G* calculations predict an energy difference between the b1g and b2g distorted COT-• ring systems of less tha...

X-Band (9.8 GHz) EPR measurements show that the free energy change controlling the electron transfer from the anion radical of perdeuterated [16]annulene to neutral [16]annulene (C16D16•- + C16H16 ⇋ C16H16•- + C16D16) is ΔG° = −0.65 kcal/mol. When supplied with vibrational frequencies from B3LYP/6-31+G* calculations, the QUIVER program determines a ΔG° value of −0.142 kcal/mol. Thus, the experimental and theoretical values are in qualitative agreement. This result is the opposite of that obtained for the [8]annulene system, where the solution electron affinity of C8D8 proved to be slightly greater that that for C8H8. 1H NMR (400 MHz) experiments reveal that the barrier to ring flattening is greater in the C16D16 system than in the C16H16 system. Coupled with the DFT prediction that the C16D16•- is nearly planar, this accounts for the equilibrium isotope effect observed in the electron transfer. The W-Band (94 GHz) EPR spectra, showing that the isotropic g-factor of the [16]annulene anion radical is not al...

A series of new alkoxycyclooctatetraene ethers was synthesized and their anion radicals generated in hexamethylphosphoramide. The EPR measured spin densities can be explained in terms of the odd electron occupying MOs, ae4′ ) [1/2x(n 2 + 1)](na1 + a2 - na3 - a4 + na5 + a6 - na7 - a8) and ae5′ ) [1/2x(n 2 + 1)](na1 - a2 - na3 + a4 + na5 - a6 - na7 + a8), where n increases with the electronreleasing nature of the alkoxy group. The anion radicals of n-propoxycyclooctatetraene and ibuprofoxycyclooctatetraene exhibit a small (ca. 0.35 G) splitting for the A proton on the sp 3 hybridized carbon. Further, the EPR pattern for the tert-butoxycyclooctatetraene anion radical is consistent with a relatively smaller value for n (in ae4′ and ae5′). These observations are consistent with a rather unusual homohyperconjugative interaction involving overlap of the U-bond to the A-hydrogen and the ﷿-system of the conjugated COT ring.

The C−O and C−H bonds of 18-crown-6 are activated when 18-crown-6 is complexed with the potassium salt of the benzene anion radical. Evacuated glass bulbs containing the solid anion radical salt of potassium 18-crown-6 benzene anion radical were plunged into a bath at 320 °C, resulting in mini-explosions and generating a series of compounds including dioxane, 2-methyl-1,3-dioxolane, divinyl ether, hydrogen, methane, and 15-crown-5. Deuterium labeling studies proved that all of these compounds originated from the 18-crown-6. Further, these labeling studies were an aid in discerning the mechanism of the decomposition. Benzene, 1,4-cyclohexadiene, and cyclohexene were also generated. The last two originated from the reaction of the anion radical of benzene with hydrogen.

1H NMR studies (400 MHz) on isopropoxycyclooctatetraene (C8H7-O-C3H7) and its ring-d7 analogue (C8D7-O-C3H7) show that there is an inverse isotope effect on the rate of ring inversion of kH/kD = 0.68−0.57 in the temperature range from −10 to −50 °C. These experiments confirm the validity of previously published DFT calculations on cyclooctatetraene/cyclooctatetraene-d8, which predict an inverse isotope effect of about this size on the rate of ring inversion in this temperature range. The large inverse isotope effect upon ring inversion explains why the similarly large normal equilibrium isotope effect, found in the reduction of benzene to its corresponding anion radical, is not observed in the analogous reduction of cyclooctatetraene.

The solid dianion salt of 1,2-di-13C-cyclooctatetraene was synthesized in order to measure the first 13C−13C NMR coupling in an aromatic annulene other than benzene and to find out if this dianion will undergo high-temperature automerizations analogous to those previously observed in the benzene system. The solid potassium salt was heated to over 600 °C for 2 h, and although decomposition with H2 and CH4 evolution takes place, there is no observable scrambling of the 13C's. The positions of the 13C's were monitored via NMR, which necessitated a rather complete understanding of the NMR couplings for the cyclooctatetraene dianion system. Interestingly, the 1JCH and 1JCC couplings for the aromatic COT2- system of 145.9 and 55.8 Hz are all quite comparable to those recently reported for the 1,2-di-13C-benzene system (158.6 and 55.8 Hz, respectively).

7Li NMR spectra of solutions of the lithium salts of the R and S chiral isomers of the sec-butoxycyclooctatetraene dianion (C8H7−OC4H92-) in S,S-(+)-2,3-dimethoxy-1,4-bis(dimethylamino)butane were found to be remarkably different. The lithium cations in both solutions exist as mixtures of solvent-separated ion pairs and contact ion pairs with the dianion of C8H7−OC4H9. However, the relative concentration of the contact ion pair is much greater for the R isomer of C8H7−OC4H92- than for the S isomer. The complexity of steric interactions involving the chiral solvent and the R and S sec-butoxy groups results in the solvent being much more capable of partially separating Li+ from the S isomer of C8H7−OC4H92- than from the R isomer.

B3LYP/6-31+G* density functional calculations have been performed in order to understand why large, equilibrium isotope effects have been observed in the reduction of benzene to the corresponding radical anion but not in the reduction of cyclooctatetraene (COT) to COT•-. The calculations reproduce these experimental trends. However, the calculations also find that reduction of planar COT, like that of benzene, has a substantial, equilibrium isotope effect. Therefore, the small isotope effect, both calculated and observed, for reduction of COT is due to an inverse isotope effect on the planarization of the tub-shaped ring in COT. The isotope effect computed for forming planar (D8h) triplet COT/COT-d8 at 173 K is 0.38. This is the predicted isotope effect on the adiabatic singlet−triplet splitting in COT. The isotope effect computed for forming planar (D4h) singlet COT/COT-d8 at the same temperature is 0.41. This is the predicted isotope effect on ring inversion. The reason why planarization of COT has an i...

The solid potassium salts of the nitrobenzene anion radical [K+C6H5NO2•-(solid)] and all three nitrotoluene anion radicals were generated via the potassium reduction of the nitroaromatic in liquid ...

The equilibrium isotope effects (EIE) for the one-electron transfer between pyrene and seven regioselectively deuteriated pyrene isotopic isomers in dimethylformamide with 0.1 M tetrabutylammonium hexafluorophosphate were measured electrochemically. These data correlate linearly with the free energies (ΔG°) obtained in tetrahydrofuran using electron paramagnetic resonance (EPR) techniques. However, the slope of the resulting line is not unity, and it indicates that the EIE in the DMF system is only two-thirds of that in the THF system. PM3 calculated ΔG°'s, which would correspond to the gas phase electron transfers, also correlate linearly with both sets of experimental data, but the predicted magnitudes of the EIE's are smaller than those observed experimentally by either technique. The nonunity slopes probably reflect slight differences in ion solvation and/or ion association parameters between the anion radicals of the isotopic isomers. No general relationship between the EIE and the charge on the hydr...

EPR techniques, including spectral double integration, were utilized to measure the equilibrium contants in dimethoxyethane at 195 K for electron transfer between perdeuteriated p-xylene and xylene, α-d3-p-xylene and α,α′-d6-p-xylene. The results, coupled with the law of Hess, yield all the relative solution electron affinities (EA). It was found that methyl deuteriation lowers the solution EA by 160 J l mol−1 per deuterium, whereas ring deuteriation in these systems lowers the solution EA by about 370 J l mol−1 per deuterium, which is about the same effect as is observed in the benzene system. The results are discussed in terms of hyperconjugative, inductive and solvation effects.

The very reactive Rieke cadmium metal was allowed to react under vacuum with benzoquinone in tetrahydrofuran. This resulted in the formation of several different paramagnetic species whose EPR spectra prove them to have doublet multiplicities. The tetrahedral coordination sphere of each of these species consists of three THF molecules and an anion radical that is either asymmetrically coordinated or symmetrically coordinated to the metal dication. This latter species yields a 'IlCd hyperfine splitting of 6.86 G. The second anion radical lies outside this coordination sphere, and it can be either asymmetrically ion associated with or dissociated from the tetrahedral metal complex. All species have the general formula [Cd(CBH402'-)(~3]+,CsH402'or ([Cd(CsH402*-)(THF)31+ + C6H40;-}.

An equilibrium isotope effect (confirmed via physical separation of the isotopic isomers involved) was observed via the EPR analysis of a mixture of benzoquinone and benzoquinone- 13 C 6 competing for a deficient number of electrons in a tetrabydrofuran-liquid ammonia mature. The k eq for the reaction C 6 H 4 O 2 .- + 13 C 6 H 4 O 2 =C 6 H 4 O 2 + 13 C 6 H 4 O 2 .- is 0.66±0.04 at 200 K. An analogous competition for electrons between benzoquinone and perdeuterated benzoquinone sbows no equilibrium isotope effect. The 13 C effect is attributed almost exclusively to the carbonyl carbons

The addition of D 2 O to hexamethylphosphoramide solutions of the potassium salt of the [8]annulene anion radical results in the slow (days) formation of the monodeuteriated anion radical (C 8 H 7 D .- ). However, several days after a similar addition to the sodium salt solution, no C 8 H 7 D .- is present. Instead, the anion radical of [16]annulene is found. These observations led to EPR and NMR studies, which have revealed the mechanism of each process

EPR studies show that the anion radicals of α,α,α-d 3 -p-xylene and α,α'-d 6 -p-xylene (CD 3 -C 6 H 4 -CD 3 .- ) exhibit hyperfine coupling constants for the ring protons that are 12 and 23 mG larger than those of the p-xylene anion radical itself. This has been attributed to a further lifting of the degeneracy of the antibonding molecular orbitals due to the replacement of the protons with deuteriums to an extent of 29 J/mol per deuterium. These results seem to support the conclusion that both inductive and hyperconjugative effects are responsible for the lifting of this degeneracy due to the methyl groups

A series of electron transfer competition reactions between several isotopically different benzophenones was established in liquid ammonia. The resulting electron transfer (A .- +B=A+B .- ) equilibrium constants were determined via EPR studies and via the physical separation of the anion radical phase from the neutral molecule phase. This anion radical-neutral molecule separation leads to a partial separation of the isotopic isomers involved due to the deviation of the equilibrium constants from unity

The solid potassium salts of the nitrobenzene anion radical [K+C6H5NO2•-(solid)] and all three nitrotoluene anion radicals were generated via the potassium reduction of the nitroaromatic in liquid ...

EPR analysis shows that the anion radical of 2,6-dinitrotoluene (DNT) in liquid ammonia exists with the counterion (either K+ or Na+) associated with one of the two nitro groups. This tight association (−NO2•-M+) persists after solvent removal, and it renders the anion radical very susceptible to loss of metal nitrite. The slightest agitation of the solid potassium salt of DNT•- leads to detonation, and formation of KNO2 and polymer (in the solid phase) and CH4, HCN, H2, and N2O (in the gas phase). Trapping experiments suggest that the methane comes from carbenes, and it is suggested that the HCN comes from an anthranil radical intermediate. The potassium anion radical salts of 1,3-dinitrobenzene, 2,6-dinitrotoluene, 1,3,5-trinitrobenzene, and 2,4,6-trinitrotoluene all readily lose KNO2, and the ease of C−NO2•-M+ bond rupture increases with the degree of nitration. In the cases of the two trinitrated systems dissociation takes place immediately upon anion radical formation in liquid ammonia. This observat...

1H NMR studies (400 MHz) on isopropoxycyclooctatetraene (C8H7-O-C3H7) and its ring-d7 analogue (C8D7-O-C3H7) show that there is an inverse isotope effect on the rate of ring inversion of kH/kD = 0.68−0.57 in the temperature range from −10 to −50 °C. These experiments confirm the validity of previously published DFT calculations on cyclooctatetraene/cyclooctatetraene-d8, which predict an inverse isotope effect of about this size on the rate of ring inversion in this temperature range. The large inverse isotope effect upon ring inversion explains why the similarly large normal equilibrium isotope effect, found in the reduction of benzene to its corresponding anion radical, is not observed in the analogous reduction of cyclooctatetraene.

Alkali metal over-reduction of an electron acceptor in the presence of a hydrogen atom donor, in hexamethylphosphoramide (HMPA), results in a radical that is not simply the anion radical of the acceptor. This new species exhibits an enigmatic EPR pattern. Using 15N and 2H labeling studies, the "HMPA degradation product" was found to be the anion radical of N,N'-dimethyl-1,4-diazabutadiene. DFT calculations support this assignment and a mechanism for its formation.

Solutions of 1,4-bis(dihydroquininyl)-anthraquinone {(DHQ)2AQN} in either hexamethylphosphoramide (HMPA) or liquid ammonia undergo a photoinduced electron transfer from the solvent to the (DHQ)2AQN. The resulting anion radical {(DHQ)2AQN•-} yields coupling to the six (3 sets of 2 equivalent) protons on the anthraquinone moiety upon EPR analysis. The same anion radical can be generated via alkali metal reduction in tetrahydrofuran. Further exposure of the HMPA solution to visible light causes the anion radical to undergo a conformational change. The photorearranged product allows delocalization of spin into the γ proton on the sp3 hybridized alkoxy carbon. In NH3(liq) and THF, hydrogen bonding and ion association prevents this photorearrangement, respectively.

A number of techniques have been found to generate annulynes. Some of the annulynes have been found to spontaneously dimerize to biannulenylenes and to form triannulenylenes. The reaction products, thermodynamics, and kinetic stabilities of the annulenylenes, annulynes, and their parent annulenes prove to be extremely dependent upon the number of pi electrons. In fact, the addition of an extra electron can trap some "fugitive" systems and render them sufficiently stable for spectroscopic study. Even the number of neutrons can perturb the conjugation and, presumably, the stability of annulenes that have internal protons.

When a cold (200 K) THF solution of 1,6-heptadiyne is exposed to potassium tert-butoxide, in the presence of 18-crown-6, a green, EPR active solution is spontaneously formed. The intensity of the EPR signal can be augmented by exposure to alkali metal. Analysis of the EPR splitting pattern indicates that the signal originates from the anion radical of 7,14-di-trans-1,5- [14]annuldiyne. Allowing the green-colored solution to warm to ambient temperatures causes an immediate color change (to deep purple) and loss of the EPR activity. Reduced pressure distillation of the solution affords a colorless THF solution containing (spiro[2.6]nona-2,6,8-triene), which is only the second spirocyclopropene compound reported. The base condensation of the diyne is of a general nature as the same spirocyclopropenyl system is obtained from 1,6-heptadiyne, 1,7-octadiyne, and 1,8-nonadiyne. Laser irradiation (337 nm) of tungsten hexacarbonyl in the presence of the spirocyclopropenyl compound yields the stable organometallic: eta2-olefin pentacarbonyl complex.

Electron paramagnetic resonance spectroscopy has been used to discriminate between the R- and S-forms of the anion radical of camphorquinone. In a chiral solvent [SS- or RR-2,3-dimethoxy-1,4-bis(dimethylamino)butane saturated with sodium iodide], ion association between the semidione and Na+ takes place. PM3 calculations suggest that the complex relationship between the solvent, anion, and cation varies sufficiently with changes in the chiral nature of the solvent or anion radical to alter the appearance of the EPR signal allowing EPR chiral discrimination.

Calorimetric techniques have revealed that the enthalpy of reaction with water is more exothermic by about 2.2 kcal/mol, for the perdeuteriated naphthalene anion radical (K + C 10 D 8 •- (s) + H 2 O(liq) → 1/2C 10 D 8 H 2 (s) + 1/2C 10 D 8 (s) + KOH(aq)) than it is for the perprotiated system. These results, when coupled with the known enthalpy of electron transfer between naphthalene and its perdeuteriated analogue imply that the heat of hydrogenation of naphthalene decreases by about 1.8 kcal/mol upon perdeuteriation of the naphthalene.

The one-electron reduction of neutral pi-stacked di- and trifluorenes (F-2 and F-3) in HMPA, where ion association is absent, results in the formation of anion radicals in which the odd electron resides predominantly on just one of the external fluorene moieties, as established by EPR spectroscopy. However, in the case of tetrafluorene, introduction of a single electron leads to a kinetically controlled anion radical F-4(int)*- in which the odd electron undergoes rapid exchange between two central fluorene rings, where the anionic charge is partially shielded from solvation due to the presence of external fluorene rings. On a time scale of minutes, anion radical F-4(int)*- converts to a thermodynamically stabilized anion radical F-4(ext)*-, with the electron exhibiting coupling from the protons on an external fluorene moiety. The charge and spin residing on an external moiety allow efficient solvation of the anionic charge. A similar fast exchange of a single electron (probably with the involvement of quantum mechanical tunneling) among three and four internal fluorene moieties is initially observed via EPR spectroscopy in the penta- and hexafluorene derivatives, F-5 and F-6, respectively.

Only one isomer of o-benzyne ([6]annulyne or 1,2-didehydrobenzene) exists, but the dehydro analogue of the "ring-opened double benzene", [12]annulyne, was generated in several isomeric forms. 1,5-Hexadiyne undergoes self-condensation in the presence of potassium tert-butoxide to yield two isomers of [12]annulyne (3,11-di-trans-[12]annulyne and 5,9-di-trans-[12]annulyne), both of which exhibit a weak paratropic ring current in their 1H NMR spectra and are oxygen sensitive. They can be reduced to their respective dianions, which are diatropic. A third isomer (3,9-di-trans-[12]annulyne) was generated via the complete dehydrohalogenation of hexabromocyclododecene and found to be much less stable but can be tamed via one- or two-electron reduction. A tight association of the cation (K+) with the p(y)-orbitals within the alkyne moiety results in an unusually low-field resonance for an adjacent external proton.