Tertiary Protons Research Articles

Signatures of volatiles in the lunar proton albedo

We find evidence for hydrated material in the lunar regolith using “albedo protons” measured with the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and are inconsistent with the latitude trends of heavy element enrichment (e.g., enhanced Fe abundance). The latitudinal distribution of albedo protons anti-correlates with that of epithermal or high energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron–proton collisions in hydrated regolith that is more prevalent near the poles. The CRaTER instrument may thus provide important measurements of volatile distributions within regolith at the Moon and potentially, with similar sensors and observations, at other bodies within the Solar System.

Cathodic immobilization of tertiary C―H moieties onto glassy carbon via secondary alkyl halides. A versatile way for surface modification

The complex structure of glassy carbon is exploited by means of its powerful reacting abilities under cathodic charge in aprotic solvents at quite negative potentials. Under polarization, the preliminary stage corresponds to the formation of nucleophilic centers (by reduction of graphitized and/or fullerenized) dispersed at (or in the vicinity of) the surface of such polarized materials. In the presence of electrophilic organic species such as organic halides, surface modification(s) may be obtained. These processes are expected to correspond to nucleophilic substitution (SN). While primary alkyl halides were reported to be easily fixed onto carbon in common polar aprotic solvents, secondary (and tertiary) alkyl halides were noticed to be not reactive under such conditions. Contrariwise, aprotic solvents with high dielectric constant (like propylene carbonate) permit to boost the interfacial reactivity of those halides. Thus, secondary bromides and iodides lead to compact deposits possessing tertiary protons identified by a two-electron oxidation step at about +1.2V vs. Ag/AgCl. Specifically, 2-bromoadamantane yields an organic layer assigned to grafted 2-adamantyl moiety. The chemical versatility of such deposits is presented.

A novel substitution reaction of perylene bisimides with Ph2PLi at the α-position

A novel substitution reaction of perylene bisimides has been developed. The Ph2PO group was attached to the PBI core at the α-position instead of the usual bay position. This substitution kept the high fluorescence of the PBI dyes and caused the adjacent proton at the bay position and a tertiary proton at the cyclohexyl group to be shifted significantly in the 1H-NMR spectra.

Hydrogen isotope exchange as a means of labeling lactides

Lactic acid-containing polymers obtained by the ring opening polymerization of lactides are now commercially available as bioresorbable polymers, or as devices that can be assimilated by the human body, or by living species present in the outdoor environment. Studying the mechanisms of lactide polymerization or polylactide degradation and monitoring the fate of the degradation compounds produced from the polymers when they degrade in complex media is thus very important and basically feasible via the labeling of polymer chains. Therefore, the possibility of exchanging some of the protons borne by lactide monomer molecules by deuterium or tritium was investigated. The substitution reactions involving deuterium were conducted and optimized using the High Temperature Solid State Catalytic Isotopic Exchange (HSCIE) method and applied to solid DL-lactide in the presence of various catalysts. The most active and stable catalyst was palladium on calcium carbonate. The analyses of the resulting deuterated compounds by 1H NMR and mass spectrometry showed that substitution involved mainly the tertiary proton and that the reaction temperature and flask volume were critical factors. The experimental conditions that led to convenient hydrogen-deuterium exchange yields were then applied to hydrogen-tritium exchange. Highly radioactive DL-lactide having a specific activity of 150 GBq/mmol. (4.05 Ci/mmol.) was successfully synthesized. Copyright © 1998 John Wiley & Sons, Ltd.

Tertiary proton diagnostics in future inertial confinement fusion experiments

Recently, it was proposed to use energetic (up to 31 MeV) tertiary protons produced during the final stage of inertial confinement fusion implosions to measure the fuel areal density of compressed deuterium–tritium (DT). The method is based on seeding the fuel with He3. The reaction of He3 ions with the energetic knock-on deuterons, produced via the elastic scattering of 14.1 MeV neutrons, is a source of very energetic protons capable of escaping from very large areal density targets. This work presents results of detailed time-dependent Monte Carlo simulations of the nuclear processes involved in producing and transporting these protons through imploding targets proposed for direct-drive experiments on OMEGA [D. K. Bradley et al., Phys. Plasmas 5, 1870 (1998)] and the National Ignition Facility [S. W. Haan et al., Phys. Plasmas 2, 2480 (1995)].

A Mechanistic and Structural Investigation of the (−)-Sparteine Mediated Asymmetric Benzylic Lithiation Substitution Reactions of N-Boc-N-(p-methoxyphenyl)benzylamine

Mechanistic and structural studies show the high enantioenrichments in the products from lithiation−substitutions of N-Boc-N-(p-methoxyphenyl)benzylamine (1) by n-BuLi/(−)-sparteine (6) arise from an enantioselective deprotonation of 1 to provide configurationally stable (R)-2/6. NMR spectroscopy establishes that 13C, 6Li labeled (R)-2/6 and (S)-2/6 are monomeric with lithium complexed to the benzylic position, the carbonyl of the Boc group and (−)-sparteine. Deprotonations of the tertiary protons in (R)- and (S)-N-Boc-N-(p-methoxyphenyl)-α-methylbenzylamine ((R)-8 and (S)-8) with n-BuLi/TMEDA provide (R)-9/TMEDA and (S)-9/TMEDA, respectively, with high enantioenrichments. Absolute configurations assigned to (R)-2 and (R)-1-d1 allow analysis of the electrophile dependent stereochemistry of the reactions of these configurationally stable organolithium intermediates.

Implosion symmetry and ρ R measurements on the National Ignition Facility from nascent 27–31 MeV tertiary protons (invited) (abstract)

Tertiary protons with birth energies from ∼27 to 30.8 MeV result from the implosion of ignition-scale inertial confinement fusion targets, such as those planned for the National Ignition Facility (NIF). Measurement of the tertiaries’ slowing can provide a determination of the imploded areal density of the fuel capsule, as well as implosion asymmetry that results from anisotropy of the areal density and plasma temperature. In order to determine the utility of tertiaries for all phases of the NIF, we analyze three representative cases: a gas capsule (0.7 kJ yield); a cryogenic fuel capsule that fails to ignite (15 kJ); and a cryogenic fuel capsule that ignites and burns (13 000 kJ). In each case, tertiaries escape from the capsule and convey critical information about implosion dynamics. In addition, we show that for some gas-capsule implosions anticipated on OMEGA, tertiaries may be the only species of energetic charged particles that can determine the fuel areal density. Presently, we are building a charge-coupled device (CCD)-based charged particle spectrometer for OMEGA and for NOVA. In addition to the tertiaries, the spectrometers are sensitive to a variety of the energetic charged particles, such as knock-on protons, deuterons, and tritons, and He3-burnup protons. In fact the latter set of charged particles will usually be the dominant signal. We will describe the basic features of the spectrometers and the measured response of the CCDs to 1–5 MeV protons, 1–5 MeV alphas, and 14 MeV neutrons (and associated gammas), the latter constitute the principal source of noise. This work is done in collaboration with C. K. Li, D. Hicks, and F. Seguin of MIT; with B. Burke of LL/MIT; with M. Cable, S. Pollaine, S. Haan, T. Bernat, T. Phillips, and J. Kilkenny of LLNL; with J, Knauer, S. Cremer, C. Verdon, and B. Kremens of University of Rochester; and with C. Ruiz and R. Leeper of SNL. This work is supported in part by LLNL Subcontract B313875 and University of Rochester Subcontract 410025-G.

Design of an electronic charged particle spectrometer to measure 〈ρ𝓡〉 on inertial fusion experiments

The design and fabrication of a new diagnostic that measures the energy spectra of charged particles from targets on the Omega Upgrade are actively underway. Using seven 512×512 charge coupled devices (CCDs) and a 7.5 kG permanent magnet, this instrument will uniquely determine particle identities and measure particle energies from 1 MeV up to the maximum charged particle energies of interest for ρR measurements (10.6 MeV knock-on tritons, 12.5 MeV knock-on deuterons and 30.8 MeV tertiary protons). The resolution of the diagnostic will be better than 5%. We have tested the response of SITe back-illuminated CCDs to 1.2–13.6 MeV protons from our Cockcroft–Walton accelerator and to alpha particles from an Am241 source, and the results agree extremely well with predictions. With its high density picture elements, each CCD has 105 single-hit detectors. In the case of a low DT yield of 109 neutrons, about 100 knock-on charged particles will be detected when the spectrometer aperture is 60 cm from the implosion. Measurements of ρR up to 150 mg/cm2 can be obtained from knock-on D and T spectra, and values up to 300 mg/cm2 can be determined from secondary proton spectra. The sensitivity of the CCDs to 14 and 2.5 MeV neutrons has been experimentally determined using our Cockcroft–Walton accelerator source and indicates that by incorporating neutron shielding, the signal to neutron noise ratio at a yield of 1011 will be better than 100:1. In the development phases of this program, we plan to utilize CR-39 track detectors concurrently with the CCDs.

Measuring Implosion Symmetry and Core Conditions on the National Ignition Facility.

Tertiary protons with birth energies from 27 to 30.8 MeV result from the implosion of ignition-scale inertial confinement fusion targets, such as those planned for the National Ignition Facility. Measurement of the tertiaries' slowing can provide a determination of the imploded areal density of the fuel capsule, as well as information about implosion asymmetry that results from anisotropy of the areal density and plasma temperature. To determine the utility of tertiaries for all phases of ignition experiments, we analyze three representative cases: a gas capsule (0.7 kJ yield), a cryogenic fuel capsule that fails to ignite (15 kJ), and a cryogenic fuel capsule that ignites and burns (13 000 kJ). In each case, tertiaries escape from the capsule and convey critical information about implosion dynamics.

Kinetic isotope effects in the deprotonation of chiral formamidines

Metallation of 6,7-dimethoxy isoquinoline formamidines show a kinetic isotope effect, in contrast to the metallation of the 6,7-dihydro system; the isotope effect for the secondary proton in the dimethoxy system is smaller than usual (2.0) while the isotope effect for tertiary proton removal is somewhat larger (∼4.0), this is explained by the magnitude of pKa on isotope effect as well as competition between the pre-complexation step and the deprotonation step.

1H and 13C NMR study of the neomenthyl halides: A very high field proton shift in the iodide

AbstractComplete analyses o the 1H NMR spectra of neomethyl iodide (1), the bromide (2) and the chloride (3) are reported. Of paticular interest is the very high‐field resonance at −0.16 ppm in 1 which is assigned to H‐4. The same poton in the bromide is also found upfield at 0.78 ppm. H‐4 in these neomenthyl derivatives is tertiary and β‐antipeiplanar to the halogen atom. A similar upfield shift has been reported previously for the tertiary proton in trans‐9‐iododecalin. The reasons or these unusual shifts are not readily apparent and the 13C NMR spectra of 1 and 2, which are reported here for the first time, provide no additional clues to explain the shifts.

α-amino carbanions. A second generation formamidine for facile deprotonation leading to α-quaternary substitution

Formamidines derived from o-methoxymethylaniline (MMA) allow proton removal of tertiary protons in 1-substituted-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines.

Depth of Penetration of the Plasma Fluorination Reaction into Various Polymers

ABSTRACTThe surfaces of a variety of polymers presenting either primary, secondary, tertiary, vinyl or aromatic protons to the reactive gas environment were fluorinated by glow discharge treatment. Depth profiles of the plasma surface reaction were obtained by SIMS with oxygen ion sputtering. Further information was obtained from the appearance of ESCA traces of these substrates before and after the reaction.

Conformational analysis of methylsuccinic acid by 1H NMR spectroscopy and circular dichroism

The pH-dependence of the 1H NMR and Circular Dichroism (CD) spectra of 2-methylsuccinic acid was investigated. Both spectra undergo dramatic changes between pH 4 and 6, where both carboxylic groups become ionized. From the coupling constants of the tertiary proton with the assigned 1 diastereotopic methylene protons, it is concluded that below pH 4 the syn-clinal ( 2) and above pH 6 the anti-periplanar ( 1) conformation of methylsuccinic acid prevail. The diesters of methylsuccinic acid also assume mainly the syn-clinal conformation ( 2). The pH-dependence of the CD spectra is discussed in terms of conformation and/or ionization effects.

A stereodynamic investigation of antivitamins K in the dicoumarol series. II. Differentiation between the two hydroxyl groups by the nuclear Overhauser effect

Dicoumarol derivatives, substituted at the bridgehead, show a double restricted rotation. This hindered rotation is manifest through the appearance of two signals, the hydroxyl protons being diastereotopic at low temperatures.In this work we assign the two respective signals by the nuclear Overhauser effect. The high-field signal corresponds to a hydroxyl site close to the bridgehead tertiary proton, while the other corresponds to a site in proximity to the substituent R. The case of structurally analogous dimethones has been investigated by the same technique with identical conclusions. This disproves the interpretation made previously on the basis of steric and anisotropic effects.The interatomic distances concerned have been calculated, and these have yielded an estimate of deformations induced by the bridgehead substituents.Evidence is supplied for the different behavior of the two sites and this study gives evidence for a very facile intermolecular chemical exchange of the hydroxyl site close to the tertiary bridgehead proton in the presence of traces of protonated compounds.The overall behavior is the result of the asymmetry of the molecules of this series in their chelated form.

Anomalous hydrogen-1 and carbon-13 spectra of some new N-acyl-N′-aryldiazene complexes of osmium

The complex [OsCl3O(PPh3)2] reacts with the hydrazides 4-RC6H4NHNHCOR′(R = MeO, Me, H, Cl, or NO2; R′= H, Me, Et, Prn, But or CH2Ph) to give the N-acyl-N′-aryldiazene complexes [OsCl2(4-RC6H4·N2·COR′)(PPh3)2]. Although apparently diamagnetic, their 1H and 13C n.m.r. spectra show shifts of a pattern and magnitude characteristic of paramagnetic species. Moreover these shifts are restricted to certain protons and carbon atoms of the diazene ligand, and the tertiary phosphine protons and carbon atoms show no anomalies. The magnitude of the shifts is highly dependent on the nature of the substituents in the diazene N-phenyl group, and there is an approximately linear relation between the shifts and Hammett σ constants for the substituent. Variable-temperature 1H n.m.r. spectra suggest that a second-order paramagnetic effect may be responsible for the shifts.

Mechanism of photolytic formation of trityl ions from triphenylmethane on acidic solids

The mechanism of the photo-generation of Ph3C+ ions from Ph3CH on the surfaces of acidic solids is deduced from observations on the chemisorption of Ph3CH, Ph3COH, and related compounds on anhydrous magnesium perchlorate and zirconium phosphate. Protonation of one of the phenyl groups of Ph3CH is followed by light absorption and elimination of the tertiary proton from the carbonium ion in the excited state. The net result is an endothermic isomerization to diphenylmethylenecyclohexadiene which rapidly yields the Ph3C+ ion by loss of a hydride ion, especially in the presence of O2, at acidic sites.

NMR spectrum of poly(propene sulfide)

AbstractThe 100 MHz spectra of polymers of propene sulfide and propene‐2‐d1 sulfide have been determined in CDCl3, CCl4, and C6D6. In the deuterated polymer the main‐chain protons give rise to two overlapping AB quartets in which the two pairs of upfield B lines are coincident and the two pairs of downfield A lines are resolved. With CdCO3 as polymerization catalyst the downfield quartet is twice as strong as the upfield quartet. The former is ascribed to an isotactic dyad: magnified image and the latter to a syndiotactic dyad: magnified image Other catalysts (ZnCO3, CuCO3, SiO2/Al2O3, Na) produce an essentially atactic structure. The values τA = 7.125, τA′ = 7.155, τB = 7.45, JAB = −12.9 Hz, derived from the spectrum of the deuterated polymer (in CCl4) were used to obtain the following values from the spectrum of the undeuterated polymer (tertiary proton = Hc): τC = 7.131, JBC = 10.0 Hz, JCA = 4.1 Hz. The magnitudes of the vicinal coupling constants indicate a preferred trans conformation for the mainchain CC bond. τA, τB, and τC are somewhat dependent on solvent; τCH3 = 8.63, independent of solvent, and JCH3, HC = 6.2 Hz.

Über 1, 5‐Diphenyl‐2, 3, 6, 7‐tetrahydro‐1H, 5H‐pyrazolo[1, 2‐a]pyrazole(2, 6‐Diphenyl‐1, 5‐diazabicyclo[3, 3, 0]octane)

AbstractThe synthesis of a 1, 5‐diphenyl perhydro‐pyrazolo‐[1, 2‐a] pyrazole (IV) (m. p. = 170–171°) by LiAlH4‐reduction of its 3, 7‐dioxo derivative Va, one of the stereoisomers of V, is described. Va was obtained in small yield by the reaction of cinnamic acid with its hydrazide or with hydrazine. It proved to be identical with the compound obtained previously by interaction of cinnamic acid hydrazide with iodine which in the literature erroneously had been described as N, N′‐dicinnamoyl hydrazine. This hydrazine now was obtained by bis‐acylation of hydrazine with cinnamoyl chloride.In Va the extremely low NMR. absorption of the tertiary protons at ρ = 4,6 ppm is probably due to the spatial grouping magnified image with the proton situated in the deshielding region of the carbonyl group.Previously, another tertiary proton with a very low NMR. absorption at ρ = 4,85 ppm has been observed in the «bisimide M», the main criss‐cross addition product of one mole benzaldazine and two moles of N‐(n‐butyl)‐maleinimide. A stereostructure for bisimide M is now proposed, which is a hybrid between those of the bisimides L and H.

Konfigurations- und konformationsanalyse von 2-substituierten cycloheptanolen

The cis-trans-isomers of 2-substituted cycloheptanols can be distinguished by the different chemical shifts of the proton at the C atom bearing the hydroxyl group. Decoupling experiments show also a significant difference between the coupling constants of the two tertiary protons in the cis- and trans- isomers and give the coupling constants to the adjacent protons. The different NMR spectra are only due to the configuration of the substituents and not to a preferred conformation of the 7-membered ring system.