scholarly journals Molecular surgical synthesis of H 2 @C 60 : recollections

2013 ◽  
Vol 371 (1998) ◽  
pp. 20110636 ◽  
Author(s):  
Koichi Komatsu
Keyword(s):  
Chemical Reactions ◽  
Molecular Hydrogen ◽  
Total Yield ◽  
Hole Size ◽  
Endohedral Fullerene ◽  
Entire Process ◽  
Surgical Method ◽  
H Nmr ◽  
Guest Species ◽  
Free Hydrogen

The first synthesis of endohedral fullerene containing molecular hydrogen, H 2 @C 60 , is briefly summarized. The synthesis was conducted according to what we call the ‘molecular surgical method’, that is, opening a hole on a C 60 surface, enlargement of the hole, insertion of a guest species and enclosure of the hole without loss of the encapsulated guest. The entire process involves three chemical reactions to open the hole and four reactions to gradually reduce the hole size and finally close the hole. The total yield of the product, H 2 @C 60 , based on consumed C 60 was 9%. The encapsulated molecule of hydrogen exhibited a 6 ppm upfield-shifted 1 H NMR signal when compared with free hydrogen, indicating the aromaticity at the inner centre of the C 60 cage.

Preparation of (20E)-21-Ethoxycarbonyl-14β,17α-pregna-5,20-dien-3β-yl Hydrogen Butanedioate

1995 ◽  
Vol 60 (4) ◽  
pp. 715-718 ◽  
Author(s):  
Vladimír Pouzar ◽  
Ivan Černý
Keyword(s):  
Title Compound ◽  
Nmr Spectra ◽  
Total Yield ◽  
Reaction Sequence ◽  
Pregnane Series ◽  
H Nmr

The title compound X was prepared according to the recently published procedure for preparation of analogous derivatives in the 5β-pregnane series, using the reaction sequence I -> II -> III -> IV -> V -> VI -> VII -> VII -> IX -> X (total yield 18%). The configuration at ring D centers (14β,17α) follows from the structure of the starting ketone I and was also checked by comparing diol IV with the sample prepared by an independent route. The epimeric purity at C-17 was carefully monitored during the whole synthesis by 1H NMR spectra (singlet of 18-H3).

Bonded Hydrogen and Trapped H2 in a-Si1−xGex:H Alloys

1989 ◽  
Vol 149 ◽  
Author(s):  
E. J. Vanderheiden ◽  
G. A. Williams ◽  
P. C. Taylor ◽  
F. Finger ◽  
W. Fuhs
Keyword(s):  
Temperature Dependence ◽  
Molecular Hydrogen ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
H Nmr ◽  
Local Environments

ABSTRACT1H NMR has been employed to study the local environments of bonded hydrogen and trapped molecular hydrogen (H2) in a series of a-Si1−xGex:H alloys. There is a monotonic decrease of bonded hydrogen with increasing x from ≈ 10 at. % at x = 0 (a-Si:H) to ≈ 1 at. % at x = 1 (a-Ge:H). The amplitude of the broad 1H NMR line, which is attributed to clustered bonded hydrogen, decreases continuously across the system. The amplitude of the narrow 1H NMR line, which is attributed to bonded hydrogen essentially randomly distributed in the films, decreases as x increases from 0 to ≈ 0.2. From x = 0.2 to x ≈ 0.6 the amplitude of the narrow 1H NMR line is essentially constant, and for x ≥ 0.6 the amplitude decreases once again. The existence of trapped H2 molecules is inferred indirectly by their influence on the temperature dependence of the spin-lattice relaxation times, T1. Through T1, measurements it is determined that the trapped H2 concentration drops precipitously between x = 0.1 and x = 0.2, but is fairly constant for 0.2 ≤ x ≤ 0.6. For a-Si:H (x = 0) the H2 concentration is ≈ 0.1 at. %, while for x ≥ 0.2 the concentration of H2 is ≤ 0.02 at. %.

Synthesis of One Novel Thieno[2,3-D]Pyrimidine Derivative Bearing a Sulfonylurea Moiety

2014 ◽  
Vol 1015 ◽  
pp. 577-580
Author(s):  
Chen Chen ◽  
Cheng Yu Sun ◽  
Shan Xu ◽  
Yuan Biao Tu ◽  
Peng Wu Zheng ◽  
...  
Keyword(s):  
Total Yield ◽  
Pyrimidine Derivative ◽  
H Nmr

A novel thieno [2,3-d] pyrimidine compound (1) bearing a sulfonylurea moiety was synthesized from methyl 2-aminothiophene-3-carboxylate (2) through five steps including cyclization, chlorination, substitution with morpholine and piperazine, amidation and its structure was confirmed by 1H NMR and MS spectrum. The total yield of the five steps was 16.2% ( calculated from methyl 2-aminothiophene-3-carboxylate).

scholarly journals Solvent Derived Artifacts in Natural Products Chemistry

2009 ◽  
Vol 4 (3) ◽  
pp. 1934578X0900400 ◽  
Author(s):  
Federica Maltese ◽  
Frank van der Kooy ◽  
Robert Verpoorte
Keyword(s):  
Natural Products ◽  
Natural Product ◽  
Chemical Reactions ◽  
Critical Role ◽  
Total Yield ◽  
Purification Method ◽  
Active Compounds ◽  
Natural Product Chemistry ◽  
Extraction And Purification ◽  
Product Chemistry

Solvents play an important and critical role in natural product chemistry. They are mainly used during the extraction and purification of metabolites from a biological matrix. To a lesser extent, solvents are also used as reagents or catalysts to perform chemical reactions. This review focuses on the most important classes of solvents, including alcohols, halogen-containing solvents, esters, ethers, acids and bases. The chemical reactions associated with the use of these solvents to form the so-called “artifacts” are discussed and the most common contaminants found in these solvents are also reviewed. The formation of artifacts and the use of contaminated solvents mainly leads to the formation of new compounds, loss of activity of active compounds, formation of active compounds from inactive ones (false positives), loss in total yield of important compounds during isolation, formation of toxic compounds and difficulty in reproducing an extraction or purification method. Finally, the need for stability studies of purified natural products is emphasized, as this is a common overlooked aspect in natural product chemistry.

Hydridoiridium(III) sulfoxide complexes and their reactivity toward dioxygen

1986 ◽  
Vol 64 (5) ◽  
pp. 897-903 ◽  
Author(s):  
Brian R. James ◽  
Robert H. Morris ◽  
Pal Kvintovics
Keyword(s):  
Hydrogen Peroxide ◽  
Oxidative Addition ◽  
H Nmr ◽  
Rate Determining Step ◽  
Free Hydrogen ◽  
Synthetic Routes

Synthetic routes to hydridoiridium(III) dimethylsulfoxide complexes via oxidative addition of HCl or H2 to precursor insitu iridium(I) species are described. The complexes, trans, mer-IrHCl2(DMSO)3 (1a) and cis, mer-IrH2Cl(DMSO)3 (2), have been characterized by 1H nmr and ir, and contain only S-bonded sulphoxide, DMSO. Comparison is made with data for other isomers reported in the literature, and some discrepancies are discussed. The decomposition of 1a and 2 in chloroform leads to isomers of IrCl3(DMSO)3, while (2) with HCl generates cis,cis IrHCl2(DMSO)2(DMSO) with the O-bonded sulfoxide trans to hydride. The reaction of 1a in dichloromethane with dioxygen occurs with a 1:1 stoichiometry and generates two complexes tentatively formulated as Ir(OH)Cl2(DMSO)2H2O (3) and IrCl2(O2)(DMSO)2DMSO (4); a hydroperoxide intermediate (Ir—OOH) initially formed from 1a is considered to react with further 1a in the rate-determining step. Oxidation of coordinated DMSO to the sulphone is not observed, implying that such a catalyzed O2-oxidation reported earlier in aqueous 2-propanol proceeds via reaction of IrOOH with free DMSO, or else via free hydrogen peroxide.

scholarly journals Membranes for Hydrogen Purification: An Important Step toward a Hydrogen-Based Economy

MRS Bulletin ◽  
2006 ◽  
Vol 31 (10) ◽  
pp. 735-744 ◽  
Author(s):  
Tina M. Nenoff ◽  
Richard J. Spontak ◽  
Christopher M. Aberg
Keyword(s):  
Chemical Reactions ◽  
Molecular Hydrogen ◽  
Glassy Polymer ◽  
Surface Flow ◽  
Pure Hydrogen ◽  
Hydrogen Purification ◽  
High Solubility ◽  
Porous Support ◽  
Basic Principles ◽  
Molecular Sieving

AbstractProduction of pure molecular hydrogen is essential to the realization of the proposed “hydrogen economy” that could ultimately provide hydrogen as a clean, renewable source of energy; eliminate the industrialized world's dependence on petroleum; and reduce the generation of greenhouse gases linked to global warming. A crucial step in obtaining pure hydrogen is separating it from other gaseous compounds—mainly CO2—that often accompany hydrogen in industrial chemical reactions. Advanced membrane technology may prove to be the key to the successful, economical production of molecular hydrogen.Size-sieving glassy polymer membranes can separate H2 on the basis of its small size. Alternatively, reverse-selective rubbery polymers can expedite the passage and, hence, removal of CO2 due to its relatively high solubility in such membranes alone or in conjunction with dissociative chemical reactions. Transition-metal membranes and their alloys can adsorb H2 molecules, dissociate the molecules into H atoms for transport through interstitial sites, and subsequently recombine the H atoms to form molecular H2 again on the opposite membrane side. Microporous amorphous silica and zeolite membranes comprising thin films on a multilayer porous support exhibit good sorption selectivity and high diffusion mobilities for H2, leading to high H2 fluxes. Finally, carbon-based membranes, including carbon nanotubes, may be viable for H2 separation on the basis of selective surface flow and molecular sieving. A wide variety of materials challenges exist in hydrogen purification, and the objective of this issue of MRS Bulletin is to address those challenges and their potential solutions from basic principles.

Synthesis of 4-(2-(Piperazin-1-Yl)-7,8-Dihydro-5H-Thiopyrano[4,3-d]Pyrimidin-4-yl)Morpholine and 4-Morpholino-2-(Piperazin-1-Yl)- 7,8-Dihydro-5H-Thiopyrano[4,3-d]Pyrimidine 6,6-Dioxide

2014 ◽  
Vol 651-653 ◽  
pp. 111-114 ◽  
Author(s):  
Shan Xu ◽  
Cheng Yu Sun ◽  
Fei Lei ◽  
Yuan Biao Tu ◽  
Wei Peng Zeng ◽  
...  
Keyword(s):  
Total Yield ◽  
Mtor Inhibitors ◽  
Pyrimidine Derivatives ◽  
H Nmr ◽  
Synthetic Routes

Two novel thiopyrano [4,3-d] pyrimidine derivatives 7 and 8 were synthesized from dimethyl 3,3'-thiodipropanoate through six steps including two times of cyclization, chlorination, oxidation, substitution with morpholine and piperazine and their structures were confirmed by1H NMR and MS spectrum. The total yield of the six steps was 18.6% (calculated from methyl dimethyl 3,3'-thiodipropanoate). The synthetic routes of them can be used to synthesize PI3K/mTOR inhibitors bearing a thiopyrano [4,3-d] pyrimidine nucleus.

Synthesis and Analysis of 1-Methyl-4-Phenyl-1H-Imidazol-2-Amine

2018 ◽  
Vol 42 (12) ◽  
pp. 608-610
Author(s):  
Qifan Zhou ◽  
Fangyu Du ◽  
Yajie Shi ◽  
Ting Fang ◽  
Guoliang Chen
Keyword(s):  
Scale Up ◽  
Total Yield ◽  
Chemical Entity ◽  
Synthetic Route ◽  
H Nmr ◽  
C Nmr

A practical synthetic route to an important pharmaceutical intermediate 1-methyl-4-phenyl-1H-imidazol-2-amine, via a three-step sequence involving cyclisation, hydrolysis and methylation, is reported. In the process of optimisation, a novel chemical entity was isolated and confirmed to be 2,6-diphenyl-1H-imidazo[1,2-a]imidazole by MS, 1H NMR and 13C NMR. The scale-up experiment was carried out to provide 1-methyl-4-phenyl-1H-imidazol-2-amine in 27.4% total yield.

scholarly journals Unprecedented adsorption of molecular hydrogen in the porous hydride framework

2014 ◽  
Vol 70 (a1) ◽  
pp. C1473-C1473
Author(s):  
Yaroslav Filinchuk ◽  
Nikolay Tumanov ◽  
Voraksmy Ban ◽  
Hyunchul Oh ◽  
Michael Hirscher ◽  
...  
Keyword(s):  
Small Molecules ◽  
Molecular Hydrogen ◽  
Hydrogen Molecule ◽  
Polynuclear Complexes ◽  
Heats Of Adsorption ◽  
Adsorption Sites ◽  
Guest Species ◽  
Saturation Capacity ◽  
In Situ Diffraction

"Recently the first porous hydride, gamma-Mg(BH4)2, featuring so-called ""borohydride framework"" and capable to store reversibly guest species was discovered [1]. This example clearly shows that the covalently bound hydride anions, such as borohydride, can act as directional ligands, capable to form molecular and polynuclear complexes, as well as framework structures typically occurring in classical coordination chemistry. Various small molecules are reversibly absorbed in gamma-Mg(BH4)2. In this work we show that molecular hydrogen and nitrogen have different adsorption sites in gamma-Mg(BH4)2, leading to different capacities on saturation and to different H2 and N2 BET areas. Only up to 0.66 N2 molecules are adsorbed per Mg atom, but the saturation capacity is double for the smaller hydrogen molecule. Moreover, at higher pressures, the second hydride phase forms with unprecedented hydrogen content of ~22 weight % (!). The density of hydrogen adsorbed into the pores is much higher than in liquid hydrogen, having no analogues among other porous systems. On the technical side, we will illustrate how in-situ diffraction at neutron and synchrotron sources allows to follow adsorption isobars, aiming for extraction of isosteric heats of adsorption directly from diffraction data, as well as for clarifying the microscopic mechanisms in terms of guest-host and guest-guest interactions."

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