Tag: M.W=200-250

Tong, Xiaoyu published the artcileCatalytic Enantioselective α-Alkylation of Amides by Unactivated Alkyl Electrophiles, Formula: C6H13I, the publication is Journal of the American Chemical Society (2022), 144(32), 14856-14863, database is CAplus and MEDLINE.

Herein the achievement of this objective, demonstrating that a nickel catalyst could accomplish enantioselective intermol. alkylations of racemic Reformatsky reagents with unactivated electrophiles; the resulting α-alkylated carbonyl compounds could be converted in one addnl. step into a diverse array of ubiquitous families of chiral mols was described. Applying a broad spectrum of mechanistic tools, have gained insight into key intermediates (including the alkylnickel(II) resting state) and elementary steps of the catalytic cycle.

Journal of the American Chemical Society published new progress about 638-45-9. 638-45-9 belongs to iodides-buliding-blocks, auxiliary class Iodide,Aliphatic hydrocarbon chain, name is 1-Iodohexane, and the molecular formula is C21H33BN2O6S, Formula: C6H13I.

Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com

Milzarek, Tobias M. published the artcileEvaluation of the Substrate Promiscuity of SorbC for the Chemo-Enzymatic Total Synthesis of Structurally Diverse Sorbicillinoids, Safety of 1-Iodohexane, the publication is ACS Catalysis (2022), 12(3), 1898-1904, database is CAplus.

In the present work, the effects of structural changes to the natural substrate sorbicillin was systematically screened by HPLC-based anal. and comparative determination of key kinetic parameters. This not only provided important insight into substrate promiscuity of SorbC but also facilitated the efficient chemo-enzymic preparation of unnatural dimeric sorbicillinoids possessing modified backbones or hydroxylated sorbyl side chains. In addition, the total syntheses of the natural saturnispol C, saturnispol D, and trichosorbicillin A, as well as of demethyltrichosorbicillin A and dihydroxybisorbicillinol, both not yet known in nature, were reported.

ACS Catalysis published new progress about 638-45-9. 638-45-9 belongs to iodides-buliding-blocks, auxiliary class Iodide,Aliphatic hydrocarbon chain, name is 1-Iodohexane, and the molecular formula is C6H13I, Safety of 1-Iodohexane.

Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com

McCaffery, E. L. published the artcilePolymetallophilic organic compounds. III. Competitive intramolecular Grignard coupling reactions, Application In Synthesis of 31253-08-4, the publication is Journal of Organometallic Chemistry (1972), 44(2), 227-31, database is CAplus.

Ring formation via an intramol. Grignard coupling reaction of trihalo alkanes is presented. 2-Methyl-2-(chloromethyl)-1,5-dichloropentane was prepared and treated with two equivalent Mg in THF to study the possible ring formation through 1,5 and/or 1,3 coupling reactions. A 1,3 Grignard coupling reaction was shown to occur preferentially, and a cyclopropane derivative I was formed. A 1,5 coupling reaction could not be realized under the prevailing reaction conditions. A diradical mechanism for the Grignard coupling reaction is proposed to account for the behavior of this compound and other similar polymetallophilic systems in their reaction with Mg.

Journal of Organometallic Chemistry published new progress about 31253-08-4. 31253-08-4 belongs to iodides-buliding-blocks, auxiliary class Iodide,Ester, name is Ethyl 2-Iodopropionate, and the molecular formula is C5H9IO2, Application In Synthesis of 31253-08-4.

Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com

Powell, D. B. published the artcileInfrared spectra and the stabilities of chelate metal-ethylenediamine complexes, Formula: C5H5ClIN, the publication is Journal of the Chemical Society (1961), 1112-14, database is CAplus.

cf. CA 54, 18078i. The suggestion that type A spectra are confined to complexes in which the ethylenediamine adapts the gauche configuration, while in the type B spectra the ligand has the cis configuration, has been abandoned because of x-ray studies. The spectra of PtCl₄^— salts of the ethylenediamine complex cations of Pt(II), Rh(III), Co(III), Pd(II), Cr(III), Hg(II), Cu(II), Ni(II), Co(II), Zn(II), and Cd(II) were studied. Frequencies of 2 bands assigned to N-H rocking and a band assigned to metal-N stretching decreased in the same order as the decrease in log K_av. The N-H rocking bands occur, 800-600 cm.^-1, while the metal-N stretching bands are at 585-478 cm.^-1.

Journal of the Chemical Society published new progress about 6443-90-9. 6443-90-9 belongs to iodides-buliding-blocks, auxiliary class Pyridines, name is Pyridine Iodochloride complex, and the molecular formula is C5H5ClIN, Formula: C5H5ClIN.

Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com

Bousrez, Guillaume published the artcileReady Access to Anhydrous Anionic Lanthanide Acetates by Using Imidazolium Acetate Ionic Liquids as the Reaction Medium, COA of Formula: C6H13I, the publication is Chemistry – A European Journal (2021), 27(52), 13181-13189, database is CAplus and MEDLINE.

Access to lanthanide acetate coordination compounds is challenged by the tendency of lanthanides to coordinate water and the plethora of acetate coordination modes. A straightforward, reproducible synthetic procedure by treating lanthanide chloride hydrates with defined ratios of the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]) has been developed. This reaction pathway leads to two isostructural crystalline anhydrous coordination complexes, the polymeric [C₂mim]_n[{Ln₂(OAc)₇}_n] and the dimeric [C₂mim]₂[Ln₂(OAc)₈], based on the ion size and the ratio of IL used. A reaction with an IL : Ln-salt ratio of 5 : 1, where Ln = Nd, Sm, and Gd, led exclusively to the polymer, while for the heaviest lanthanides (Dy-Lu) the dimer was observed Reaction with Eu and Tb resulted in a mixture of both polymeric and dimeric forms. When the amount of IL and/or the size of the cation was increased, the reaction led to only the dimeric compound for all the lanthanide series. Crystallog. analyses of the resulting salts revealed three different types of metal-acetate coordination modes where η²μκ² is the most represented in both structure types.

Chemistry – A European Journal published new progress about 638-45-9. 638-45-9 belongs to iodides-buliding-blocks, auxiliary class Iodide,Aliphatic hydrocarbon chain, name is 1-Iodohexane, and the molecular formula is C6H13I, COA of Formula: C6H13I.

Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com

Hassel, O. published the artcileStructure of the 1:1 compound pyridine-iodomonochloride, Formula: C5H5ClIN, the publication is Acta Chemica Scandinavica (1956), 696-8, database is CAplus.

cf. C.A. 48, 12115f; 50, 12592f. Pyridine-iodomonochloride, yellow monoclinic needles, m. 132°, space group P2₁/c, has parameters: a 4.25, b 12.29, c 14.07 A., β 94.4°, and bond distances I-Cl 2.51, N-Cl 2.26 A. Experiments show that the I, Cl, and N atoms are at least very nearly on a straight line, and suggest that the C atom opposite the N atom is also on this line, but do not appear to strengthen the suggestion that the “outer” halogen atom attains a strong neg. charge. Previous structure studies of ether-halogen addition compounds are compared with these on N compounds The strong interaction between the O or N atom and the nearest halogen atom is evident from the short separation between these atoms, this effect being greatest in the case of N. It is probable that electrons associated with the atoms forming the O-halogen or N-halogen bond are partially promoted to d orbitals.

Acta Chemica Scandinavica published new progress about 6443-90-9. 6443-90-9 belongs to iodides-buliding-blocks, auxiliary class Pyridines, name is Pyridine Iodochloride complex, and the molecular formula is C5H5ClIN, Formula: C5H5ClIN.

Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com

Poyac, Ludivine published the artcileSynthesis, Characterization, and Encapsulation Properties of Rigid and Flexible Porphyrin Cages Assembled from N-Heterocyclic Carbene-Metal Bonds, Safety of 1-Iodohexane, the publication is Inorganic Chemistry (2021), 60(24), 19009-19021, database is CAplus and MEDLINE.

Four porphyrins equipped with imidazolium rings on the para positions of their meso aryl groups were prepared and used as tetrakis(N-heterocyclic carbene) (NHC) precursors for the synthesis of porphyrin cages assembled from eight NHC-M bonds (M = Ag⁺ or Au⁺). The conformation of the obtained porphyrin cages in solution and their encapsulation properties strongly depend on the structure of the spacer -(CH₂)_n– (n = 0 or 1) between meso aryl groups and peripheral NHC ligands. In the absence of methylene groups (n = 0), porphyrin cages are rather rigid and the short porphyrin-porphyrin distance prevents the encapsulation of guest mols. like 1,4-diazabicyclo[2.2.2]octane (DABCO). By contrast, the presence of methylene functions (n = 1) between meso aryl groups and peripheral NHCs offers addnl. flexibility to the system, allowing the inner space between the two porphyrins to expand enough to encapsulate guest mols. like water mols. or DABCO. The peripheral NHC-wingtip groups also play a significant role in the encapsulation properties of the porphyrin cages.

Inorganic Chemistry published new progress about 638-45-9. 638-45-9 belongs to iodides-buliding-blocks, auxiliary class Iodide,Aliphatic hydrocarbon chain, name is 1-Iodohexane, and the molecular formula is C6H13I, Safety of 1-Iodohexane.

Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com

Landauer, S. R. published the artcileThe organic chemistry of phosphorus. I. Some new methods for the preparation of alkyl halides, Recommanded Product: Ethyl 2-Iodopropionate, the publication is Journal of the Chemical Society (1953), 2224-34, database is CAplus.

cf. C.A. 45, 9456e. (MeO)₃P (I) (0.1 mol) refluxed 30 min. at 100° with MeI and the product distilled, gave MePO(OMe)₂ (II); with molar ratios of I:MeI = 1:1, 2:1, 10:1, and 100:1, the yields of II were 90, 88, 93, and 80%, resp. I (6.2 g.) and 0.06 g. Me₂SO₄ refluxed 15 min. at 100° gave 8% recovered I and 81% II, b₁₂ 66°. (PhO)₃P (III) (31 g.) and 21 g. MeI refluxed 36 h. with exclusion of H₂O, the mixture treated with anhydrous ether, and the solid washed with anhydrous ether, dried, and weighed in vacuo, gave 42 g. (PhO)₃PMeI (IV), which was stored under ether, dried, and weighed in vacuo before use; IV taken up in Me₂CO and precipitated with anhydrous ether gave pure IV, m. 146°. IV (7.95 g.) in 30 mL. absolute EtOH and 150 mL. saturated alc. AgNO₃ gave after 3, 6, 10, 20, 80, 150, and 1440 min. 67, 73, 76, 79, 86, 92, and 100%, resp., total yield of AgI (204.5 mg. IV gave 09.6% AgI after 3 min.). IV (21 g.) shaken several min. with 35 mL. absolute EtOH and the solution distilled, gave 62% EtI, b. 72° (PhNEtMe₂I, m. 136-7°), PhOH, and 91% MePO(OPh)₂ (V), m. 35-6°. In a 2nd experiment in which the mixture was distilled at 0.5 mm., 66% EtI was collected in a trap at -80°; the residue, washed with 2N NaOH gave 86% V; the alk. washings gave with acid 96% PhOH. Iodides were similarly prepared from IV and the appropriate alc., cooling being necessary with reactive alcs., warming with less reactive alcs.; the iodide was isolated by distillation of the reaction mixture in vacuo, with the iodide collected at -80° in a trap (when the b.p. was much lower that of PhOH), by distillation with PhOH in vacuo and separation of the PhOH with cold dilute NaOH, or by removal of the PhOH from the reaction mixture with dilute NaOH and distillation The method is satisfactory with primary, secondary, tertiary (76% yield of Me₃CI), and unsaturated alcs. (83% yield of MeCH:CHCH₂I, b_40-5 55-6°), glycols (95% yield of CH₂(CH₂I)₂, b_0.5 50-1°, n²¹_D 1.6420), and Et lactate (92% yield of MeCHICO₂Et, b₈ 65-6°, n^20.5_D 1.5000), giving 60-95% yields. Cholesterol (9.5 g.) mixed with 12 g. IV, 10 mL. MeI added, the mixture refluxed 1 h. at 50-60°, kept overnight, extracted with 100 mL. petr. ether (b. 40-60°), the extract evaporated, the residue treated with 100 mL. H₂O, the insoluble part washed with Me₂CO, taken up in 200 mL. hot Me₂CO, cooled, and the solution decanted from the oil and cooled at 2° gave 30% cholesteryl iodide, m. 105° (from EtOAc), [α]^21.2_D -12.7° (CHCl₃). III (34 g.) and 13 g. PhCH₂Cl heated 60 h. at 170-5° and the mixture washed with petr. ether (b. 40-60°), gave 25 g. oily (PhO)₃P(CH₂ph)Cl (VI). VI (10 g.) kept overnight at room temperature with 2 g. (+)-2-octanol, α^21.4_D 7.72°, and the mixture distilled gave 79% (-)-2-chloroöctane, b₁₃ 60°, n²⁰_D 1.4275, [α]^22.4_D -24.72°. PCl₃ (23 g.) added (20 min.) to 54 g. stirred, cooled PhCH₂OH, 61 g. PhNMe₂, and 100 mL. absolute ether, the mixture filtered, and the filtrate distilled twice gave 8 g. (PhCH₂O)₂P(O)H, b_0.05 145-60°, 10 g. mixture, b_0.05 160-80°, and 18 g. (PhCH₂O)₃P (VII), b_0.05 180-95°, m. 52° (from petr. ether). VII and MeI heated 30 h. at 100° gave no addition product; heated 3 h. at 150°, VII and MeI gave PhCH₂I. Summaries are given for the preparation of 12 iodides, 4 bromides, and 5 chlorides directly from III, the halide (MeI, PhCH₂Br, or PhCH₂Cl), and the alc. III (68 g.), 40 g. BuI, and 6.4 g. absolute MeOH heated 24 h. at 165-85°, with the MeI fractionated off continuously, gave 16 g. MeI, b. 42-3°, n²⁰_D 1.5290. MeBr passed slowly (through a sintered glass plate) into a mixture of 50 g. III and 11 g. BuOH heated 12 h. (155-35°), the mixture distilled, and the product collected at -80°, gave 63% BuBr, b. 101.5°, n²⁰_D 1.4400. (EtO)₃P (16.6 g.), 14.2 g. MeI, and 22.2 g. BuOH refluxed 1 h. gave 64% impure EtI and 36% BuI, b. 110-30°, n²⁰_D 1.4935. Dry HCl passed (1.5 h.) into equimol. amounts of III and BuOH gave 76% BuCl, b. 77-9°, n¹⁷_D 1.4025; similarly (-)-2-octanol (kept overnight with III before HCl was added for 1 h.) gave 44% (+)-2-chloroöctane, b_8-10 53-6°, [α]^22.2_D 18.8°; 2 g. cholesterol, 5 g. III, and HCl (30 min. addition), treated with 20 mL. Me₂CO, gave 2.2 g. cholesteryl chloride, m. 95° (from EtOAc), [α]²⁰_D -33.3° (CHCl₃). III (34 g.), 7.4 g. BuOH, and 6 g. NH₄Cl refluxed 84 h. at 140° gave 63% BuCl, b. 77-8°, n²²_D 1.4015. Similarly III and BuOH with 6 g. NaCl (heated 120 h. at 170-80°) gave 16% BuCl; with 9.6 g. LiBr (heated 64 h. at 140°), 40% BuBr; with 16.5 g. NaI (heated 64 h. at 160-70°), 18.5% BuI. IV (7 g.), 1.5 g. absolute EtOH, and 3 g. PhNMe₂ warmed 15 min. on a steam bath and diluted with ether gave 3.8 g. PhNMe₂EtI, m. 131° (from EtOH). III (68 g.) and 14.8 g. BuOH heated 16 h. at 100° gave 18.5 g., b₁₀ 60-80° (mainly PhOH), 7.5 g., b₁₀ 80-120°, n²⁵_D 1.4580 [mainly (BuO)₃P], 7.8 g. mixture, b₁₀ 120-40°, n²⁵_D -1.4840, of (BuO)₃P and (BuO)₂P(O)Ph, 9 g., b₁₀ 140-70°, n²⁵_D 1.5302, [mainly BuOP(OPh)₂ (VIII)], 4.1 g., b₁₀ 170-80°, n²⁵_D 1.5819, (mixture of VIII and III), and 28 g. residue, n²⁵_D 1.5815. III (68 g.) and 14.8 g. BuOH kept 30 min. at room temperature and distilled gave 18 g. PhOH and a mixture of phosphites which, refluxed 3 h. with 13 g. MeI, gave 13 g. BuI, n²³_D 1.4990; the residue heated 24 h. with 28 g. MeI gave 15.1 g. addnl. BuI, b. 125-31°, n²²_D 1.4980. IV (23 g.) and 3 g. V refluxed 1 h. and distilled gave 5 g. MeI, b. 42-4°, n²⁰_D 1.5055. IV (5 g.) and 2.5 g. (BuO)₃P mixed to give a solution and distilled gave 1.8 g. BuI, b. 125-32°, n²³_D 1.4970. Et(O)PCl₂ (IX) (147 g., b. 117-18°) and 500 mL. absolute ether cooled in a freezing mixture and treated portion wise with NaOMe (from 46 g. powd. Na and 64 g. MeOH) in 500 mL. ether, the mixture kept 1 h. at room temperature, filtered, the filtrate distilled, and the product fractionated gave 56 g. EtOP(OMe)₂ (X), b. 124-7°, equivalent 138.0 (equivalents were determined by hydrolysis of about 150 mg. alkyl phosphite 1 h. at 100° with 5 mL. 70% alc. NaOH, dilution with 0.1N HCl, and titration of the excess alkali with bromophenol blue; the authors found that equivalents gave a better criterion of purity than elemental anal.). X (27.6 g.) refluxed 1 h. with 28.4 g. MeI and fractionated gave 27.5 g. MeI and 27 g. EtO(MeO)P(O)Me, b₁₅ 74-5°, equivalent 137.8. X (13.8 g.), 2 g. H₂O, and 10 mL. Me₂CO kept 1 h. and distilled gave P-containing fractions, 1.3 g., b_15-17 65-73°, 9 g. EtO(MeO)(HO)P, b_15-17 73-5°, equivalent 124.0, and 1.3 g., b_15-17 75-7°. Absolute MeOH (32 g.) and 121 g. PhNMe₂ added (1 h.) to 137 g. PCl₃ cooled, stirred in 1 l. absolute ether, 92 g. absolute EtOH, and 242 g. PhNMe₂ then added (2 h.), the mixture diluted with 500 mL. ether, filtered, the filtrate distilled, and the fraction, b_10-15 50-90°, fractionated gave 35 g. (EtO)₂POMe (XI), b. 136-9°, equivalent 152.6. XI (10 g.) and 8.5 g. MeI refluxed 30 min. and distilled gave 6.8 g. MeI and 6 g. (EtO)₂P(O)Me, b. 190-2°, n²³_D 1.4110, equivalent 152.0. XI (10 g.), 1.5 g. H₂O, and 10 mL. Me₂CO gave 5.3 g. (EtO)₂POH, b₈ 65-6°, n²¹_D 1.4070, equivalent 137.2. iso-PrOH (120 g.) and 242 g. PhNMe₂ added (80 min.) to cold 130 g. IX in 500 mL. absolute ether, the mixture stirred 30 min. and filtered, and the filtrate fractionated gave 97 g. (iso-PrO)₂POEt (XII), b₁₀ 69-71°, equivalent 192.1. XII (19.5 g.) and 14.2 g. MeI refluxed 30 min. at 100° and distilled gave 12 g. EtI, b. 71-3°, and 17 g. (iso-PrO)₂P(O)Me, b₅ 7-5-6°, n²⁰_D 1.4158. XII (19.5 g.), 2 g. H₂O, and 10 mL. Me₂CO refluxed 14 h. and distilled gave 12.5 g. (iso-PrO)₂P.OH, b₁₀ 89-90°, equivalent 159.3. The mechanism for the formation of alkyl halides is discussed. Halides included in tables: EtI, iso-PrI, n-BuI, sec-BuI, tert-BuI, (+)- and (-)-2-iodoöctane, cyclohexyl iodide, CH₂:CHCH₂I, MeCH:CHCH₂Cl, PhCH₂I, PhCH₂CH₂I, PhCHIMe, CH₂(CH₂I)₂, MeCHICO₂Et, Me₂C(CH₂I)₂, and Me₃CCH₂I; BuBr, CH₂:CHCH₂Br, CH₂(CH₂2Br)₂, MeCHBrCO₂Et; BuCl, CH₂:CHCH₂Cl, CH₂(CH₂Cl)₂, MeCHClCO₂Et, and n-C₆H₁₃Cl.

Journal of the Chemical Society published new progress about 31253-08-4. 31253-08-4 belongs to iodides-buliding-blocks, auxiliary class Iodide,Ester, name is Ethyl 2-Iodopropionate, and the molecular formula is C5H9IO2, Recommanded Product: Ethyl 2-Iodopropionate.

Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com

Popov, Alexander I. published the artcileThe chemistry of halogens and of polyhalides. XI. Molecular complexes of pyridine, 2-picoline, and 2,6-lutidine with iodine and iodine halides, Recommanded Product: Pyridine Iodochloride complex, the publication is Journal of the American Chemical Society (1957), 4622-5, database is CAplus.

cf. C.A. 51, 7931a. Crystalline addition compounds of 2-picoline, 2,6-lutidine, and pyridine were prepared with ICI and IBr. The dissociation constants of these 6 compounds and of the 3 mol. complexes, amine-I₂, were determined spectrophotometrically in CCl₄ solutions The order of stability for the halogen series was ICI > IBr > I₂, in agreement with the acidic strength of the halogens. The order of stability for the amine series was 2-picoline > pyridine > 2,6-lutidine. The low stability of 2,6-lutidine complexes is ascribed to steric effects. The absorption spectra of acetonitrile solutions of the 6 addition compounds had maximum at either the 227 mμ peak of ICl₂^–, or the 256 mμ peak of IBr₂^–, indicating an ionic dissociation in this polar solvent, as opposed to mol. dissociation in nonpolar CCl₄.

Journal of the American Chemical Society published new progress about 6443-90-9. 6443-90-9 belongs to iodides-buliding-blocks, auxiliary class Pyridines, name is Pyridine Iodochloride complex, and the molecular formula is C5H5ClIN, Recommanded Product: Pyridine Iodochloride complex.

Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com

Jouanno, Laurie-Anne published the artcileExpeditious Microwave-Assisted Synthesis of 5-Alkoxyoxazoles from α-Triflyloxy Esters and Nitriles, Safety of Ethyl 2-Iodopropionate, the publication is Journal of Organic Chemistry (2012), 77(19), 8549-8555, database is CAplus and MEDLINE.

A rapid and general access to diversely substituted 5-alkoxyoxazoles from easily accessible α-triflyloxy/hydroxy esters and nitriles with good yields (41-76%) is reported. The versatility of the cyclization is shown for a range of substrates with high selectivity toward triflates over tosylates and proved to be compatible with sensitive functional groups. As an illustration of this transformation, the first synthesis of the recently isolated hydroxypyridine Me multijuguinate (I) was achieved in four steps through a hetero Diels-Alder reaction of the 5-alkoxyoxazole II and acrylic acid, followed by a protodecarboxylation reaction.

Journal of Organic Chemistry published new progress about 31253-08-4. 31253-08-4 belongs to iodides-buliding-blocks, auxiliary class Iodide,Ester, name is Ethyl 2-Iodopropionate, and the molecular formula is C5H9IO2, Safety of Ethyl 2-Iodopropionate.

Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com