http://blogs.najah.edu/author/emp_2143 An-Najah Blogs :: en-us Fri, 19 Apr 2024 21:06:42 IDT Fri, 19 Apr 2024 21:06:42 IDT [email protected] [email protected] http://blogs.najah.edu/staff/emp_2143/article/OsmiumVIII-Catalyzed-Oxidation-of-Some-Cyclic-Amines-by-Potassium-HexacyanoferrateIII-in-Alkaline-Media-a-Kinetics-and-Mechanistic-StudyPublished ArticlesReactions of morpholine piperidine and piperazine with OsVIII-catalyzed hexacyanoferrateIII in alkaline media to produce the corresponding lactam have been studied at constant temperature and ionic strength The reactions followed first-order kinetics with respect to [amine] and [OsVIII] but were independent of [FeCN6 3-] and [OH-] The effects of introduced electrolytes potassium hexacyanoferrateII relative permitivity and temperature have also been studied A mechanism accounting for these results has been proposed Chemistry of Heterocyclic Compounds Volume 39 Number 4 April 2003 http:wwwspringerlinkcomcontentj06688m34677p8w0http://blogs.najah.edu/staff/emp_2143/article/Kinetics-and-mechanisms-of-oxidation-of-1-octene-and-heptanal-by-crown-ether-solubilized-potassium-permanganate-in-non-aqueous-solventsPublished ArticlesThe kinetics of oxidation of 1-octene and heptanal by 18-crown-6-ether-solubilized KMnO4 in benzene and CH2Cl2 have been investigated In benzene the oxidation of 1-octene is first order with respect to the oxidant and zero order with respect to the substrate whereas in CH2Cl2 the reaction is first order with respect to both substrate and oxidant The reaction of heptanal followed different kinetics being first order with respect to both substrate and oxidant regardless of whether benzene or CH2Cl2 was employed as the solvent The values of activation energy E-a standard enthalpy DeltaH standard entropy change DeltaS and standard free energy DeltaG for the reaction are reported Mechanistic pathways for the studied reactions are also proposedhttp://blogs.najah.edu/staff/emp_2143/article/Oxidation-of-some-Alicyclic-Amines-by-Potassium-Hexacyanoferrate-III-in-Alkaline-Medium-A-Kinetic-and-Mechanistic-StudyPublished ArticlesOxidation of some alicyclic amines morpholine piperazine and piperidine by potassium hexacyanoferrate??? in basic medium has been investigated at 35C Stoichiometric results showed that four moles of hexacyanoferrateIII were consumed per mole of piperidine or morpholine whereas piperazine consumed eight moles of the oxidant to produce the corresponding lactams Kinetic studies indicated that piperidine and morpholine also followed different kinetics from that of piperazine being first order in the amine concentration and independent of the concentrations of hexacyanoferrate??? and hydroxide ion while in the case of piperazine the reaction was first order in both oxidant and substrate concentrations and zero order with respect to the concentration of hydroxide ion The changes in reaction rate due to changing ionic strength of the medium as well as other factors has also been investigated The activation parameters of the oxidation process have been evaluated and a mechanism consistent with the observed kinetics has been proposed Keywords: Hexacyanoferrate??? morpholine piperazine piperidine oxidation lactam An-Najah University Journal for Research - Natural Sciences A ISSN: 1727-2114 Volume 15 2001 Pages: 029-039http://blogs.najah.edu/staff/emp_2143/article/Polysiloxane-supported-decacarbonyldimanganese0-catalyst-for-terminal-olefin-hydrosilylation-reactions-the-effect-of-the-support-on-the-catalyst-selectivity-activity-and-stabilityPublished ArticlesA new class of supported carbonyl manganese catalyst was prepared by treating the dimeric decacarbonyldimanganese0 Mn2CO10 with insoluble aminated polysiloxane surface Solid state FT-IR spectra indicated that the supported catalyst is a dimeric complex that is substituted with two amine ligands one at each Mn atom The supported manganese complex was investigated as catalyst for the hydrosilylation reaction of terminal olefins Contrary to the homogeneous Mn2CO10 catalytic system the supported manganese complex was completely selective toward the hydrosilylation reaction with no detectable olefin isomerization or other side-reaction products Furthermore the catalyst was selective to produce the linear hydrosilylation product rather than the branched one No lowering in catalyst activity due to the support was observed A good proportion of the catalyst activity after separation and reuse was retained for at least four times Highly reproducible catalytic activity measurements were obtained with catalytic samples taken from same prepared batch Different prepared batches showed lower reproducibility The effect of different reaction parameters such as the solvent effect the temperature effect the concentration effect and the added-ligand effect have also been studied Laines kinetic studies indicated that the cluster remained intact during the reaction Journal of Molecular Catalysis A: Chemical Volume 144 Issue 1 22 July 1999 Pages 47-59 http://blogs.najah.edu/staff/emp_2143/article/Terminal-Olefin-Isomerization-Reactions-Catalyzed-By-PolySiloxane-Supported-Ru3Co12---The-Effect-Of-The-Support-On-The-Catalyst-Selectivity-Activity-And-StabilityPublished ArticlesDodecacarbonyltriruthenium0 Ru3CO12 1 has been chemically anchored to the aminated polysiloxane surface 2 The resulting supported ruthenium complex 3 was evaluated as catalyst for the olefin isomerization reactions Contrary to its homogeneous catalyst counterpart 1 the supported catalyst 3 showed exceptionally high selectivity towards 1-octene isomerization and trans-2-octene was the sole product of the reaction mixture The olefin isomerization reaction was markedly activated by the presence of the tertiary silane EtO3SiH No hydrosilylation reaction products were detected Preliminary kinetic study indicated catalysis by lower nuclearity catalytic species where the cluster fragments during the reaction process The effects of different reaction parameters on the rate of the reaction have been investigatedhttp://blogs.najah.edu/staff/emp_2143/article/Emodin-A-Naturally-Occuring-Anthraquinone-Its-Isolation-and-Spectrophotometric-Determination-in-Rumex-Cyprius-PlantPublished ArticlesA new method for isolation and specrophotometric determination of emodin is presented Emodin was isolated by thin layer chromatography tlc and column chromatography cc techniques as an orange long crystalline substance Emodin exhibits two absorption maxima at 420 and 520 nm Stability of the color and the effect of pH were studied Beers law is obeyed in the range 2-30 ppm The method is applied to the determination of emodin in roots stems and leaves of Rumex cyprius plant Spectroscopy Letters Volume 29 Issue 8 December 1996 pages 1539 - 1543http://blogs.najah.edu/staff/emp_2143/article/The-catalytic-activity-of-polysiloxane-supported-metalloporphyrins-in-olefin-oxidation-reactions-the-effect-of-the-support-on-the-catalytic-activity-and-selectivityPublished ArticlesSupported tetra-4-pyridylporphyrinato-manganeseIII [MnIIITPyP] and -tinIV [SnIVTPyP]2 have been prepared The solid support was iodonated polysiloxane surface prepared by condensation reactions of EtO4Si with MeO3SiCH23I The supported metalloporphyrins were employed as catalysts for the oxidation reactions of 1-octene and of cyclohexene NaBH4 was used to reduce [MnIIITPyP] and [SnIVTPyP]2 back to their catalytically active MnII and SnII forms respectively Contrary to their homogeneous counterparts both of the supported metalloporphyrins catalysed the cyclohexene oxidation reaction to yield only 2-cyclohexen-1-one with no other products over a reaction time of 10 h In addition to cyclohexene oxidation the supported [MnIIITPyP] catalysed 1-octene oxidation as well whereas the supported [SnIVTPyP]2 was inactive for the oxidation of 1-octene Journal of Molecular Catalysis A: Chemical Volume 113 Issues 1-2 25 November 1996 Pages 35-44 http://blogs.najah.edu/staff/emp_2143/article/Reaction-of-octafluorotoluene-35-dichlorotrifluoropyridine-3-chlorotetrafluoro-yridine-and-tetrafluoropyrimidine-with-alkali-metal-oximatesPublished ArticlesTreatment of octafluorotoluene 2 with approximately one-molar equivalents of the oximates R1R2C = NO~ M R1 = R2=Me;R1 = R2 = Ph; R1 = Me R2 = Ph;M = Na 6a-c in diethyl ether gives 4-R1R2C = NOC6F4CF3 7a-c as the only isolated products Corresponding reaction of 35-dichlorotrifluoropyridine 3 with the oximates 6a-c affords 4-and 2-R1R2C = NOC5F2C12N 8a-c and 9a-c respectively 4-2ratios at 35 C: 65:35; 30:70; 12:88 ; the lithium oximates R1 = R2 =Ph ; R1 = Me R2 = Ph; M = Li 6d and 6e give comparable results With 3-chlorotetrafluoropyridine 4 treatment with sodium oximate 6c gives 4-PhCMe = NO-3-ClC5F3N 10 and 2-PhCMe = NO-5ClC5F3N 11 ratio 44:56 at 35 C Such competition between SNAr attack of these alkali-metal oximates at the C-4 and C-2 positions of chlorofluoropyridines 3 and 4 can be rationalized by invoking chelation of an alkali-metal cation with ring nitrogen in the transition state leading to formation of an orthio-quinonoidal -complex Exclusive initial attack at the C-4 ring site appears to occur in the reaction of tetrafluoropyrimidine 5 with oximates 6a and 6c to afford 4-MeC = NOC4F3N2 12a and 4-PhCMe=NOC4F3NN2 12b respectively; Some further attack on product 12b by oximate 6c at the C-6 site takes place to give the disubstituted derivative 46-PhCMe=NO2C4F2N2 13 http://blogs.najah.edu/staff/emp_2143/article/Reaction-of-pentafluoropyridine-with-lithium-hydrazonides-competing-monosubstitution-at-the-2--and-4-positionsPublished ArticlesTreatment of pentafluoropyridine 1 in diethyl ether with approximately 1 M equiv of the hydrazonides Ph2C=NNHLi 3a and Ph2C=NNLiPh 3b under mild conditions gives good yields 62 and 83 of 4- and 2-Ph2C=NHC5F4N 5a and 6a and 4- and 2-Ph2C=NPhC5F4N 5b and 6b respectively containing unusually large amounts of 2-substituted products 5a6a = 50:50; 5b6b = 65:35 The increased ease of displacement of a 2-F substituent from 1 6a and 6b in these cases is ascribed to chelation of the lithium cation in the transition state involved in the rate-determining step leading to formation of an ortho-quinonoidal -complex Catalytic hydrogenation of a 1:1 mixture of hydrazones 5a and 6a affords the corresponding hydrazines 4- and 2-H2NNHC5F4N 7 and 8 in good yield 78; acidic hydrolysis hot HCl aq of the 5a6a mixture yields tetrafluoro-4-hydrazinopyridine 9 and depending on the conditions tetrafluoro-2-hydrazinopyridine 10 or 2-aminotetrafluoropyridine 11 http://blogs.najah.edu/staff/emp_2143/article/Reaction-of-metal-diethylnitroxides-with-pentafluoropyridine-pentafluorobenzene-octafluorotoluene-and-2-chloro-3--or-5-nitropyridinePublished ArticlesTreatment of the nitroxides Et2NO M 2a-c M = Na Li K and Et2NO2 Ba2 2d with pentafluoropyridine 3 at room temperature 1 d gave in all cases the compounds Py-NEt2 8 Py-ONEt2 9 Py-NHEt 10 and Py-OH2NEt2 11 where Py = tetrafluoro-4-pyridyl in the approximate ratio 1:30:30:35 The radical traps 14-dinitrobenzene or galvinoxyl retarded the reaction 5 d required for complete consumption of 3 but the same products were formed in a similar ratio and compounds 811 were also formed by decomposition of the amine oxide Py-NŌEt2 20 [synthesised by the route: 3 Et2NH 8 57; 8 CF3CO2OH2O220 81 as the monohydrate] It is proposed that the products 811 arose mainly via an SRNl mechanism involving single electron transfer SET from the nitroxide 2 to the substrate 3 leading to the radical anion 21 and hence the tetrafluoro-4-pyridyl radical 22 which reacted with 2 at nitrogen to afford the amine oxide 20 Major Meisenheimer rearrangement of 20 gave hydroxylamine 9 while minor rearrangement afforded the hydroxylamine Py-NEtOEt 23 which eliminated ethanal to yield the secondary amine 10 Competing deoxygenation of 20 gave the tertiary amine 8 and the salt 11 [synthesised by reaction of Py-OH 26 with Et2NH] was formed via decomposition of 8 in light or on heating involving homolytic fission of the weak N-O bond Treatment of 9 with the acids AHF or CF3SO3H resulted in exothermic reaction and gave compounds 8 27 11 10 16 18 and 11 13 25 via competing protonation at oxygen and nitrogen The corresponding reactions of nitroxide 2a with the substrates C6HF5 4 and C6F5CF3 5 afforded the salt 4-H-C6F4-O H2NEt2 12 15 and a mixture of the compounds 4-CF3-C6F4-R [R = ONEt2 13 23;R = NHEt 14 2;R = O H2NEt2 15 12] respectively while treatment of 2a with 2-chloro-3-nitropyridine 6 and 2-chloro-5-nitropyridine 7 gave the tertiary amines 2-NN-diethylamino-3-nitropyridine 16 35 or 2-NN-diethylamino-5-nitropyridine 18 25 together with N-2-chloro-3-pyridyl-N-3-nitro-2-pyridylamine 17 13 or N-2-chloro-5-pyridyl-N-5-nitro-2-pyridylamine 19 27 via presumed SRNl pathways http://blogs.najah.edu/staff/emp_2143/article/Cluster-Catalysis-of-Olefin-Hydrosilylation-and-Isomerization-Thermal-Reaction-Using-Co4Co10PPh2Published ArticlesThe cobalt cluster [Co4C010PPh2] 1~ has been evaluated as a catalyst for 1-octene thermal hydrosilylation and isomerization reactions The kinetics indicates that the hydrosilylation reaction occurs via cluster catalysis at temperatures ranging from 50-70c The 1 - octene isomerization was selective to trans-2-octene only The kinetics indicates that at 50c or lower isomerization reaction occurs via cluster catalysis whereas at 70c or higher catalysis by lower nuclearity species is involved The effects of solvent silane temperature and catalyst and reactant concentrations on the rates of hydrosilylation and isomerization reactions have been investigated Plausible mechanisms based on experimental data have been proposedhttp://blogs.najah.edu/staff/emp_2143/article/Stoichiometry-Kinetics-and-Mechanism-of-Oxidation-of-L-Cysteine-by-Hexacyanoferrate-III-In-Acidic-MediaPublished ArticlesThe Stoichiometry kinetics and mechanism of oxidation of L-cysteine by hexacyanoferrate III in acidic media at constant ionic strength have been studied spectrophotometrically A1:1 L-cysteine:hexacyanoferrate III has been established with 1-cysteine as the only product The reaction is zero order in hexacyanoferrate III first order in L-cysteine and inverse first in hydrogen ion concentration The activation parameters were evaluated in the temperature range 15-40C Ea = 282 kJmol S = -1924 Jmol deg The oxidation was inhibited in the presence of added hexacyanoferrate II The effects of other added salts and composition of the solvent have been rationalized Two mechanisms are offered to explain the kinetic datahttp://blogs.najah.edu/staff/emp_2143/article/5-Fluoro-88-Dimethyl-7-Oxa-39-Diazabicyclo430Nona-59-Diene-24-Dione-C8h7fn2o3---A-Novel-Product-From-Pyrolysis-Of-N-Isopropylidene-O-Tetrafluoro-4-Pyridylhydroxylamine-In-GlassPublished ArticlesSlight delocalization and strategically placed double bonds have combined to make this unique ring system planar Pairs of molecules interact across a crystallographic inversion centre to form hydrogen-bonded dimers utilizing a ketonic O atom and an adjacent amine H atom [N O 29073 N-H 0833 H O 208 3 Angstrom; N-H O 1723degrees]http://blogs.najah.edu/staff/emp_2143/article/-E-Acetophenone-O-3456-Tetrafluoro-2-PyridylOxime-Formed-By-2-Substitution-of-Pentafluoropyridine-by-E-Acetophenone-OximatePublished ArticlesDespite the oxyimino chain being unconjugated [N-O 1434 2 and C-N 1278 2 angstrom] in the title compound C13H8F4N2O the planar alpha-phenylethylimino and tetrafluoro-2-oxopyridine moieties are only slightly twisted relative to each other [C-O-N-C 1676 2-degrees] This facilitates stacking along the ac diagonal so that fluorinated pyridine substituents alternate with non-fluorinated phenyl ringshttp://blogs.najah.edu/staff/emp_2143/article/Benzophenone-O-2356-Tetrafluoro-4-PyridylOxime-Formed-By-4-Substitution-of-Pentafluoropyridine-by-Benzophenone-OximatePublished ArticlesThe asymmetric unit of the title compound C18H10F4N2O is composed of two identical molecules having different configurations Although both molecules adopt a trans configuration about the N-O bond [C-N-O-C 1642 3 and -1620 2-degrees] substantial twists of all the aromatic rings relative to the C=N-O plane show no correlation between the conformers Despite the apparently random molecular configurations the packing arrangement involves several pi interactions between adjacent moleculeshttp://blogs.najah.edu/staff/emp_2143/article/Plumbagin-a-Naturally-Occurring-Naphthoquinone-Its-Isolation-Spectrophotometric-Determination-in-Roots-Stems-and-Leaves-in-Plumbago-Europaea-LPublished ArticlesA new method for isolation and spectrophotometric determination of plumbagin is presented Plumbagin was isolated by thin layer chromatography TLC and column chromatography CC techniques as an orange tinged yellow long crystalline substances Plumbagin exhibits two absrop-tion maxima at 410 and 510 nm Stability of the color pKa value and the effect of pH were studied Beers law is obeyed over the range 09-45 ppm The method is applied to the determination of plumbagin in roots stems and leaves of Plumbago europaea L plant Spectroscopy Letters Volume 27 Issue 4 May 1994 pages 409 - 416http://blogs.najah.edu/staff/emp_2143/article/The-Mechanism-of-1--Octene-Isomerization-and-Hydrosilylation-Reaction-Catalysed-by-Ru3CO12Published ArticlesIsomerization and hydrosilylation reactions of terminal olefins have been reported under thermal and photochemical conditions using Ru3 C0 12 1 and HRu3 CO 211 0 In a very recent work we reported E LI that 1 catalyses both Isomerization and hydrosilylation reactions of 1-octene eq 1 It has been found that the isomerization reaction occurs via lower nuclearity catalytic species that result from fragmentation of the mother cluster 1 Evidence in favour of concurrent cluster catalysis was also reported On the other hand the hydrosilylation reaction occurred via cluster catalysis at first and after some-time fragment catalysis occurredhttp://blogs.najah.edu/staff/emp_2143/article/Cluster-Versus-Noncluster-Catalysis-in-Olefin-Thermal-Isomerization-and-Hydrosilylation-in-the-Presence-of-Ru3Co12Published ArticlesThe ruthenium cluster Ru3CO12 1 has been evaluated as a catalyst precursor for the thermal reactions of 1-octene with Eto3SiH in a mixture of dioxane and benzene at temperatures of 50-75-degrees-C At 70-degrees-C or higher olefin isomerization and hydrosilylation reactions were observed; the products trans-2-octene and C5H11CH2CH2CH2SiOEt3 2 were identified The reactions were accompanied by a side reaction that involved generation of hydrogen gas The sum of the rates of appearance of 2 and H-2 equalled the rate of disappearance of EtO3SiH No significant isomerization was observed in the absence of EtO3SiH Maximum turnover number values of 750 70 and 70 were obtained for isomerization hydrosilylation and H-2 production reactions respectively At 60-degrees-C or lower no hydrosilylation or hydrogen production was observed and the only product was trans-2-octene No detectable disappearance of EtO3SiH was observed Acetophenone was also hydrosilated by use of cluster 1 as catalyst; the only product obtained was Eto3SiOCPhHCH3 Kinetic studies indicated that the reactions of 1-octene and the reaction of acetophenone involved a catalytically active species of lower nuclearity There was evidence of concurrent cluster catalysis especially during the first few minutes of the reactionhttp://blogs.najah.edu/staff/emp_2143/article/Olefin-Hydrogenation-and-Isomerization-Catalyzed-by-Ru3Co12-and-its-Derivatives---Cluster-vs-Noncluster-CatalysisPublished ArticlesThe systems Ru3CO12nL L = PPh3 CH3CN EtO3SiCH23NH2; n = 0-3 15 have been employed as catalysts andor catalyst precursors for thermal hydrogenation and isomerization reactions of 1-octene under moderate reaction conditions 1 atm at 70-degrees-C or below In the hydrogenation reaction the system Ru3CO1215CH3CN showed the highest activity with turnover numbers up to 1000 For this system the kinetics indicated that the hydrogenation occurs via a lower nuclearity catalytic species formed by fragmentation of the mother cluster On the other hand the isomerization reaction occurs after a 10-20 min induction period by higher-nuclearity catalytic species The isomerization gave trans-2-octene only and none of the cis-isomer The effects of other factors on the rates of hydrogenation and isomerization reactions are describedhttp://blogs.najah.edu/staff/emp_2143/article/Diethylammonium-tetrafluoro-4-pyridinolatePublished ArticlesC4H12NC5F4NO- Mr = 2402 triclinic P1BAR a = 9268 6 b = 9637 7 c = 7209 4 angstrom alpha = 10706 5 beta = 9522 5 gamma = 6370 4-degrees V = 5513 7 angstrom 3 Z = 2 Dx = 145 Mg m-3 lambdaMo K-alpha = 071069 angstrom mu = 013 mm-1 F000 = 248 T = 293 K R = 0049 for 1455 unique reflexions [F greater-than-or-equal-to 3-sigmaF] The title compound H2NEt2NC5F4O- forms as an unexpected by-product during the synthesis of NN-diethyl-O-tetrafluoro-4-pyridyl-hydroxylamine Strong hydrogen bonds link two anioncation pairs into a cyclic centrosymmetric dimer [NO 2741 8 2765 7; HO 160 6 208 6 angstrom; N-HO 172 5 161 7-degrees] which may in part explain the salts stability and hence ease of formationhttp://blogs.najah.edu/staff/emp_2143/article/Snar-Displacement-of-Fluorine-from-Pentafluoropyridine-by-Sodium-Oximates---Unprecedented-Substitution-PatternsPublished ArticlesJournal of the Chemical Society-Chemical Communications Issue: 17 Pages: 1268-1269 Published: Sep 1 1989http://blogs.najah.edu/staff/emp_2143/article/Reaction-of-Sodium-Diethylnitroxide-with-Fluorobenzenes-Pentafluoropyridine-and-HalogenopyridinesPublished ArticlesJournal of Fluorine Chemistry Volume: 44 Issue: 3 Pages: 441-444 Published: Sep 1989