The Effect of Lithium Alkoxides on Deprotonizations by Superbases Made from Butyllithium and Potassium tert-Pentoxide

1993 ◽  
Vol 58 (6) ◽  
pp. 1445-1451 ◽  
Author(s):  
Lubomír Lochmann ◽  
Hana Jakubův ◽  
Lambert Brandsma
Keyword(s):  
High Reactivity ◽  
The Other ◽  
Molar Ratio ◽  
Side Chain ◽  
Other Hand

The presence or absence of lithium tert-pentoxide (t-PeOLi) in Superbases, prepared from butyllithium (BuLi) and potasium tert-pentoxide (t-PeOK), affects the metallation rate of toluene only slightly, the rate factors being between 1.0 and 0.3. Thus, lithium alkoxide is not essential for the high reactivity of Superbases. However, the ring-to-side chain metallation ratio is increased in the presence of t-PeOLi. On the other hand, an excess of t-PeOK (molar ratio t-PeOK/BuLi ≥ 3)considerably increases in the rate and yield of the side chain methallation of toluene and suppresses its ring mrtallation. In this way, alkoxides enable some control on regioselectivity in Superbase reactions.

Comparison of the Potency of 8-L-Arginine, 8-D-Arginine and 8-D-Homoarginine Vasopressin Analogs with Substituted Phenylalanine in Position 2

1994 ◽  
Vol 59 (6) ◽  
pp. 1439-1450 ◽  
Author(s):  
Miroslava Žertová ◽  
Jiřina Slaninová ◽  
Zdenko Procházka
Keyword(s):  
Amino Acid ◽  
Solid Phase Synthesis ◽  
Solid Phase ◽  
Basic Amino Acid ◽  
The Other ◽  
Side Chain ◽  
Inhibitory Potency ◽  
Phase Synthesis ◽  
Other Hand ◽  
Order Of Magnitude

An analysis of the uterotonic potencies of all analogs having substituted L- or D-tyrosine or -phenylalanine in position 2 and L-arginine, D-arginine or D-homoarginine in position 8 was made. The series of analogs already published was completed by the solid phase synthesis of ten new analogs having L- or D-Phe, L- or D-Phe(2-Et), L- or D-Phe(2,4,6-triMe) or D-Tyr(Me) in position 2 and either L- or D-arginine in position 8. All newly synthesized analogs were found to be uterotonic inhibitors. Deamination increases both the agonistic and antagonistic potency. In the case of phenylalanine analogs the change of configuration from L to D in position 2 enhances the uterotonic inhibition for more than 1 order of magnitude. The L to D change in position 8 enhances the inhibitory potency negligibly. Prolongation of the side chain of the D-basic amino acid in position 8 seems to decrease slightly the inhibitory potency if there is L-substituted amino acid in position 2. On the other hand there is a tendency to the increase of the inhibitory potency if there is D-substituted amino acid in position 2.

Degradation of chlorpyriphos in water by advanced oxidation processes

2010 ◽  
Vol 10 (1) ◽  
pp. 1-6 ◽  
Author(s):  
R. Murillo ◽  
J. Sarasa ◽  
M. Lanao ◽  
J. L. Ovelleiro
Keyword(s):  
Reaction Time ◽  
Light Source ◽  
Advanced Oxidation Processes ◽  
Advanced Oxidation ◽  
The Other ◽  
Molar Ratio ◽  
Optimum Conditions ◽  
Oxidation Processes ◽  
Other Hand ◽  
Initial Ph

The degradation of chlorpyriphos by different advanced oxidation processes such as photo-Fenton, TiO2, TiO2/H2O2, O3 and O3/H2O2 was investigated. The photo-Fenton and TiO2 processes were optimized using a solar chamber as light source. The optimum dosages of the photo-Fenton treatment were: [H2O2]=0.01 M; [Fe3 + ]=10 mg l−1; initial pH = 3.5. With these optimum conditions total degradation was observed after 15 minutes of reaction time. The application of sunlight was also efficient as total degradation was achieved after 60 minutes. The optimum dosage using only TiO2 as catalyst was 1,000 mg l−1, obtaining the maximum degradation at 20 minutes of reaction time. On the other hand, the addition of 0.02 M of H2O2 to a lower dosage of TiO2 (10 mg l−1) provides the same degradation. The ozonation treatment achieved complete degradation at 30 minutes of reaction time. On the other hand, it was observed that the degradation was faster by adding H2O2 (H2O2/O3 molar ratio = 0.5). In this case, total degradation was observed after 20 minutes.

scholarly journals Determination of the Ratios of Ligands to Metal Ion of some Metal Complexes of Triazoles by Using Eleetronie Speetra in Organie Solvents

2004 ◽  
Vol 1 (1) ◽  
pp. 110-115
Author(s):  
Baghdad Science Journal
Keyword(s):  
Solid State ◽  
Metal Complexes ◽  
Electronic Spectra ◽  
Metal Ion ◽  
The Other ◽  
Molar Ratio ◽  
Other Hand

We found that 4,5- diphenyl- 3(2- propynyl) thio- 1??-triazole [1? forms a complex with Pd (11) ion of ratio 1:1 which absorbs light in CH2CI2 at 400 nm, and 4,5- diphenyl- 3(2- propenyl) thio- 1,2,4- triazole [II] forms complexes with Pd (II) ion of ratio 1:1 which absorbs light at 390 nm, and of ratio 2:1 which absorbs light at 435 nm. On the other hand, we found that the new derivative 4- phenyl- 5( p- amino phenyl) -3- mercapto- 1,2,4- triazole ?111? forms complexes with Cu (II) ion of the ratio 1:1 which absorbs light at 380 nm, with Ni (II) ion of the ratio 3:1 which absorbs light at 358 nm; and with Co (11) ion of the ratio 3.2:1 which absorbs light at 588 nm. The ratio of the complexes were determined by measuring the electronic spectra of the complexes in CH2G2 and (CH^NCHO at different concentrations ofthe ligands and f?xed ' •' of the metal ion in every case, then applying the molar ratio plots on the data. Our results were confirmed by precipitating most ofthe above complexes in solid state, and then each complex was analyzed elementally.

scholarly journals Structural and Functional Changes of Reconstituted High-Density Lipoprotein (HDL) by Incorporation of α-synuclein: A Potent Antioxidant and Anti-Glycation Activity of α-synuclein and apoA-I in HDL at High Molar Ratio of α-synuclein

Molecules ◽  
2021 ◽  
Vol 26 (24) ◽  
pp. 7485
Author(s):  
Kyung-Hyun Cho
Keyword(s):  
Amino Acids ◽  
Secondary Structure ◽  
Expression System ◽  
Lipoprotein Metabolism ◽  
The Other ◽  
Ldl Oxidation ◽  
Molar Ratio ◽  
Binding Ability ◽  
Functional Changes ◽  
Other Hand

α-synuclein (α-syn) is a major culprit of Parkinson’s disease (PD), although lipoprotein metabolism is very important in the pathogenesis of PD. α-syn was expressed and purified using the pET30a expression vector from an E. coli expression system to elucidate the physiological effects of α-syn on lipoprotein metabolism. The human α-syn protein (140 amino acids) with His-tag (8 amino acids) was expressed and purified to at least 95% purity. Isoelectric focusing gel electrophoresis showed that the isoelectric point (pI) of α-syn and apoA-I were pI = 4.5 and pI = 6.4, respectively. The lipid-free α-syn showed almost no phospholipid-binding ability, while apoA-I showed rapid binding ability with a half-time (T1/2) = 8 ± 0.7 min. The α-syn and apoA-I could be incorporated into the reconstituted HDL (rHDL, molar ratio 95:5:1:1, palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC):cholesterol:apoA-I:α-syn with the production of larger particles (92 Å) than apoA-I-rHDL (86 and 78 Å) and α-syn-rHDL (65 Å). An rHDL containing both apoA-I and α-syn showed lower α-helicity around 45% with a red shift of the Trp wavelength maximum fluorescence (WMF) from 339 nm, while apoA-I-HDL showed 76% α-helicity and 337 nm of WMF. The denaturation by urea addition showed that the incorporation of α-syn in rHDL caused a larger increase in the WMF than apoA-I-rHDL, suggesting that the destabilization of the secondary structure of apoA-I by the addition of α-syn. On the other hand, the addition of α-syn induced two-times higher resistance to rHDL glycation at apoA-I:α-syn molar ratios of 1:1 and 1:2. Interestingly, low α-syn in rHDL concentrations, molar ratio of 1:0.5 (apoA-I:α-syn), did not prevent glycation with more multimerization of apoA-I. In the lipid-free and lipid-bound state, α-syn showed more potent antioxidant activity than apoA-I against cupric ion-mediated LDL oxidation. On the other hand, microinjection of α-syn (final 2 μM) resulted in 10% less survival of zebrafish embryos than apoA-I. A subcutaneous injection of α-syn (final 34 μM) resulted in less tail fin regeneration than apoA-I. Interestingly, incorporation of α-syn at a low molar ratio (apoA-I:α-syn, 1:0.5) in rHDL resulted destabilization of the secondary structure and impairment of apoA-I functionality via more oxidation and glycation. However, at a higher molar ratio of α-syn in rHDL (apoA-I:α-syn = 1:1 or 1:2) exhibited potent antioxidant and anti-glycation activity without aggregation. In conclusion, there might be a critical concentration of α-syn and apoA-I in HDL-like complex to prevent the aggregation of apoA-I via structural and functional enhancement.

scholarly journals Synthesis of Ca-hydroxyapatite Bioceramic from Egg Shell and its Characterization

1970 ◽  
Vol 43 (4) ◽  
pp. 501-512 ◽  
Author(s):  
Samina Ahmed ◽  
Mainul Ahsan
Keyword(s):  
Crystalline Phase ◽  
Hexagonal Structure ◽  
The Other ◽  
Molar Ratio ◽  
Apatite Phase ◽  
Other Hand ◽  
Ft Ir ◽  
Egg Shell

Ca-hydroxyapatite (HA) was synthesised from egg shell under different conditions and characterised by using AAS, FT-IR, XRD, SEM and EDS techniques. The results of these analyses combined together indicate that sintered HA sample1 resembles the feature of pure and single apatite phase having hexagonal structure. A Ca/P molar ratio of 1.69 was achieved in this case. On the other hand HA obtained from calcined egg shell is a combination of both amorphous and crystalline phase and revealed a sub-stoichiometric Ca-deficient apatite form with a Ca/P ratio of 1.50. Keywords: Ca-hydroxyapatite, Biomaterials, Hexagonal, stoichiometric apatite, Ca-deficient apatite   doi: 10.3329/bjsir.v43i4.2240 Bangladesh J. Sci. Ind. Res. 43(4), 501-512, 2008

Activity Comparison of MCM-41 and V-MCM-4 Catalysts for Ethanol Selective Oxidation and DRIFTS Analysis

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Yesim Gucbilmez ◽  
Timur Dogu ◽  
Suna Balci
Keyword(s):  
Hydrogen Atom ◽  
Gas Phase ◽  
Selective Oxidation ◽  
The Other ◽  
Lattice Oxygen ◽  
Molar Ratio ◽  
Surface Species ◽  
Other Hand ◽  
Activity Comparison ◽  
Mcm 41

The activity of a V-MCM-41 catalyst with a V/Si molar ratio of 0.04 was compared with the activity of a pure MCM-41 catalyst and some DRIFTS studies were performed in order to understand the mechanism of selective oxidation of ethanol. V-MCM-41 was found to be much more active than pure MCM-41, favouring the formation of high amounts of ethylene over 300°C. MCM-41, on the other hand, was found to favour the formation of acetaldehyde over ethylene at all studied temperatures. It was shown by reaction findings that over V-MCM-41, ethylene was produced mainly in the presence of gas phase oxygen whereas acetaldehyde was produced using the lattice oxygen even in the absence of gas phase oxygen. DRIFTS studies indicated the formation of acetaldehyde molecules from acetate-like surface species which were formed by the removal of a hydrogen atom from the ?-carbon of chemisorbed ethoxy species by the help of the lattice oxygen. On the other hand, removal of a hydrogen atom from the ?-carbon of the ethoxy species, in the presence of gas phase oxygen, resulted in the formation of vinyl-like surface species which then yielded ethylene molecules.

scholarly journals Reaktive E=C(p – p)π-Systeme, XX [1] / Reactive E=C(p–p)π-Systems, XX [1]

1990 ◽  
Vol 45 (2) ◽  
pp. 148-160 ◽  
Author(s):  
Joseph Grobe ◽  
Marianne Hegemann ◽  
Duc Le Van
Keyword(s):  
Chemical Properties ◽  
Vapour Phase ◽  
Diels Alder ◽  
The Other ◽  
Molar Ratio ◽  
One Pot ◽  
Nmr Data ◽  
Other Hand ◽  
And Chemical Properties

The vapour phase pyrolysis of the stannylphosphane Me3SnP(CF3)C2F5 (5) at 330 °C leads to 1,2-elimination of Me3SnF yielding a mixture of the two isomeric perfluorophosphaalkenes F3CP=C(F)CF3 (3) and F5C2P=CF2 (4) in a 3:1 molar ratio. 3 is more labile than 4 and proves to be similar to the perfluoro-3-phosphapent-2-ene F5C2P=C(F)CF3 (2) with respect to NMR data and chemical properties. On the other hand 4 resembles the perfluoro-2-phosphapropene F3CP=CF2 (1). These results have been deduced from the following reactivity studies: (i) The rate of dimerization being higher for 3 than for 4. (ii) Reaction of the mixture with diethylamine yielding the aminophosphane derivative F3CP(NEt2)CF(H)CF3 (13) as a product of 3 and the C-aminophosphaalkene F5C2P=C(F)NEt2 (14) as the derivative of 4. (iii) Reaction of the mixture with methanol giving the methoxyphosphane F3CP(OMe)CF(H)CF3 (15) from 3 and the secondary phosphane F5C2P(H)CF2OMe (16) from 4 as precursors. 3 and 4 prove to be effective dienophiles in reactions with 2,3-dimethyl-1,3-butadiene and 1,3-cyclohexadiene, respectively, producing the corresponding Diels-Alder adducts 9 to 12. For these preparations 5 can be used as an equivalent of 3 in a one-pot procedure at 70 °C. On the other hand the phosphane HP(CF3)C2F5 (8) is suited as precursor for 3 in preparing HX addition products.

Effects of Dy3+/ Eu2+ Molar Ration on SrAl2O4：Eu2+，Dy3+Long Persistence Phosphors by Microwave Plasma Synthesisd Method

2011 ◽  
Vol 197-198 ◽  
pp. 298-301 ◽  
Author(s):  
Wen Zhou Sun ◽  
Yu Hong Chen ◽  
Liang Jiang ◽  
Fei Han
Keyword(s):  
Phase Composition ◽  
Microwave Plasma ◽  
The Other ◽  
Molar Ratio ◽  
Plasma Method ◽  
Long Afterglow ◽  
Other Hand ◽  
Defect Levels ◽  
Electric Transition ◽  
The One

SrAl2O4:Eu2+, Dy3+ long persistence phosphors are synthesized by microwave plasma method. The effects of molar ratio of Dy3+ and Eu2+ on the phase composition, the spectrum properties and long afterglow property of phosphors are investigated in the paper. The analysis results show that spectrum properties depressed clearly following the increase of Dy3+/ Eu2+. And the afterglow property of phosphors are improved by doping of the Dy3+, but suppressed by excessive doping. On the one hand, this is because that the number of electrons trapped by defect levels increased with the increase of Dy3+. But on the other hand, it’s difficult to occur electric transition if doping excessive Dy3+, so leads to performance depressed. Above-mentioned results, it’s confirm that the optimized Dy3+/Eu2+ molar ratio is 2:1 when SrAl2O4:Eu2+, Dy3+ phosphors synthesized by microwave plasma method.

Synthesis of 2-Acetoacetyl- and 2-OxaIoacetyl-1,3-indandiones and Related Compounds

1988 ◽  
Vol 43 (7) ◽  
pp. 897-900 ◽  
Author(s):  
W. S. Hamama ◽  
M. Hammouda ◽  
E. M. Afsah
Keyword(s):  
Ethyl Acetate ◽  
Mannich Reaction ◽  
Selenium Dioxide ◽  
The Other ◽  
Molar Ratio ◽  
Diethyl Oxalate ◽  
Phenyl Hydrazine ◽  
Claisen Condensation ◽  
Other Hand ◽  
Related Compounds

Abstract Claisen condensation of 2-acetyl-1,3-indandione (1) with ethyl acetate afforded the 2-acetoacetyl-1,3-indandione (2) which upon treatment with benzylamine and paraformaldehyde in a molar ratio of (1:1:2) and (1:2:4) afforded the piperidinone and the diazabicyclic derivative (4) and (5) respectively. On the other hand, Claisen condensation of 1 with diethyl oxalate yielded two products (6) and (9). The behaviour of 6 towards phenyl hydrazine, and of 9 towards selenium dioxide and double Mannich reaction were also investigated.

The preparation of porphyrin S-411 (dehydrocoproporphyrin) and harderoporphyrin from protoporphyrin IX

1981 ◽  
Vol 59 (5) ◽  
pp. 779-785 ◽  
Author(s):  
David Dolphin ◽  
Ramani Sivasothy
Keyword(s):  
Dimethyl Ester ◽  
Protoporphyrin Ix ◽  
The Other ◽  
Side Chain ◽  
Side Chains ◽  
Positional Isomers ◽  
Other Hand ◽  
Hydroxyethyl Group

Protoporphyrin IX dimethyl ester has been converted into the two 2,4-positional isomers bearing hydroxyethyl and methoxycarbonylvinyl side chains. The 4-(2-hydroxyethyl) group was extended to a methoxycarbonylethyl group to give the tetramethyl ester of porphyrin S-411 (2-methoxycarbonylvinyl-4-methoxycarbonylethyldeuteroporphyrin dimethyl ester). On the other hand reduction of the 4-methoxycarbonylvinyl to the corresponding methoxycarbonylethyl group and dehydration of the 2-(2-hydroxyethyl) to a vinyl side chain gave the trimethyl ester of harderoporphyrin (2-vinyl-4-methoxycarbonylethyldeuteroporphyrin dimethyl ester).

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