A QM/MM SIMULATION METHOD APPLIED TO THE SOLUTION OF Zr4+ IN LIQUID AMMONIA

The structural and dynamics properties of solution Zr (IV) in liquid ammonia has been investigated by the method of ab initio QM/MM molecular dynamics simulations at the Hartree-Fock level. In this method, region with a high interest in the ion solvation layer of Zr (IV) were investigated by ab initio quantum mechanical Born-Oppenheimer while the rest of the system is described as classical 2-body potential. Structural properties were indicated by the coordination number, radial distribution, and angle distribution, while the dynamic properties were characterized by the mean ligand residence time. The Solvation number of 5 was found through methods of QM/MM with the modified LANL2DZ ECP basis set for Zr(IV) ion and DZP for N and H, in contrast to 10 obtained through 2-body potential simulation. No ligand migration occurs between the first and second shell. The mean ligand residence time in the second solvation shell is 8.67 ps

STRUCTURE OF IRIDIUM(III)HYDRATIONBASED ON AB INITIOQUANTUMMECHANICAL CHARGE FIELD MOLECULAR DYNAMICSSIMULATIONS

ABSTRACT Structural properties of Iridium(lII) hydration have been studied based on an ab initio Quantum Mechanical Charge Field (QMCF) Molecular Dynamics (MD) Simulations. The most chemical-relevantregion was treated by ab initio calculation at Hartree-Fock level. For the remaining region was calculated by Molecular Mechanics method. LANL2DZ ECP and DZP Dunning basis sets were applied to Ir+ ion and water, respectively. The average distance of Ir-O in the first hydration shell is 2.03 A. The QMCF MD Simulation can detect only one complex structure with coordination number of 6 in the first hydration shell. Bond angle analysis shows that Ir+ ion hydration in the first hydration shell has octahedral structure. Keywords: ab initio, hydration structure, Iridium(III), MD simulations, QMCF stud

Metilasi Asam Galat Menggunakan Agen Metilasi Dimetil Sulfat (DMS) atau Dimetil Karbonat (DMC)

Methylation of gallic acid has been conducted by the use of dimethyl sulfate (DMS) or dimethyl carbonate (DMC) as methylating agents. Methylation of gallic acid using DMS was carried out by various methods, i.e. mild condition at ambient temperature, reflux and sonication. The best method was achieved by methylation under reflux yielded 48.9% efficiency of 3,4,5-trimethoxybenzoic acid. Methylation of gallic acid with DMC was performed with several variations on the type and amount of base and phase transfer catalyst (PTC). In addition, green methods sonochemistry and microwave irradiation have also been done. Unfortunately, the methylation of gallic acid failed to give 3,4,5-trimethoxybenzoic acid. Methylation of gallic acid using green reagent DMC gave high yield at mole ratio of gallic acid : DMC : K2CO3 : KI : PTC of tetrabuthyl ammonium bromide (TBAB) = 5 : 320 : 20 : 5 : 8 under reflux for 10 hours and produced 75.96% of methyl 3,4,5-trimethoxybenzoate. Atom economy of gallic acid methylation method using DMC is 37.95%, which is not very different from that of DMS method (30.47%). However, the methylation method using DMC produced by products, which have the lower toxicity compared to that of methylation using DMS

Karakteristik potensial badan-3: Sistem Zn(II)-air-amoniak

Telah dilakukan penelitian tentang karakteristik potensial badan-3 untuk system Zn(II)- H2O-NH3. Dengan mengetahui karakteristik potensial badan-3 dapat diprediksi sumbangan energi ini dalam penentuan struktur solvasi sistem tersebut. Karakteristik potensial badan-3 dipelajari melalui perhitungan ab initio sejumlah energi titik sistem Zn(II)-H2O-NH3 pada tingkat RHF dengan menggunakan basis set LANL2 DZ ECP yang dikembangkan oleh Hay dan Wadt untuk Zn2+, SBKJC DZP ECP untuk O dan H, dan SBKJC VDZ ECP augmented untuk N. Perhitungan dilakukan pada beberapa konfigurasi geometri, yaitu: jarak 1.6 Å ≤ r Zn2+-NH3≤ 6 Å dan sudut 0o<<180o, 0o<≤60o, untuk tiap-tiap r Zn-2+-H2O = 2.06 Å, 2.01 Å, 3.26 Å, 5.06 Å. Hasil penelitian menunjukkan bahwa potensial badan-3 bersifat sedikit tarik-menarik pada jarak pendek (≤ r Zn2+-NH3, r Zn-2+-H2O ≤1,8 Å) dan bersifat tolak-menolak pada jarak menengah antara 1.8 Å sampai 3.2 Å, kemudian menurun mendekati nol sampai pada jarak 6 Å. Potensial badan-3 mencapai 20 kkal/mol pada r Zn-2+-H2O =2 Å, r Zn-2+-HN3 =1.95 Å atau 2 Å untuk sekitar 90o

The Kinetic of Cyclization-acetylation (R)-(+)-citronellal with Anhydride Acetic Acid Which Catalyzed of Zn2+-natural Zeolite

Reaction kinetic of acetylation-cyclization (R)- (+)-citronellal with acetic acid anhydride which catalyzed Zn2+-zeolite (Zn2+-Za) was analyzed by Langmuir- Hinshelwood Models. (R)-(+)-citronellal isolated from lemongrass oil with fractionation distillation reduced pressure and analyzed anantiomer ratio with GC chiral column β- DEX 225. Catalyst preparation of Zn2+-Za conducted by acid activation on natural zeolite Malang 100 mesh using 1% HF and 6 M HCl, then soaked on 0,1 M NH4Cl. Calcination was done at 450oC during 1 hour with N2 flow to achieved H-natural zeolite (HZa). Cation exchange H-Za with 0,1 M ZnCl2 conducted to obtain Zn2+-natural zeolit (Zn2+-Za). Reactions of Cyclization-acetylation (R )-(+)- citronellal using a catalyst of Zn2+-Za was done by varying molar ratio of (R )-(+)- citronellal with acetic acid anhydride, namely 0.25, 0.5, 1.0; 1 , 25; 1.5. During the reaction, into system, samples were taken each 1 mL of reaction with duration 10, 20, 30, 60, 120, 180 minutes. Reaction product was extracted with n-hexana. Structure elucidation was done by GC-MS, FTIR spectrophotometer, and 1H-NMR spectrometer. The result showed a greater molar ratio (R)-(+)-citronellal against quantity of acetic acid anhydride acetic, pulegil total was decline. Acetylation-cyclization catalyzed with Zn2+-Za on duration of 30 minutes and 80°C has k of 30.964 to 47.619 mmol (minute.gram catalyst)-1 and KSIT/KAA of 7.09

Simulasi monte carlo sistem Zn2+ dalam campuran amoniak air Monte carlo simulation of Zn2+ in water ammonia mix system

Monte Carlo Simulation of Zn2+ in 41.43 mol% water-ammonia mixed system was carried out using pair potential including three-body potential in order to study preferential solvation system. Interaction potential of H20-H20, NH3-NH3, H2O-NH3, Zn2+-H20, Zn2+-NH3, Zn2+-H2O-H20, Zn2+-NH3-NH3 were adopted from literature while three-body potential of Zn2+- H2O-NH3 was constructed in this study. Potential function of Zn2+-H2O-NH3 was constructed by collecting 2212 interaction energy points between ammonia and water molecules around Zn2+ ion. The energy of the system was calculated by ab initio method at RHF level of theory using LANL2DZ ECP basis set for Zn2+, SBKJC DZP ECP for 0 and H atoms, and SBKJC VDZ ECP augmented for N atom. Fitting function result of three-body potential by Simplex-quasi Newton method was written as: V3b = A 1[– + – cp exp[–A3 (r12 + r22)] exp (–A4 / r3-2 )I[(a2 –r12)(a2–r22)] where V3b in kJ/ mol, rl, r2 and r3 were distance (A) of Zn2+-0, Zn2+-N, and N-0 respectively, cp is H20-Zn2+-NH3 angle in radian, n=3.14, a is cut-off limit set as 6 A, A1=0.647566 kJ/mol, A2=0.564364, A3=0.155746 A-2, A4=0.203131A-2. Simulation system consisted of 1 ion Zn2+, 123 H2O molecules, and 87 NH3 molecules. Temperature of the system was set at 263.15 K resulted simulation box lenght of 19.2012663 A. The result showed that first solvation shell of Zn2+ consist of average 1 H2O molecule and 5 ammonia molecules withp first potential only eometr led to of trigonal antipyramida. Appl g y structure ying pair solvation shell of average 3 H20 molecules and 5 NH 3 Ligand exchange reaction was particularly easy to occur molecul between es. first and second solvation sphere of Zn2+. i are energy enerand Thmum of Zn2+-H2O potential otential affects to shift pair interaction energy max Zn2+-NH3 about 25.10-29.29 kr/mol. Three-body ptential of Zn2+-H2O-NH3 with eve age contribution of o 21.80 favourably affects three-body potential of Zn2+- kJ/mol kli H2O-H20 comp with Zn2+-NH3-NH3. There was an excess amount of NI-I first solvation shell about 41.57% compare with the bulk. 3 in th

STRUCTURE OF IRIDIUM(III) HYDRATION BASED ON AB INITIO QUANTUM MECHANICAL CHARGE FIELD MOLECULAR DYNAMICS SIMULATIONS

Structural properties of Iridium(III) hydration have been studied based on an ab initio Quantum Mechanical Charge Field (QMCF) Molecular Dynamics (MD) Simulations. The most chemical-relevant region was treated by ab initio calculation at Hartree-Fock level. For the remaining region was calculated by Molecular Mechanics method. LANL2DZ ECP and DZP Dunning basis sets were applied to Ir3+ ion and water, respectively. The average distance of Ir-O in the first hydration shell is 2.03 Å. The QMCF MD Simulation can detect only one complex structure with coordination number of 6 in the first hydration shell. Bond angle analysis shows that Ir3+ ion hydration in the first hydration shell has octahedral structure

Simulasi monte carlo sistem Zn2+ dalam campuran amoniak air=Monte carlo simulation of Zn2+ in water ...

Monte Carlo Simulation of Zn2+ in 41.43 mol% water-ammonia mixed system was carried out using pair potential including three-body potential in order to study preferential solvation system. Interaction potential of H20-H20, NH3-NH3, H2O-NH3, Zn2+-H20, Zn2+-NH3, Zn2+-H2O-H20, Zn2+-NH3-NH3 were adopted from literature while three-body potential of Zn2+- H2O-NH3 was constructed in this study. Potential function of Zn2+-H2O-NH3 was constructed by collecting 2212 interaction energy points between ammonia and water molecules around Zn2+ ion. The energy of the system was calculated by ab initio method at RHF level of theory using LANL2DZ ECP basis set for Zn2+, SBKJC DZP ECP for 0 and H atoms, and SBKJC VDZ ECP augmented for N atom. Fitting function result of three-body potential by Simplex-quasi Newton method was written as: V3b = A 1[â + â cp exp[âA3 (r12 + r22)] exp (âA4 / r3-2 )I[(a2 âr12)(a2âr22)] where V3b in kJ/ mol, rl, r2 and r3 were distance (A) of Zn2+-0, Zn2+-N, and N-0 respectively, cp is H20-Zn2+-NH3 angle in radian, n=3.14, a is cut-off limit set as 6 A, A1=0.647566 kJ/mol, A2=0.564364, A3=0.155746 A-2, A4=0.203131A-2. Simulation system consisted of 1 ion Zn2+, 123 H2O molecules, and 87 NH3 molecules. Temperature of the system was set at 263.15 K resulted simulation box lenght of 19.2012663 A. The result showed that first solvation shell of Zn2+ consist of average 1 H2O molecule and 5 ammonia molecules withp first otential only eometr led to of trigonal antipyramida. Appl g y structure ying pair solvation shell of average 3 H20 molecules and 5 NH 3 Ligand exchange reaction was particularly easy to occur molecul between es. first and second solvation sphere of Zn2+. i are energy enerand Thmum of Zn2+-H2O potential otential affects to shift pair interaction energy max Zn2+-NH3 about 25.10-29.29 kr/mol. Three-body ptential of Zn2+-H2O-NH3 with eve age contribution of o 21.80 favourably affects three-body potential of Zn2+- kJ/mol kli H2O-H20 comp with Zn2+-NH3-NH3. There was an excess amount of NI-I first solvation shell about 41.57% compare with the bulk. 3 in the Key words : MC simulation, three-body potential, preferential solvatio