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Articles 391 - 420 of 440

Full-Text Articles in Chemistry

Microscale Preparation Of Pyrocatechol: The Use Of Sodium Percarbonate In The Dakin Reaction, T. Evans Yamazaki, Dominic T.C. Yang Jan 1993

Microscale Preparation Of Pyrocatechol: The Use Of Sodium Percarbonate In The Dakin Reaction, T. Evans Yamazaki, Dominic T.C. Yang

Journal of the Arkansas Academy of Science

No abstract provided.


S-H Stretching Frequencies In Ruthenium Mercaptan Complexes And The Crystal And Molecular Structures Of [Cpru(Pph3)2(S-C4h, Haengsoon Park, David Minick, Mark Draganjac, Joey W. Crump, A. W. Cordes, Elizabeth M. Holt Jan 1993

S-H Stretching Frequencies In Ruthenium Mercaptan Complexes And The Crystal And Molecular Structures Of [Cpru(Pph3)2(S-C4h, Haengsoon Park, David Minick, Mark Draganjac, Joey W. Crump, A. W. Cordes, Elizabeth M. Holt

Journal of the Arkansas Academy of Science

No abstract provided.


Determination Of Hammett Pyridine 3-Aza And 4-Aza Replacement Constants By 1h Nmr Studies Of Amide Systems, Frank L. Setliff, Nikhil G. Soman, Alan D. Toland Jan 1993

Determination Of Hammett Pyridine 3-Aza And 4-Aza Replacement Constants By 1h Nmr Studies Of Amide Systems, Frank L. Setliff, Nikhil G. Soman, Alan D. Toland

Journal of the Arkansas Academy of Science

Values for Hammett pyridine 3-aza and 4-aza replacement constants were obtained by correlation of the amide proton chemical shifts (in DMSO) of some N-(3-pyridyl)-and N-(4-pyridyl)-dichloronicotinamides, benzamides and acetamides with those of their N-(substituted phenyl) amide analogs using standard Hammett a values


Rapid Reduction Of Nitrate Ion In Rain Water, David M. Chittenden Ii Jan 1993

Rapid Reduction Of Nitrate Ion In Rain Water, David M. Chittenden Ii

Journal of the Arkansas Academy of Science

No abstract provided.


Hammett Correlations In The 1H Nmr Spectra Of Some N-Arlydihalonicotinamides, Frank L. Setliff, Nikhil G. Soman, Jody Z. Caldwell, Debra L. Rogers Jan 1992

Hammett Correlations In The 1H Nmr Spectra Of Some N-Arlydihalonicotinamides, Frank L. Setliff, Nikhil G. Soman, Jody Z. Caldwell, Debra L. Rogers

Journal of the Arkansas Academy of Science

Excellent linear correlations of amide proton chemical shifts (Snh) (in DMSO-d6 ) with Hammett substituent constants (5) for a series of 4-substituted anilides of four dihalonicotinic acid systems were observed. Dihalonicotinanilides with chlorine in the pyridine 2 - position exhibited a more positive slope in a Hammett plot of S^H vs - aR- where R is the substituent in the 4 position of the benzene ring. This observation is explained in terms of the inductive effect of chlorine which results in a slightly more acidic amide proton, which in turn causes an enhanced hydrogen bonding tendency to solvent. Four disubstituted …


Model For The Co Poisoning Of Hydrodesulfurization Catalysts. Synthesis And Structure Of {Ru(Co)[Pph2sc12h7)]2cl2}.2ch2br2, Mark Draganjac, Thomas B. Rauchfuss, Arnold L. Rheingold Jan 1992

Model For The Co Poisoning Of Hydrodesulfurization Catalysts. Synthesis And Structure Of {Ru(Co)[Pph2sc12h7)]2cl2}.2ch2br2, Mark Draganjac, Thomas B. Rauchfuss, Arnold L. Rheingold

Journal of the Arkansas Academy of Science

The treatment of {Ru[(PPh2SC12H7)]2Cl2} with CO at ambient conditions results, after work up, in the isolation of the monocarbonylated species {Ru(CO)[(PPh2SC12H7)]2Cl2}, I. Crystals of I(C51H38Br4Cl20P2RuS2; F.W. = 1284.6) are triclinic; Ppa= 11.587(3), b = 13.010(4), c = 17.309(4) A, a = 93.32(2)°, p = 106.51(2)°, y = 91.29(2)°; Z= 2; V=2495(1) A';d^,. = 1.709 gem 1 X(MoKa) = 0.71073 A, = 37.7 cm 1 ;R =0.0748; Rw = 0.0714 for 4141 unique reflections. The geometry about the Ru(II) center is pseudooctahedral, with the phosphine ligands in the trans configuration. The Ru-S bond distance is 2.425(3) A.


4-Substituted Anilides Of 2,6- And 5,6- Dichlorolicotinic Acid. Potential Agricultural Agents, Frank L. Setliff, Nikhil G. Soman Jan 1992

4-Substituted Anilides Of 2,6- And 5,6- Dichlorolicotinic Acid. Potential Agricultural Agents, Frank L. Setliff, Nikhil G. Soman

Journal of the Arkansas Academy of Science

A series of 4-substituted anilides of 2,6- and 5,6 dichloronicotinic acid were prepared. The acids were first converted to their acid chlorides, which were in turn treated with the appropriate 4-substituted aniline in chloroform. A total of 16 anilides was thus prepared, and their structures confirmed. These compounds were prepared for testing as possible herbicidal, pesticidal or fungicidal agents


Scf-Mo And Monte Carlo Calculations Of Poly (Dimethylsiloxane), Shannon H. Brownfield, Jerry A. Darsey Jan 1992

Scf-Mo And Monte Carlo Calculations Of Poly (Dimethylsiloxane), Shannon H. Brownfield, Jerry A. Darsey

Journal of the Arkansas Academy of Science

Self-consistent-field molecular orbital calculations are being used more and more extensively in determining the energies and properties of various confirmations of polymers. We are using the semi-quantum mechanical procedure MNDO (moderate neglect of differential overlap) to obtain various rotational conformations states of poly(dimethylsiloxane) (PDMS). Before calculation of these states, the molecule is geometrically optimized by using the ab initio procedure Guassian 86 at the 3-21G basis set level. Generations of 144 rotational states by rotating about two bonds simultaneously in increments of 30° were created. A potential energy surface was created from which Monte Carlo generated several polymer characteristics including …


Preparation Of A Series Of N-Phenylamides Of 5-Bromo-6-Chloronicontinic Acid And 5-Bromo-2-Chloronicontinic Acid, Frank L. Setliff, Jody Z. Caldwell Jan 1991

Preparation Of A Series Of N-Phenylamides Of 5-Bromo-6-Chloronicontinic Acid And 5-Bromo-2-Chloronicontinic Acid, Frank L. Setliff, Jody Z. Caldwell

Journal of the Arkansas Academy of Science

A series of N-phenylamides of 5-bromo 6-chloronicotinic acid and 5-bromo-2-chloronicotinic acid were synthesized by treatment of their freshly prepared acid chlorides with the appropriately ring substituted anilines. Thirty new compounds were prepared, and their structures were ascertained by elemental analyses and spectroscopic techniques. Spectroscopic trends in the infrared spectra of the two series were examined in an attempt to correlate structural and electronic effects to hydrogen bonding tendencies.


Preparation Of A Series Of Substituted N-Phenyl-5-Bromo-6-Chloro- And 5-Bromo-6-Chloronicotinates Of Potential Agricultural Interest, Frank L. Setliff, Maximillia M. Muguluma, Jody Z. Caldwell Jan 1991

Preparation Of A Series Of Substituted N-Phenyl-5-Bromo-6-Chloro- And 5-Bromo-6-Chloronicotinates Of Potential Agricultural Interest, Frank L. Setliff, Maximillia M. Muguluma, Jody Z. Caldwell

Journal of the Arkansas Academy of Science

Substituted phenyl esters of 5-bromo-2-chloronicotinic acid and 5 bromo 6-chloronicotinic acid were prepared. The acids were first converted to their respective acid chlorides using thionyl chloride, and the acid chlorides were immediately transformed to the esters by treatment with the appropriately substituted phenol in sodium hydroxide solution. Aunique chloride displacement of bromide was observed on attempting to convert 5,6-dibromonicotinic acid to its acid chloride


Study Of Deposition Methods For Silicon Powder, Kamesh V. Gadepally, Kevin B. Tennal, Roger M. Hawk, Al Robles, James A. Gribel Jan 1990

Study Of Deposition Methods For Silicon Powder, Kamesh V. Gadepally, Kevin B. Tennal, Roger M. Hawk, Al Robles, James A. Gribel

Journal of the Arkansas Academy of Science

Silicon powder tends to agglomerate at normal atmospheric conditions and is, hence, difficult to aerosolize. Several methods of aerosolizing silicon powder and finally depositing it on various substrates were investigated. This paper presents the investigated methods of aerosolization. The electrostatic spray coating used in dry paint application was found to be the most suitable. The general merits of this method and its use for silicon powder deposition to form films are discussed.


Comparison Of The Molecular Structures Of Monovalent Cation Salets Of N,N-Dimethyldithiocarbamate. Novel Synthesis And Crystal Structure Of (Phi4)(S2cn(Ch3)2)2h2o, Mark Draganjac, David Minick, Elizabeth M. Holt Jan 1990

Comparison Of The Molecular Structures Of Monovalent Cation Salets Of N,N-Dimethyldithiocarbamate. Novel Synthesis And Crystal Structure Of (Phi4)(S2cn(Ch3)2)2h2o, Mark Draganjac, David Minick, Elizabeth M. Holt

Journal of the Arkansas Academy of Science

Crystals of the tetraphenylphosphonium N,N-dimethyldithiocarbamate dihydrate (C₂₇H₃₀NO₂PS₂; F.W. = 495.6) are monoclinic; P2₁/n; a = 13.349(6), b = 20,968(6), c = 9.800(4) Å, β = 109.01(3)°; Z = 4; V = 2593.4(16) Å^3; Dₓ = 1.269 gcm- 3 . Data were collected at ambient temperature using MoKα radiation (λ = 0.71069 Å).F(000) = 1048, linear absorption coefficient, n = 2.80 cm- 1. The structure was solved by direct methods and subsequently refined by full matrix least squares techniques. Final R value = 0.064 for 1 61 0 reflections and 298 varied parameters. Due to the nature of the cation, interactions …


Design Of A Viscometer Using Magnetostriction Of Ferromagnetic Probes, Subhendra Nath Sarkar Jan 1990

Design Of A Viscometer Using Magnetostriction Of Ferromagnetic Probes, Subhendra Nath Sarkar

Journal of the Arkansas Academy of Science

On-line measurement of viscosity of process liquids at process temperature is difficult though industrially very important. A viscometer is designed which can do this up to about 300 °C almost on-line within about 1-8% accuracy except for very viscous liquids like glucose. It uses a ferromagnetic probe designed to mechanically vibrate in the ultrasonic frequency range. An excitation coil sends repeated excitation current pulses to induce mechanical vibration in the probe tip. When placed in a process fluid, the vibration amplitude is damped due to the viscosity of the fluid, and the damped vibration is sensed by Faraday's principle by …


7li Nmr Of Normal Human Erythrocytes, Rao P. Gullapalli, Roger M. Hawk, Richard A. Komoroski Jan 1989

7li Nmr Of Normal Human Erythrocytes, Rao P. Gullapalli, Roger M. Hawk, Richard A. Komoroski

Journal of the Arkansas Academy of Science

Lithium has been known to be an effective medication for people with bipolar disorder. The mechanisms of action of lithium in the brain is not very well understood. NMR spectroscopy and imaging are effective both in determining lithium levels in tissue and brain. We have monitored lithium levels in red blood cells. We have been able to separate intra- and extracellular compartments of lithium using shift reagents, thereby obtaining T^1 's of both the compartments. Lithium uptake as a function of hematocrit was monitored weekly over a 3 week period. The time constant of 50 mM lithium uptake at 25°C …


Preparation Of A Series Of Pyridyl Phenylureas Of Potential Agricultural Interest, Frank L. Setliff, Steve H. Rankin, Mark W. Milstead Jan 1989

Preparation Of A Series Of Pyridyl Phenylureas Of Potential Agricultural Interest, Frank L. Setliff, Steve H. Rankin, Mark W. Milstead

Journal of the Arkansas Academy of Science

Substituted phenylurea derivatives of 3-amino-2-chloro-5-methylpyridine and 5-amino-2-chloro-3- methylpyridine were prepared by treating the amines with appropriately substituted phenyl isocyanates. Structure- confirming spectral data are also presented.


Improved Synthesis Of 5-Methylbenz(A)Anthracene, Jia Che, Dominic T.C. Yang Jan 1987

Improved Synthesis Of 5-Methylbenz(A)Anthracene, Jia Che, Dominic T.C. Yang

Journal of the Arkansas Academy of Science

A revised synthesis of 5-methylbenz(a)anthracene is reported. It involves only three simple and convenient steps starting from a commercially available compound, and gives a 82% overall yield. Bromination of 5-methylbenz(a)anthracene with N-bromosuccinimide (NBS) in carbon tetrachloride furnishes 5-bromomethylbenz(a)anthracene in a 92% yield. When bromination is carried out using dimethylformamide as the solvent, 7-bromo-5-methylbenz(a)anthracene is formed as the exclusive product.


Anomalous Concentrations Of Co-58 And Cs-137 In Dardanelle Reservoir, David M. Chittenden Ii Jan 1986

Anomalous Concentrations Of Co-58 And Cs-137 In Dardanelle Reservoir, David M. Chittenden Ii

Journal of the Arkansas Academy of Science

The unforseen occurrence of significant concentrations of Co-58 and Cs-1 37 in a quiescent backwater of Dardanelle Reservoir provided an opportunity to observe the equilibrium distribution of Cs-1 37 between solution and suspended solids. This equilibrium has not been observed in other areas of the reservoir because small amounts of this nuclide are regularly injected into the lake by the AP&L Nuclear I facility. The systematics of the Co-58 concentration lead to the conclusion that significant amounts of these two nuclides had been injected into the sampling area from a source unknown.


Electrochemistry Of Dihalogenated Nicotonic Acids In Aqueous And Aprotic Media, Ali U. Shaikh, Tappi A. Dixon, Lourie A. Battles, Frank L. Setliff Jan 1986

Electrochemistry Of Dihalogenated Nicotonic Acids In Aqueous And Aprotic Media, Ali U. Shaikh, Tappi A. Dixon, Lourie A. Battles, Frank L. Setliff

Journal of the Arkansas Academy of Science

The electrochemical reduction of several 2,5- and 5,6- dihalonicotinic acids have been studied in dimethyl sulfoxide as well as in aqueous buffers of different pH. The polarographic half-wave potentials for the reduction of these compounds in both media are reported here. The compounds appear to reduce at the carboxyl group. The presence of halogen atoms on the pyridine ring facilitates reduction.


Evaluation Of Sugar Cane Bagasse And Rice Straw As Process Substrates For The Production Of Ethyl Alcohol, Douglas B. Rivers, Gisella M. Zanin, George H. Emert Jan 1984

Evaluation Of Sugar Cane Bagasse And Rice Straw As Process Substrates For The Production Of Ethyl Alcohol, Douglas B. Rivers, Gisella M. Zanin, George H. Emert

Journal of the Arkansas Academy of Science

No abstract provided.


Microcomputer-Assisted Colorimetric Determination Of Iron, A. M. Hoyt Jr. Jan 1983

Microcomputer-Assisted Colorimetric Determination Of Iron, A. M. Hoyt Jr.

Journal of the Arkansas Academy of Science

No abstract provided.


Chemistry Of The Spring Waters Of The Ouachita Mountains Excluding Hot Springs, Arkansas, George H. Wagner, Kenneth F. Steele Mar 1980

Chemistry Of The Spring Waters Of The Ouachita Mountains Excluding Hot Springs, Arkansas, George H. Wagner, Kenneth F. Steele

Arkansas Water Resources Center Technical Reports

This report is based on the chemical analysis of the waters from 93 springs and 9 wells. Springs, when free from metal plumbing, provide an uncontaminated source of the ground water and it was desired to obtain water uncontaminated with metals. A few wells were added to the list, usually because of their unique location in the sampling grid.


Concentrations Of Total Dissolved Solids And Selected Cations In Dardanelle Lake, Arkansas, David M. Chittenden Ii Jan 1980

Concentrations Of Total Dissolved Solids And Selected Cations In Dardanelle Lake, Arkansas, David M. Chittenden Ii

Journal of the Arkansas Academy of Science

No abstract provided.


Factors Affecting The Sr-90 Concentration In Dardanelle Lake, Arkansas, David M. Chittenden Ii Jan 1980

Factors Affecting The Sr-90 Concentration In Dardanelle Lake, Arkansas, David M. Chittenden Ii

Journal of the Arkansas Academy of Science

No abstract provided.


Fate Of Some Common Radionuclides Found In Dardanelle Lake, David M. Chittenden Ii Jan 1979

Fate Of Some Common Radionuclides Found In Dardanelle Lake, David M. Chittenden Ii

Journal of the Arkansas Academy of Science

Four factors influence the concentrations of radionuclides in Dardanelle Lake water: injections due to fallout and discharge from Nuclear I coupled with losses due to decay, to dilution and to sedimentation. It is possible to estimate the first three factors and to measure monthly changes in the concentrations of Sr-89, Ce-141, Cs-137, Co-38, Ce-144, and Sr-90 - Y-90 during periods when the concentrations of these nuclides are abnormally high (after large releases or the Chinese weapons tests) or abnormally low (during reactor refueling).


Concentration Of Radionuclides In Dardanelle Lake, Arkansas, David M. Chittenden Ii, Larry Mcfadden Jan 1978

Concentration Of Radionuclides In Dardanelle Lake, Arkansas, David M. Chittenden Ii, Larry Mcfadden

Journal of the Arkansas Academy of Science

Concentrations of the nuclides ⁹⁰Sr - ⁹⁰Y, ¹⁴⁴Ce - ¹⁴⁴Pr, ¹³⁷Cs, ³⁸Co, ¹¹⁰ͫAg, ¹⁴¹Ce and ⁸⁹Sr have been measured monthly since November, 1975. The results from the period September, 1976, to August, 1977, depend on the relative intensities of the sources of the radionuclides; emissions from Nuclear I, the Chinese nuclear tests of Fall, 1976, and fallout from older atmospheric tests.


Catecholborane Reductions Of Ditosylhydrozones To The Corresponding Methylene Derivatives, Dominic T.C. Yang, Michael C.W. Yang, George W. Kabalka, J. H. Chandler Jan 1977

Catecholborane Reductions Of Ditosylhydrozones To The Corresponding Methylene Derivatives, Dominic T.C. Yang, Michael C.W. Yang, George W. Kabalka, J. H. Chandler

Journal of the Arkansas Academy of Science

The smooth deoxygenation of diketones via the Catecholborane reduction of the corresponding ditosylhydrzaones is described. The reductions occur under mild conditions and are suitable for sensitive compounds.


Experimental Testing Program In Elementary Chemistry: A Preliminary Report, Billie G. Broach, Howard L. Hodges Jan 1976

Experimental Testing Program In Elementary Chemistry: A Preliminary Report, Billie G. Broach, Howard L. Hodges

Journal of the Arkansas Academy of Science

An experimental testing program is described which utilizes questions that are partly computer composed, in addition to a section composed by the instructor, and a retesting option to the student. Results from a trial of the program for one term indicate that (1) course grades were improved, (2) the student withdrawal failure rate was unaffected, and (3) the employed students took greater advantage of the retest than did the unemployed students.


Composition Of Arkansas Grapes During Maturation, Cameron Jones, Dominic T.C. Yang, Thomas O. Whitley Jan 1976

Composition Of Arkansas Grapes During Maturation, Cameron Jones, Dominic T.C. Yang, Thomas O. Whitley

Journal of the Arkansas Academy of Science

Changes in organic acid and glucose content during maturation and ripening of grapes grown in Arkansas in 1973 are shown for four French hybrid varieties, S5279, S10878, SV23- 657, and S13053, and for four rotundifolia varieties, Scuppernong, Tarheel, Fry, and Magoon. In all varieties the concentrations of malates and tartrates were highest in the early stages of berry growth after veraison. During ripening the titratable acidity decreased and Balling and pH measurements increased. Although varieties reached maturity on different dates, changes in parameters followed similar curves typical for grapes of the species but occurring over a short period (Johnson and …


Semiquantitative Infrared Analysis Of Diketones And Anhydrides In A Reaction Mixture, Dominic T.C. Yang, F. H. Watson Jr., J. O. Lay, R. Getty Jan 1976

Semiquantitative Infrared Analysis Of Diketones And Anhydrides In A Reaction Mixture, Dominic T.C. Yang, F. H. Watson Jr., J. O. Lay, R. Getty

Journal of the Arkansas Academy of Science

The ozonolysis of a hydroxymethylene ketone yields a mixture of diketone and anhydride. Treatment of hydroxymethylene camphor with ozone affords, in addition to the expected camphor quinone, a surprisingly large amount of camphoric anhydride (56%) via Baeyer-Villager reaction. Use of infrared absorption to analyze the relative amounts of camphor quinone and camphoric anhydride in a reaction mixture was studied by comparing peak heights of their carbonyl stretching bands.


Chemistry Departments In Predominantly Black Institutions, James O. Wear, Nirmal K. Shastri Jan 1974

Chemistry Departments In Predominantly Black Institutions, James O. Wear, Nirmal K. Shastri

Journal of the Arkansas Academy of Science

Chemistry programs in 87 predominantly Black institutions were compared by questionnaire survey. Advanced undergraduate courses were offered for chemistry majors by 86% of these schools, but only 28% offered research and independent study for undergraduates. Although there were extremes, most of the faculty taught 15 to 18 contact hours and their median salaries were below the national median. Library support seemed adequate with 1 to 1.5% of the total library materials being chemistry books, texts and reference, and the libraries of most schools had holdings of 15 principal chemistry-related journals. More than 90% of the schools were well-equipped with laboratory …