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Articles 61 - 90 of 112

Full-Text Articles in Chemistry

Double Cysteine Mutations In Staphylococcal Nuclease: The Effect Of Artificially Introduced Disulfide Bonds On Protein Structure And Stability, Anna Terry Jan 2000

Double Cysteine Mutations In Staphylococcal Nuclease: The Effect Of Artificially Introduced Disulfide Bonds On Protein Structure And Stability, Anna Terry

Inquiry: The University of Arkansas Undergraduate Research Journal

Since a protein's function depends on its structure, basic research in protein structure facilitates the solution of many practical problems, such as the synthesis of more effective medicines. With this larger goal in sight, the purpose of this research project is to understand better the chemical principles that underlie protein structure and stability. Disulfide bonds are a potentially stabilizing feature of many proteins. They may form between cysteine residues in close proximity to one another if the orientation is favorable. Often found in proteins produced by organisms that grow at high temperatures, disulfide bonds may anchor side chains together, making …

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Studies Of Tryptophans In Membrane- Spanning "Walp" Peptides By Deuterium Nmr Spectroscopy, Nichole Reed Jan 2000

Studies Of Tryptophans In Membrane- Spanning "Walp" Peptides By Deuterium Nmr Spectroscopy, Nichole Reed

Inquiry: The University of Arkansas Undergraduate Research Journal

WALP pep tides of sequence acetyl-Gly-Trp-Trp-(Leu-Ala)-Trp-Trp-Ala-ethanolamine insert into lipid bilayers as membrane-spanning a-helices and modulate the lipid phase behavior as functions of n and the lipid acyl chain length. A key feature of the WALP peptides is the positioning of tryptophan (Trp) indole rings at the membrane/water interface. For the examples WALP19 with n = 6.5 and WALP23 with n = 8.5, we have labeled individual indoles with deuterium and incorporated the labeled peptides in oriented, hydrated bilayers of Dimyristoyl-phosphatidylcholine (DMPC). Deuterium NMR spectra from these samples show sharp resonances when the membrane normal is aligned either parallel (Beta = …

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Media Coverage Of Epa's Draft Dioxin Reassessment Report, Sharon M. Friedman, Megan A. Fitzpatrick, Brenda P. Egolf Jun 1999

Media Coverage Of Epa's Draft Dioxin Reassessment Report, Sharon M. Friedman, Megan A. Fitzpatrick, Brenda P. Egolf

RISK: Health, Safety & Environment (1990-2002)

Using content analysis, the authors examine the utility of news media in democratic decision making.

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Preparation Of Methyl 5-Chloro-6-Fluoronicotinate By Fluoride-Chloride Exchange, Frank L. Setliff, Leslie B. Coop Jan 1998

Preparation Of Methyl 5-Chloro-6-Fluoronicotinate By Fluoride-Chloride Exchange, Frank L. Setliff, Leslie B. Coop

Journal of the Arkansas Academy of Science

No abstract provided.

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Analysis Of A Mixture Of Several Dihalonicotinic Acids By Gas Chromotography And Gas Chromotography-Mass Spectrometry, Cheryl L. Fossler, Frank L. Setliff, Ali U. Shaikh Jan 1998

Analysis Of A Mixture Of Several Dihalonicotinic Acids By Gas Chromotography And Gas Chromotography-Mass Spectrometry, Cheryl L. Fossler, Frank L. Setliff, Ali U. Shaikh

Journal of the Arkansas Academy of Science

Six 2,5- and 5,6- dihalonicotinic acids in a mixture were converted to their corresponding methyl esters and then analyzed by gas chromatography and gas chromatography-mass spectrometry. Four methods of conversion were compared for their GC sensitivity, efficiency and analysis time. In Method #1, using HC1 and methanol as the reagents, the displacement of the halogens by chlorine (from HC1) at 2- and 6-positions was a common occurrence, rendering the method inefficient. In Method #2 (BF3/methanol), the displacement of halogens by methoxide was evident. Method #3 (dicyclohexylcarbodiimide/methanol) produced a mixture of derivatives with a poor yield. Method #4 (diazomethane) gave a …

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Reductive Dechlorinatin Of A 2-Chloronicotinic Acid Under Finkelstein Conditions, Frank L. Setliff, Leslie B. Coop Jan 1997

Reductive Dechlorinatin Of A 2-Chloronicotinic Acid Under Finkelstein Conditions, Frank L. Setliff, Leslie B. Coop

Journal of the Arkansas Academy of Science

No abstract provided.

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Electrodeposition Of Copper Indium Sulfide Films From Organic Solutions, Arif Raza, Robert Engelken, Brandon Kemp, Imran Khan, Wasim Aleem, Chris Barber Jan 1996

Electrodeposition Of Copper Indium Sulfide Films From Organic Solutions, Arif Raza, Robert Engelken, Brandon Kemp, Imran Khan, Wasim Aleem, Chris Barber

Journal of the Arkansas Academy of Science

We report on organic solutions ofCuCl 2 ,InClg, and elemental sulfur for electrodepositing CuIn x Sv films. CuInS 2 and CuInSe 2 are promising solar cellmaterials; our work on CuInSg prefaces planned work on plating CuInSe 2 from nonaqueous solvents. Two promising solvent systems are (1) mixed propylcne carbonate and water and (2) mixed ethylene glycol, propionic acid, and water (Engelken et al., 1988). Gray-brown films ofCuInx Sy (nominally GuInS2 ) have been plated from both baths. Major problems include (1) reduction ofCu+2 to Cu and Cu x S by the solvent at high temperatures (T>l()0°C), hence depleting Cu+2,(2) …

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Hammett Correlations Of Carbonyl 13c Chemical Shifts In A Series Of N-(4-Substituted Phenyl)-6-Chloro-5-Fluoronicotinamides, Frank L. Setliff, John W. Hawley, Alan D. Toland Jan 1995

Hammett Correlations Of Carbonyl 13c Chemical Shifts In A Series Of N-(4-Substituted Phenyl)-6-Chloro-5-Fluoronicotinamides, Frank L. Setliff, John W. Hawley, Alan D. Toland

Journal of the Arkansas Academy of Science

A series of nine N-(4-substituted phenyl)-6-chloro-5- fluoronicotinamides exhibited excellent correlations of their carbonyl 13C shifts (5CO,ppm as measured in DMSO) with the standard Hammett substituent constants (c?R) of the substituent inthe 4-position. The linear relationship was defined by the equation 8CO ¦ 1.22

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Scf-Mo Conformational Analysis Of Polycroconaine, T. E. Ezell, Jerry A. Darsey Jan 1995

Scf-Mo Conformational Analysis Of Polycroconaine, T. E. Ezell, Jerry A. Darsey

Journal of the Arkansas Academy of Science

Abinitio calculations at the STO-3G basis set level using GAUSSIAN 92 were conducted on the monomer unit of polycroconaine, a conducting polymer with conductive properties similar to several metals, in order to determine the most probable conformation of the monomer. We also compared the energy difference between the highest occupied and lowest unoccupied molecular orbitals. Successive calculations were performed at dihedral angle intervals of 30° around the central bond of the monomer. Minimum energy was observed at 0° bond rotation, consistent with a theory that the polymer owes many of its conductive properties to a planar configuration in combination with …

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Boron Phosphate And Aluminum Phosphate Aerogels, David A. Lindquist, Steven M. Poindexter, Sterling S. Rooke, D. Ritchie Stockdale, Kirk B. Babb, Alison L. Smoot, William E. Young Jan 1994

Boron Phosphate And Aluminum Phosphate Aerogels, David A. Lindquist, Steven M. Poindexter, Sterling S. Rooke, D. Ritchie Stockdale, Kirk B. Babb, Alison L. Smoot, William E. Young

Journal of the Arkansas Academy of Science

Anhydrous sol-gel condensation of triethyl phosphate [(CH3CH2O)3PO] with boron trichloride (BCL3 ) or triethyl aluminum [(CH3CH2 ) 3A1] in organic solvents, led to formation of metallophosphate gels. The pore fluid of the gels was removed under supercritical conditions in a pressurized vessel to form aerogels. The aerogels were then calcined at progressively higher temperatures to produce high surface area phosphates. Since the initial gel reagent mixtures contained several NMR active nuclei, the condensation chemistry prior to the gel point was monitored by solution nB NMR. The surface areas, distribution of pore sizes, and total pore volumes of the aerogel products …

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Reaction Of Titanocene Dichloride With Acetylenedicarboxylate, Tanya L. Hagler, Mark Draganjac, Paul M. Nave, J. Ed Bennett, Farooq Kahn, Robert Engelken, Gerard Williams, Chris Poole, Kwok Fai Yu Jan 1994

Reaction Of Titanocene Dichloride With Acetylenedicarboxylate, Tanya L. Hagler, Mark Draganjac, Paul M. Nave, J. Ed Bennett, Farooq Kahn, Robert Engelken, Gerard Williams, Chris Poole, Kwok Fai Yu

Journal of the Arkansas Academy of Science

The reaction of Cp2TiCl2 with either the mono- or dipotassium salt of acetylenedicarboxylic acid (ADC) gives high yields of an insoluble orange product. The insoluble compound shows potential semiconductor behavior, as evidenced by an apparent bandgap in the orange region of the visible spectrum. Under N2 ,the compound decomposes at 238° C, eventually losing approximately 46% total mass up to 1350° C. The exothermic decomposition in air, beginning at 235° C, results in the formation of titanium oxides.

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Analysis Of Ammunition By X-Ray Fluorescence, Michael W. Rapp, Teddy L. Townsend Jan 1994

Analysis Of Ammunition By X-Ray Fluorescence, Michael W. Rapp, Teddy L. Townsend

Journal of the Arkansas Academy of Science

Nondestructive analysis of lead shotgun pellets by X-ray fluorescence (XRF) shows considerable promise in assignment of the identity of the ammunition source. X-ray fluorescence spectra of various shotgun pellets and of standard alloys were obtained using an energy-dispersive instrument and an Am-241 source. The correlation obtained between the precent antimony in the standard alloys and the intensity of the Ka fluorescence peak from antimony was excellent. Peak areas from antimony in shotgun pellets were measured and compared to calibration plots from the standard alloys. The method was capable of distinguishing among lead-based alloys, such as ammunition, with antimony content as …

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Ultrasound Assisted Oxidative Cleavage Of Alpha-Keto, Alpha-Hydroxy And Alpha-Halo Ketones By Superoxide, Yi Hong Cao, A. Toland, Dominic T.C. Yang Jan 1994

Ultrasound Assisted Oxidative Cleavage Of Alpha-Keto, Alpha-Hydroxy And Alpha-Halo Ketones By Superoxide, Yi Hong Cao, A. Toland, Dominic T.C. Yang

Journal of the Arkansas Academy of Science

No abstract provided.

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Effective, Reliable, Inexpensive Cryofixation Device, Lawrence A. Mink, Roger A. Buchanan Jan 1994

Effective, Reliable, Inexpensive Cryofixation Device, Lawrence A. Mink, Roger A. Buchanan

Journal of the Arkansas Academy of Science

No abstract provided.

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Hammett Correlations Of Half-Wave Reduction Potentials In A Series Of N-(Aryl Substituted)-Dichloronicotinamides, Cecil C. Persons, Ali U. Shaikh, Julie Shiflett, Frank L. Setliff Jan 1994

Hammett Correlations Of Half-Wave Reduction Potentials In A Series Of N-(Aryl Substituted)-Dichloronicotinamides, Cecil C. Persons, Ali U. Shaikh, Julie Shiflett, Frank L. Setliff

Journal of the Arkansas Academy of Science

Excellent correlations of Hammett substituent constants (sigmaR) of a series of N-(R-substituted aryl) -2,6-, 2,5-, and 5,6- dichloronicotinamides with polarographic half-wave potentials were observed. Although the correlations demonstrate that all three series of amides experience comparable sensitivity to the R groups at the carbonyl reduction site, the relative ease of reduction varies according to the chlorine substitution pattern on the pyridine ring. These differences are suggested to be due to combinations of mesomeric, inductive, and field effects which operate differently in the three systems. Correlation analysis also revealed that Hammett heteroatomic replacement constants previously determined by NMR studies are valid …

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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

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Suppression Of The Oxidation Of S(Iv) In Rainwater, David M. Chittenden Ii Jan 1993

Suppression Of The Oxidation Of S(Iv) In Rainwater, David M. Chittenden Ii

Journal of the Arkansas Academy of Science

No abstract provided.

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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.

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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.

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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.

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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

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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 …

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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 …

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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

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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.

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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 …

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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.

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Going Beyond Single Figure Fertilizer Recommendations, S J. Burgess Jan 1988

Going Beyond Single Figure Fertilizer Recommendations, S J. Burgess

Journal of the Department of Agriculture, Western Australia, Series 4

Single-figure fertilizer recommendations are useful guidelines but they do not tell a farmer anything about the consequences of applying fertilizer at rates other than those recommended.

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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.

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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.

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