Edwin M. Kaiser

HPLC-PFD determination of priority pollutant PAHs in water, sediment, and semipermeable membrane devices

High performance liquid chromatography coupled with programmable fluorescence detection was employed for the determination of 15 priority pollutant polycyclic aromatic hydrocarbons (PPPAHs) in water, sediment, and semipermeable membrane devices (SPMDs). Chromatographic separation using this analytical method facilitates selectivity, sensitivity (ppt levels), and can serve as a non-destructive technique for subsequent analysis by other chromatographic and spectroscopic techniques. Extraction and sample cleanup procedures were also developed for water, sediment, and SPMDs using various chromatographic and wet chemical methods. The focus of this publication is to examine the enrichment techniques and the analytical methodologies used in the isolation, characterization, and quantitation of 15 PPPAHs in different sample matrices.

Sequestration of priority pollutant PAHs from sediment pore water employing semipermeable membrane devices

Semipermeable membrane devices (SPMDs) were employed to sample sediment pore water in static exposure studies under controlled laboratory conditions using (control pond and formulated) sediments fortified with 15 priority pollutant polycyclic aromatic hydrocarbons (PPPAHs). The sediment fortification level of 750 ng/g was selected on the basis of what might be detected in a sediment sample from a contaminated area. The sampling interval consisted of 0, 4, 7, 14, and 28 days for each study. The analytical methodologies, as well as the extraction and sample cleanup procedures used in the isolation, characterization, and quantitation of 15 PPPAHs at different fortification levels in SPMDs, water, and sediment were reported previously (Williamson, M.S. Thesis, University of Missouri-Columbia, USA; Williamson et al., Chemosphere (This issue--PII: S0045-6535(02)00394-6)) and used for this project. Average (mean) extraction recoveries for each PPPAH congener in each matrix are reported and discussed. No procedural blank extracts (controls) were found to contain any PPPAH residues above the method quantitation limit, therefore, no matrix interferences were detected. The focus of this publication is to demonstrate the ability to sequester environmental contaminants, specifically PPPAHs, from sediment pore water using SPMDs and two different types of fortified sediment.

Lateral metallation of methylated nitrogenous heterocycles

Abstract Me groups on nitrogenous heterocycles can be conveniently metallated by a variety of strongly basic reagents to afford synthetically useful carbanions. The negative charge of such anions resides predominantly on the ring N atoms. The site of lithiation on pyridines and quinolines bearing Me groups in both the 2- and 4-positions depends upon the ability of the ring N atom to complex with the metallating agents. Carbanions derived from methylated pyridines, quinolines, naphthyridines, isoquinolines, pyrido[4,3-b]carbazoles, pteridines, pyrido[3,4-b] indoles and quinoxalines are discussed. References are provided describing condensations of these reagents with a variety of both common and uncommon electrophiles.

Preparation and reactions of the mono- and dialkali salts of dimethyl sulfone, dimethyl sulfoxide, and related compounds☆

Abstract Certain sulfones and sulfoxides are rapidly and conveniently converted to their novel 1,3-dialkali salts which, in many cases, are stabilized only by the -SO 2 - and -SO- groups, respectively. That such species are formed is demonstrated by subsequent synthetically useful double aldol-type condensations and alkylations, and, in a few cases, by deuterations. Profound metallic cation effects are observed in several of the aldol-type reactions. Finally, the anions of dibenzyl sulfoxide, though stable at low temperatures, readily decompose to trans -stilbene under much milder conditions than previously described.

Lithiated tolunitriles: Preparation and reactions

Metalation of m-tolunitrile has been achieved by means of lithium dimethylamide and lithium diisopropylamide in THF/HMPA to afford a new, synthetically useful organometallic reagent. o-Tolunitrile and the p-isomer also react with such bases to give the corresponding lithiated derivatives. Each of the lithiotolunitriles readily undergoes condensations with various electrophiles.

Regiointegrity of carbanions derived by selective metalations of dimethylpyridines and -quinolines

Abstract Metalation of 2,4-dimethylpyridine and -quinolines by strong basic reagents in ethyl ether in the absence of HMPA affords 2-lithiomethyl derivatives regardless of the reaction length. The use of THF in such metalations promotes the formation of the 2-lithiomethyl reagents which isomerize to the more thermodynamically stable 4-lithiomethyl derivatives after relatively long reaction periods or in the presence of amines or an excess of the parent heterocycle. The latter derivatives appear to be formed directly from the heterocycles in ammonia or in the presence of HMPA. The results are discussed in terms of “coordination-only” versus “acid-base” limiting mechanisms for metalations as a function of ion pairing. NMR spectra for certain of the carbanions in ethyl ether and THF are described which support the above concepts. Related metalations of 2,4-dimethylquinoline-N-oxide give only the 2-lithiomethyl derivative. Similar reactions of 7-hydroxy-2,4-dimethyl-1,8-naphthyridine lead in synthetically useful yields to derivatization of the 2- and 4-methyl groups via dianions by using n-butyllithium in ethyl ether and sodium amide in liquid ammonia, respectively, followed by the addition of appropriate electrophiles.

Improved preparation of tris(organoamino)boranes

Abstract Tris(organoamino)boranes may be rapidly and conveniently prepared by the interaction of boron trifluoride diethyl etherate and N-lithiodialkyl-, diaryl-, and alkylarylamides in tetrahydrofuran. The procedure is more general and is less sensitive to steric effects than older ones and affords previously described as well as new tris(organoamino)boranes in high yields.

Preparation and condensation of 1-lithiomethyl-3-methylisoquinoline and its 6,7-dimethoxy derivative

Abstract 1,3-Dimethylisoquinoline and 6,7-dimethoxy-1,3-dimethylisoquinoline have been conveniently metalated by n-butyllithium and lithium diisopropylamide in ethers/hexane and by sodium amide in liquid ammonia to afford only the 1-alkalimethyl derivatives. Although the isomeric 3-alkalimethyl-1-methylisoquinolines could not be obtained by metallation of the parent dimethylisoquinolines, 3-lithiomethyl-1-methylisoquinoline was prepared by reduction of 3-methoxymethyl-1-methylisoquinoline with lithium metal. The 1-alkalimethylisoquinoline derivatives were condensed with a variety of electrophiles to give alcohols, enols, enamines, and alkyl compounds in good to excellent yeilds. Isomerizations between 1-lithiomethyl-3-methylisoquinoline and 3-lithiomethyl-1-methylisoquinoline were not observed.

Preparation and reactions of the lithio and dilithio salts of 2,3-dimethylquinoxaline

Abstract Metalation of 2,3-dimethylquinoxaline has been achieved by means of lithium diisopropylamide in THF/HMPA to afford either mono- or dicarbanions depending upon the stoichiometry of the metalating agents. The carbanions obtained have been condensed with representative electrophiles to give a variety of 2,3-disubstituted quinoxalines.

Nucleophilic addition versus metalation of 4- and 2-methylpyridine studied by multinuclear magnetic resonance spectroscopy

Interaction of 4-methylpyridine with n-butyl-lithium in THF affords a 67:33 mixture of the 1,2-nucleo-philic addition product and the laterally metalated derivative of the heterocycle, respectively, as shown by 13C and 15N n.m.r. spectroscopy. While mixtures were also obtained from 4-methylpyridine and methyl- or t-butyl-lithium. only metalation was realized with the lithium salts of di-isopropylamine and 2,2,6,6- tetramethylpiperidine. A regular trend was noted with other 4-alkylpyridines and n-butyl-lithium culminating in exclusive 1,2-addition on 4-n-butylpyridine. The 13C n.m.r. spectrum from 2-methyl-pyridine and n-butyl-lithium also showed the presence of both addition and metalation derivatives; however, the former material was present only to the extent of 3%.