Dimethylethylamine Research Articles

AlxGa1−xAs/GaAs quantum well structures grown by metalorganic molecular beam epitaxy using dimethylethylamine alane

Dimethylethylamine alane (DMEAA) has been used as an Al precursor for the growth of AlGaAs alloys and AlGaAs/GaAs quantum wells by metalorganic molecular beam epitaxy (MOMBE). It is shown that DMEAA is a very convenient source in terms of in situ calibration of growth rates and alloy composition by reflection high-energy electron diffraction. As indicated by secondary ion mass spectroscopy, low residual O and C impurity content is obtained by using this source. GaAs quantum well structures have been characterized by photoluminescence spectroscopy and compared to equivalent structures grown by standard solid-source molecular beam epitaxy. They are also compared with the results recently reported in the literature for analogous structures grown by MOMBE using alternate aluminum sources.

Growth and Doping of AlAs by Mombe

ABSTRACTA comparison of dimethylethylamine alane (DMEAA) and trimethylamine alane (TMAA) as aluminum sources and CBr4 and CC14 as carbon doping sources for deposition of AlAs by metalorganic molecular beam epitaxy (MOMBE) has been carried out. DMEAA was found to produce the lowest oxygen levels in AlAs, 5 x 1017 cm-3 VS. 1021 cm-3 for TMAA, even at growth temperatures as low as 500°C. This reduction is likely due to the absence of oxygenated solvents used during synthesis of the DMEAA. Undoped films grown from either source were fully depleted as-grown. Through the use of CBr 4, hole concentrations up to 4.5x1019 cm-3 were achieved in AlAs layers grown fiom DMEAA. Attempts to increase the hole concentration beyond this level resulted in a decrease in the hole concentration even though SIMS analysis showed the carbon concentration to increase with increasing dopant flow. Though the carbon sources did not appear to introduce additional oxygen, they appear to introduce other impurities, such as Cl and Br. Also, due to parasitic etching reactions with the adsorbed halogen, the use of these sources reduces the Al incorporation rate.

Particle contamination in low pressure organometallic chemical vapor deposition reactors: Methods of particle detection and causes of particle formation using a liquid alane (AlH3) precursor

Two methods of analyzing particles were interfaced to a low pressure chemical vapor deposition reactor used to deposit Al films from the liquid precursor dimethylethylamine alane. A laser light scattering particle counter was used to monitor particles (≳200 nm) in real time and established that the appearance of particles corresponded to the flow of precursor into the reactor. A particle impaction system was used to collect particles (≳20 nm) for analysis using analytical transmission electron microscopy and electron diffraction. Typical sizes of the Al particles were in the range 20–1000 nm. Purposely introducing trace amounts of H2O, CO, and O2 into the reactor during the flow of the precursor caused an increase in the number of particles. Our results suggested that Al particle formation was induced by impurities in the gas phase (particularly H2O) although competing mechanisms could not be ruled out.

Solvent- and substrate-dependent rates of imine metalations by lithium diisopropylamide: understanding the mechanisms underlying krel

Rate studies of the metalation of imines derived from cyclohexanone and 2-methylcyclohexanone with lithium diisopropylamide (LDA) in tetrahydrofuran (THF), N,N,N',N'-tetramethylethylenediamine (TMEDA), and dimethylethylamine (DMEA) mixtures are described. The N-isopropylimines appear to metalate via a mechanism involving deaggregation of the LDA dimer to give reactive monomers without participation of additional donor solvent. TMEDA functions as an η 1 ligand in both the starting LDA dimer and the rate-determining monomeric transition state as evidenced by analogous behavior with DMEA. Comparisons of the N-isopropylimine metalations with previously described rate studies of the isostructural N,N-dimethylhydrazones provide no evidence that a Me 2 N-Li interaction facilitates the metalation

Heteroepitaxial growth of AlAs using dimethylethylamine alane as an Al precursor

Dimethylethylamine alane (DMEAA) has been used to grow AlAs thin films by metalorganic molecular beam epitaxy. In situ reflection high-energy electron diffraction (RHEED) and Auger electron spectroscopy (AES) measurements indicate that high-quality AlAs films with atomically smooth surfaces can be epitaxially grown on GaAs(100) at relatively low temperatures (less than 550 °C) with no detectable carbon or oxygen content by AES. Strong oscillations in the specular RHEED intensity indicates a layer-by-layer growth mode of AlAs using this new Al precursor. The growth rate, determined from the period of the intensity oscillations, is linearly dependent on the DMEAA partial pressure, but is independent of substrate temperature, at least in the range from 320 to 620 °C. An enhancement of the Al adatom mobility over that obtained using an elemental Al source was observed.

Aluminum Particle Formation in the GaS Phase of a Low Pressure Chemical Vapor Deposition Reactor Using Dimethylethylamine Alane (AlH3) as a Precursor

ABSTRACTParticle formation in the gas phase during the chemical vapor deposition of Al using dimethylethylamine alane was studied. Typical sizes of the crystalline Al particles monitoredwere in the range 20 nm to 1000 nm. Introducing trace amounts of H2O, CO and O2 into the reactor during the flow of the precursor caused an increase in the number of particles. Our results suggested that Al particle formation was induced by impurities in the gas phase although competing mechanisms could not be ruled out.

Experimental study on the metabolism of dimethylethylamine in man

Dimethylethylamine (DMEA) is an aliphatic tertiary amine, which is used as a catalyst in the mould core manufacturing. During 8 h, four healthy volunteers were exposed to four different DMEA air concentrations (10, 20, 40 and 50 mg/m3; 20 mg/m3, two subjects only). DMEA was biotransformed into dimethylethylamine N-oxide (DMEAO). On average, DMEAO, accounted for 90% of the combined amount of DMEA and DMEAO excreted into the urine. The half-lives of DMEA and DMEAO in plasma were 1.3 and 3.0 h, respectively. The urinary excretion of DMEA and DMEAO followed a two-phase pattern. The half-lives in the first phase were 1.5 h for DMEA and 2.5 h for DMEAO. In the second phase, which started about 9 h after the end of exposure, half-lives of 7 h for DMEA and 8 h for DMEAO were recorded. The combined concentration of DMEA and DMEAO, in both plasma and urine, showed an excellent correlation with the air concentration of DMEA. Thus, both urinary excretion and plasma concentration can be used for biological monitoring of exposure to DMEA. An 8-h exposure to 10 mg DMEA/m3 corresponds to a postexposure plasma concentration and 2-h postexposure urinary excretion of 4.9 mumol/l and 75 mmol/mol creatinine, respectively.

Methods for the Determination of Dimethylethylamine and Dimethylethylamine-N-Oxide in Air, Plasma and Urine Samples

Abstract Sensitive routine gas-liquid chromatographic methods for the determination of dimethylethylamine (DMEA) in air and of DMEA and dimethylethylamine-N-oxide (DMEAO) in plasma and urine, have been developed. DMEA was extracted in di-n-butyl ether and analysis was performed on an alkalitreated packing material (Carbowax 20M/0.8% KOH) with a nitrogen-sensitive detector. The detection limit for DMEA in air was 0.01 mg/m3 (151 sample). DMEAO in blood and urine was determined as difference of DMEA after and before reduction of the sample. The standard curves were linear for DMEA levels up to 400 mg/1 (5.5 mmol/1) and the detection limit was 0.01 mg/1 (0.1 μmol/1). Urinary DMEA and DMEAO concentrations could be determined with a precision of 1–3 and 2–4%, respectively. The precisions for DMEA and DMEAO in plasma were 6 and 4–6%, respectively. The methods were validated to exposure levels of DMEA of up to 100 mg/m3 and corresponding plasma levels and urinary excretion of DMEA and DMEAO.

Dimethylethylamine in mould core manufacturing: exposure, metabolism, and biological monitoring.

The exposure and metabolism of dimethylethylamine (DMEA) was studied in 12 mould core makers in four different foundries using the Ashland cold box technique. The mean time weighted average (TWA) full work shift DMEA exposure concentration was 3.7 mg/m3. Inhaled DMEA was excreted into urine as the original amine and as its metabolite dimethylethylamine-N-oxide (DMEAO). This metabolite made up a median of 87 (range 18-93) % of the sum of DMEA and DMEAO concentrations excreted into the urine. Occupational exposure did not significantly increase the urinary excretion of dimethylamine or methylethylamine. The data indicate half lives after the end of exposure for DMEA in urine of 1.5 hours and DMEAO of three hours. The postshift summed concentration of DMEA and DMEAO in plasma and urine is a good indicator of the TWA concentration in air during the workday, and might thus be used for biological monitoring. An air concentration of 10 mg/m3 corresponds to a urinary excretion of the summed amount of DMEA and DMEAO of 135 mmol/mol creatinine.

Visual disturbances in man as a result of experimental and occupational exposure to dimethylethylamine.

Experimental exposure of four volunteers to 40-50 mg/m3 of dimethylethylamine (DMEA) for eight hours caused irritation of the mucous membrane of their eyes, subjective visual disturbances (haze), and slight oedema of the corneal epithelium. The thickness of the cornea showed a slight but consistent increase in all four subjects at these exposures and in two subjects exposed to 10 mg/m3. Concentrations of 80 and 160 mg/m3 for 15 minutes caused eye irritation but no visual disturbances or corneal oedema. Occupational exposure for eight hours to about 25 mg/m3 of DMEA (with peaks above 100 mg/m3) was also associated with eye irritation, haze, and corneal oedema. The divergence between our findings and other reports in which visual disturbances occurred at lower concentrations during occupational exposure may be due to peak concentrations.

Dimethylethylamine alane and N-methylpyrrolidine alane. A convenient synthesis of alane, a useful selective reducing agent in organic synthesis

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDimethylethylamine alane and N-methylpyrrolidine alane. A convenient synthesis of alane, a useful selective reducing agent in organic synthesisEverett M. Marlett and Won Suh ParkCite this: J. Org. Chem. 1990, 55, 9, 2968–2969Publication Date (Print):April 1, 1990Publication History Published online1 May 2002Published inissue 1 April 1990https://doi.org/10.1021/jo00296a078RIGHTS & PERMISSIONSArticle Views1476Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (318 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Determination of Tertiary Amines in Air

Abstract Methods have been developed for air sampling of gaseous tertiary amines on solid sorbents. Sampling was performed at three different air levels and at 20 percent and 85 percent relative air humidity, respectively. Desorption was carried out by solvent extraction prior to high-resolution gas chromatographic analysis with flame ionization or nitrogen-phosphorus detection. Seven amines, differing in the length and shape of the carbon chains, were selected for the study and divided into three groups. The members of the first group, consisting of dimethylethylamine (DMEA), methyldiethylamine (MDEA), and triethylamine (TEA) were collected using charcoal tubes and desorbed with 5 percent ethanol in dichloromethane. The amine air levels were 1, 10, and 50 ppm. The recoveries of these amines were 92–100% (n = 6, RSD = 1–4%). Storage studies (5 days at room temperature followed by 9 days in a freezer) showed recoveries of 87 percent (DMEA), 89 percent (MDEA), and 82 percent (TEA). Determination of DMEA in an air sample from an iron foundry was also carried out. The larger amines were studied at 0.5, 5, and 25 ppm air level. The members of the second group, consisting of ethylmorpholine (EM) and dimethylcyclohexylamine (DMCA), were collected on Amberlite XAD-2 and desorbed with ethyl acetate. The recoveries were 81–99 percent for EM (n = 6, RSD = 1–4%). The storage studies were performed in darkness at room temperature for 14 days. The recoveries were then 96 percent (EM) and 87 percent (DMCA). The members of the third group, consisting of dimethyldodecylamine (DMDA) and dimethylhexadecylamine (DMHA), were collected on Amberlite XAD-7 and desorbed with 5 percent ethanol in ethyl acetate. The recoveries were 93–97 percent (n = 6, RSD = 2–6%). The recoveries were still > 94 percent for both amines after 14 days' storage in darkness at room temperature.

Occupational exposure to volatile nitrosamines in foundries using the “Ashland” core-making process

Eight foundries using the "Ashland" process for the production of cores were surveyed to assess the occupational exposure to carcinogenic volatile nitrosamines. Personal and area samples were collected by means of artifact-free cartridges during the core-making and the molding/casting/shake-out operations. Analyses were carried out with gas chromatography/Hall detector and gas chromatography/TEA (thermal energy analyzer) for validation. The core-making workshops had the highest concentration for at least two nitrosamines, N-nitrosodimethylamine (NDMA) and N-nitrosoethylmethylamine (NEMA), but the levels of NDMA never exceeded 0.35 microgram/m3 with an arithmetic mean between 0.23 and 0.02 microgram/m3. In a number of samplings, two other peaks, both on TEA and Hall detector, could not be identified. The foundries per se (molding/casting/shake-out) had lower nitrosamine levels (CNDMAmax = 0.15 microgram/m3, CNDMA less than 0.03 microgram/m3). For the first time NEMA was identified as an industrial contaminant in foundries but its concentration was always lower than that of NDMA. The nitrosamines found were presumably produced from dimethylethylamine (DMEA). Industries producing or using tertiary or secondary amines should be controlled for their possible nitrosamine contamination.

The molecular structure of dimethyl ethyl amine in the gas phase, determined by electron diffraction

The molecular structure of dimethyl ethyl amine in the gas phase, determined by electron diffraction

The temperature dependence of saturated amine fluorescence

The temperature dependence of fluorescence intensity of several saturated amines was studied. For “flexible” amines such as triethylamine (TEA), dimethylethylamine (DMEA), triethylemine, tri- n-octylamine (TOA), and N-methylpiperidine (NMP), it was found that I f increased as the temperature was increased. For example, in DMEA, I f increases by a factor of ca. 77 between −100 and 100°C. These results are interpreted in terms of an activated configurational change from the initially-formed (nonfluorescent) state to a relaxed (fluorescent) state in these compounds. Activation energies for these conversions range from about 1.8 kcal/mole for TOA to about 4.3 kcal/mole for TEA. Rigid, bicyclic amines having bridgehead N-atoms such as 1-azabicyclo [2.2.2] octane (ABCO) and its [3.3.3] analog were found to have temperature independent fluorescence intensities. These results were assumed to reflect the difference in energetics between the initially-formed and relaxed states relative to the “flexible” amines.