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PubMed2002

Evaporation and discharge dynamics of highly charged droplets of heptane, octane, and p-xylene generated by electrospray ionization.

We report studies of the evaporation and discharge dynamics of highly charged droplets generated by electrospray ionization from n-heptane, n-octane, and p-xylene doped with Stadis-450, a conductivity-enhancing agent. A phase Doppler anemometer (PDA) characterizes individual droplets moving through the uniform electric field within an ion mobility cell according to size, velocity, and charge. Repeated reversal of the electric field allows multiple PDA measurements on selected droplets with diameters ranging from 3 to 60 microm and up to 10(7) elementary positive charges. This "ping-pong" technique provides individual droplet histories from which we determine the dynamics of solvent evaporation and charge loss. On average, n-heptane discharges at 101% of the Rayleigh limit of charge, while n-octane and p-xylene droplets discharge at 87% and 89% of their respective limits. Discharge events release an average of 19% of the charge in n-heptane and 17% of the charge in both n-octane and p-xylene. Within the limits of the measurements, no detectable change in droplet diameter accompanies observed discharge events, indicating the loss of a relatively small fraction of the total volume. We compare these results to previous experiments, theoretical models for droplet evaporation and discharge, and predictions from the Rayleigh model. We report both Stadis-450 and triethylamine mass spectra in octane and discuss issues regarding the use of hydrocarbon solvents in electrospray mass spectrometry.

Journal Article↗
PubMed1996

Facile Preparation of 3,7-Diazabicyclo[3.3.0]octane and 3,7,10-Triheterocyclic [3.3.3]Propellane Ring Systems from 1,5-Diazacyclooctane 3,7-Derivatives(1).

The cyclodimerization of p-toluenesulfonamide and 3-chloro-2-(chloromethyl)-1-propene to prepare N,N'-bis(p-toluenesulfonyl)-3,7-bis(methylene)-1,5-diazacyclooctane (1a) and its ozonation to the corresponding 3,7-dione 2a are reported. Unusual transannular cyclizations initiated by lithium aluminum hydride treatment or bromination of 1a and oxidative coupling of the dioxime derived from 2a are described. These reactions lead, respectively, to the following derivatives of the little-studied 3,7-diazabicyclo[3.3.0]octane ring system: 1,5-dimethyl-3,7-diazabicyclo[3.3.0]octane (5), N,N'-bis(p-toluenesulfonyl)-1,5-bis(bromomethyl)-3,7-diazabicyclo[3.3.0]octane (8), and N,N'-bis(p-toluenesulfonyl)-1,5-dinitro-3,7-diazabicyclo[3.3.0]octane, (12). Acid-catalyzed hydration of 1a, in contrast, gives the expected 5-methyl-3,7-diazabicyclo[3.3.1]nonan-1-ol (10). Reaction of the dibromide 8 with the nucleophiles, sodium sulfide, sodium oxide, and sodium p-toluenesulfonamide conveniently delivers the corresponding novel 3,7,10-triheterocyclic [3.3.3]propellanes.

Journal Article↗
PubMed2004

Phase behavior of 1-alkylpyridinium octane-1-sulfonates. effect of the 1-alkylpyridinium counterion size.

The temperature-versus-composition phase diagrams of eight different 1-alkylpyridinium octane-1-sulfonates (APOSs) in water were studied by 1H NMR, 2H NMR, pulsed gradient spin-echo NMR, small-angle X-ray diffraction, differential scanning calorimetry, surface tension and conductivity measurements, and polarizing microscopy. The number of carbons (n(c)) in the hydrocarbon chain of the pyridinium counterions was varied from n(c) = 1 to n(c) = 8 to study how the phase behavior of the APOS/2H2O systems was affected by a change in the chain length of the counterion. The sodium octane-1-sulfonate (NaOS)/water system was used as a reference. This system formed an isotropic micellar solution (L1) phase and a normal hexagonal (H(I)) phase. All APOSs were readily soluble in water and formed L1 phases. The surface tension above the critical micelle concentration for n(c) between 1 and 3 was higher than that for NaOS, and it decreased steadily for the different APOSs with increasing chain length. The area per molecule at the air/solution interfaces was rather constant at 68 A2 for n(c) between 1 and 7. For 1-octylpyridinium octane-1-sulfonate (OPOS), it was about 5 A2 smaller, which was just outside the estimated error. However, the smallest area was obtained for NaOS. At higher surfactant concentrations, liquid crystalline phases formed. Both cubic and H(I) phases were found for n(c) = 1 and 2, while for n(c) between 3 and 5 only an H(I) phase was observed. H(I) and lamellar liquid crystalline (Lalpha) phases formed for n(c) = 6 and 7. The only liquid crystalline phase found in the OPOS system was a Lalpha phase. The NaOS H(I) phase was the only liquid crystalline phase that showed a linear relation between the 2H2O NMR quadrupolar splitting (deltaW) and Xsurf/X(W), where Xsurf and X(W) are the mole fractions of surfactant and water. The OPOS lamellae were found to be much thinner than expected, indicating a defect lamellar structure. This was further supported by the behavior of the quadrupolar splitting ofdeuterated OPOS. The anomalous behaviors of the 2H2O NMR quadrupolar splitting observed in the Lalpha phases of 1-heptylpyridinium octane-1-sulfonate and OPOS were interpreted in terms of changes in the population of the water molecules residing in different sites combined with a continuous rearrangement of the lamellae surface with the possible development of holes. The appearances of the phase diagrams were discussed in terms of surfactant molecular geometry and the packing of the amphiphiles in the aggregates formed.

Journal Article↗
PubMed1999

Isolation, identification, and enantioselective synthesis of octane-1,3,7-triol: determination of its absolute configuration

Extracts obtained by solid-phase extraction from apples were separated by multilayer countercurrent chromatography. In the most polar fractions, the novel octane-1,3,7-triol was identified by 1H and 13C NMR as well as LC-MS and by comparison with the synthesized racemic reference compound. Resolution of the enantiomers was achieved after acetylation of the triol followed by GC separation. The enantioselective synthesis of the stereoisomers of octane-1,3, 7-triol was performed using the building blocks (R)- and (R, S)-butane-1,3-diol and (S)- and (R,S)-butane-1,2,4-triol. Comparison with the isolated products indicated that the natural compound consisted of a mixture of (3R,7S)- and (3R,7R)-octane-1,3,7-triol in a ratio of 2:3. Since the C3 chiral center is enantiomerically pure, the triol might be biogenetically related to the known antimicrobial (R)-(+)-octane-1,3-diol, the major volatile compound of some apple cultivars.

Journal Article↗
PubMedDate not supplied

Perfluoro-n-octane as a postoperative vitreoretinal tamponade in the management of giant retinal tears.

BACKGROUND: Despite recent advances in giant retinal tear repair, retinal redetachment remains an issue. This may be due to inadequate retinal tamponade with silicone oil or perfluorocarbon gas that allows fluid to seep back under the edge of the tear. We propose short-term postoperative retinal tamponade with perfluoro-n-octane liquid to overcome this problem. Theoretical advantages include the reduced likelihood of proliferative vitreoretinopathy. It is easier to remove than silicone oil due to its lower viscosity, and supine posturing is more manageable from a patient perspective. METHODS: A retrospective case series of 16 giant retinal tear repairs without significant proliferative vitreoretinopathy is presented. Lens-sparing vitrectomy was performed with endolaser to the edge of the tear and the entire retinal periphery. Scleral buckling was not utilized. Perfluoro-n-octane was used as a postoperative tamponade for a mean of 16.4 days (range, 6-50 days). RESULTS: The retina was reattached at the end of the procedure in all 16 cases. Redetachment occurred in only 1 (6.3%) of 16 cases. CONCLUSION: Postoperative tamponade with perfluoro-n-octane may decrease the rate of redetachment in giant retinal tear repair compared with silicone oil or perfluorocarbon gas alone. We found no adverse effects directly attributable to perfluoro-n-octane.

Adult↗
PubMed2000

Synthesis of 1-azabicyclo[3.3.0]octane derivatives and their effects as piracetam-like nootropics.

A useful pharmaceutical intermediate, 5-nitromethyl-1-azabicyclo[3.3.0]octane (1), was prepared in one step from 1,7-dichloro-4-heptanone (4) under mild conditions. Catalytic hydrogenation of 1 over Raney Ni in the presence of sodium hydroxide afforded 5-aminomethyl-1-azabicyclo[3.3.0]octane (2) in high yield. Piracetam analogues 20-23, which were pyrrolidine derivatives involving a 1-azabicyclo[3.3.0]octane ring, were synthesized. Pharmacological tests showed that N-[(1-azabicyclo[3.3.0]octan-5-yl)methyl]-2-oxo-1-pyrrolidineacetamid e (20) improves cerebral function.

Animals↗
PubMed1975

[Bicyclic analogs of piperazine. XIII (1). Derivatives of 3,8-diazabicyclo[3.2.1]octane with potential anti-inflammatory activity].

The Authors describe the synthesis of some 8-acyl-3-methyl-3,8-diazabicyclo[3.2.1]octanes and 3-acyl-8-methyl-3,8-diazabicylo[3.2.1] octanes. The compounds were prepared by acylation of the corresponding methyl derivatives with the purpose of obtaining antiinflammatory compounds. The synthesis of some 3-alkyl-8-propionyl-3,8-diazabicylo[3.2.1]octanes is also described. These compounds were prepared in analogy with some 8-pripionyl-3,8-diazabicyclo[3.2.1]octanes endowed with high analgesic and antiinflammatory activity.

Anti-Inflammatory Agents↗
PubMed2001

Water treatment by TiO2 photocatalysis and/or ultrasound: degradations of phenyltrifluoromethylketone, a trifluoroacetic-acid-forming pollutant, and octan-1 -ol, a very hydrophobic pollutant.

TiO2 photocatalysis and ultrasound are advanced oxidation processes for water treatment. Our study aimed at showing, via the purposely chosen title compounds, that these techniques can be complementary. For C6H5COCF3 (PTMK), the photocatalytic removal rate was higher than the ultrasonic (515 kHz) removal rate in the presence of TiO2 in the dark, whereas it was the opposite for octan-1-ol under the conditions employed. Simultaneous UV and ultrasound irradiation of the TiO2 suspension led, for PTMK, to a removal rate about equal to the sum of the removal rates observed for separate irradiations, and decreased by a factor of approximately 20% for octan- 1 -ol as if the photocatalytic degradation was suppressed by the dominant distribution of octan-1-ol to the cavitation bubbles. This distribution was substantiated by the large detrimental effect of octan- 1-ol on the PTMK ultrasonic removal rate. The concurrent use of both techniques allowed a faster removal of both pollutants in binary mixtures. The amount of CF3COOH from PTMK was approximately eight times lower in sonicated, than in UV-irradiated, TiO2 suspensions. Several intermediate products showed the occurrence of chemical transformations occurring in and/or on the cavitation bubbles. COD decline and CO2 formation were initially higher for ultrasonic than for photocatalytic treatment. However, complete mineralization (except for CF3COOH) was achieved more rapidly by photocatalysis and even more rapidly by simultaneous use of both techniques.

1-Octanol↗
PubMed1980

n-Octane and n-nonane induced alterations in xenobiotic metabolising enzyme activities and lipid peroxidation of rat liver.

After 2 and 7 days on n-octane and n-nonane administration (intraperitoneally) to female albino rats, alterations in the levels of hepatic xenobiotic metabolising enzyme activities and TBA reactants were observed. Fifty to eighty per cent reduction in the specific activities of benzo[a]pyrene hydroxylase, benzphetamine-N-demethylase, p-nitroanisole-O-demethylase and glutathione-S-transferase were observed. Cytochrome P-450 and free sulfhydryl contents of liver were also decreased significantly after 7 days treatment on n-octane and n-nonane. A 2- and 3- fold increase in liver lipid peroxidation estimated as TBA reactants was observed in the animals treated for 2 or 7 days with n-octane or n-nonane.

Alkanes↗
PubMed1986

The metabolism of n-octane in Fischer 344 rats.

The urinary metabolites of n-octane in Fischer 344 rats given the hydrocarbon by gavage included 2-octanol, 3-octanol, 5-oxohexanoic acid, and 6-oxoheptanoic acid. The sex of the animals influenced the relative amounts of metabolites formed. Analyses were performed by gas-liquid chromatography (GC) and gas-liquid chromatography/mass spectrometry (GC/MS). This is the first reported finding of keto acids in hydrocarbon oxidative metabolism. No kidney damage was found as a result of n-octane dosing although the 2,2,4-trimethylpentane (iso-octane) isomer does cause kidney lesions in male rats.

Administration, Oral↗
PubMed2004

2,3-disubstituted 6-azabicyclo[3.2.1]octanes as novel dopamine transporter inhibitors.

A series of cis and trans 3beta-aryl-2-carbomethoxy-6-azabicyclo[3.2.1]octanes, with different substitution at the para-position of the aryl group, were synthesized and examined for reuptake inhibition at the dopamine transporter (DAT). The potency for inhibition of DA reuptake was compared with that of cocaine to determine the significance of the replacement of the 8-azabicyclo[3.2.1]octane (tropane nucleus), displayed in cocaine, for the 6-azabicyclo[3.2.1]octane (normorphan framework). This bicyclic core structure constitutes a novel chemical scaffold in DAT inhibitor design, which may provide new insights into the 3D structure of the DAT and its interaction with cocaine and DA. Among these compounds, the trans-amine series 8 were the most potent ligands at the DAT. In particular, the normorphan analogue 8c (bearing a p-chloro substituent at the beta-aryl group, IC(50)=452 nM) displayed a potency that is in the same range as cocaine (IC(50)=459 nM) itself.

Animals↗
PubMed2004

Synthesis and nicotinic acetylcholine receptor binding affinities of 2- and 3-isoxazolyl-8-azabicyclo[3.2.1]octanes.

A series of epiboxidine homologues, 2- and 3-isoxazole substituted 8-azabicyclo[3.2.1]octane derivatives was synthesized and evaluated as potential ligands for neuronal nicotinic acetylcholine receptors in [(3)H]cytisine labeled rat brain. The 2beta-isoxazolyl-8-azabicyclo[3.2.1]octane 9b (K(i)=3 nM) was the most potent compound of the series with a binding affinity twice that of nicotine. The 3beta-isoxazolyl-8-azabicyclo[3.2.1]octane 15b (K(i)=148 nM) exhibited moderate affinity while the corresponding 2alpha- and 3alpha-isomers exhibited micromolar binding affinity.

Animals↗
PubMed2002

Octane and the environment.

One of the most important technical issues of the automotive fuel regulatory regime that has evolved in the United States since 1973 is the need to provide sufficient octane while at the same time meeting increasingly stringent fuel content requirements designed to reduce emissions and protect public health. There are several ways for refiners to provide octane and all of them have environmental consequences. This paper traces the technological and environmental trade-offs that have occurred from initial lead reduction rules in 1973 through the first phase of the reformulated gasoline program ending in 2000. Overall, increasingly stringent fuel regulations during this period have contributed to significant declines in pollutant emissions and concurrent reductions in risks to public health. Each improvement, however, was accompanied by a unique trade-off that sometimes led to unintended consequences. To address these trade-offs as they emerged, more regulation was required and additional trade-offs resulted. This analysis suggests that the complex process of gasoline regulation and the technological response to maintain octane quality is characterized by the continual emergence of new risks as the regulatory system evolves. This pattern demonstrates the omnipresence of risk trade-offs and potential for unintended consequences to occur as a result. Public perception, regulatory design, and technological choice influence the nature of these trade-offs and play an important role in addressing unintended consequences.

Automobiles↗
PubMed2004

Oxidation of methyl tert-butyl ether by alkane hydroxylase in dicyclopropylketone-induced and n-octane-grown Pseudomonas putida GPo1.

The alkane hydroxylase enzyme system in Pseudomonas putida GPo1 has previously been reported to be unreactive toward the gasoline oxygenate methyl tert-butyl ether (MTBE). We have reexamined this finding by using cells of strain GPo1 grown in rich medium containing dicyclopropylketone (DCPK), a potent gratuitous inducer of alkane hydroxylase activity. Cells grown with DCPK oxidized MTBE and generated stoichiometric quantities of tert-butyl alcohol (TBA). Cells grown in the presence of DCPK also oxidized tert-amyl methyl ether but did not appear to oxidize either TBA, ethyl tert-butyl ether, or tert-amyl alcohol. Evidence linking MTBE oxidation to alkane hydroxylase activity was obtained through several approaches. First, no TBA production from MTBE was observed with cells of strain GPo1 grown on rich medium without DCPK. Second, no TBA production from MTBE was observed in DCPK-treated cells of P. putida GPo12, a strain that lacks the alkane-hydroxylase-encoding OCT plasmid. Third, all n-alkanes that support the growth of strain GPo1 inhibited MTBE oxidation by DCPK-treated cells. Fourth, two non-growth-supporting n-alkanes (propane and n-butane) inhibited MTBE oxidation in a saturable, concentration-dependent process. Fifth, 1,7-octadiyne, a putative mechanism-based inactivator of alkane hydroxylase, fully inhibited TBA production from MTBE. Sixth, MTBE-oxidizing activity was also observed in n-octane-grown cells. Kinetic studies with strain GPo1 grown on n-octane or rich medium with DCPK suggest that MTBE-oxidizing activity may have previously gone undetected in n-octane-grown cells because of the unusually high K(s) value (20 to 40 mM) for MTBE.

Culture Media↗
PubMed1981

Oxidase determination of plasma cholesterol as cholest-4-en-3-one using iso-octane extraction.

Cholesterol esters in 20 microliter of plasma are hydrolysed with hot ethanolic KOH. Preformed cholesterol and cholesterol released by hydrolysis is reacted with cholesterol oxidase to form hydrogen peroxide and cholest-4-en-3-one, which is extracted from alkaline 50% v/v ethanolic solution with iso-octane. The absorbance of the ketone in iso-octane at the 232 nm peak is used to measure the cholesterol originally present. Plasma blanks obtained by omitting the cholesterol oxidase from the reagent shown negligible absorbance even when samples are grossly icteric, lipaemic, or haemolysed. The test is carried out in a single glass screw-capped tube, and the absorbance given by a sample containing 6.25 mmol/1 cholesterol is approximately 0.44, corresponding to a molar absorbance of approximately 17 500. The conversion of cholesterol to cholest-4-en-3-one is stoichiometric, and the absorbance of the iso-octane layer is stable for at least 48 hours. A single determination occupies 30 minutes, 30 samples can be analysed in 1 1/2 hours.

3-Hydroxysteroid Dehydrogenases↗
PubMed1999

Biosynthesis of R-(+)-octane-1,3-diol. Crucial role of beta-oxidation in the enantioselective generation of 1,3-diols in stored apples.

The biosynthesis of R-octane-1,3-diol and R-5(Z)-octene-1,3-diol, two natural antimicrobial agents in apples and pears, was investigated in stored apples after application of [9,10,12,13-3H]linoleic acid, [9,10,12,13,15,16-3H]linolenic acid, [1-14C]linoleic acid, [U-14C]oleic acid, lipoxygenase-derived metabolites of [9,10,12,13-3H]linoleic acid, 13C18-labeled linoleic acid hydroperoxides, and 2H-labeled octanol derivatives. Analysis of the products and quantification of incorporation and labeling pattern were achieved by high-performance liquid chromatography-radiodetection, capillary gas chromatography (GC)-isotope ratio mass spectrometry, and GC-mass spectrometry analysis. Almost all the applied precursors were partly transformed into R-octane-1,3-diol. Linoleic acid derivatives, still containing the 12,13 cis double bond, and octanol derivatives oxy-functionalized at carbon 3 were the most efficient precursors of the 1,3-diol. The data imply that R-octane-1,3-diol is generated in stored apples in the course of the beta-oxidation from R-3-hydroxy-octanoyl-SCoA originating from 2-cis-octenoyl-SCoA by enoyl-CoA hydratase. In an analogous fashion, R-5(Z)-octene-1,3-diol is formed from the unsaturated intermediate.

Carbon Radioisotopes↗
PubMed2005

Synthesis and evaluation of the antitrypanosomal and antiplasmodial activities of new 4-aminobicyclo[2.2.2]octane derivatives.

Several new 4-amino-6,7-diphenylbicyclo[2.2.2]octane derivatives, methylthiosemicarbazones of bicyclo[2.2.2]octan-2-ones and esters of bicyclo[2.2.2]octan-2-ols were prepared. Their antitrypanosomal activities against Trypanosoma brucei rhodesiense (STIB 900) and their antiplasmodial activity against the K1 strain of Plasmodium falciparum (resistant to chloroquine and pyrimethamine) were investigated using microplate assays. In addition to that, the cytotoxicity of the new compounds was determined using L-6 cells. The methylthiosemicarbazones show moderate antiprotozoal activities whereas some of the esters of piperonylic acid, homopiperonylic acid and 2-naphtoic acid exhibit remarkable antitrypanosomal and antiplasmodial activity.

Animals↗
PubMed2006

Synthesis of new esters and oximes with 4-aminobicyclo[2.2.2]octane structure and evaluation of their antitrypanosomal and antiplasmodial activities.

New 4-amino-6,7-diphenylbicyclo[2.2.2]octane derivatives, esters of bicyclo[2.2.2]octan-2-ols and O-methyl oximes of bicyclo[2.2.2]octan-2-ones were synthesised. Their activities against Trypanosoma brucei rhodesiense (STIB 900) and their activity against the K1 strain of Plasmodium falciparum (resistant to chloroquine and pyrimethamine) were determined by use of microplate assays. The cytotoxicity was assessed using L6 cells. The antiprotozoal activities of the new compounds are compared with those of former prepared derivatives and drugs in use. Structure-activity relationships are discussed.

Animals↗