Surfactant control of gas uptake: effect of butanol films on HCl and HBr entry into supercooled sulfuric acid

The entry of HCl into 60-68 wt % D(2)SO(4) and HBr into 68 wt % acid containing 0-0.18 M 1-butanol was monitored by measuring the fractions of impinging HCl and HBr molecules that desorb as DCl and DBr after undergoing H --> D exchange within the deuterated acid. The addition of 0.18 M butanol to the acid creates butyl films that reach approximately 80% surface coverage at 213 K. Surprisingly, this butyl film does not impede exchange but instead enhances it: the HCl --> DCl exchange fractions increase from 0.52 to 0.74 for 60 wt % D(2)SO(4) and from 0.14 to 0.27 for 68 wt % D(2)SO(4). HBr --> DBr exchange increases even more sharply, rising from 0.22 to 0.65 for 68 wt % D(2)SO(4). We demonstrate that this enhanced exchange corresponds to enhanced uptake into the butyl-coated acid for HBr and infer this equivalence for HCl. In contrast, the entry probability of the basic molecule CF(3)CH(2)OH exceeds 0.85 at all acid concentrations and is only slightly diminished by the butyl film. The OD groups of surface butanol molecules may assist entry by providing extra interfacial protonation sites for HCl and HBr dissociation. The experiments suggest that short-chain surfactants in sulfuric acid aerosols do not hinder heterogeneous reactions of HCl or HBr with other solute species.     

Explorative data analysis of two-dimensional electrophoresis gels

Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening of gels is presented. First, an approach is demonstrated in which no prior knowledge of the separated proteins is used. Alignment of the gels followed by a simple transformation of data makes it possible to analyze the gels in an automated explorative manner by principal component analysis, to determine if the gels should be further analyzed. A more detailed approach is done by analyzing spot volume lists by principal components analysis and partial least square regression. The use of spot volume data offers a mean to investigate the spot pattern and link the classified protein patterns to distinct spots on the gels for further investigation. The explorative approach in analysis of 2-D gels makes it possible, in a fast and convenient way, to screen many gels in order to determine the protein patterns that form clusters and could be selected for further examination.     

Synthesis and stereodynamics of highly constrained 1,8-bis(2,2'-dialkyl-4,4'-diquinolyl)naphthalenes

The syn and anti isomers of axially chiral 1,8-diquinolylnaphthalenes have been synthesized via Pd-catalyzed Stille coupling of 1,8-dibromonaphthalene and 2-alkyl-4-trimethylstannylquinolines. Optimization of the cross-coupling reaction allowed the preparation of highly constrained 1,8-bis(2,2'-dimethyl-4,4'-diquinolyl)naphthalene, 2, and 1,8-bis(2,2'-diisopropyl-4,4'-diquinolyl)naphthalene, 3, in 42% and 41% yield, respectively. Employing Pd(PPh(3))(4) and CuO as the cocatalysts in the coupling reaction of 1,8-dibromonaphthalene and 2-alkyl-4-trimethylstannylquinolines proved to be superior over other catalysts such as PdCl(2)(dppf), Pd(2)(dba)(3)/P(t-Bu)(3), and POPd. The C(2)-symmetric anti isomers of 2 and 3 were found to be more stable than the corresponding meso syn isomer. The ratio of the two enantiomeric anti conformers to the syn conformer was determined as 7.9:1 for 2 and 8.6:1 for 3 by NMR and HPLC analysis. The atropisomers of 2 and 3 were found to be stable to rotation about the chiral axis at room temperature and all three stereoisomers of 2 were isolated by semipreparative HPLC on a Chiralpak AD column. The diastereoisomers of 3 were separated via preferential crystallization of the anti isomers from diethyl ether. Slow syn/anti interconversion was observed for both atropisomers at enhanced temperature, and the diastereomerization and enantiomerization processes were monitored by NMR and HPLC. The Gibbs activation energy, DeltaG++, for the isomerization of 2 was determined as 116.0 (112.1) kJ/mol for the conversion of the anti (syn) to the syn (anti) isomer at 71.0 degrees C. The rotational energy barrier of 3 was determined as 115.2 (111.1) kJ/mol for the conversion of the anti (syn) to the syn (anti) isomer at 66.2 degrees C.     

Structure and Thermodynamics of NaF-AlF(3) Melts with Addition of CaF(2) and MgF(2)

The NaF-AlF(3) system with additions of CaF(2) and MgF(2) has been studied with Raman and vapor pressure measurements for 3 >/= CR (NaF/AlF(3) molar ratio) >/= 1 and up to 50 mol % additive. The results show that the binary melt can be described using the two equilibria AlF(6)(3)(-) = AlF(6)(2)(-) + F(-) and AlF(5)(2)(-) = AlF(4)(-) + F(-) with equilibrium constants 0.25 and 0.05, respectively, at 1293 K. Both reactions have positive reaction enthalpies. The first equilibrium is strongly shifted to the right resulting in a melt mixture with very low AlF(6)(3)(-) concentrations even at the Na(3)AlF(6) composition. Evidence for nonideal mixing of anions was found. For the ternaries, models based on Raman data are presented and compared with vapor pressure measurements. Good agreement is observed when association between the additives, CaF(2) or MgF(2), with the AlF(5)(2)(-) ions in the melt was considered. This association could be experimentally observed through a band broadening and a slight shift in the AlF(5)(2)(-) band frequency. Our vapor pressures and Raman data both indicate that MgF(2) clearly acts as an acid when added to NaF-AlF(3) melts of any composition. When CaF(2) is added, a slight decrease of vapor pressure occurs. Raman data indicate a decrease of AlF(4)(-) concentration, corresponding to a dissociation of CaF(2) with liberation of F(-) ions. All these results are, however, very much dependent on the initial melt composition. These data are explained in terms of acid-base, dilution, and association reactions of the solute with the solvent.     

Maximal flow through a domain

It is proved that, if the DFP or BFGS algorithm with step-lengths of one is applied to a functionF(x) that has a Lipschitz continuous second derivative, and if the calculated vectors of variables converge to a point at which ?F is zero and ?² F is positive definite, then the sequence of variable metric matrices also converges. The limit of this sequence is identified in the case whenF(x) is a strictly convex quadratic function.     

The mass spectrometric fragmentation of n-benzylacetamide

The low energy mass spectra of N-benzylacetamide have been recorded. The major fragmentations of the molecular ion are similar to those observed in the acetanilide spectrum. In addition, the secondary dissociation of the [C₆H₅CH₂NH]⁺ ion by loss of HCN is shown to occur with transfer of the -N–H hydrogen to the ring.     

Coupling insertion reactions of diphenylbuta-1, 4-diyne into iron-carbene bonds of [Fe2(CO)7{μ-C(Ph)C(NEt2}]. Syntheses and reactivities of the ferracyclopentadiene [Fe2(CO)6{C(Ph)C(NEt2)C(Ph)C(C2Ph)}] with [Fe2(CO)9]

The diiron ynamine complex [Fe₂(CO)₇{-C(Ph)C(NEt₂)}] (1) reacts with the diphenylbuta-1, 4-diyne, PhCC-CCPh, in refluxing hexane to yield three isomer complexes [Fe₂(CO)₆{C(Ph)C(NEt₂)C(Ph)C(C₂Ph}] (2a), [Fe₂(CO)₆{C(Ph)C(NEt₂)C(C₂Ph)C(Ph)}] (2b), and [Fe₂(CO)₆{NEt₂)C(Ph)C(C₂)C(Ph)}] (2c) All three compounds were identified by their¹H NMR spectra. Compounds2a and2c were characterized by single crystal X-ray diffraction analyses. Crystal data: for2a: space group = P2₁/n,a = 17.873(1) Å, = 18.388(6) Å,c = 9.429(3) Å = 91.99(3)°,Z = 4.3751 reflections,R = 0.044; for2c: space group = P2₁/n,a = 40.58(2) å,b = 12.101(9) Å,c = 12.551(5) Å, = 94.29(7)°,Z = 8.4723 reflection,R = 0.076. Complexes2a and2b result from a [2 + 2] cycloaddition between one of the CC triple bonds of the diyne ligand and the FeC carbene bond, whereas2c results from insertion of one of the CC group into the bridging carbene. Addition of [Fe₂(CO)₉] on2a gave two major products, the tripledecker [Fe₃(CO)₈{C(Ph)C(NEt₂)C(C₂Ph)}], (3 and a tetrairon cluster [Fe₄(CO)₁₁{C(Ph)C(NEt₂)C(Ph)C(C₂Ph)}] (4). Both compounds were characterized by single crystal diffraction analyses. Crystal data: for3: space group = P2₁/n,a = 12.039(3) Å,b = 18.046(3) å,c = 15.270(2) Å, = 90.11(2)°,Z = 4, 1430 reflections,R = 0.067; for4 space group = C2/c,a = 18.633(3) Å,b = 21.467(1)_Å,c = 20.742(2) Å, = 115.03(8)°,Z = 8.992 reflections, R = 0.076. Complex4 is based on a spiked triangular cluster with the alkynyl triple bond attached in ₃-parallel mode on the triangular grouping.     

Neutron activation determination of noble metals for the analysis of technological and natural materials

Two previously developed methods of noble metal neutron activation (NA) determination have been applied for the analysis of technological materials. While comparing the data obtained by both methods with those obtained in Central Chemical Laboratory the systematical discreapences have been shown to be absent. A new method of Pd, Au, Pt and Ir NA determination in natural and technological specimens based on the selective extraction of Pd and Au preliminary to irradiation has been developed. Results of the analysis of “Glomar Cellenger”'s deep-water drilling samples are discussed obtained by this method.     

Gas‐phase functionalized carbon‐carbon coupling reactions catalyzed by Ni (II) complexes

Gas‐phase C―C coupling reactions mediated by Ni (II) complexes were studied using a linear quadrupole ion trap mass spectrometer. Ternary nickel cationic carboxylate complexes, [(phen)Ni (OOCR¹)]⁺ (where phen = 1,10‐phenanthroline), were formed by electrospray ionization. Upon collision‐induced dissociation (CID), they extrude CO₂ forming the organometallic cation [(phen)Ni(R¹)]⁺, which undergoes gas‐phase ion‐molecule reactions (IMR) with acetate esters CH₃COOR² to yield the acetate complex [(phen)Ni (OOCCH₃)]⁺ and a C―C coupling product R¹‐R². These Ni(II)/phenanthroline‐mediated coupling reactions can be performed with a variety of carbon substituents R¹ and R² (sp³, sp², or aromatic), some of them functionalized. Reaction rates do not seem to be strongly dependent on the nature of the substituents, as sp³‐sp³ or sp²‐sp² coupling reactions proceed rapidly. Experimental results are supported by density functional theory calculations, which provide insights into the energetics associated with the C―C bond coupling step.     

Identification of small molecule inhibitors that distinguish between non-transferrin bound iron uptake and transferrin-mediated iron transport

Chemical genetics is an emerging field that takes advantage of combinatorial chemical and small molecule libraries to dissect complex biological processes. Here we establish a fluorescence-based assay to screen for inhibitors of iron uptake by mammalian cells. Using this approach, we screened the National Cancer Institute's Diversity Set library for inhibitors of non-transferrin bound iron uptake. This screen identified 10 novel small molecule inhibitors of iron transport with IC(50) values that ranged from 5 to 30 microM. Of these ten compounds, only two blocked uptake of iron mediated by transferrin. Thus, this study characterizes the first small molecule inhibitors that distinguish between different pathways of iron transport.