Pure CHCl3 Research Articles

Two-Dimensional Melting and Phase Change of Binary Mixtures of CCl4 and CHCl3 Confined in ACF Nanospace Studied Using Solid-State 1H NMR

Abstract Two-dimensional melting and phase changes of binary mixtures of CCl4 and CHCl3 confined in activated carbon fiber were examined using differential thermal analysis and 1H wide-line NMR. Molecular assembly of CCl4 confined in ACF nanospace with a slit width of 1.1 nm showed succeeding thermal anomalies corresponding to crystal–hexatic and hexatic–liquid transitions. Results showed that these thermal anomalies did not occur in a mixture of CHCl3 and CCl4. This behavior differed greatly from the phase diagram for the bulk mixture between CHCl3 and CCl4. Furthermore, the dynamic features of CHCl3 molecule were examined using the 1H wide-line NMR spectrum. The activation energy of the hopping motion changed from 7 kJ mol−1 for pure CHCl3 to 13 kJ mol−1 for CHCl3 with a 0.016 molar ratio in CCl4. In particular, a drastic increase in the activation energy was observed for doping with a trace amount of CHCl3, suggesting that molecular self-assembly of CCl4 takes place in the ACF nanoslit because of the effective intermolecular interaction between CCl4 molecules. The existence of CHCl3 in CCl4 brings about the remarkable impurity effect on two-dimensional melting and phase transition of CCl4 confined in ACF nanospace.

Processing and characterization of electrospun poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) nanofibrous membranes

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) nanofibrous membranes were first fabricated via electrospinning from chloroform (CHCl3) or CHCl3/dimethylformamide (DMF) polymer solutions. The electrospinning conditions such as the polymer concentration, the solvent composition, and the applied voltage were optimized in order to get smooth and nano-sized fibers. The crystalline structure, the melting behaviors and the mechanical properties of the obtained nanofibrous membranes were characterized. With pure CHCl3 as the solvent in the electrospinning process, the finest smooth PHBHHx fibers were about 1μm in diameter. When DMF is added to CHCl3 as a co-solvent, the conductivity and volatility of the solution increased and reduced, respectively, and the electrospinnability of the polymer solution increased as a result. The averaged diameters of PHBHHx fibers could be reduced down to 300–500nm when the polymer concentration was kept at 3wt%, the ratio of DMF/CHCl3 was maintained at 20/80 (wt%), and the applied voltage was fixed at 15kV during electrospinning. WAXD and DSC results indicated that the crystallization of the PHBHHx nanofibers was restricted to specific crystalline planes due to the molecular orientation along the axial direction of the fibers. The crystallization behaviors of the electrospun nanofibers were significantly different from that of the cast membranes because of the rapid solidification and the one-dimensional fiber size effect in the electrospinning process. Mechanically, the electrospun PHBHHx nanofibrous membranes were soft but tough, and their elongation at break averaged 240–300% and could be up to 450% in some cases. This study demonstrated how the size of electrospun PHBHHx fibers could be reduced by adding DMF in the solvent and gave a clue of the presence of oriented molecular chain packing in the crystalline phase of the electrospun PHBHHx fibers.

Pulsed laser deposition vs. matrix assisted pulsed laser evaporation for growth of biodegradable polymer thin films

Thin films of poly (lactide-co-glycolide) (PLGA), a biodegradable polymer, were deposited on Si wafers by both conventional pulsed laser deposition (PLD) and matrix assisted pulsed laser evaporation (MAPLE) using chloroform (CHCl3) as a matrix solvent. This research represents an initial study to investigate the deposition characteristics of each technique at comparable conditions to gain insight into the transport and degradation mechanisms of each approach. The deposited materials were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC) with refractive index (RI) detection. While FTIR and NMR results do not show a measurable departure from the native, in sharp contrast GPC results show a significant change (up to 95%) in molecular weight for both deposition methods. This result makes it clear that it is possible to overlook substantial degradation when incomplete chemical analysis is conducted. Optical transmission measurements of the starting MAPLE targets yielded laser penetration depths on the order of 0.362 cm and 0.209 cm for pure CHCl3 and 1 wt. % PLGA in CHCl3, respectively. Straightforward application of the Beer–Lambert law for laser energy deposition predicts a negligible temperature rise of less than 1 K at the target surface, which is in clear contradiction with ablation rates of 1.85 μm/pulse experimentally measured for polymer loaded samples. With an ablation process of this magnitude, the material ejection is likely due to contributions of nonlinear or non-homogeneous laser light absorption rather than evaporation. Severe non-uniformity of the final surface morphologies of the MAPLE films, similar to solvent wicking artifacts found in spin casting supports the spallation scenario in MAPLE.

Large-Scale Synthesis and Resolution of TRISPHAT [Tris(tetrachlorobenzenediolato) Phosphate(V)] Anion

Both enantiomers of TRISPHAT anion can be obtained on a multigram scale through a novel resolution procedure. The Lambda enantiomer is isolated as the tri-n-butylammonium salt, [(n)()Bu(3)NH][Lambda-1], which is soluble in pure CHCl(3) and CH(2)Cl(2). The Delta enantiomer is prepared as the cinchonidinium derivative, which is only soluble in polar solvent mixtures (>7.5% DMSO in CHCl(3)).

Photodegradation of Pyrene-Labeled Polystyrene Adsorbed on Silica Surface in Chloroform

Photodegradation of Pyrene-Labeled Polystyrene Adsorbed on Silica Surface in Chloroform

Radiolysis of the trichloromethane-water two-phase system

The radiolysis of the CHCl3-water two-phase system in the absence of oxygen has been investigated by continuous γ-ray irradiation. The major products of radiolysis were determined to be the same, except for tetrachloromethane, as in the case of the radiolysis of pure CHCl3, however, the radiolytical yields were different. The dependencies of gross radiation yields of the radiolysis products on the CHCl3 volume fraction follow the two-phase rule of additivity. The partial yields of all products determined were calculated for both phases and revealed that the major products HCl and C2H2Cl4 are formed in both phases. The other organic products are formed mainly in the organic phase. The decrease of organic product yields is probably caused by the presence of water in the organic phase. The radiolysis of CHCl3-water did not proceed in the diffusional regime even at high absorbed doses due to the relatively high solubility of CHCl3 in water andvice versa.

Poly(ethylene oxide-co-β-benzyl l-aspartate) Block Copolymers: Influence of the Poly(ethylene oxide) Block on the Conformation of the Poly(β-benzyl l-aspartate) Segment in Organic Solvents

The conformation of the poly(β-benzyl l-aspartate) segment in the poly(ethylene oxide-co-β-benzyl l-aspartate) (PEO/PBLA) block copolymers (Mw of PEO = 5000 and 20 units of β-benzyl l-aspartate) was investigated by 1H NMR, by specific optical rotation measurements, and by 2D 1H,1H NOESY NMR in chloroform, dimethyl sulfoxide (DMSO), and mixtures of chloroform/DMSO. The comparison between the 1H NMR spectra of the block copolymer in CDCl3 and the one in DMSO-d6 showed that the PBLA blocks adopt a different conformation depending upon the solvents. The specific rotation of the block copolymer at 546 nm demonstrated that the PBLA segments adopt a left-handed α-helix conformation in chloroform. PBLA homopolymer with the same molecular weight as the PBLA segment in the block copolymer showed no evidence of α-helix formation in the same conditions, indicating that the PEO segment in the block copolymer is essential to allow PBLA to take the α-helix structure. On the other hand, the specific rotation of the PEO/PBLA block copolymer in DMSO at the same wavelength showed that the PBLA segments have a random-coil conformation in this solvent. Moreover, the measurement of the specific rotation of the block copolymer in mixtures of x% CHCl3/(100 − x)% DMSO (0 ≤ x ≤ 100) demonstrated that the left-handed α-helix conformation adopted by the PBLA segments in chloroform is stable. Conversely, the PBLA homopolymer cannot be solubilized in mixtures of CHCl3/DMSO, although this homopolymer is soluble in pure CHCl3 and in pure DMSO. The 2D 1H,1H NOESY NMR spectrum in CDCl3 gave evidence of interactions between the methylene protons (CO2CH2C6H5) of the PBLA segments and the methylene protons of the PEO blocks on one hand and between the benzyl protons of the PBLA segments and the methylene protons of the PEO blocks on the other. Such interactions are not observed in DMSO-d6. Thus, the stability of the left-handed α-helix conformation of the PBLA blocks (having low molecular weights) in chloroform can be explained by the interactions existing between the PBLA and the PEO blocks. Moreover, these interactions also allow the solubilization of the block copolymer in mixtures of CHCl3/DMSO.

Response of Adsorbed Polystyrene Layers to Desorption Conditions

Response of Adsorbed Polystyrene Layers to Desorption Conditions

Pulsed Terahertz Transmission Spectroscopy of Liquid CHCl3, CCl4, and their Mixtures

The frequency-dependent absorption coefficient of CHCl3, CCl4, and their mixtures are measured by pulsed terahertz time domain transmission spectroscopy. The absorbance spectrum for neat CHCl3 is shown to compare well with existing experimental data including coverage of the previously difficult to access 0.3−0.9 THz range. Furthermore, fitted curves to the absorbance spectra of the liquid mixtures, based on mole fraction weighted sums of the absorption coefficients of pure CHCl3 and CCl4, indicate the presence of a bulk dipole reducing mechanism, possibly due to clustering of CHCl3 molecules about CCl4. An algebraic extension of the mole fraction weighted fits allows discrimination between relative strengths of the various bimolecular absorption processes. The integrated absorption coefficient for collisionally induced absorption of CHCl3−CCl4 collisions was found to be less than that for CHCl3−CHCl3 collisions by 2.6 ± 0.4 THz cm-1 (integrated absorption coefficient units). Finally, a new procedure for ...

Syntheses of 6-hydroxycortisol 6-hemisuccinate (author's transl)

The selective acetylation of 17α, 20, 20, 21-BMD-pregnan-5α, 6β, 11β-triol-3-one (IV), derived from cortisone, was led to its 6β-acetate (V). A solution of V in CHCl3 containing EtOH (0.7%) was treated with HCI gas to give 17α, 20, 20, 21-BMD-4-pregnene-6α, 11β-diol-3-one-6-acetate (VIa) and in pure CHCl3 to give 6β-derivative (VIb). The hydrolysis of 6-O-acetate of VIa with K2CO3 followed by succinylation with succinic anhydride gave 17α, 20, 20, 21-BMD-4-pregnene-6α, 11β-diol-3-one 6-hemisuccinate (VIIIa). 6α-Hydroxy- cortisol 6-hemisuccinate (IXa) was obtained by the hydrolysis of the bismethylenedioxy protecting group in VIIIa with 50% AcOH. 6β-Hydroxycortisol 6-hemisuccinate (IXb) was also obtained from VIb by the same procedure.

Positive Ion Scavenging in the Radiolysis of Liquid Chloroform

The effects of the positive ion scavengers NH3 and n-C4H9OH, on the organic product yields in the radiolysis of liquid CHCl3 at 25°C were investigated. As the solute concentrations increase, the values for G(CH2Cl2), G(C2HCl5), and G(C2Cl6) increase, G(sym-C2H2Cl4) and G(C2Cl4) remain unchanged, and G(CCl4) decreases. These results are consistent with a free radical mechanism for all the radiolysis products except CCl4. The decrease in G(CCl4) indicates that CCl4 is formed by a secondary positive ion reaction. The concentration dependence of this decrease can be described by the expression G(CCl4)O−G(CCl4)S=G(CCl4)O((α[S])1/2/{1+(α[S])1/2}), where G(CCl4)O is the 100-eV yield in the absence of a scavenger, and α is an empirical parameter proportional to the reactivity of the solutes, and [S] is the concentration of the scavenger in moles per liter. Values of α were determined for each solute and compared to published values determined in cyclohexane. In chloroform, values for α were 4–19 times larger than in cyclohexane suggesting that the solutes are more efficient in the alkyl halide than in the hydrocarbon. One mechanism accounting for this efficiency increase is the formation of anions by the free electrons in the alkyl halide. This anion formation increases the average lifetimes of the ions in the alkyl halide and hence the efficiencies of the scavengers. The increase in the 100-eV yields of three of the products formed by the free radical mechanism indicates that the presence of a cation scavenger increases the radical yields. Thus, some of the charge neutralizations in pure CHCl3 do not produce radicals. This observation is in accord with the existence of the collisionally stabilized CHCl3− anion in the irradiated solutions. It is suggested that this anion may be an intermediate in the formation of CCl4.