Gas chromatographic mass spectrometric indication of double bond position in monounsaturated primary acetates and alcohols without derivatization

Electron impact mass spectra of straight chain, monounsaturated C₁₂ to C₁₈ acetates and alcohols have been shown to be useful in the indication of the double bond position on an empirical basis. The ratio of intensities of the m/z 55 and m/z 54 ions increases proportionately as the double bond is moved away from the acetate or alcohol functional group. The intensity of the m/z 61 ion also can be correlated with the double bond position. Results are generally accurate to ±1 carbon atom.     

Interaction energies of ZnO in acrylic polymer lattices

Water‐based acrylic polymers are frequently used as binders in ceramic materials that contain ZnO as a major component. Thin flexible ceramic films used in semiconductor elements are prepared from ceramic powder, polymer binder, dispergant and plasticizer. In the present work, the chemical reaction of acrylic acid, a part of the polymer, and ceramic powder (ZnO) has been studied by semi‐empirical calculations and Fourier transform infrared spectroscopy (FTIR). Systematic evaluation of model structures using varying contents of acrylic acid showed that ZnO adhesion increases as the carboxylate content in the polymer system increases. Interaction energy surfaces provide a quantitative insight into the spatial distribution of ZnO particles in various model structures. These results are also in good agreement with our infrared spectroscopy measurements.     

Structure–property relationships of ionene polymers

The synthesis of new ionenes was accomplished by the reaction of novel diamines and dihalides. A new class of crosslinkable ionenes was made possible by the synthesis of tertiary diamines with acrylate functionality, generated ultimately from diepoxides and secondary amines. Other tertiary diamines were produced by endcapping of diols with tolylene diisocyanate, followed by reaction with N,N-dimethylethanolamine and also termination of living poly(tetrahydrofuran) polymer with dimethylamine. New dihalides were produced by the opening of diepoxides with ω-bromoacids. These diamines and dihalides underwent Menschutkin reactions providing novel ionenes for structure–property relationship studies. Correlations were drawn concerning amine nucleophilicity, dihalide nucleofugascity, and molecular weight. Stress–strain and thermal data reflected the effects of ionic domains and large flexible segments in the polymers. Also considered were the electrical conductivity, moisture–vapor transmission, and oxygen permeability of these materials.     

Three dimensional structure-activity relationships (3D-QSAR) for insect repellency of diastereoisomeric compounds: a hierarchical molecular overlay approach

2-(2-Hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester (Picaridin), and 1-(cyclohex-3-ene-1-ylcarbonyl)-2-methylpiperidine (AI3-37220; 220) are alternatives to DEET (N,N-diethyl-3-methylbenzamide), the most popular mosquito repellent. Picaridin and AI3-37220 exhibit polychiral diastereoisomerism and each has four diastereoisomers due to the presence of two asymmetric centers in their molecules. The diastereoisomers of these compounds have differing degrees of mosquito-repellent activity according to quantitative behavioral assays conducted at the United States Department of Agriculture. An insight into the stereochemical requirements for repellency is of great importance in the development of better repellents. Molecular overlay of the optimized geometries of the diastereoisomers was considered as a novel tool for Stereochemical Structure-Activity Relationship (SSAR) modeling. An earlier study using molecular mechanics (MM2) optimized geometries showed good promise. In continuation of this effort and to overcome certain defects in using MM2 geometries, a hierarchical overlay approach was developed. In this method geometry of the low energy conformer of each diastereoisomer was optimized using: the following quantum chemical methods in a graduated manner: (a) semiempirical AM1, (b) Hartree Fock (STO3G, 3-21G, 6-31G, and 6-311G), and (c) Density Functional Theory (B3LYP/6-31G, B3LYP/6-311G). The optimized geometries of different diastereoisomers were overlaid in various user defined combinations to calculate the root mean square distances (RMSD) of the overlaid structures. The RMSD with respect to the most active diastereoisomer (220SS) were found to have a strong relationship with biological potency. Common motifs in shapes and molecular surfaces that are probably critical for effective repellent activity were identified. The hierarchical approach gave valuable information on the quantum chemical level (basis set) at which optimization must be carried out to get the correct order of repellency of the diastereoisomers of Picaridin and 220.     

Three dimensional structure-activity relationships (3D-QSAR) for insect repellency of diastereoisomeric compounds: a hierarchical molecular overlay approach¶

2-(2-Hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester (Picaridin), and 1-(cyclohex-3-ene-1-ylcarbonyl)-2-methylpiperidine (AI3-37220; 220) are alternatives to DEET (N,N-diethyl-3-methylbenzamide), the most popular mosquito repellent. Picaridin and AI3-37220 exhibit polychiral diastereoisomerism and each has four diastereoisomers due to the presence of two asymmetric centers in their molecules. The diastereoisomers of these compounds have differing degrees of mosquito-repellent activity according to quantitative behavioral assays conducted at the United States Department of Agriculture. An insight into the stereochemical requirements for repellency is of great importance in the development of better repellents. Molecular overlay of the optimized geometries of the diastereoisomers was considered as a novel tool for Stereochemical Structure-Activity Relationship (SSAR) modeling. An earlier study using molecular mechanics (MM2) optimized geometries showed good promise. In continuation of this effort and to overcome certain defects in using MM2 geometries, a hierarchical overlay approach was developed. In this method geometry of the low energy conformer of each diastereoisomer was optimized using: the following quantum chemical methods in a graduated manner: (a) semiempirical AM1, (b) Hartree Fock (STO3G, 3-21G, 6-31G, and 6-311G), and (c) Density Functional Theory (B3LYP/6-31G, B3LYP/6-311G). The optimized geometries of different diastereoisomers were overlaid in various user defined combinations to calculate the root mean square distances (RMSD) of the overlaid structures. The RMSD with respect to the most active diastereoisomer (220SS) were found to have a strong relationship with biological potency. Common motifs in shapes and molecular surfaces that are probably critical for effective repellent activity were identified. The hierarchical approach gave valuable information on the quantum chemical level (basis set) at which optimization must be carried out to get the correct order of repellency of the diastereoisomers of Picaridin and 220.     

Structural,Vibrational, and Gasochromic Properties of Porous WO<Subscript>3</Subscript> Films Templated with a Sol-Gel Organic–Inorganic Hybrid

Summary.  The structure and the gasochromic properties of sol-gel-derived WO₃ films with a monoclinic structure (m-WO₃) were studied by focusing attention on the size of the monoclinic grains. The size of the m-WO₃ grains is modified by the addition of an organic–inorganic hybrid to the initial peroxopolytungstic acid (W-PTA) sols which are based on chemically bonded poly-(propylene glycol) to triethoxysilane end-capping groups (ICS-PPG). The results obtained with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the heat treatment (500°C) of WO₃/ICS-PPG (0.5, 1, 2, 5, and 10 mol%) composite films results in a change of their morphology, and nanodimensional pores are formed between the grains. High-resolution TEM (HRTEM) analysis revealed the presence of an amorphous phase on the outside of the m-WO₃ grains, whereas energy-dispersive X-ray spectra (EDXS) showed that this amorphous phase contained W and Si. Impregnation of the WO₃/ICS-PPG film with H₂PtCl₆/i-propanol solution followed by heat treatment at 380°C gave the films their gasochromic properties. Infrared and Raman spectroscopic studies of the WO₃/ICS-PPG film confirmed the results of the corresponding HRTEM and EDXS analysis. In situ UV/Vis and in situ IR spectra of the films were measured in hydrogen and in air, and colouring/bleaching changes and the corresponding kinetics were assessed. The IR spectra of gasochromically coloured films showed that the mesoporous WO₃/ICS-PPG (1 mol%) film transforms to tetragonal H _x WO₃ bronze. The IR spectra of the H _x WO₃ bronze are discussed with the aim to establish the existence of the metal-OH vibrations of gasochromically formed oxyhydroxide tungsten bronze. Received October 4, 2001. Accepted (revised) November 19, 2001     

Structural, Vibrational, and Gasochromic Properties of Porous WO3 Films Templated with a Sol-Gel Organic–Inorganic Hybrid

 The structure and the gasochromic properties of sol-gel-derived WO₃ films with a monoclinic structure (m-WO₃) were studied by focusing attention on the size of the monoclinic grains. The size of the m-WO₃ grains is modified by the addition of an organic–inorganic hybrid to the initial peroxopolytungstic acid (W-PTA) sols which are based on chemically bonded poly-(propylene glycol) to triethoxysilane end-capping groups (ICS-PPG). The results obtained with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the heat treatment (500°C) of WO₃/ICS-PPG (0.5, 1, 2, 5, and 10 mol%) composite films results in a change of their morphology, and nanodimensional pores are formed between the grains. High-resolution TEM (HRTEM) analysis revealed the presence of an amorphous phase on the outside of the m-WO₃ grains, whereas energy-dispersive X-ray spectra (EDXS) showed that this amorphous phase contained W and Si. Impregnation of the WO₃/ICS-PPG film with H₂PtCl₆/i-propanol solution followed by heat treatment at 380°C gave the films their gasochromic properties. Infrared and Raman spectroscopic studies of the WO₃/ICS-PPG film confirmed the results of the corresponding HRTEM and EDXS analysis. In situ UV/Vis and in situ IR spectra of the films were measured in hydrogen and in air, and colouring/bleaching changes and the corresponding kinetics were assessed. The IR spectra of gasochromically coloured films showed that the mesoporous WO₃/ICS-PPG (1 mol%) film transforms to tetragonal H _x WO₃ bronze. The IR spectra of the H _x WO₃ bronze are discussed with the aim to establish the existence of the metal-OH vibrations of gasochromically formed oxyhydroxide tungsten bronze.     

The di-π-methane rearrangement of systems with simple vinyl moieties : Mechanistic and exploratory organic photochemistry

3,3-Dimethyl-1,1-diphenyl-1,4-pentadiene and two 5-substituted derivatives were synthesized and studied. The regioselectivity, stereochemistry, quantum efficiency, multiplicity, and excited state reaction rates were studied in each case. The parent hydrocarbon, 5-MeO-derivative, and 5-cyano-diene—all rearranged on direct irradiation to give vinylcyclopropanes. The first compound led to 3,3-dimethyl-2,2-diphenyl-1-vinylcyclopropane. The second afforded 3,3-dimethyl-2,2-diphenyl-1-(2'-methoxyvinyl)cyclopropane. The last gave 1-cyano-3,3-dimethyl-2-(2',2'-diphenylvinyl)cyclopropane. Thus, the vinyl and methoxyvinyl groups survive in the products intact, while the cyanovinyl group is incorporated in the three-ring. In the two substituted dienes, cis-reactant gave cis-product and trans-reactant gave trans-product, both where the substituent was on the vinyl group of the product and where it became a ring substituent. The substituted di-π-methane systems underwent only cis-trans isomerization on sensitization, while the parent, unsubstituted diene led to di-π-methane product on sensitized as well as direct photolysis. While the quantum yields for the hydrocarbon diene were the same at room temperature for the direct and sensitized runs, only the sensitized runs showed a temperature dependence of efficiency with a dramatic, 5-fold increase on a 46° temperature increase. Thus, evidence was obtained for a singlet rearrangement in all cases and a triplet process only in the case of the unsubstituted diene. A sizable activation energy was seen for the triplet but not for the singlet. The room temperature quantum yields in the direct irradiations were: φ(parent diene)=0.011, φ(trans-methoxydiene)=0.051, φ(cis-methoxy-diene)= 0.050, φ(trans-cyanodiene)=0.36, and φ(cis-cyano-diene) = 0.20. A competing side reaction was cis-trans isomerization but these quantum yields were lower. Single photon counting was employed to obtain excited singlet reaction and decay rates at low temperature (i.e. 77°K) and the method of magic multipliers was used to obtain room temperature rates. These were: k_r(parent diene) = 4.7 × 10⁸ sec^?1, k_r(trans-cyano-diene)= 1.5 ×10¹⁰ sec^?1, k_r(cis-cyano-diene)= 8.0 × 10⁹sec^?1, and k_r(trans-methoxy-diene) = 1.9 × 10⁹ sec^?1. The results are discussed in terms of excited state molecular structure.An SCF-CI molecular orbital treatment of the reaction was developed. This used a cyclopropyldicarbinyl diradical species, with Walsh cyclopropane basis orbitals, as representing the half-reacted species. The energy of formation of this species from vertical excited state reactant was calculated for all three dienes and an excellent correlation with observed excited singlet rates was obtained. Similarly, dissection of the excited diradical energy into bond components led to a correlation between regioselectivity and weakness of the three-ring bond broken in the regioselectivity-determining step. Evidence was adduced for localization of the excitation energy in S₁ of reactant in the diphenylvinyl chromophore with migration of electronic excitation into the cyclopropyldicarbinyl diradical moiety during the vinyl-vinyl bridging process. A general method for quantitatively partitioning excitation energy was developed and applied to the case in hand. Finally, there was predicted a greater probability of di-π-methane three-ring fission in the excited state compared to the diradical ground state where Grob fragmentation proved energetically more favorable.