Towards physical interpretation of Hammett constants: charge transferred between active regions of substituents and a functional group

The charges transferred between substituents and two functional groups: nitroso and N,N-dimethylamine in disubstituted benzene rings, were calculated at the B3LYP/cc-pVDZ level, using Natural Population Analysis. They were compared with the charges transferred between active regions of the substituents and of the groups. The transferred charge was well correlated with the Hammett constants, but only when the charges were calculated for the corresponding active regions instead of being calculated for the substituents and functional groups themselves. The results were compared for substituents introduced at the para and meta position to the NO and N(CH₃)₂ groups.     

Effect of chemical structure in photochromic polymers of the mercury thiocarbazonate series

The effects of the chemical structure of the functional portion as well as the comonomer composition on the photochromic behavior of vinyl polymers containing mercury thiocarbazonate functional groups in the side chains were investigated. It was found that, for p-acrylamidophenyl mercuric thiocarbazonate polymers, the uses of β-naphthyl and strongly electron-releasing p-methoxyphenyl groups for the thiocarbazone residue provide absorption maxima shifted somewhat to longer wavelengths as compared with the use of unsubstituted phenyl groups, whereas the electron-withdrawing o-trifluoromethylphenyl group brings about much larger shifts towards shorter wavelengths, the o-trifluoromethylphenyl group and those groups capable of exerting steric hindrances such as β-naphthyl and o-methylphenyl groups causing slower light and dark reactions too. The increase of free volumes in the polymers by regulating the comonomer composition, i.e., the lowering of T_g, was found to improve photochromic responses strikingly.     

Thermal stability of high-energy compounds

The influence of molecular structure on the stability of high-energy compounds is considered. The kinetic parameters of the decomposition of various energy-rich groups in monofunctional compounds are established. Data on decomposition of compounds with mixed functional groups are described. The sites of primary breakdown are determined and the mutual influence of functional groups on the stability is considered. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 231–234, February, 2000.     

Chemoselective Synthesis of Z‐Olefins through Rh‐Catalyzed Formate‐Mediated 1,6‐Reduction

Z‐olefins are important functional units in synthetic chemistry; their preparation has thus received considerable attention. Many prevailing methods for cis‐olefination are complicated by the presence of multiple unsaturated units or electrophilic functional groups. In this study, Z‐olefins are delivered through selective reduction of activated dienes using formic acid. The reaction proceeds with high regio‐ and stereoselectivity (typically >90:10 and >95:5, respectively) and preserves other alkenyl, alkynyl, protic, and electrophilic groups.     

Structure elucidation with lanthanide-induced shifts 5. Evaluation of the binding ability of various functional groups

The equilibrium binding constants have been evaluated for the association in CCl₄ of the lanthanide shift reagent. Eu(fod)₃, with a series of adamantane derivatives containing a variety of different functional groups. It is shown that if steric effects are held constant the binding abilities of the adamantane derivatives exhibit a good correlation with the proton affinities of the methyl analogs containing the same functional groups. The results permit the prediction of binding strength of other functional groups with Eu(dpm)₃ as well as with Eu(fod)₃ and thus can be of great assistance in planning and interpreting the results of experiments with lanthanide shift reagents.Part 4:D. J. Raber, M. D. Johnston, jr., C. M. Campbell, C. M. Janks, andP. Sutton, Org. Mag. Res.11, 323 (1978).     

Selective polymerization of functional monomers with Novozym 435

Two novel monomers, ambrettolide epoxide and isopropyl aleuriteate, encompassing functional groups, were obtained in a single step from commercially available materials. Novozym 435 catalyzed ring opening polymerization of ambrettolide epoxide furnished a polymer of M_n = 9.7 kg/mol and PDI = 1.9 while the epoxide groups remained unaffected during the polymerization. Selective polymerization of the primary hydroxyl groups of isopropyl aleuriteate using Novozym 435 was feasible and a polymer with moderate molecular weight (M_n = 5.6 kg/mol, PDI = 3.2) was isolated in moderate yield (43%). Subsequently, copolymerization of isopropyl aleuriteate with ε‐CL in different ratios was performed, resulting in soluble, hydroxy functional polymers with good molecular weights (M_n = 10.4–27.2 kg/mol) in good yield (71–78%). The secondary hydroxy groups in the polymer reacted easily with hexyl isocyanate, showing the potential of isopropyl aleuriteate as a comonomer for the synthesis of functional polyesters. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5968–5978, 2007     

The role of the medium in electrochemical functionalization and dispersion of carbon nanotubes

An electrochemical method for dispersion of single-walled carbon nanotubes (SWNTs) is described. The technique is based on grafting of oxygen-containing functional groups to the nanotube surface during electrolysis in aqueous and nonaqueous potassium bromide solutions. A dependence of the degree of functionalization of nanotubes on the solvent was revealed experimentally. Nanotubes treated in DMSO have about 14 carbon atoms per oxygen atom from functional groups (cf. nearly four C atoms per oxygen atom in the nanotubes treated in aqueous solutions). The corresponding maximum specific capacities of the electrodes are nearly 10 and 60 F g⁻¹. The samples treated in solutions of KBr in DMSO have about 300 carbon atoms per bromine atom on the nanotube surface (cf. only 30 carbon atoms in the samples treated in aqueous solution). A mechanism of electrochemical modification of SWNTs is proposed. Its key step is production of atomic oxygen that oxidizes the nanotube surface with the formation of functional groups.     

The effect of molecular structure upon the response of the flame ionization detector

Summary It is known that the response of the FID is proportional to the number of carbon atoms in hydrocarbon molecules. If there is a heteroatom in the molecule, the response of the FID decreases. It is possible to calculate the sensitivity to any organic molecule if the signal-decreasing effect of a heteroatom or functional group is known. The sensitivity of a detector to an organic molecule containing heteroatoms is referenced to normal hydrocarbons by means of the effective carbon-atom number (ECN). Several authors have dealt with the determination ofECN values of different molecules and the effective carbon-atom number increment (ECN _inc) values for different functional groups and heteroatoms. In our previous work [1]ECN _inc values of several components were studied for homologous series. In this study we have investigated the effects of molecule structure upon ECN values by comparing theECN _inc of functional groups which are attached to molecules of different structure.     

T-for-H exchange reaction between HTO vapor and two functional groups in an aromatic compound in a gas-solid system

The hydrogen-isotope exchange reaction (T-for-H exchange reaction) between HTO vapor and an aromatic compound having two different kinds of functional groups has been observed at several temperatures. The rate constant (k) for each functional group in the T-for-H exchange reaction was obtained by using both theA″-McKay plot method and the data observed. Comparing thesek with each other has led to the following four conclusions in the T-for-H exchange reaction. (1) The reactivity of both the COOH and OH groups increases with a rise in temperature. (2) As to the degree of the effect of the COOH group on the reactivity of monosubstituted phenols, the degree inp-hydroxybenzoic acid is greater than that inm-hydroxybenzoic acid. (3) The HAMMETT rule is useful for estimating the reactivity of a certain aromatic compound. (4) TheA″-McKay plot method is also useful not only investigating the reactivity of the compounds having one kind of functional group, but also doing the reactivity of the compounds having two different kinds of functional groups.     

Synthesis and antibacterial activities of water‐soluble methacrylate polymers containing quaternary ammonium compounds

New water‐soluble methacrylate polymers with pendant quaternary ammonium (QA) groups were synthesized and used as antibacterial materials. The polymers with pendant QA groups were obtained by the reaction of the alkyl halide groups of a previously synthesized functional methacrylate homopolymer with various tertiary alkyl amines containing 12‐, 14‐, or 16‐carbon alkyl chains. The structures of the functional polymer and the polymers with QA groups were confirmed with Fourier transform infrared and ¹H and ¹³C NMR. The degree of conversion of alkyl halides to QA sites in each polymer was determined by ¹H NMR to be over 90% in all cases. The number‐average molecular weight and polydispersity of the functional polymer were determined by size exclusion chromatography to be 32,500 g/mol and 2.25, respectively. All polymers were thermally stable up to 180 °C according to thermogravimetric analysis. The antibacterial activities of the polymers with pendant QA groups against Staphylococcus aureus and Escherichia coli were determined with broth‐dilution and spread‐plate methods. All the polymers showed excellent antibacterial activities in the range of 32–256 μg/mL. The antibacterial activity against S. aureus increased with an increase in the alkyl chain length for the ammonium groups, whereas the antibacterial activity against E. coli decreased with increasing alkyl chain length. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5965–5973, 2006     

Metallation of unsaturated polymers and formation of graft copolymers

The use of N,N,N′,N′-tetramethylethylenediamine (TMEDA) is known to enhance the metallation of capability of butyllithium. It has been found that this TMEDA–BuLi reagent smoothly metallates olefins in high yields at 50°C in less than 4 hr by replacement of allylic hydrogen. This reaction has been applied to unsaturated polymers such as polybutadiene and polyisoprene. The resulting products have lithium atoms scattered along the chain. The amount of lithium on the chain can be varied over wide limits. Each lithium atom on the chain can act as a site for grafting or adding functional groups to the base polymer. Thus, this method allows the preparation of polymers having controlled amounts of branching as well as the introduction of functional groups into the polymer. Through the use of this metallation technique, polymers containing styrene and butadience grafts are specifically reported. In addition, polymers containing hydroxyl or carboxyl groups along the backbone are prepared by using this technique.     

L-glutamic acid as a versatile platform for rapid synthesis of functional polyesters via facile Passerini multicomponent polymerization

In this work, a series of polyesters with different functional side groups were successfully prepared by Passerini three-component polymerization (P-3CP) in “one-pot” from biorenewable l -glutamic acid (l -GA)-based monomers. First, the polymerization conditions including monomer feed ratios, solvents and comonomer were systematically studied using Boc-protected l -GA with adipaldehyde and tert-butyl isocyanide. Under the optimal polymerization conditions, a variety of N-substituted l -GA-based monomers as well as functional isocyanides were attempted in the P-3CP to produce polyesters with different functionalities. Moreover, it was found that after removal of pendant protecting groups, the obtained l -GA-based polyester degraded spontaneously into small molecules via 1,5-intramolecular cyclization between the pendant amine groups and the ester groups in polymer backbone. The structures and thermal properties of obtained polymers were determined by ¹H NMR, IR, SEC, MALDI-ToF-MS, DSC, and TGA measurements. Starting from biorenewable l -GA, this approach will provide a facile and straightforward route to produce functional and biodegradable polyesters, thus effectively expanding the range of biodegradable polymers.     

Synthetic porphyrins. I. Synthesis and spectra of some para-substituted meso - Tetraphenylporphines

A series of derivatives of meso-tetraphenylporphine, with neutral, acidic and basic functional groups, has been prepared. Several of these compounds were synthesized directly via the Rothemund reaction, under a variety of conditions to obtain optimal yields; others were prepared by interconversions of various functional groups. Drastic reaction conditions employed for hydrolysis, alcoholysis, or lithium aluminum hydride reduction did not affect the porphine ring system. The two amino derivatives showed anomalous spectra in the visible range.     

Quantum Chemical Calculation of Conformations and Rotation Barriers of Functional Groups in Arylsulfonyl Halides

The semiempirical PM3 method is used to calculate the potential functions of internal rotation of the functional groups –SO₂Cl, –NO₂, –CH₃, –OCH₃, and –NH₂ of benzenesulfonyl halide molecules (PhSO₂Hal, Hal = F, Cl, Br, I) and twelve substituted derivatives of benzenesulfonyl chloride. Molecular conformations have been determined and internal rotation barriers of the functional groups have been calculated. For meta- and para-substituted benzenesulfonyl chlorides, the projection of the S–Hal bond is perpendicular to the plane of the benzene ring. The rotation barriers of the –SO₂Hal group of benzenesulfonyl halides increase in the series Hal = F, Cl, Br, I. The rotation barriers of the –SO₂Cl group of benzenesulfonyl chloride with meta- and para-substituents slightly increase with the electron-donor properties of the substituent. The rotation barriers of the functional groups of ortho-substituted benzenesulfonyl chlorides are 3 or 4 times as high as those of the meta- and para-isomers. For para-substituted benzenesulfonyl chlorides, the rotation barriers of the functional groups increase in the order –CH₃, –NO₂, –SO₂Cl, –OCH₃, –NH₂.     

Reactivity of functional groups toward H+ and SiMe3 + ions

No correlation was observed between the gas-phase basicities of various functional groups toward H⁺ and SiMe₃ ⁺ ions. Differences in the reactivity of functional groups studied toward SiMe₃ ⁺ ions are smaller than those in the reactivity toward protons. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 565–567, March, 2000.     

Synthesis of a Pillar[5]arene with Both Hydroxyl and Methoxycarbonyl‐Methoxy Groups and Its Host‐Guest Complexation with a Bis(imidazolium) Salt

By the introduction of methoxycarbonyl‐methoxy groups and hydroxyl groups into a pillar structure, a pillararene entirely with two types of functional groups was successfully prepared, which can form a stable 1:1 complex with a bis(imidazolium) salt in CHCl₃/acetone solution (V:V=1:1).     

Synthesis and phase‐separation behavior of α,ω‐difunctionalized diblock copolymers

A series of diblock copolymers of n‐pentyl methacrylate and methyl methacrylate (PPMA/PMMA BCP) with one or two terminal functional groups was prepared by sequential anionic polymerization of PMA and MMA using an allyl‐functionalized initiator and/or and end‐capping with allyl bromide. Allyl functional groups were successfully converted into OH groups by hydroboration. The morphology in bulk was examined by temperature‐dependent small‐angle X‐ray measurements (T‐SAXS) and transmission electron microscopy (TEM) showing that functional groups induced a weak change in d‐spacings L₀ as well as in the thermal expansion behavior. T‐SAXS proved that the lamellar morphologies were stable over multiple heating/cooling cycles without order‐disorder transition (ODT) until 300 °C. While non‐functionalized BCP formed parallel lamellae morphologies, additional OH‐termination at the PMMA block forced in very thin films (ratio between film thickness and lamellar d‐spacing below 1) the generation of perpendicular lamellae morphology through the whole film thickness, as shown by Grazing‐incidence small‐angle X‐ray scattering experiments (GISAXS) measurements. Functionalized BCP were successfully used in thin films as templates for silica nanoparticles in an in‐situ sol–gel process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Photosensitivity and photochemical reactions of poly(vinyl p-azidocinnamate)

The spectral sensitivity of poly(vinyl p-azidocinnamate)(PVACi) was discussed by comparison with poly(vinyl cinnamate)(PVCi) and poly(vinyl p-azidobenzoate). The photochemical reaction of PVACi was investigated with respect to the reactivity of two functional groups, namely, azido and cinnamoyl groups. It was found that cinnamoyl groups dimerized like PVCi and azido groups did not add to double bonds appreciably. The quantum yield of photolysis of azido groups was two times that of dimerization of cinnamoyl groups. A marked wavelength dependence of π–π^* and n–π^* absorption was observed in both the reactions of azido and cinnamoyl groups.     

Effect of solvent on the reactivity of functional groups in polycondensation reactions

The effect of solvent on solution or interfacial polycondensations was investigated in terms of selectivity and control of functional groups such as amine or hydroxyl groups toward polycondensation reactions. Solution polycondensation of a mixture of resorcinol (RL) and m-xylyenediamine (m-XD) with isophthaloyl chloride was affected by solvents to such extent as to change the course of the polycondensation reaction, and hexamethylenephosphoramide (HMPA) caused the formation of amide-rich polymer, while tetrahydrofuran (THF) was a solvent favoring formation of a polyamide ester with a regular structure. Polycondensation of 3,3′-dihydroxybenzidine (DHB) with isophthaloyl chloride yielded exclusively a linear polyamide in HMPA solution, while with aldehyde as a solvent polyester was obtained owing to the preservation of the amine group. Thus, it was found that the course of polycondensation reactions of monomers having different functional groups could be controlled by selection of a suitable solvent.