CH2OH Group Research Articles

Electrospray mass spectrometric and DFT study of substituent effects in Ag+ complexation to polycyclic aromatic hydrocarbons (PAHs)

Complexation of Ag(i) cation to a series of substituted anthracenes (AN), phenanthrenes (PH), pyrenes (PY) and cyclopenta[a]phenanthrenes (CPaPH) was studied in competitive experiments by allowing PAHs to react in pairs with AgOTf. The resulting complexes were examined by electrospray mass spectrometry (ES-MS) to determine relative abundances of the corresponding monomeric and dimeric complexes. Based on this data a sequence of complexation ability rankings was derived for each group. Among the substituents examined, a -COMe group when placed at the meso position in AN and PH, or at the C-1 in PY is most effective in Ag(+) complexation, whereas an -NO(2) group is least efficient. Methyl groups at the meso positions are better than in the terminal rings. For the CPaPH series, bay region substitution (methyl and alkoxy) have limited effect as does carbonyl substitution in the annelated CP ring. In the PY series, a -COPh or a -CH(Me)OH group at C-1 is as efficient as -COMe. Based on extensive potential energy searches, four types of complexation modes were identified by B3LYP/LANL2DZ calculations involving Ag(+) complexation to -NO(2) oxygens, to -COMe or to -OH and a peri-carbon, to just one ring carbon, or by bridging two ring carbons. Among these modes, the first two are most favorable. The energetic preferences were rationalized with charge decomposition analysis (CDA). Effect of Ag(+) complexation on relative aromaticity in various rings was examined by NICS (nucleus independent chemical shift) in two representative cases. Structures and energies of the acetyl pyrene-Ag(+)-pyrene hetero-dimer and acetyl pyrene-Ag(+)-acetyl pyrene homo-dimer complexes were determined with the same model. These complexes have sandwich structures.

Molecular dynamics of [(CH2OH)3CNH3]2SiF6 by phase transition of 178 K

We have investigated the molecular motions of TRIS+ ([(CH2OH)3CNH3]+) and SiF62− ions in the [(CH2OH)3CNH3]2SiF6 crystal below room temperature from the measurements of the spin-lattice relaxation time T1 and the NMR absorption line of 1H and 19F nuclei, in order to elucidate the changes of the molecular motions by the phase transition of Tc=178K. The narrowing of the 19F-NMR line was observed around Tc=178K and the reorientation of the SiF62− anion appears above Tc. Moreover, from the analysis of the temperature dependence of T1, we have observed that the activation energy of the reorientational motion of SiF62− ions changes from 0.168eV (T>Tc) to 0.185eV (T<Tc). Based on these results, we found that the reorientational motion of SiF62− ions is closely related to the origin of the phase transition at Tc. In addition, from the measurement of the 1H-NMR line, we also found that the reorientational motion of H2 in the –CH2OH group becomes active accompanied by the phase transition.

Energetics of galactose- and glucose-aromatic amino acid interactions: implications for binding in galactose-specific proteins.

An aromatic amino acid is present in the binding site of a number of sugar binding proteins. The interaction of the saccharide with the aromatic residue is determined by their relative position as well as orientation. The position-orientation of the saccharide relative to the aromatic residue was found to vary in different sugar-binding proteins. In the present study, interaction energies of the complexes of galactose (Gal) and of glucose (Glc) with aromatic residue analogs have been calculated by ab initio density functional (U-B3LYP/ 6-31G**) theory. The position-orientations of the saccharide with respect to the aromatic residue observed in various Gal-, Glc-, and mannose-protein complexes were chosen for the interaction energy calculations. The results of these calculations show that galactose can interact with the aromatic residue with similar interaction energies in a number of position-orientations. The interaction energy of Gal-aromatic residue analog complex in position-orientations observed for the bound saccharide in Glc/Man-protein complexes is comparable to the Glc-aromatic residue analog complex in the same position-orientation. In contrast, there is a large variation in interaction energies of complexes of Glc- and of Gal- with the aromatic residue analog in position-orientations observed in Gal-protein complexes. Furthermore, the conformation wherein the O6 atom is away from the aromatic residue is preferred for the exocyclic -CH2OH group in Gal-aromatic residue analog complexes. The implications of these results for saccharide binding in Gal-specific proteins and the possible role of the aromatic amino acid to ensure proper positioning and orientation of galactose in the binding site have been discussed.

Intramolecular Hydrogen Bonding and Double H-Atom Transfer in Peroxy and Alkoxy Radicals from Isoprene

Quantum mechanical calculations were used to determine the structure and stability of second-generation peroxy and alkoxy radicals formed in the atmospheric degradation of isoprene (2-methyl-1,3-butadiene). Certain of these radicals exhibit a novel hydrogen bonding motif, consisting of two intramolecular hydrogen bonds. The hydrogen bonds are donated in series, with an enol group donating a hydrogen bond to a −CH2OH group, which donates in turn to the oxygen radical center. This hydrogen bonding motif opens a new reaction pathway: the simultaneous transfer of two H-atoms across the hydrogen bonds with a barrier of only ∼5 kcal/mol in the alkoxy radicals, but ∼20 kcal/mol in the peroxy radicals. Rate constants for these reactions were calculated, and the effects of tunneling on the rate constant were examined. All species and reactions were analyzed at the B3LYP/6-311G(2df,2p) level of theory; the transition states for the double H-atom transfer reactions were also studied using the MPW1K functional and t...

Telechelic and star-shaped poly(L-lactide)s by means of bismuth(III) acetate as initiator.

L-lactide was polymerized as concentrated solution in chlorobenzene with Bi(OAc)3 as initiator. When tetra(ethylene glycol) was added as co-initiator (CoI), telechelic polylactides having two CH-OH end groups were obtained. With 1,1,1-tri(hydroxy methyl)propane (THMP) as co-initiator, three-armed stars having three CH-OH end groups were formed. Analogously, tetrafunctional star-shaped poly(L-lactide)s were obtained with pentaerythritol as co-initiator. The chain lengths were varied via the monomer/CoI ratio. Time-conversion curves proved that Bi(OAc)3 is slightly less reactive as initiator than tin(II) 2-ethylhexanoate. However, bismuth acetate (or other carboxylates) have a particularly low toxicity as documented in the literature and by numerous Bi3+-containing pharmaceutical products.

Studies on pyrrolidinones: a reaction of methylene dichloride under Friedel–Crafts conditions. Synthesis of an α-hydroxymethyl ketone in the hexahydrobenzo[ f]indolizine series

When carried out in methylene dichloride, the Friedel–Crafts cyclization of N-arylmethyl pyroglutamates can lead to addition of a CH 2OH group in the position α to the newly formed ketone function.

19F-NMR Study in Phase Transition of [(CH2OH)3CNH3]2SiF6

Measurements of 19F and 1H-NMR absorption lines have been carried out in [(CH2OH)3CNH3]2SiF6 below room temperature. It was found that the 19F-NMR absorption line width becomes narrow with the increase of temperature above around 100 K and becomes almost constant above Tc= 178 K. This result indicates that motional narrowing of 19F-NMR line accompanied by the phase transition at 178 K is observed. It is deduced from this narrowing that the SiF6 2− anions are reoriented with the correlation time which is fast enough to narrow the 19F-NMR absorption line above Tc. Moreover, we have observed the drastic change of 1H-NMR absorption line above Tc. This result indicates that the ─CH2OH groups begin to reorient by the phase transition at Tc. It is deduced from these results that the motions of SiF6 2− anions and ─CH2OH groups play an important role in the phase transition at 178 K.

Molecular dynamics in solid pyridoxine as studied by 1H NMR

Spin–lattice relaxation times T 1 and T 1d as well as NMR second moment were employed to study molecular dynamics of pyridoxine (vitamin B 6) in the temperature range 10–350 K. The T 1 minimum observed at low temperatures at 200 MHz is attributed to a motion of methyl group. The motion is interpreted in terms of Haupt's theory, which takes into account the tunneling assisted relaxation. At low temperatures, where T 1 is temperature independent, occupation of the ground state only is assumed. A motion of proton of the hydroxyl groups or CH 2OH groups probably provides additional mechanism of relaxation, in the high-temperature region.

The electronic states of 2-furanmethanol (furfuryl alcohol) studied by photon absorption and electron impact spectroscopies

The photoelectron spectrum of 2-furanmethanol (furfuryl alcohol) has been measured for ionization energies between 8 and 11.2 eV and the first three ionization bands assigned to π3, π2, and no ionizations in order of increasing binding energy. The photoabsorption spectrum has been recorded in the gas phase using both a synchrotron radiation source (5–9.91 eV, 248–125 nm) and electron energy-loss spectroscopy under electric-dipole conditions (5–10.9 eV, 248–90 nm). The (UV) absorption spectrum has also been recorded in solution (4.2–6.36 eV, 292–195 nm). The electronic excitation spectrum appears to be dominated by transitions between π and π* orbitals in the aromatic ring, leading to the conclusion that the frontier molecular orbitals of furan are affected only slightly on replacement of a H atom by the –CH2OH group. Additional experiments investigating electron impact at near-threshold energies have revealed two low-lying triplet states and at least one electron/molecule shape resonance. Dissociative electron attachment also shows to be widespread in furfuryl alcohol.

5‐Methyl‐6‐aza‐2′‐deoxyisocytidine.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Evaporation Rate Measurement of Water and Liquid 1-Alkanols across Air–Liquid Interface Using Thermogravimetry

Abstract Evaporation rate measurements of water across air/water interface were made by using a thermogravimetry technique. A sample liquid was held in a partially filled, open-topped pan in a furnace tube, through which dry air was flowing. The effect of the flow rate of the dry air on the evaporation rate was very large at lower flow rates, while it became smaller at higher flow rates. The evaporation rate of water over the temperature range 298.2–333.2 K was studied in order to obtain the activation energy for the evaporation. The energy was found to decrease with increasing temperature. A newly developed equation was used to analyze the evaporation rate. Purified liquid 1-alkanols (carbon number = 4, 6, 8, 10, and 12) were employed as test substances in order to estimate the effects of terminal –CH2OH group and of residual CH2 groups on the activation energy. The contribution of –CH2OH group to the activation energy was found to slightly decrease with increasing temperature, while the contribution of residual CH2 group increased with increasing chain length; the temperature-dependence remained almost the same irrespective of the alkyl chain.

Solid-state 13C and 1H spin diffusion NMR analyses of the microfibril structure for bacterial cellulose

To obtain further information about the cause for the rather large splitting of the C4 resonance line into the downfield (C4D) and upfield (C4U) lines in CP/MAS 13C NMR spectra for native cellulose, 13C and 1H spin diffusion measurements have been conducted by using different types of bacterial cellulose samples. In 13C spin diffusion measurements, the C4D resonance line is selectively inverted by the Dante π pulse sequence and the 13C spin diffusion is allowed to proceed from the C4D carbons to other carbons including the C4U carbons with use of the 13C4-enriched bacterial cellulose sample. The analysis based on the simple spin diffusion theory for the process experimentally observed reveals that the C4U carbons may be located at distances less than about 1 nm from the C4D carbons. In 1H spin diffusion measurements, poly(vinyl alcohol) (PVA) films in which ribbon assemblies of bacterial cellulose are dispersed are employed and the 1H spin diffusion process is examined from the water-swollen PVA continuous phase to the dispersed ribbon assemblies by the 13C detection through the 1H– 13C CP technique. As a result, it is found that the C4D and C4U carbons are almost equally subjected to the 1H spin diffusion from the PVA phase, indicating that the C4U carbons are not localized in some limited area, e.g. in the surfacial region, but are distributed in the whole area in the microfibrils. These experimental results suggest that the C4U carbons may exist as structural defects probably due to conformational irregularity associated with disordered hydrogen bonding of the CH 2OH groups in the microfibrils.

Enantioselective hydrogenation of aromatic ketones: structural effects

Enantioselective hydrogenation of acetophenone derivatives demonstrates the potential of the Pt–cinchona system in the synthesis of chiral alcohols that possess no functional group in the α-position to the CHOH group. Electron-withdrawing functional groups in the aromatic ring increased the reaction rate and enantiomeric excess (ee), and the position of the group ( o-, m-, or p-) was also important. 60% ee was obtained in the hydrogenation of 3,5-di(trifluoromethyl)acetophenone under ambient conditions, though the special role of reaction parameters has not been investigated yet. Addition of cinchonidine slowed down all hydrogenation reactions—an unprecedented behaviour for chirally modified Pt.

5-Methyl-6-aza-2′-deoxyisocytidine

In the title compound, 3-amino-2-(2-deoxy-beta-D-erythro-pentofuranosyl)-6-methyl-1,2,4-triazin-5(2H)-one, C(9)H(14)N(4)O(4), the conformation of the N-glycosidic bond is high-anti and the 2-deoxyribofuranosyl moiety adopts a North sugar pucker ((2)T(3)). The orientation of the exocyclic C-C bond between the -CH(2)OH group and the five-membered ring is ap (gauche, trans). The crystal packing is such that the nucleobases lie parallel to the ac plane; the planes are connected via hydrogen bonds involving the five-membered ring.

Crystal Structure Refinements of Cellulose Polymorphs using Solid State 13 C Chemical Shifts

Force field methods in combination with chemical shift target functions are used to investigate the structures of cellulose I and II. Since diffraction investigations of biopolymers like cellulose II are only of poor resolution, different models for the structure are discussed in the literature. These models were used as the starting point for force field optimizations with 13C chemical shift target functions. In these optimizations additionally to the total energy a pseudo-energy is minimized that depends harmonically on the difference between calculated and observed chemical shifts. In the case of cellulose II all four criteria: (i) total energy, (ii) pseudo-energy, (iii) chemical shift rms (root mean square) difference, and (iv) deviation from the diffraction data favour the structure model of Kolpak and Blackwell with two antiparallel carbohydrate chains. The CH2–OH group of one chain is in tg and that of the other chain in gt conformation. The chemical shift optimized fractional coordinates for cellulose II, Iα and Iβ are presented together with the calculated and experimental 13C chemical shifts.

Dimethylmorpholinium Chloride Analogs and Their Effect on Plants

Relations between the chemical structure of new analogs of dimethylmorpholinium chloride (DMC) and their growth retardant activity were investigated. Some of these substances exerted a specific impact on the growth of individual organs in monocot (Triticum aestivum L., Hordeum vulgare ssp. distichon (L.) Koern.) and dicot (Phaseolus vulgaris L., Brassica napus L.) plants. Within the group of bis-quaternary ammonium salts, the derivatives of N-methylmorpholinium (1-DMC) and N-benzylmorpholinium (3-DMC) manifested high retardant activity on growth of barley and wheat plants. The molecules of these compounds comprise the chain of two methylene groups bridging the nitrogen atoms. An N-acetylmorpholinium derivative 17-DMC, with nitrogen atoms in morpholinium rings linked by two methylene groups with a CHOH group between them, produced a physiological effect on rape and kidney bean plants.

Antitumor AHMA linked to DNA minor groove binding agents: synthesis and biological evaluation.

DNA minor groove binder hybrid molecules, netropsin derivatives such as N-[2-(dimethylamino)ethyl]-1-methyl-4-aminopyrrolo-2-carboxamide (MePy) or its derivatives containing two units of N-methylpyrrolecarboxamide (diMePy) and bisbenzimidazole (Ho33258), were linked to the NH(2) function of AHMA or to the CH(2)OH group of AHMA-ethylcarbamate to form AHMA-N-netropsins (13-16) and AHMA-ethylcarbamate-O-netropsins (19-22), and AHMA-bisbenzimidazole (AHMA-Ho33258, 25), respectively. These conjugates' in vitro antitumor activity, inhibition of a variety of human tumor cell growth, revealed that AHMA-ethylcarbamate-O-netropsin derivatives were more cytotoxic than AHMA-N-netropsin compounds. In the same studies, all compounds bearing MePy were more potent than those compounds linked with diMePy. Moreover, AHMA-netropsin derivatives bearing a succinyl chain as the linking spacer were more potent than those compounds having a glutaryl bridge. Among these hybrid molecules, AHMA-ethylcarbamate-O-succinyl-MePy (19) was 2- to 6-fold more cytotoxic than the parent compound AHMA (5) in various cell lines, whereas compound 25 had very poor solubility and was inactive. Studies on the inhibitory effect against topoisomerase II (Topo II) and DNA interaction of these conjugates showed no correlation between the potency of DNA binding and inhibitory activity against Topo II.

Trans hexaco-ordinate complexes of copper(II) and nickel(II) with 4(5)-hydroxymethyl-5(4)-methylimidazole—crystal structure and physico-chemical properties

Trans complexes of Cu(II) and Ni(II) with 4-hydroxymethyl-5-methylimidazole (L), of the general formula [ML 4](NO 3) 2 have been obtained. The complexes were characterized by single X-ray diffraction, elemental analysis, EPR spectroscopy, IR, FIR and Vis–NIR spectra. In these co-ordination compounds, the azole ligand has a dual nature. Two of these molecules are monodentate, co-ordinated through the ‘3’ ‘pyridynic’ nitrogen atom of the imidazole ring, while the remaining two are bidentate ligands, the oxygen atom of the CH 2OH group being another electron donor (giving CuN 4O 2 and NiN 4O 2 chromophores). The structure of both chromophores is described by a slightly distorted tetragonal bipyramid. The stability constants and structures of the Cu(II) and Ni(II) complexes with the studied ligand (4-CH 2OH5-CH 3im) in aqueous solution have been determined by potentiometric and spectrophotometric methods. The stability of the transition metal complexes of 4-CH 2OH5-CH 3im depends on the presence of the hydroxymethyl group, the oxygen atom of which interacts with the metal-ion.

2H NMR Study on Phase Transitions and Crystal Dynamics of p-Chloro- and p-Bromobenzyl Alcohols

Two phase transitions of 4-chlorobenzyl alcohol (pCBA) and 4-bromobenzyl alcohol (pBBA), from the low-temperature phase (LTP) to the intermediate-temperature phase (ITP) and from ITP to the room-temperature phase (RTP), were investigated by 2H NMR and differential scanning calorimetry (DSC). The crystal dynamics in each phase were studied using the 2H NMR spectra, the spin-lattice relaxation time (T1) and the relaxation time of quadrupole order (T1Q) for the samples, where the hydrogen of the -OH group was selectively deutrated. The 2H NMR 1 of both crystals in the RTP were dominated by the fluctuation of the electric field gradient at 2H nucleus caused by vibrational motions of the -CH2OH group. In the LTP of both crystals, the fast jump of hydrogen atoms between the two sites corresponding approximately to the positions of the hydroxyl hydrogen atoms in the RTP and LTP were found from 2H NMR spectra. The results of T1 and T1Q in the LTP revealed that the jump of hydrogen atoms occurs in asymmetric potential wells and that these potential wells gradually approach symmetric ones with increasing temperature on the high-temperature side in the LTP

The influence of charges and hydrogen bond on the conformation of zwitterionic 3-(2-hydroxyalkyl-pyridinium)-propionates and their hydrobromides

The effects of intra- and intermolecular electrostatic interactions and hydrogen bonding on the conformation of 3-(2-hydroxymethyl-pyridinium)-propionic acid bromide (1) and 3-(2-hydroxyethyl-pyridinium)-propionic acid bromide (2) have been studied. In 1, the molecules are linked by Br− ion to form two intermolecular hydrogen bonds COOH⋯Br⋯HOCH2 (O(1)⋯Br=3.175(3) and O(3)⋯Br=3.305(3)Å) yielding chains. The molecules of 2 form centrosymmetric dimers connected by a pair of H-bonds between COOH and CH2OH groups (O(1)⋯O(3)=2.674(3)Å), and the H-bonded CH2OH group further interacts with the Br− ion (O(3)⋯Br=3.166(5)Å). In both the compounds, the Br− ion additionally interacts electrostatically with the positively charged nitrogen atom. To analyse these interactions theoretically, the structures of 3-(2-hydroxy-alkyl)pyridinium propionates (betaines) and their hydrogen bromides as monomers and dimers in various configurations are analysed by PM3 and B3LYP/6-31G(d,p) calculations. Although both electrostatic interactions and H-bonds strongly affect the conformation of the investigated compounds, the former effect seems to be dominant. FTIR spectra of 1 and 2 in the solid state are analysed.