The interaction between TEOS and some polyols

Hybrid organic-inorganic materials, silica – polyols (ethylene-glycol – EG; 1,2 propane diol – 1,2PG; 1,3 propane diol – 1,3PG and glycerol – GL), were prepared by a sol-gel process starting from tetraethylorthosilicate (TEOS) and polyols, in acid catalysis. The resulting materials were studied by thermal analysis (in air and nitrogen), FTIR and solid state ²⁹Si-NMR spectroscopy. These techniques evidenced the presence of polyols in the silica matrix both hydrogen bounded and chemically bounded in the silica network. The thermal analysis proves to be the most appropriate technique to evidence the organic chains linked in the matrix network and to follow the thermal evolution of the gels to the SiO₂ matrix.     

Thermal decomposition of some metal-organic precursors

In this paper we present a study on the synthesis of Fe(III) oxide, by thermal decomposition of some complex combinations of Fe(III) with carboxylate type ligands, obtained in the redox reaction between some polyols (ethylene glycol (EG), 1,2-propane diol (1,2PG), 1,3-propane diol (1,3PG) and glycerol (GL)) and NO₃ ^– ions (from ferric nitrate). Fe₂O₃ was obtained by thermal decomposition of the synthesized metal-organic precursors at low temperatures. γ-Fe₂O₃ was obtained as nanoparticles at 300°C, while at higher temperatures α-Fe₂O₃ starts to crystallize and becomes single phase at ~500°C. The formation of the metal-organic precursors and their thermal decomposition were studied by thermal analysis and FTIR spectroscopy.     

Volumetric,Viscometric, and Refractive Index Behaviour of Glycine in Aqueous Diols at Different Temperatures

Densities, ρ, viscosities, η, and refractive indices, n_D, of glycine (Gly) (0.1 — 0.5 M) in aqueous 1,2‐ethanediol (1,2‐EtD), 1,2‐propanediol (1,2‐PrD), and 1,3‐butanediol (1,3‐BuD) (30% v/v) were measured at 298, 303, 308, and 313 K. Experimental values of ρ and η were used to calculate partial molar volumes, ?⁰_v, partial molar volumes of transfer of Gly from water to aqueous diol solutions, ?⁰_v(tr), Falkenhagen and Jones ‐Dole coefficients, A and B, respectively, free energies of activation of viscous flow, Δμ⁰*₁ and Δμ⁰*₂, per mole of solvent and solute, respectively, enthalpies, ΔH* and entropies, ΔS* of activation of viscous flow. Large positive values of ?⁰_v, and an increasing value of S_v*, for all the three mixtures at each temperature suggest the presence of strong solute‐solvent interaction, and this interaction decreases as the size of alkyl moiety increases from 1,2‐EtD to 1,3‐BuD. Positive ?⁰_v(tr) values tend to decrease with increasing the number of CH₂ group, thereby indicating that the electrostriction effect in diols follows the sequence; 1,2‐EtD > 1,2‐PrD > 1,3‐BuD. Small A values, with large values of B, are indicative of weak solute‐solute and strong solute‐solvent interactions that operate in the present systems, and that the magnitudes of B are in the sequence: 1,2‐EtD > 1,2‐PrD > 1,3‐BuD and, thus, the sequence represents the strength of interaction between Gly and diol molecules. Moreover, positive SB/ST values suggest the structure‐breaking nature of Gly in diol + water mixtures. The observed values of Δμ⁰*₂ fall in the sequence: 1,2‐EtD > 1,2‐PrD > 1,3‐BuD which, like ?⁰_v and S_v*, reinforce that Gly‐diol interaction decreases with subsequent addition of CH₂ group in diols. The trends in the variation of ΔH* and ΔS* with Gly concentration also reveal the presence of significant solute‐solvent interaction in all three systems. An almost linear increase in RD with an increasing amount of Gly reveals that Gly tends to increase the polarizability of the aqueous‐diol molecules under study. The variation of all these parameters with concentration of Gly and with temperature suggests the presence of strong solute‐solvent interaction, which decreases as the size of alkyl moiety in diols increases from 1,2‐EtD to 1,3‐BuD.     

Novel and Stereospecific Synthesis of (2S)‐3‐(2,4,5‐Trifluorophenyl)propane‐1,2‐diol from D‐Mannitol

A stereospecific synthesis of (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol from D ‐mannitol has been developed. The reaction of 2,3‐O‐isopropylidene‐D ‐glyceraldehyde with 2,4,5‐trifluorophenylmagnesium bromide gave [(4R)‐2,2‐dimethyl‐1,3‐dioxolan‐4‐yl](2,4,5‐trifluorophenyl)methanol in 65% yield as a mixture of diastereoisomers (1 : 1). The Ph₃P catalyzed reaction of the latter with C₂Cl₆ followed by reduction with Pd/C‐catalyzed hydrogenation gave (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol with >99% ee and 65% yield.     

2,3‐Diaryl‐3‐hydroxy­propionic acid inter­mediates in the synthesis of threo forms of 1,2‐diaryl‐1,3‐propane­diols

Racemic threo‐3‐hydroxy‐2,3‐diphenyl­propionic acid, C₁₅H₁₄O₃, (I), crystallizes from ethyl acetate as a conglomerate of separate (+)‐ and (−)‐crystals. The geometries of (I) and its methyl ester are compared. Reduction of (I) gives threo‐1,2‐diphenyl‐1,3‐propane­diol. The synthesis of threo forms of 1,2‐diaryl‐1,3‐propane­diols via 2,3‐diaryl‐3‐hydroxy­propionic acids is discussed.     

Stereoisomers of 1,2‐diaryl‐1,3‐propanediols: erythro forms

Racemic erythro‐1,2‐diphenyl‐1,3‐propane­diol, C₁₅H₁₆O₂, is a model compound representative of erythro forms of structural elements of the 1,2‐diaryl‐1,3‐propane­diol type in lignins. In the crystal structure, the torsion angle between the bulky phenyl groups is −62.26 (11)°. Strong hydrogen bonds take part in a directed co‐operative O—H⋯O—H⋯O—H⋯O—H pattern that is assumed to have a decisive influence on the conformation. This is supported by comparisons with the geometries of related compounds.     

Synthesis and Structure of Novel Double Flexible Spacer Bridged Biscalix[4]arenes

25, 25′, 27, 27′‐Bis(1,3‐dioxypropane)‐bis(5, 11, 17, 23‐tetra‐tert‐butylcalix[4]arene‐26,28‐diol) (4) and 25, 25′, 27, 27′‐bis(1, 4‐dioxybutane)‐bis (5, 11, 17, 23‐tetra‐tert‐butylcalix‐[4]arene‐26, 28‐diol) (5) were synthesized by the reaction of p‐tert‐butylcalix[4]arene (1) with preorganized 25, 27‐bis(3‐bromoproxyl)calix[4]arene‐26, 27‐diol (2) and 25, 27‐bis(3‐bromobutoxyl)calix[4]arene‐26, 27‐diol (3) in the presence of K₂CO₃ and KI. Compounds 4 and 5 were characterized with X‐ray analysis and the selectivity of 4 and 5 toward K⁺ over other alkali metal ions, alkaline metal ions as well as NH₄⁺ were investigated with an ion‐selective electrode.     

A supramolecular ladder motif in 2‐(2,2,6,6‐tetra­methyl­piperidin‐1‐yl­oxy)­propane‐1,3‐diol

An O—H⋯O hydrogen‐bonded step‐ladder motif was observed in the crystal structure of the title compound, C₁₂H₂₅NO₃. The ladder arrangement is typical of 1,2‐ and 1,3‐diols with a synclinal orientation of the diol functionality.     

Kinetics of the reaction of O3 with selected benzenediols

The kinetics of the reaction of O₃ with the aromatic vicinal diols 1,2‐benzenediol, 3‐methyl‐1,2‐benzenediol, and 4‐methyl‐1,2‐benzenediol have been investigated using a relative rate technique. The rate coefficients were determined in a 1080‐L smog chamber at 298 K and 1 atm total pressure of synthetic air using propene and 1,3‐butadiene as reference compounds. The following O₃ reaction rate coefficients (in units of cm³ molecule^?1 s^?1) have been obtained: k(1,2‐benzenediol) = (9.60 ± 1.12) × 10^?18, k(3‐methyl‐1,2‐benzenediol) = (2.81 ± 0.23) × 10^?17, k(4‐methyl‐1,2‐benzenediol) = (2.63 ± 0.34) × 10^?17. Absolute measurements of the O₃ rate coefficient have also been carried out by measuring the decay of the dihydroxy compound in an excess of O₃. The results from these experiments are in good agreement with the relative determinations. Atmospheric implications are discussed. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 223–230, 2003     

1H NMR spectra of alkane‐1,3‐diols in benzene: GIAO/DFT shift calculations

The proton nuclear magnetic resonance (NMR) spectra of propane‐1,3‐diol, 2‐methylpropane‐1,3‐diol, 2,2‐dimethylpropane‐1,3‐diol, butane‐1,3‐diol, 3‐methylbutane‐1,3‐diol, pentane‐2,4‐diols (dl and meso), 2‐methylpentane‐2,4‐diol and cyclohexane‐1,3‐diols (cis and trans) in benzene have been analysed. The conformer distribution and the NMR shifts of these diols have been computed on the basis of density functional theory, the solvent being included by means of the integral equation formalism phase continuum model (IEFPCM) implemented in Gaussian 09. Relative Gibbs energies of all conformers are calculated at the Perdew, Burke and Ernzerhof (PBE)0/6‐311 + G(d,p) level, and NMR shifts by the gauge‐including atomic orbital method with the PBE0/6‐311 + G(d,p) geometry and the cc‐pVTZ basis set. Vicinal coupling constants for 1,2‐ and 1,3‐diols are rationalised in terms of relative conformer populations and geometries. The NMR shifts of hydrogen‐bonded protons in individual conformers of alkane‐1,n‐diols show a very rough correlation with the OH?OH distances. The computed overall NMR shifts for CH protons in 1,2‐ and 1,3‐diols are systematically high but correlate very well with the experimental values, with a gradient of 1.07 ± 0.01. Some values for nonequivalent methylene protons in 1,3‐diols are reversed, calculation giving enhanced values for the proton anti to the C? OH bonds. Errors in the NMR shifts computed for the OH protons of nonsymmetrical diols appear to be related to relative populations of conformers where one or other of the OH groups is the donor. Some results based on the second‐order Møller–Plesset approach, the Becke three‐parameter Lee‐Yang‐Parr method and on the IEFPCM solvation model implemented in Gaussian 03 are included. Copyright © 2013 John Wiley & Sons, Ltd.     

The mixed diol–dithiol 2,2‐bis(sulfanylmethyl)propane‐1,3‐diol: characterization of key intermediates on a new synthetic pathway

A new synthetic route to 2,2‐bis(sulfanylmethyl)propane‐1,3‐diol, (II), is described starting from the commercially available 2,2‐bis(hydroxymethyl)propane‐1,3‐diol. The structures of two intermediates on this route are described. 5,5‐Dimethenyl‐2,2‐dimethyl‐1,3‐dioxane bis(thiocyanate) (systematic name: {[5‐(cyanosulfanyl)‐2,2‐dimethyl‐1,3‐dioxan‐5‐yl]sulfanyl}formonitrile), C₁₀H₁₄N₂O₂S₂, (X), crystallizes in the space group P2₁/c with no symmetry relationship between the two thiocyanate groups. There is a short intramolecular N...S contact for one thiocyanate group, while the second group is positioned such that this type of interaction is not possible. 1,3‐(Hydroxymethyl)propane‐1,3‐diyl bis(thiocyanate), C₇H₁₀N₂O₂S₂, (XI), also features a single short N...S contact in the solid state. Hydrogen bonding between two molecules of compound (XI) results in the formation of dimers in the crystal, which are then linked together by a second hydrogen‐bond interaction between the dimers. In addition, the structures of two intermediates from an unsuccessful alternative synthesis of (II) are reported. 2,2‐Bis(chloromethyl)propane‐1,3‐diol, C₅H₁₀Cl₂O₂, (VI), crystallized as an inversion twin with a minor twin fraction of 0.43 (6). It forms a zigzag structure as a result of intermolecular hydrogen bonding. The structure of 9,9‐dimethyl‐2,4,8,10‐tetraoxa‐3λ⁴‐thiaspiro[5.5]undecan‐3‐one, C₈H₁₄O₅S, (VII), shows evidence for a weak S...O contact with a distance of 3.2529 (11) Å.     

One‐Pot,Pseudo‐Five‐Component Synthesis of Bis[2‐(arylimino)‐1,3‐thiazolidin‐4‐ones]

Synthesis and characterization of bis[2‐(arylimino)‐1,3‐thiazolidin‐4‐ones] are described. The one‐pot, pseudo‐five‐component reaction of an aliphatic diamine, isothiocyanatobenzene, and dialkyl but‐2‐ynedioate at room temperature in anhydrous CH₂Cl₂ gives the title compound in relatively high yield. Under the same conditions, aromatic 1,2‐diamines yield 2‐(arylimino)‐N‐(enaminoaryl)‐1,3‐thiazolidin‐4‐ones in a pseudo‐four‐component reaction. Their structures were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of cyclization is proposed (Scheme 3).     

Rate coefficients for the gas‐phase reaction of OH radicals with selected dihydroxybenzenes and benzoquinones

Rate coefficients have been determined for the gas‐phase reaction of the hydroxyl (OH) radical with the aromatic dihydroxy compounds 1,2‐dihydroxybenzene, 1,2‐dihydroxy‐3‐methylbenzene and 1,2‐dihydroxy‐4‐methylbenzene as well as the two benzoquinone derivatives 1,4‐benzoquinone and methyl‐1,4‐benzoquinone. The measurements were performed in a large‐volume photoreactor at (300 ± 5) K in 760 Torr of synthetic air using the relative kinetic technique. The rate coefficients obtained using isoprene, 1,3‐butadiene, and E‐2‐butene as reference hydrocarbons are k_OH(1,2‐dihydroxybenzene) = (1.04 ± 0.21) × 10⁻¹⁰ cm³ s⁻¹, k_OH(1,2‐dihydroxy‐3‐methylbenzene) = (2.05 ± 0.43) × 10⁻¹⁰ cm³ s⁻¹, k_OH(1,2‐dihydroxy‐4‐methylbenzene) = (1.56 ± 0.33) × 10⁻¹⁰ cm³ s⁻¹, k_OH(1,4‐benzoquinone) = (4.6 ± 0.9) × 10⁻¹² cm³ s⁻¹, k_OH(methyl‐1,4‐benzoquinone) = (2.35 ± 0.47) × 10⁻¹¹ cm³ s⁻¹. This study represents the first determination of OH radical reaction‐rate coefficients for these compounds. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 696–702, 2000     

trans‐Selective Insertional Dihydroboration of a cis‐Diborene: Synthesis of Linear sp3‐sp2‐sp3‐Triboranes and Subsequent Cationization

The reaction of aryl‐ and amino(dihydro)boranes with dibora[2]ferrocenophane 1 leads to the formation 1,3‐trans‐dihydrotriboranes by formal hydrogenation and insertion of a borylene unit into the B=B bond. The aryltriborane derivatives undergo reversible photoisomerization to the cis‐1,2‐μ‐H‐3‐hydrotriboranes, while hydride abstraction affords cationic triboranes, which represent the first doubly base‐stabilized B₃H₄⁺ analogues.     

HET acid based oligoesters - TGA/FTIR studies

One of the important reactive halogenated dicarboxylic acids used in the synthesis of flame retardant unsaturated polyester resins is 1,4,5,6,7,7-hexachlorobicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic acid (HET acid). In the present investigation four different oligoesters are synthesized using HET acid as the diacid component and 1,2-ethane diol, 1,2-propane diol, 1,3-propane diol and 1,4-butane diol as the aliphatic diols. Melt condensation technique in vacuum is used for the synthesis of the oligoesters. The number average molecular weights of the oligoesters are determined using end group analysis. The degree of polymerization is estimated to be 3-5. The structural characterization is done using FTIR and NMR (¹H and ¹³C) techniques. In the present investigation, TGA-FTIR studies for the different oligoesters are carried out in nitrogen atmosphere. The materials are heated from ambient to 600 °C at a heating rate of 20 °C/min. The main volatile products identified are CO, HCl, H₂O, CO₂, hexachlorocyclopentadiene and HET acid/anhydride. The evolution profile of these materials with respect to the structure of the oligoesters is discussed in detail and presented. The importance of β-hydrogens in the diol component and the plausible mechanism for the flame retardant behavior of these oligoesters are presented.     

Novel Reactions for the Simple and Sensitive Spectrophotometric Determination of Traces of Selenium in Environmental Samples

Two rapid, highly sensitive, and selective spectrophotometric methods for the determination of traces of selenium(IV) were studied. The methods are based on either the oxidation of 4‐aminoantipyrine (=4‐amino‐1,2‐dihydro‐1,5‐dimethyl‐2‐phenyl‐3H‐pyrazol‐3‐one; 4‐AAP; 1 ) by selenium in basic medium and coupling with N‐(naphthalen‐1‐yl)ethane‐1,2‐diamine dihydrochloride (NEDA; 2 ?2 HCl) to give a violet derivative 3 or on the oxidation of dopamine hydrochloride (=4‐(2‐aminoethyl)benzene‐1,2‐diol hydrochloride; DPH; 4 ?HCl) by selenium in H₂SO₄ medium and coupling with 1 to yield a red derivative 5 (see Scheme). The violet derivative 3 with λ_max 563 nm is stable for 8 days and the red derivative 5 with λ _max 495 nm for more than a week. Beer's law is obeyed for selenium in the concentration range 0.03–3.5 μg ml^?1 (violet derivative 3 ) and 0.07–2.5 μg ml^?1 (red derivative 5 ), respectively. The optimum reaction conditions and other important analytical parameters were established. Interference due to various non‐target ions were also investigated. The proposed methods, were applied to the analysis of selenium in polluted water, natural water, plant material, soil samples and synthetic mixtures. The results of the analyses were superior in precision to those obtained by reported methods.     

Multicyclic polyethers by the polycondensation of 1,2‐ or 1,3‐dicyanotetrafluorobenzene with flexible diphenols

1,2‐Dicyanotetrafluorobenzene (1,2‐DCTB) was polycondensed with various flexible diphenols in a molar ratio of 1:2, and experimental parameters such as the concentration and temperature were varied. Certain diphenols allowed a complete substitution of all C? F bonds, so perfect multicyclic polyethers (B_nCN, where B stands for bridge units, C represents cycles, and N is the degree of polymerization) were the main reaction products. Despite complete conversion, gelation was avoidable under optimized reaction conditions. However, in the case of 1,3‐dicyanotetrafluorobenzene (1,3‐DCTB), complete tetrasubstitution was not feasible with a feed ratio of 1:2. Yet, because of the inductive and mesomeric electronic interactions of all substituents in 1,3‐DCTB, the three C? F groups in the ortho position with respect to the cyano groups were significantly more reactive than the fourth C? F bond. Therefore, polycondensations with diphenols in a 3:2 feed ratio showed a relatively clean course, yielding soluble multicycles of structure B_{n /2}CN. All the multicyclic polyethers were amorphous and possessed molar mass distributions with polydispersities greater than 2. Heating with Cu²⁺ salts caused crosslinking of the multicycles derived from 1,2‐DCTB because of the formation of phthalocyanine complexes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5546–5556, 2006     

The synthesis and cytotoxic evaluation of a series of benzodioxole substituted titanocenes

Using 6‐benzo[1,3]dioxolefulvene ( 1a ), a series of benzodioxole substituted titanocenes was synthesized. The benzyl‐substituted titanocene bis[(benzo[1,3]dioxole)‐5‐methylcyclopentadienyl] titanium (IV) dichloride ( 2a ) was synthesized from the reaction of Super Hydride with 1a . An X‐ray determined crystal structure was obtained for 2a . The ansa‐titanocene {1,2‐di(cyclopentadienyl)‐1,2‐di‐(benzo[1,3]dioxole)‐ethanediyl} titanium(IV) dichloride ( 2b ) was synthesized by reductive dimerisation of 1a with titanium dichloride. The diarylmethyl substituted titanocene bis(di‐(benzo[1,3]dioxole)‐5‐methylcyclopentadienyl) titanium(IV) dichloride ( 2c ) was synthesized by reacting 1a with the para‐lithiated benzodioxole followed by transmetallation with titanium tetrachloride. When titanocenes 2a–c were tested against pig kidney (LLC‐PK) cells inhibitory concentrations (IC₅₀) of 2.8 × 10^?4, 1.6 × 10^?4 and 7.6 × 10^?5 M , respectively, were observed. These values represent improved cytotoxicity against LLC‐PK, when compared with unsubstituted titanocene dichloride, but are not as impressive as values obtained for titanocenes previously synthesized using the above methods. Copyright © 2006 John Wiley & Sons, Ltd.     

An Iron(III) Catalyst with Unusually Broad Substrate Scope in Regioselective Alkylation of Diols and Polyols

In this study, [Fe(dibm)₃] (dibm=diisobutyrylmethane) is shown to have unusually broad scope as a catalyst for the selective monoalkylation of a diverse set of 1,2‐ and 1,3‐diol‐containing structures. The mechanism is proposed to proceed via a cyclic dioxolane‐type intermediate, formed between the iron(III) species and two adjacent hydroxyl groups. This approach represents the first transition‐metal catalysts that are able to replace stoichiometric amounts of organotin reagents in regioselective alkylation. The reactions generally lead to very high regioselectivities and high yields, on par with, or better than, previous methods used for regioselective alkylation.     

Spectroscopic analysis of imidazolidines. Part II: 1H NMR spectroscopy and conformational analysis of 1,2 and 1,3‐diarylimidazolidines

¹H NMR spectra of a series of 1,2 and 1,3‐diarylimidazolidines are analyzed and correlated with their conformational features. Results were interpreted on the basis of chemical shifts and coupling constants of hydrogen atoms and confirmed by ID nOe difference experiments. 1,3‐Diarylimidazolidines ( 1–7 ) show a fast inversion of the N‐aryl nitrogen in all studied cases. 1,2‐Diaryl‐3‐methyl (or benzyl) imidazolidines ( 8–13 ) display a preferential conformation with a transoid orientation of N₃ and C₂ substituents.