Investigation and radiometric determination of saturated and unsaturated aliphatic dicarboxylic acids

Radiometric determination of saturated and unsaturated aliphatic dicarboxylic acids has been developed using a precipitation reaction. The influence of the conditions of precipitation, the composition of the calcium salts of the acids, thepH, and the composition of solvent mixtures were investigated. The solubility of the calcium salts diminished with an increase of the ethanol content in weakly alkaline medium. Linear relations were found between the solubilities of the calcium salts and the dielectric constants of the solvent mixtures. The calcium salts have poor solubilities atpH 9 in 20% aqueous ethanol containing ammonia. The radiometric titrations were carried out in 0.05M solutions, using 0.05M ⁴⁵Ca-labelled CaCl₂ solution in 20% aqueous ethanol. The titrations were done in an apparatus suitable for the detection of soft β-emitting isotopes.     

193-nm Photodissociation of ions from saturated and unsaturated aliphatic molecules

To determine the analytical utility of photodissociation as a general fragmentation technique for tandem mass spectrometry of organic ions, the ability to fragment those ions considered least likely to absorb photons efficiently was investigated. To this end, the ability to photodissociate ions of aliphatic compounds by using 193-nm photons has been studied. Three fragment ions, the C₄H ₉ ⁺ ion from n-hexane, the C₄H ₇ ⁺ ion from 2-hexene, and C₄H ₅ ⁺ from 2-hexyne, have been photodissociated. The fragmentation efficiencies for all three ions studied were between 25 and 45%. The photofragment ion spectrum for each precursor ion studied is made up of characteristic fragments. These spectra demonstrate the ability to photodissociate aliphatic ions that originate from both saturated and unsaturated molecules. This provides substantial hope that virtually all organic ions will be able to be photodissociated by using 193-nm photons.     

Investigation and radiometric determination of saturated and unsaturated aliphatic monocarboxylic acids and aromatic dicarboxylic acids

Investigations have been carried out on the precipitation of calcium salts of saturated and unsaturated aliphatic monocarboxylic acids and of aromatic dicarboxylic acids. The optimum ethanol/water solvent ratio has been studied at which the sodium, ammonium or triethylammonium salts of the acids have a good solubility, whereas the calcium salts are poorly soluble and can be precipitated. Based on these investigations the radiometric determination of formic acid, palmitic acid, stearic acid, methacrylic acid, oleic acid, and o-, m- and p-phthalic acids has become possible. A linear correlation has been found between the solubilities of the calcium salts of o-, m- and p-phthalic acids and the dielectric constant of the solvent mixture. CaCl₂ solution labelled with⁴⁵CaCl₂ was used for the titrations, with a solvent composition identical to that of the solution to be titrated. Radiometric titrations were carried out in 0.05M solutions for dicarboxylic acids, and in 0.1M solutions for monocarboxylic acids. For palmitic and stearic acids titrations were also carried out in the 0.01M concentration range. The equipment used for titrations was capable of detecting isotopes of soft β-radiation.     

Use of fluorinated diphenylolmethane derivatives for preparing heat-resistant elastic polyurethanes

Fluorinated diphenylolmethane derivatives were used for the first time as chain extenders in urethane formation reactions in preparation of elastic materials. Fluorinated diphenylolmethane derivatives exhibit positive surface activity. Owing to this fact and to the presence of reactive hydroxy groups, these derivatives allow preparation of fluorinated polyurethane materials with enhanced resistance to heat and aggressive media.     

Curing thermodynamics and kinetics of unsaturated polyester resin with different chain length of saturated aliphatic binary carboxylic acid

Journal of Thermal Analysis and Calorimetry - The saturated aliphatic binary carboxylic acid, including succinic acid, adipic acid and sebacic acid, were used to improve the curing process of...     

Dialkylaluminum derivatives of saturated and unsaturated acids

Summary Some salts of dialkylaluminum with both saturated and unsaturated acids were obtained. The salts of dialkylaluminum with unsaturated acids are capable of being polymerized and copolymerized in the presence of azobisisobutyronitrile as initiator.     

Crystallization studies on linear aliphatic n‐polyurethanes

A detailed crystallization study of the linear n‐polyurethane (n‐PUR) family for n ranging from 5 to 12 was carried out by DSC supported by polarizing optical microscopy. The study embraces crystallization of all the n‐PUR under both nonisothermal and isothermal conditions. The odd and even series of n‐PUR defined by the parity of the number of methylenes (n) contained in the polymer repeating unit are considered and separately analyzed. All the members of the two series showed a thermal behavior consistent with their chemical constitution. Isothermal crystallization data were analyzed by the kinetics Avrami approach which revealed that the “crystallizability” of n‐PUR increases steadily with the flexibility of the polyurethane chain. Melting and enthalpy temperatures of isothermally and nonisothermally crystallized n‐PUR were found to vary with n according to a zig‐zag plot characteristic of odd–even effect. Given the structural similitude of n‐PUR with (n + 2)‐nylons, results were referenced to those reported for this family of polyamides. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1368–1380, 2009     

Synthetic applications of aliphatic unsaturated alpha-H-alpha-amino acids

This article provides an overview of the literature concerning synthetic applications of unsaturated aliphatic amino acids in the period May 2000 to December 2004.     

Proton affinities of saturated aliphatic methyl esters

The kinetic method was used to determine the proton affinities of methyl esters of several saturated fatty acids. Decompositions of the proton-bound dimers of the methyl esters, AHB⁺, were observed under different conditions with two instruments. The proton affinities (PAs) of the methyl esters increase continually with increasing carbon number in the acid. Equilibrium and initial rate experiments were performed with a Fourier transform ion cyclotron resonance mass spectrometer on the methyl ester of the C₂₂ saturated acid (methyl behenate). These experiments give values for PA (methyl behenate) that are perhaps slightly lower than those obtained with the kinetic method. The PAs of the methyl esters of the fatty acids could be correlated with the equation: PA (ester) = (40.0 ± 2.5)*log(n) + (784.7 ± 3.9) kJ/mol or PA (ester) = (864 ± 2) − (479 ± 41)/n, wheren = number of atoms in the molecule. Proton affinities of smaller sets of 1-alkylamines and 1-alkanols can be fit to similar equations.     

Solvent‐free and nonisocyanate melt transurethane reaction for aliphatic polyurethanes and mechanistic aspects

A novel melt transurethane polycondensation route for polyurethanes under solvent‐free and nonisocyanate condition was developed for soluble and thermally stable aliphatic or aromatic polyurethanes. The new transurethane process was investigated for A + B, A‐A + B, and A‐A + B‐B (A‐urethane and B‐hydroxyl) ‐type condensation reactions, and also monomers bearing primary and secondary urethane or hydroxyl functionalities. The transurethane process was confirmed by ¹H and ¹³C NMR, and molecular weight of the polymers were obtained as M_n = 10–15 × 10³ and M_w = 15–45 × 10³ g/mol. The mechanistic aspects of the melt transurethane process and role of the catalyst were investigated using model reactions, ¹H NMR, and MALDI‐TOF‐MS. The model reactions indicated the occurrence of 97% reaction in the presence of catalyst, whereas its absence gave only less than 2% of the product. The polymer samples were subjected for end‐group analysis using MALDI‐TOF‐MS, which confirms the Ti‐catalyst mediated nonisocyanate pathway in the melt transurethane process. Almost all the polyurethanes were stable up to 280 °C, and the T_g of the polyurethanes can be easily fine‐tuned from ?30 to 120 °C by using appropriate diols in the melt transurethane process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2445–2458, 2008     

Excited orbitals of sulphur in aliphatic and unsaturated sulphides

The energies of some electron configurations of sulphur in organic sulphides involving 3d and 4s orbitals have been derived by simulating the radial and angular perturbation of the molecular environment on sulphur valence orbitals, with electrostatic potentials. In order to discuss the relevance of the electron configurations in the molecular valence state and the role of the excited orbitals 4s and 3d to bonding, the energies were minimized in respect of size and orientation of sulphur valence orbitals. Interatomic exchange terms were included and the importance of interatomic exchange terms involving the electrons on carbons is discussed. The results are indicative for a negligible participation of 3d and 4s orbitals of sulphur to the ground state of aliphatic and unsaturated sulphides.     

New insight into the substituent effects on the hydrolytic deamination of saturated and unsaturated cytosine

Ab initio calculations were carried out to understand the effect of electron donating groups (EDG) and electron withdrawing groups (EWG) at the C5 position of cytosine (Cyt) and saturated cytosine (H₂Cyt) of the deamination reaction. Geometries of the reactants, transition states, intermediates, and products were fully optimized at the B3LYP/6-31G(d,p) level in the gas phase as this level of theory has been found to agree very well with G3 theories. Activation energies, enthalpies, and Gibbs energies of activation along with the thermodynamic properties (ΔE, ΔH, and ΔG) of each reaction were calculated. A plot of the Gibbs energies of activation (ΔG^‡) for C5 substituted Cyt and H₂Cyt against the Hammett σ-constants reveal a good linear relationship. In general, both EDG and EWG substituents at the C5 position in Cyt results in higher ΔG^‡ and lower σ values compared to those of H₂Cyt deamination reactions. C5 alkyl substituents ( H,  CH₃,  CH₂CH₃,  CH₂CH₂CH₃) increase ΔG^‡ values for Cyt, while the same substituents decrease ΔG^‡ values for H₂Cyt which is likely due to steric effects. However, the Hammett σ-constants were found to decrease at the C5 position of cytosine (Cyt) and saturated cytosine (H2Cyt) on the deamination reaction. Both ΔG^‡ and σ values decrease for the substituents Cl and Br in the Cyt reaction, while ΔG^‡ values increase and σ decrease in the H₂Cyt reaction. This may be due to high polarizability of bromine which results in a greater stabilization of the transition state in the case of bromine compared to chlorine. Regardless of the substituent at C5, the positive charge on C4 is greater in the TS compared to the reactant complex for both the Cyt and H₂Cyt. Moreover, as the charges on C4 in the TS increase compared to reactant, ΔG^‡ also increase for the C5 alkyl substituents ( H,  CH₃,  CH₂CH₃,  CH₂CH₂CH₃) in Cyt, while ΔG^‡ decrease in H₂Cyt. In addition, analysis of the frontier MO energies for the transition state structures shows that there is a correlation between the energy of the HOMO–LUMO gap and activation energies.     

Fourier-transform Raman spectroscopic study of unsaturated and saturated waxes

The application of Fourier-transform (FT)-Raman spectroscopy to the non-destructive analysis of plant biomaterials, comprising ten different waxes, is illustrated in this work. All the wax specimens studied are multicomponent systems and comparison of the individual spectra was effected. This leads to a means of distinguishing the individual wax specimen using FT-Raman spectroscopy. The samples were not pre-treated before analysis and were used directly from their respective storage collections.