Mechanistic study of drying of alkyd resins using ethyl linoleate as a model substance

Air drying of alkyd resins under the influence of cobalt driers was studied using ethyl esters of fatty acids as model compounds. In order to get insight into the crosslink reactions taking place during initial drying as well as through-hardening of alkyds the reaction was followed for a considerable period of time using several analytical techniques. Ethyl linoleate appeared to react completely in three days whereas the oleate required more than three months for a similar conversion. Crosslinks were detected using POMMIE ¹³C NMR, a technique which yields a carbon NMR spectrum having separate traces for methine, methylene and methyl carbons. Broad methine carbon signals around 73 and 83 ppm indicated the presence of ether and peroxy crosslinks, respectively. Remaining double bonds gave a signal at 120–140 ppm. The relative intensity of these signals changed over a period of one year, indicating further reaction of double bonds to form ether crosslinks. These reactions are therefore likely to occur during through-hardening of alkyds. Crosslinking yielded oligomers up to the pentamer as was demonstrated with size exclusion chromatography (SEC). With secondary ion mass spectroscopy (SIMS) five groups of lines were obtained, the individual lines within each group being 16 mass units apart. The results point to the formation of oligomers with various amounts of oxygen, including non-oxygenated oligomers. Fast atom bombardment MS (FAB-MS) and direct chemical ionization-MS (DCI-MS) gave a similar distribution for the dimer and the trimer, respectively. Quantitative determination by means of GC indicated the C-C linked oligomers to be formed in minor amounts.     

Soy fatty acid oxidation with sodium hypochlorite monitored by nuclear magnetic resonance spectroscopy

The oxidation process of soy fatty acids by sodium hypochlorite with ruthenium trichloride catalyst was examined at different temperatures and active chlorine:fatty acid molar ratios. ¹H and ¹³C distortionless enhancement by polarized transfer nuclear magnetic resonance (NMR) spectroscopy techniques were used to monitor oxidation of the double bonds in unsaturated lipids by measuring the peak integration ratio of double-bond peaks:methylene-methyl peaks. This NMR monitoring technique proved to be an excellent means to quantify double-bond reactions. Gas chromatography-mass spectrometry was used to identify mono- and diacid products, separated by hexane/methylene chloride extraction, as well as other oxidation products. While the presence of ruthenium catalyst increased the initial rate of oxidation, it also catalyzed the decomposition of hypochlorite, decreasing the available reactive chlorine, resulting in a delay in complete oxidation. A 9:1 molar ratio of active chlorine to fatty acids completely oxidized all double bonds of soy fatty acids. However, the yield of low-molecular-weight monoacid oxidation products was only 17%, indicating the probable formation of hydroxy fatty acids.     

1H NMR Study of Methyl Linoleate Ozonation.

Unsaturated fatty acids are essential components of vegetable oils and cellular membranes and the involved aspect of unsaturated fatty acids ozonation have been widely studied by different authors. In this paper, in vitro ozonolysis of unsaturated fatty acids with addition of water or ethanol has been studied by Proton Nuclear Magnetic Resonance (¹H NMR) at 250?MHz in order to explore the possibility of this technique for the detection of Criegee ozonides in characterizing ozone reaction with these substrates. The ozonolysis of methyl linoleate showed that signal intensities from formed ozonides were increased with ozone concentration increments. However, the signal intensities with addition of water were higher than those in ethanol addition. Signal intensities from olefinic double bonds were found to decrease with the increment in ozonide signals. Thus, a correspondence of the behavior of these signals is observed with a proportional rate reaction between the number of double bonds in the substrate molecule. Signals from aldehyde formation were poorly detected at lower ozone concentration. It was concluded that the evaluation of ozonide and olefinic double bond signals from 250?MHz ¹H NMR can be a useful tool in assessing ozone reaction with biomolecules. The reaction mechanism for the ozone reaction with unsaturated fatty acids in the presence of water or ethanol is analyzed.     

Design and incorporation of reactive diluents for air-drying high solids alkyd paints

The development of air-drying solvent borne trade paints with solvent content below that of current solids levels will necessitate reformulation using reactive diluents. The current lack of suitable reactive diluents for air-drying systems has prompted this investigation. This paper highlights some emerging aspects of the design of reactive diluents, in particular the importance of inclusion of the correct balance of sites for both initiation and coupling reaction stages into an alkyd system together with the concept of functionality as a tool to predict performance. Also reported is a new class of reactive diluents based on fumarates and succinates of octadienol (referred to as the OFS class of reactive diluents). A detailed study on the cure and performance of this class of compounds is reported. A combination of conventional and refined analytical techniques have given new insights into the mechanism of cure of these reactive diluents as well as a measurement of incorporation into the drying paint film. The findings of this performance study have confirmed the suitability of the reactive diluent design and allowed its further refinement. OFS reactive diluents have thus been found to achieve full chemical incorporation whilst maintaining high performance of the paint.     

Mass spectrometry of lipid molecules

The mechanisms of mass spectrometric fragmentation and their applications to the elucidation of structure of lipids related to fatty acids are reviewed. The mechanism of fragmentation of saturated fatty acids and the mass spectrometric determination of the position of the double bond in unsaturated esters are emphasized. The use of pyrolysis-mass spectrometry for locating double bonds is introduced. Patterns of fragmentation of wax esters and glycerides are also given. Presented at the AOCS-AACC Joint Meeting, Washington, D.C., April, 1968.     

Analysis of triglycerides using atmospheric pressure chemical ionization mass spectrometry

Atmospheric pressure chemical ionization (APCI) mass spectrometry was investigated as a new method for analysis of a mixture of triglycerides separated by reverse-phase high-performance liquid chromatography. A mixture of homogeneous (monoacid) triglyceride standards containing fatty acids with zero to three double bonds was analyzed to demonstrate the quality of mass spectra obtained by using the APCI interface. The mass spectra showed that minimal fragmentation occurs, resulting primarily in diglyceride [M−RCOO]⁺ ions and [M+1]⁺ protonated molecular ions. The degree of unsaturation within the acyl chains had a marked effect on the proportion of diglyceride ions vs. the [M+1]⁺ ions formed in the APCI source. The mass spectra of triglycerides containing fatty acids with two or three double bonds showed predominantly protonated triglyceride ions, with diglyceride peaks representing 13 to 25% of the base peak. The triglycerides containing singly unsaturated fatty acids gave diglyceride ions as the base peak, and [M+1]⁺ ions with an intensity 20 to 28% that of the base peak. Only diglyceride ions were observable in the spectra of triglycerides containing saturated fatty acids.     

Fatty Acid Methyl Esters with Two Vicinal Alkylthio Side Chains and Their NMR Characterization

The addition reaction of dimethyl disulfide (DMDS) to double bonds in alkenes and monounsaturated fatty acid esters in the presence of iodine or other catalysts to give bis(methylthio) derivatives has largely served analytical purposes in mass spectrometry with scattered reports on the addition of other disulfides to alkenes also existing. In this work, this iodine-catalyzed reaction was expanded to include the addition of other dialkyl disulfides (RSSR; R=ethyl, propyl, butyl, iso-propyl) besides DMDS to the double bonds in monounsaturated fatty acid methyl esters with 16, 18, 20, and 22 carbon atoms in the fatty acid chain to give the corresponding methyl 1,2-bis(alkylthio)alkanoates. The products are obtained in high to moderate yield after a facile purification procedure and are analytically characterized not only by mass spectrometry but also ¹H and ¹³C NMR. The threo and erythro diastereomers obtained from (Z) and (E) fatty acid methyl esters, respectively, can be easily distinguished by the NMR shifts of the protons and carbons in and close to the 1,2-bis(alkylthio) moiety. Various other effects in the NMR spectra are discussed. The 1,2-bis(alkylthio) derivatives of a symmetrical alkene, 7(E)-tetradecene, serve to confirm the NMR assignments besides NMR techniques such as 2D correlations and DEPT. The compounds may show properties of interest for various applications.     

Structure of tall oil fatty acid-based alkyd resins and alkyd–acrylic copolymers studied by NMR spectroscopy

One- and two-dimensional NMR spectroscopy was used to evaluate the structure of tall oil fatty acid (TOFA)-based alkyd resins and waterborne alkyd–acrylic copolymers. An increase in the functionality of the polyol that is used in the alkyd resin synthesis was found to increase the reactivity of the polyol towards the diacid compared with the TOFA, which causes the formation of more branched and higher molar mass alkyd resin structures. During the copolymerization, polyacrylate chains were grafted to the double bonds and allylic sites of the fatty acid chains in the alkyd resin. Butyl acrylate preferentially grafted to the double bonds, while methyl methacrylate tended to graft to the allylic position. High proportions of the double bonds remaining after copolymerization were crucial to the film formation of copolymers, because the chemical drying of copolymer films occurred by an autoxidation process.     

The prediction of fatty acid structure from selected ions in electron impact mass spectra of fatty acid methyl esters

The possibility of fatty acid identification from ions in the mass region of 50–110 amu in electron impact mass spectra has been studied by application of various multivariate techniques. The focus has mainly been on the prediction of the number of double bonds in methylene‐interrupted polyunsaturated fatty acids isolated from marine lipids. The number of double bonds in these fatty acids could be predicted with high accuracy, both by partial least squares regression on all ions in this region, and by multiple linear regressions on selected subsets of 5–6 ions. The subsets with optimal predictive power have been found, and the ability to distinguish between methylene interrupted polyunsaturated fatty acids and other fatty acids have also been evaluated.     

Composition of bovine milk lipids

Recent literature on the composition of milk lipids is reviewed and discussed. Many additional exotic fatty acids, mainly branched chain, keto, hydroxy and isomers containing double bonds, have been identified, often with the aid of mass spectrometry. It is estimated that ca. 500 fatty acids have been found in milk lipids. Components of lipid classes have been isolated and their structure determined, e.g., glucosyl and lactosyl ceramide, sphingomyelin, ether lipids, etc. The fatty acid composition of “protected” milk is discussed. This milk, obtained from cows fed polyunsaturated oils encapsulated with formaldehyde-treated casein, contains about five times more linoleic acid than regular milk. The future of research on milk lipids is promising, as there are still many intriguing problems of separation and identification. One of eight papers presented in the symposium “Milk Lipids,” AOCS Meeting, Ottawa, September 1972. Contribution No. 528, Storrs Agricultural Experiment Station, University of Connecticut, Storrs.     

2-alkenyl-4,4-dimethyloxazolines as derivatives for the structural elucidation of iosmeric unsaturated fatty acids

Several types of unsaturated fatty acid methyl esters were converted into 4,4-dimethyloxazoline (DMOX) derivatives and analyzed by mass spectrometry to further evaluate the feasibility of using this derivative for locating the positions of double bonds in isomeric fatty acids. Five isomeric 20-carbon tetraenoic acids were analyzed in which the fourcis double bonds were systematically moved from the 4,7,10,13- to the 8,11,14,17-positions. It was possible to locate the positions of all four double bonds in the 7,10,13,16- and 8,11,14,17-isomers by appropriate ions differing by 12 atomic mass units. In a similar way the three terminal double bonds in the 4,7,10,13-, 5,8,11,14- and 6,9,12,15-isomers could be assigned. Odd-numbered ions atm/z 139, 153 and 167 which are accompanied by an even mass ion at 138, 152 and 166, respectively, are diagnostic for DMOX derivatives of acids with their first double bond, respectively, at positions 4, 5 and 6. It was thus possible to assign the location of all four double bonds in these three isomers. A comparison of the spectra of the DMOX derivatives of 17,17,18,18-d ₄ vs. 9,10,12,13-d ₄ linoleic acid suggests that double bonds preferentially migrate toward the polar end of the molecule prior to fragmentation. The merit of using DMOX derivatives to locate double-bond positions in mono- and dicarboxylic acids, produced during β-oxidation of polyunsaturated fatty acids, was evaluated. The spectra of 3-cis- and 4-cis-decenoic acids differ as do the spectra of 8-carbon dicarboxylic acids with their double bonds at positions 3 and 4.     

Stand reaction of linseed oil

Several theories have been proposed concerning the stand oil reaction but no precise reaction scheme has been described. In this work, the stand reaction of linseed oil was characterized in order to determine the nature of the products formed during this reaction. Using complementary analytical techniques (more especially NMR and mass spectrometry), the existence of two different reactions was demonstrated: the Diels–Alder addition between fatty acid chains and the addition of a methylene radical on double bonds, followed by combination or elimination reactions.     

A comparison of pyrrolidide and picolinyl ester derivatives for the identification of fatty acids in natural samples by gas chromatography-mass spectrometry

The pyrrolidide and picolinyl ester derivatives of the fatty acids in two natural lipid samples rich in unsaturated fatty acids, pig testis lipids and cod liver oil were satisfactorily resolved on capillary columns of fused silica coated with stationary phases of varying polarity. The picolinyl esters, in particular, when subjected to gas chromatography-mass spectrometry on a column containing a cross-linked methyl silicone, gave distinctive mass spectra, which could be interpreted in terms of both the numbers and positions of the double bonds.     

Synthesis of Tung‐Oil‐Based Reactive Diluents

Three new reactive diluents were prepared from tung oil using a Diels‐Alder reaction. The dienophiles were methacryloxypropyl trimethoxysilane (MAS), 2,2,2‐trifluoroethyl methacrylate (TFM) and triallyl ether acrylate (TAEA). The chemical structures were evaluated using ¹H NMR, ¹³C NMR, FT‐IR, GPC and MALDI‐TOF‐MS. Spectra evidence (NMR, MS) indicated that a six‐member ring were formed in all three reactions indicating a Diels‐Alder adduct. The reactive diluents were formulated with a soya‐based alkyd to evaluate viscosity reduction and drying time. The viscosity of alkyd was reduced up to 70% using the reactive diluents. The drying time for the autoxidative reactive diluents with alkyds were 1.8‐1‐7 times faster than alkyd alone.

     

Comparison of pyrrolidides with other amides for mass spectral determination of structure of unsaturated fatty acids

Amides of unsaturated fatty acids give mass spectra which indicate the locations of the double bonds. A survey of several amides of oleic acid was made to evaluate which amide might be most suitable for routine use in elucidation of structure. Methods of preparation of several amides of oleic acid are presented with mass spectral and gas chromatographic data. Tertiary amides have most easily interpretable mass psectra which indicate the position of the double bond in the fatty acid chain. The pyrrolidide is advantageous for fatty acid gas liquid chromatography and mass spectrometry analyses because it can be prepared easily in high yield on a microscale, it is volatile enough for gas liquid chromatographic separations, and it has a simple and easily interpretable mass spectrum which indicates the structure.     

Identification of 3, 6, 9, 12, 15-octadecapentaenoic acid in laboratory-cultured photosynthetic dinoflagellates

Polar and nonpolar chromatograms of fatty acid methyl esters derived from 11 species of photosynthetic, marine dinoflagellates cultured in modified Erd-Schrieber medium contained a component (4-23%) not identifiable by conventional graphic or arithmetic methods. Hydrogenation followed by gas liquid chromatography of the product showed the unknown component to be a straight chained 18 carbon fatty acid methyl ester. Chemical (ch4) ionization mass spectrometry of the isolated ester gave a spectrum characteristic of methyl esters and a mol wt of 288, indicating an 18 carbon molecule with 5 double bonds, or equivalent unsaturation. The IR spectrum showed that the double bonds are nonconjugated, and all are cis in geometry. Electron impact mass spectrometry of the pyrorolidide derivative provided evidence that double bonds are located in the 3, 9, 15 positions and probably also in the 6 and 12 positions of the molecule. these double bond positions were confirmed by NMR spectrometry. Data obtained by quantitation of the algal methyl esters suggest the possibility that these dinoflagellates synthesize 18:5omega3 (shorthand notation for chain length: number of double bond counted from the terminal methyl group) by a 2 carbon chain shortening of 20:5omega3, rather than by the insertion of a delta3 bond into 18:4omega3.     

Autoxidation of fatty acid esters in the presence of a heavy metal catalyst “Salcomine” (Co[II]-bissalicylalethylenedi-imine): II. Formation of a reaction product from a peroxy radical and salcomine

The formation of ionic Co(II)-bis-salicylalaethylenedi-imine complexes of peroxy radicals of methyl esters of fatty acids was followed by means of UV spectra. Typical compounds were isolated and purified, and analyzed for Co content. IR spectra were determined. The mechanism of the autoxidation of fatty acid methyl esters in the presence of “Salcomine” (Co[II]-bissalicylalethylene-di-imine) has been outlined, and its effect is explained as an oxidative addition reaction, resulting from coordinative unsaturation.     

Synthesis and Characterization of Allyl Fatty Acid Derivatives as Reactive Coalescing Agents for Latexes

This work evaluated the use of allyl fatty acid esters derived from vegetable oil (palmitic acid, soybean and sunflower oils) as reactive coalescing agents in a waterborne latex system. Allyl fatty acid derivatives (AFAD) from vegetable oils were synthesized by two different processes. The synthesis was monitored by IR-spectroscopy and the final product characterized by FT-IR, GC–MS, ¹H and ¹³C NMR. The presence of conjugated double bonds in the aliphatic chain was confirmed, which is a determinant for the proposed autoxidative latexes drying mechanism. Each of the AFAD were subsequently added to a standard acrylic emulsion, in order to study its potential as reactive coalescing agent. The minimum film-forming temperature (MFT), glass transition temperature (T _g), drying time and rubbing resistance to solvents were evaluated. The results showed that, when added to water-borne acrylic resins, an AFAD acts as a non-volatile plasticizer capable of autoxidative crosslinking with itself.     

Fatty acid methyl ester as reactive diluent in thermally cured solvent-borne coil-coatings—The effect of fatty acid pattern on the curing performance and final properties

Four different fatty acid methyl esters (FAMEs): rape seed methyl ester (RME), tall oil methyl ester (TOME), and two types of linseed oil methyl ester (Linutin) have been studied as reactive diluents in thermally cured solvent-borne coil-coatings. The purpose was to evaluate the effect of fatty acid methyl ester structure on the curing performance and final properties of the coating. The permanent incorporation of the reactive diluent via transesterification reaction has been followed with ¹H NMR analysis of model systems. Dynamic mechanical analysis (DMA) measurements, of free-standing films, show that the glass transition temperature (T_g) decreases upon addition of the reactive diluent. Both the amount of incorporated reactive diluent and the final film properties are affected by the number and placement of alkene-bonds in the FAME.     

Mass spectrometry of the 4,4‐dimethyloxazoline derivatives of isomeric octadecenoates (monoenes)

Although 4,4‐dimethyloxazoline (DMOX) derivatives of fatty acids have been widely used for structural analysis of fatty acids by mass spectrometry, spectra of relatively few authentic standards have been published. Confusion can result when double bonds are located near either end of the molecule, and errors have been promulgated in the literature. Mass spectra of DMOX derivatives of the complete series of isomeric octadecenoates are described. Even when spectra are not easily interpreted mechanistically in terms of the double bond location, they usually give distinctive fingerprints.