Thermal reactions of fatty acids with diethylene triamine

Abstract

The relative reactivities of the primary and secondary amino groups of diethylene triamine with fatty acids depend on the thermal reaction conditions. Without solvents, the primary amines are more reactive than the secondary amine for steric reasons, and the reaction results mainly in the 1,3-diamide. However, in dilute solution, the secondary amine shows higher reactivity than the primary amines, and the reaction proceeds probably by way of the 1,2-diamide, which forms imidazolines under much milder conditions than from the 1,3-diamide. The hydrolysis of imidazoline to the 1,2-diamide as the major product confirmed the higher reactivity of the secondary amine. JAOCS 74, 61-64 (1997).Fatty imidazolines and fatty amides are used widely or are precursors for surface-active compounds (1,2). Industrially, imidazolines are prepared in a thermal reaction between diethylene triamine (DETA) with fatty acids, triglycerides, or methyl esters of fatty acids (3,4). However, the literature of this fatty acid-DETA reaction is contradictory. It is claimed that DETA reacts with fatty acids to form fatty acid monoamides 3 (Scheme 1), which can cyclize to imidazoline compounds 4 that contain a free primary amine group (5). Even though no structural evidence is given, the preparation of compounds 3 and 4 is still claimed in recent patents (6,7). Other researchers have reported that the reaction of DETA with fatty acids does not take place in a 1:1 molar ratio; hence fatty acid monoamides 3 and the related imidazoline derivatives 4 are unlikely (3,4,8). Additionally, discrepancies exist in the literature over the mechanism of the reaction, in particular the relative reactivities of the primary and secondary amines (3,4,8,9). To clarify the mechanism of this important thermal acylation reaction and to prepare fatty amides or imidazoline compounds that contain a free primary amine group, we have studied the reaction of fatty acids 1 and DETA 2, and report here the results of our studies. MATERIALS AND METHODS Materials and instrumentation.Melting points were measured with an Electrothermal IA9300 digital apparatus. Infrared (IR) spectra were recorded on a (CO 2 -free, dry airpurged) Digilab FTS-7 Fourier transform infrared (FTIR) spectrophotometer (Biorad, Cambridge, MA). 1 H nuclear magnetic resonance (NMR) (300 MHz) spectra (CDCl 3 ) were obtained with a Bruker AC-300 instrument (Bruker, Germany) (Me 4 Si as reference). Mass spectra were measured in a Varian VG70-250S double-focusing magnetic-sector instrument (VG Analytical, Manchester, England) at 15 ev. A model 8452A diode-array spectrophotometer (HewlettPackard, Palo Alto, CA) was used for quantitative analysis of the Schiff base-forming reactions. The analysis procedure was as follows: 20-60 mg of fatty amine compound was dissolved in 2 mL CHCl 3 in a 10-mL volumetric flask. Glacial acetic acid (0.35 mL) and salicylaldehyde (0.60 mL) were added, and the flask was placed in a water bath at 30°C. After 1 h, the solution was made up to 10.0 mL with CHCl 3 , and the absorption at 4...

Liquid chromatography/electrospray ionisation mass spectrometric investigations of imidazoline corrosion inhibitors in crude oils

“…Ever since the initial synthesis of ‘imidazolines’ described by Hofmann11 in 1888, there has been debate concerning the mechanism of the reaction between fatty acids and triamines 9,. 10,, 12,, 13 Indeed, even the existence of the compounds has been questioned 14. Yet the subject is of major importance to the efficient deployment of anti‐corrosion measures since the composition of the synthetic mixtures controls their self‐assembly as monolayers on metal surfaces and hence their efficacy 15…”

“…Much of the confusion seems to have arisen from the existence of different mechanisms in the solid‐phase and solvent‐based reactions 10. However, attempts to elucidate the mechanisms have also been hampered by the lack of sensitive, specific methods for identification of the reactants, intermediates and products in the complex mixtures resulting from such reactions.…”

“…However, attempts to elucidate the mechanisms have also been hampered by the lack of sensitive, specific methods for identification of the reactants, intermediates and products in the complex mixtures resulting from such reactions. Thus, even recent studies10 have required isolation and recrystallisation of the chemicals at each stage, followed by spectroscopic examination by nuclear magnetic resonance spectroscopy and other techniques. Powerful though these methods are, they are not sensitive to (perhaps important) minor products and intermediates, most of which are in any case removed by recrystallisation procedures.…”

“…2‐Pentadecyl‐1‐[ N ‐ethylhexadecylamide]‐2‐imidazoline (2:1‐PI; I) and 2‐heptadecenyl‐1‐[ N ‐ethyloctadecenylamide]‐2‐imidazoline (2:1‐OI; III) were synthesised by both solid‐phase and solvent‐based reactions from palmitic and oleic acids and DETA by previously published methods 9,. 10 Stock solutions were prepared in MeOH and diluted as required. Calibration solutions were prepared by serial dilution.…”

Influence of vacuum on kinetic of low quality rapeseed oil amidation by aminoethylethanolamine

“…Excess of amine does not allow for reaction masses to crystallize and because of that reaction is conducted for 12 hours in homogenous media. Influence of solvent on the process of amidation of fatty acids has been described in [9]. The reaction took place under the temperature of 145 ºС in xylene media.…”