Synthesis and evaluation of some new oxazolones and imidazolones as antioxidant additives for Egyptian lubricating oils

Petroleum Science, Sep 2012

Oxazolone derivative 2 was utilized as a key intermediate for synthesis of some new oxazolone and imidazolone derivatives. Reaction of oxazolone derivative 2 with diamines under different conditions afforded the corresponding imidazolone derivatives 3–8, respectively. Moreover, oxazolone 2 reacted with some heterocyclic amines in glacial acetic acid giving the corresponding imidazolone derivatives 9–14, respectively. Cyclocondensation of thiosemicarbazide with compound 2 in dry pyridine afforded compound 15. Addition of secondary amines to olefin double bond of compound 2 gave the corresponding addition products 16–19, respectively. Michael addition of compound 2 with some active methylene compounds afforded oxazolone derivatives 20–23, respectively. These prepared products were evaluated as antioxidant and corrosion inhibitors for gasoline lubricating oil and compounds 6a–c, 10 and 15 exhibited the highest antioxidant and anticorrosive activities. The effect of concentration of additives was studied to recommend the optimum concentration to be used. The results showed, for additive 15, 0.1 g for 1 L oil was the more effective concentration. Measurements for thermal analysis and of surface tension of oil after oxidation were also carried out.

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Synthesis and evaluation of some new oxazolones and imidazolones as antioxidant additives for Egyptian lubricating oils

Pet.Sci. Synthesis and evaluation of some new oxazolones and imidazolones as antioxidant additives for Egyptian lubricating oils Ahmed El-Mekabaty 0 1 Osman M. O. Habib 0 1 Hussein M. Hassan 0 1 Evelin B. Moawad 0 1 0 China University of Petroleum (Beijing) and Springer-Verlag Berlin Heidelberg 2012 1 Department of Chemistry, Faculty of Science, Mansoura University , Mansoura 35516 , Egypt Oxazolone derivative 2 was utilized as a key intermediate for synthesis of some new oxazolone and imidazolone derivatives. Reaction of oxazolone derivative 2 with diamines under different conditions afforded the corresponding imidazolone derivatives 3-8, respectively. Moreover, oxazolone 2 reacted with some heterocyclic amines in glacial acetic acid giving the corresponding imidazolone derivatives 9-14, respectively. Cyclocondensation of thiosemicarbazide with compound 2 in dry pyridine afforded compound 15. Addition of secondary amines to olefin double bond of compound 2 gave the corresponding addition products 16-19, respectively. Michael addition of compound 2 with some active methylene compounds afforded oxazolone derivatives 20-23, respectively. These prepared products were evaluated as antioxidant and corrosion inhibitors for gasoline lubricating oil and compounds 6a-c, 10 and 15 exhibited the highest antioxidant and anticorrosive activities. The effect of concentration of additives was studied to recommend the optimum concentration to be used. The results showed, for additive 15, 0.1 g for 1 L oil was the more effective concentration. Measurements for thermal analysis and of surface tension of oil after oxidation were also carried out. Oxazolone; imidazolone; benzoimidazole; surface tension; thermal stability; antioxidant additives - Lubricating oils produced by solvent refining of high boiling petroleum distillates consist mainly of long chain hydrocarbon molecules. In internal combustion engines, lubricating oils suffer from autoxidation as a result of contact at elevated temperatures with air for a long period and with metals, from which the engine was made. These metals act as catalysts for oxidation of lubricating oil and are responsible for the formation of oxygenated oilsoluble and insoluble products which exert an adverse effect on the performance of the lubricating oils (Hassan et al, 1985; 2000; Hassan, 1998; Façanha et al, 2007; Aucelio et al, 2007; Suzuki et al, 2009) . With increasing demands being placed on lubricants for automotive engines and transmissions and high-speed machinery, much research has been devoted to the development of improved lubricants. Not only petroleumbased lubricants, but also synthetic lubricants require additives to improve their lubricating and aging properties when exposed to many severe end use conditions, e.g., for extreme pressure applications where metal to metal contact may be encountered, additives must be used to form low inhibit oxidation; prevent rusting and improve the viscosity index and pour points of the lubricants. 2 Experimental section 2.1 Synthesis The melting points (uncorrected) of all the compounds were determined on Gallenkamp electric melting point apparatus, and Fourier transform Infrared Spectroscopy (FTIR) (KBr disk) was performed on a Mattson 5000 FTIR spectrometer which has spectral resolution of 4 cm-1 and scan number of 64 in the spectral range 400-4000 cm-1using the Faculty of Science, Mansoura University, Mansoura, Egypt. 1H-NMR spectra, were determined on a Brucker WPSY 300 MHZ spectrometer with TMS as internal standard and the at 70 ev with a Varian MAT 311. Elemental analysis was satisfactory for all the synthesized compounds 2-23, and elemental analysis was carried out in the Faculty of Science, Cairo University, Egypt. (Z)-4-((5–Oxo-2-phenyloxazol4(5H)–ylidene)methyl)phenyl-4-methylbenzene sulfonate (2) was prepared according to the previously reported method (Girges et al, 1989) . 2.1.1Reaction of oxazolone (2) with o-phenylenediamine a) By fusion at 140 ºC and at 190 ºC A mixture of oxazolone 2 (0.003 mol), o-phenylenediamine (0.003 mol) and freshly fused sodium acetate (0.2 gm) was fused at 140 °C and/or 190 °C for 3 h. In each case, the reaction mixture was cooled, washed with dilute HCl, and the separated solid product was dried and recrystallized from methanol to give compounds 3 and 4, respectively. Their characteristic spectral data are as follows: 4-(2-Benzamido-2-(1H-benzo[d]imidazol-2-yl)vinyl) phenyl4-methylbenzene sulfonate (3 -1: 1680 (CO, amidic), 3174-3289 (2NH), 1360 (SO3), 1600 (C=N), 1590 (C=C). EIMS (m/z, %): 509 (M+, 20), 422 (54), 353 (23), 268 (11), 263 (16), 191 (32), 104 (100), 77 (37). (Z)-4-((1-Phenyl-3H-benzo[d]imidazo[1,5-a]imidazol3-ylidene)methyl)phenyl-4-methyl benzenesulfonate (4). IR -1: 1360 (SO3), 1620 (C=N). EIMS (m/z, %): 489 (M+-2, 18), 341 (38), 295 (25), 213 (40), 193 (48), 147 (73), 91 (38), 44 (100). 1 CH3), 7.1-8.2 (m, 18H, Ar-H, CH=C). A mixture of oxazolone 2 (0.003 mol) and o-phenylenediamine (0.003 mol) in absolute ethanol (20 mL) was refluxed for 6 h. The solid product that separated on cooling was filtered off and recrystallized from ethanol to give compound 5. (Z)-4-(3-((2-Aminophenyl)amino)-2-benzamido-3oxoprop-1-en-1-yl)phenyl-4-methyl benzenesulfonate (5). IR -1: 1680 (CO, amidic), 3430, 3490 (2NH), 32253370 (NH2), 1360 (SO3), 1620 (C=N). EIMS (m/z, %): 527 (M+, 30), 495 (11), 480 (14), 422 (27), 380 (56), 268 (16), 253 (100), 105 (52). 1 3), 4.5 (br, 2H, NH2), 6.9-8.3 (m, 20H, Ar-H, CH=C, 2NHCO). A mixture of oxazolone 2 (0.003 mol) and o-phenylenediamine (0.003 mol) in glacial acetic acid (20 mL) containing for 7 h. The reaction mixture was left to cool, and then poured recrystallized from ethanol-ether was compound 6. ( Z ) - 4 - ( ( 1 - ( 2 - A c e t a m i d o p h e n y l ) - 5 - o x o - 2 phenyl-1H-imidazol-4(5H)-ylidene) methyl)phenyl 4-methylbenzenesulfonate (6 -1: 1698 (CO, amidic), 1665 (CONH), 3133 (NH), 1360 (SO3), 1610 (C=N). EIMS (m/z, %): 551 (M+, 45), 451 (42), 368 (25), 282 (26), 197 (19), 148 (40), 78 (51), 63 (100). 1 ppm), 2.4 (s, 3H, CH3), 2.2 (s, 3H, CH3CO), 7.1-8.2 (m, 19H, Ar-H, CH=C, NH). 2.1.2 Reaction of oxazolone (2) with p-phenylenediamine A m i x t u r e o f o x a z o l o n e 2 ( 0 . 0 0 3 m o l ) a n d p-phenylenediamine (0.003 mol) in glacial acetic acid (30 mL) containing freshly fused sodium acetate (0.2 gm) was recrystallized from acetic acid to give compound 7. (Z)-4-((1-(4-acetamidophenyl)-5-oxo-2-phenyl-1H-imidaz-ol-4(5H)-ylidene) methyl)phenyl 4-methylbenzenesulfonate (7 -1: 1700 (CO, amidic), 1660 (CON), 3350 (NH), 1360 (SO3), 1640 (C=N). EIMS (m/z, %): 552 (M+, 15), 446 (12), 342 (15), 256 (25), 157 (16), 109 (35), 84 (63), 40 (100). 1 3), 2.6 (s, 3H, CH3CO), 7.1-8.4 (m, 19H, Ar-H, CH=C, NH). A m i x t u r e o f o x a z o l o n e 2 ( 0 . 0 0 6 m o l ) a n d p-phenylenediamine (0.003 mol) in glacial acetic acid (30 mL) containing freshly fused sodium acetate (0.5 gm) was heated under reflux for 8 h. The reaction mixture was left to cool, and then poured over ice, the solid that separated out was filtered off, dried and recrystallized from dimethylformamide giving bis imidazolone 8. imi-dazole-1(5H)-yl-4(5H)-ylidene))bis(methanylylidene))bis(4,1-phenylene)bis(4-methyl benzenesulfonate) (8). IR -1: 1675-1688 (2CON), 1360 (SO3), 1620 (C=N). EIMS (m/z, %): 911 (M+, 22), 788 (33), 540 (11), 382 (100), 364 (44), 301 (8), 285 (53), 218 (17), 155 (25), 75 (33). 1H 3), 6.9-8.3 (m, 32H, Ar-H, 2CH=C). 2.1.3 Reaction of oxazolone (2) with heterocyclic amines A mixture of 2 (0.01 mol) and the appropriate heterocyclic amines namely 2-aminopyridine, 3-aminopyridine, 2-aminothiazole, 2-amino benzothiazole, 4-aminoantipyrine and 3-amino-4-(phenyldiazenyl)-1H-pyrazol-5(4H)-one (0.01 mol) and freshly fused sodium acetate (0.5gm) in glacial the reaction mixture was poured into ice-water. The solids to give imidazolone derivatives 9-14. (Z)-4-((5-Oxo-2-phenyl-1-(pyridin-2-yl)-1H-imidazol4(5H)-ylidene)methyl) phenyl-4-methyl benzenesulfonate (9). -1: 1680 (CO, amidic), 1360 (SO3), 1620 (C=N). EIMS (m/z, %): 496 (M++1, 16), 267 (14), 232 (13), 195 (18), 153 (14), 101 (12), 86 (47), 74 (100). (Z)-4-((5-Oxo-2-phenyl-1-(pyridin-3-yl)-1H-imidazol4(5H)-ylidene)methyl) phenyl-4-methyl benzenesulfonate (10 -1: 1680 (CO, amidic), 1360 (SO3), 1620 (C=N). EIMS (m/z, %): 495 (M+, 24), 378 (23), 256 (41), 202 (37), 184 (12), 126 (15), 88 (43), 58 (100). (Z)-4-((5-Oxo-2-phenyl-1-(thiazol-2-yl)-1H-imidazol4(5H)-ylidene)methyl) phenyl-4-methylbenzenesulfonate (11 -1: 1680 (CO, amidic), 1360 (SO3), 1620 (C=N). EIMS (m/z, %): 501 (M+, 41), 445 (38), 404 (48), 388 (71), 347 (41), 294 (66), 263 (33), 191 (11), 105 (81), 58 (100). (Z)-4-((1-(Benzo[d]thiazol-2-yl)-5-oxo-2-phenyl1H-imidazol-4(5H)-ylidene) methyl)-phenyl-4-methyl 1360 (SO3), 1620 (C=N). EIMS (m/z, %): 553 (M++2, 20), 423 (20), 383 (41), 305 (59), 256 (25), 227 (48), 186 (11), 156 (10), 122 (15), 75 (100). (Z)-4-((1-(1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1Hpyrazol-4-yl)-5-oxo-2-phenyl-1H-imidazol-4(5H)-ylidene)methyl)phenyl-4-methylbenzenesulfonate (13). IR (KBr), -1: 1680 (CO, amidic), 1360 (SO3), 1620 (C=N). EIMS (m/z, %): 604 (M+, 32), 450 (13), 347 (26), 290 (11), 263 (16), 231 (39), 156 (62), 105 (100). 4-((1Z)-(5-Oxo-1-(5-oxo-4-(phenyldiazenyl)-4,5-dihydro1H-pyrazol-3-yl)-2-phenyl-1H-imidazol-4(5H)-ylidene)methyl)phenyl-4-methylbenzenesulfonate (14). IR (KBr), -1: 1680 (CO, amidic), 3320 (NH), 1360 (SO3), 1620 (C=N). EIMS (m/z, %): 605 (M+, 21), 495 (16), 449 (12), 369 (23), 255 (12), 196 (16), 104 (73), 91 (100). 2.1.4 Reaction of oxazolone (2) with thiosemicarbazide Thiosemicarbazide (0.03 mol) was added to a solution of compound 2 (0.01 mol) in 30 mL dry pyridine, and the reaction mixture was heated under reflux for 8 h, left to cool and then poured into cold water with stirring. The solid recrystallized from dimethylformamide to give compound 15. (Z)-4-((5-phenyl-2-thioxo-2H-imidazo[1,5-b][1,2,4]triazol-7(3H)-ylidene)methyl) phenyl 4-methylbenzenesulfonate (15 -1: 1376 (C=S), 3442 (NH), 1340 (SO3), 1640 (C=N). EIMS (m/z, %): 475 (M+, 42), 411 (75), 320 (18), 275 (53), 167 (57), 139 (27), 91 (100), 50 (49). 1H 3), 9.8 (s, 1H, NH), 7.2-8.3 (m, 14H, Ar-H, CH=C). 2.1.5 Reaction of oxazolone (2) with secondary amines and thiophenol A mixture of oxazolone 2 (0.05 mol) and the appropriate reagent namely piperidine, morpholine, piperazine, and thiophenol (0.05 mol) in dry benzene (30 mL) was heated at 60 ºC with stirring for 3-5 h. The reaction mixture was left to stand overnight at room temperature, then petroleum ether (40-60 ºC) was added and the precipitated solid products were filtered off and recrystallized from benzene-hexane (2:1) to give 16-19, respectively. 4-((5-Oxo-2-Phenyl-4,5-dihydrooxazol-4-yl)(piperidin-1yl)methyl)phenyl-4-methyl benzenesulfonate (16). IR (KBr), max/cm-1: 1770 (CO, lactone), 1644 (C=N), 1360 (SO3). EIMS (m/z, %): 504 (M+, 12), 478 (7.1), 365 (58), 282 (10), 161 (14), 85 (100), 72 (28). 1 CH3), 2.46-2.47 (t, 4H, N(CH2)2), 1.48-1.49 (m, 6H, 3CH2 of piperidine), 4.51-4.52 (m, 2H, N-CH, CH of oxazolone), 6.98.1 (m, 14H, Ar-H, CH=C). 4-(Morpholino(5-oxo-2-phenyl-4,5-dihydrooxazol-4-yl)methyl)phenyl-4-methyl benzene sulfonate (17). IR (KBr), max/cm-1: 1780 (CO, lactone), 1640 (C=N), 1360 (SO3). EIMS (m/z, %): 506 (M+, 16), 420 (16), 265 (19), 161 (100), 117 (45), 93 (46), 57 (18). 1 CH3), 2.67-2.68 (t, 4H, N(CH2)2), 3.58-3.59 (t, 4H, O(CH2)2), 4.51-4.52 (m, 2H, N-CH, CH of oxazolone), 6.9-8.1 (m, 14H, Ar-H, CH=C). 4-((5-Oxo-2-phenyl-4,5-dihydrooxazol-4-yl)(piperazin-1yl)methyl)phenyl-4-methylbenzenesulfonate (18). IR (KBr), max/cm-1: 1780 (CO, lactone), 3423 (NH), 1638 (C=N), 1360 (SO3). EIMS (m/z, %): 505 (M+, 22), 441 (26), 395 (52), 315 (12), 277 (53), 200 (61), 148 (79), 105 (100), 48 (61). 1H 3), 2.65-2.66 (m, 8H, N(CH2)4), 4.51-4.52 (m, 2H, N-CH, CH of oxazolone), 6.9-8.1 (m, 15H, Ar-H, CH=C, NH). 4-((5-Oxo-2-phenyl-4,5-dihydrooxazol-4-yl)(phenylthio)methyl)phenyl-4-methyl benzene sulfonate (19). IR (KBr), max/cm-1: 1780 (CO, lactone), 1640 (C=N), 1360 (SO3). EIMS (m/z, %): 529 (M+, 25), 401 (19), 316 (47), 257 (29), 213 (37), 188 (15), 101 (12), 77 (20), 43 (100). 2.1.6 Reaction of oxazolone (2) with active methylene compounds A mixture of oxazolone 2 (0.03 mol), ethylcyanoacetate (0.05 mol) and few drops of piperidine in dry chloroform (50 mL) was heated under reflux for 8 hours. The solvent was evaporated under reduced pressure. The obtained solid obtain 20. ethyl2-cyano-3-(5-oxo-2-phenyl-4,5-dihydrooxazol-4-yl)3-(4-(tosyl-oxy)phenyl) propanoate (20 max/cm-1: 1780 (CO, lactone), 1730 (CO, ester), 2110 (CN), 1640 (C=N), 1360 (SO3). EIMS (m/z, %): 533 (M+, 10), 413 (19), 341 (42), 304 (25), 280 (14), 189 (17), 168 (42), 105 (44), 77 (59), 43 (100). 1 3), 1.291.30 (t, 3H, CH3CH2), 4.37-4.43 (q, 2H, CH3CH2), 4.31-4.32 (m, 3H, CH-CH, CH of oxazolone), 6.9-8.1 (m, 14H, Ar-H, CH=C). A mixture of 2 (0.005 mol) and ethylacetoacetate (0.01 mol) in 30mL ethanol was added dropwise to 10 mL sodium hydroxide (10%), the mixture was stirred at room temperature for 24 h, then poured into 5 mL of 5% HCl. The formed solid nol to give 21. 2-acetyl-4-benzamido-3-(4-(tosyloxy)phenyl)pentanedioic acid (21 max/cm-1: 1670 (CO, amidic), 1700 (CO), 3400 (OH), 3300 (NH), 1640 (C=N), 1360 (SO3). EIMS (m/z, %): 539 (M+, 46), 457 (10), 382 (100), 298 (10), 254 (35), 181 (27), 147 (16), 111 (15), 91 (56). A mixture of compound 2 (0.005 mol), the appropriate nitroalkane namely, nitromethane and/or nitroethane (0.01 mol) and few drops of triethylamine in ethanol (30 mL) was refluxed with stirring for 12 h, then poured onto ice-water, The solid that separated was filtered off and recrystallized from ethanol to give 22 and 23, respectively. 4-(2-Nitro-1-(5-oxo-2-phenyl-4,5-dihydrooxazol-4-yl)ethyl)phenyl-4-methyl benzene sulfonate (22). IR (KBr), max/cm-1: 1770 (CO, lactone), 1350 (NO2), 1640 (C=N), 1360 (SO3). EIMS (m/z, %): 482 (M+2, 19), 411 (28), 344 (36), 218 (55), 275 (100), 197 (45), 155 (47), 129 (46), 91 (67). 4-(2-Nitro-1-(5-oxo-2-phenyl-4,5-dihydrooxazol-4-yl)propyl)phenyl-4-methyl benzene sulfonate (23). IR (KBr), max/cm-1: 1770 (CO, lactone), 1350 (NO2), 1640 (C=N), 1360 (SO3). EIMS (m/z, %): 495 (M+, 23), 455 (16), 419 (80), 384 (46), 350 (63), 334 (12), 295 (60), 238 (100), 155 (36). 1 3), 1.7 (d, 3H, CH3-CH), 3.3 (t, 1H, CH), 4.31-4.32 (m, 2H, O2NCH-, CH of oxazolone), 6.9-8.1 (m, 14H, Ar-H, CH=C). 2.2 Evaluation of the prepared compounds as lubricating oil additives 2 . 2 . 1 E v a l u a t i o n o f t h e p re p a re d c o m p o u n d s a s antioxidant additives for the tested lubricating oil A lubricating sample free from additives, as well as lubricating oil samples containing different concentrations of prepared products, were subjected to severe oxidation with at 155 °C for 36 h. Samples were taken at regular intervals in 3-36 h of oxidation. The oxidation stability of these samples is expressed in terms of total acid number (TAN) according to (ASTMD-3242) (Figs.1-4) 2.2.2 Evaluation of the prepared compounds as corrosion inhibitor additives for the tested lubricating oil In order to evaluate the corrosion inhibition of the tested lubricating oil samples containing the prepared compounds, strips of three metals: iron, copper and aluminum with surface area of 1 cm2, were used in this study. Every metal was weighed and immersed in the oxidation system for 36 h under the previous conditions (155 ºC with air rate of 5 L/h). Then every metal was cleaned and weighed again. The difference in as corrosion inhibitors was evaluated by using weight loss technique according to ASTMD-130 (Table 3). 2.2.3 Effect of concentration The effect of concentration of additive, which gave the highest antioxidant efficiency for the tested lubricating oil, work, three different concentrations of additive 15 namely, 0.01, 0.05 and 0.1 g·L , were used (Fig. 5). 2.2.4 Surface tension of lubricating oil after oxidation Surface tension was measured for the lubricating oil with and without additives after 36 h at 155 °C with air rate of in order to determine the detergency effect of the additives on oil, by using surface tension apparatus (Torsion Balance White Elec. Co Ltd. No 0/17604f) (Table 4). 2.2.5 Thermal stability of prepared antioxidant additives In order to study the stability of effective antioxidant and anticorrosive additives towards heating, thermal analysis using thermogravimetric analysis (TGA) and differential H3C CHO + O S O O 1 thermal gravimetric analysis (DTGA) techniques were conducted by using Shimadzu TGA apparatus. 2.2.6 A comparison of the oxidation stability between lubricating oil containing the prepared products and lubricating oil containing a commercial additive The oxidation stability was compared between the lubricating oil containing the highly efficient prepared )and the lubricating oil containing a commercial antioxidant additive purchased from the local market (CO-OP Cosf/cc 21 w/51 oil). The results obtained (Fig. 6). 3 Results and discussion 3.1 Chemistry Many types of organic heterocyclic compounds have been used as antioxidant and anticorrosive additives for lubricating oils. In continuation of our previous studies in the field of antioxidant and anticorrosive additives (Hassan et al, 2010; 2011a; 2011b; Hassan, 2011; Amer et al, 2011; Habib et al, 2010; Habib et al, in press; Cameron, 1966) , new additives 2-23 were prepared and their antioxidant and anticorrosive activities were evaluated for some Egyptian local lubricating oils. Thus, the required (Z)-4-((5-oxo-2-phenyloxazol-4(5H)ylidene)methyl)phenyl-4-methyl benzenesulfonate 2, was prepared by means of the reaction of 4-toluenesulfonyloxy benzaldehyde 1 with hippuric acid and acetic anhydride in the presence of freshly fused sodium acetate according to the method reported in literature (Girges et al, 1989). C NHCH2COOH O Ac2O CH3COONa Fusion of oxazolone 2 with o-phenylenediamine in the presence of freshly fused sodium acetate at 140 oC and 190 oC respectively gives different products. When fusion was carried out at 140 oC, compound 3 was obtained, while fusion at 190 oC leads to the formation of compound 4. Moreover, reaction of oxazolone 2 with o-phenylenediamine in absolute ethanol under reflux afforded compound 5. Furthermore, treatment of oxazolone 2 with o-phenylenediamine in glacial acetic acid under reflux in the presence of fused sodium acetate gives imidazolone derivative 6 (Table 1) (Scheme 2). On the other hand, refluxing of one mole of oxazolone 2 with one mole of p-phenylenediamine in the presence of glacial acetic acid and fused sodium acetate afforded imidazolone 7, but using two moles of compound 2 to one mole of the other give bis imidazolone 8 (Table 1) (Scheme 3). In the present investigation, oxazolone 2 reacted with some heterocyclic amines, namely 2-aminopyridine, 3-aminopyridine, 2-aminothiazole, 2-aminobenzothiazole, 4-aminoantipyrine or 5-amino-4-phenylazo-2,4dihydropyrazol-3-one, in glacial acetic acid and fused sodium acetate giving imidazolone derivatives 9-14 (Table 1) (Scheme 4), respectively. Cyclocondensation of thiosemicarbazide with oxazolone 2 in dry pyridine afforded (Z)-4-((5-phenyl-2-thioxo-2Himidazo[1,5-b][1,2,4]triazol-(3H)-ylidene)methyl)phenyl-4methylbenzene sulfonate 15 (Table 1) (Scheme 5). The reactivity of the exocyclic (C=C) bond in the four position of the oxazolone ring is due to conjugation with the adjacent carbonyl group (Habib et al, 1989) . In the present work, the addition of piperidine, morpholine, piperazine or compound 2 gives the corresponding addition products 16-19 (Table 1) (Scheme 6), respectively. The present investigation deals also with the Michael addition on the exocyclic double bond in compound 2. Thus addition of ethylcyanoacetate to compound 2 in chloroform afforded oxazolone derivative 20, but the addition of ethylacetoacetate in the presence of sodium hydroxide afforded compound 21. On the other hand, addition of nitromethane and nitroethane to oxazolone 2 leads to the formation of compounds 22 and 23 (Table 1)(Scheme 7), respectively. Ar HN O Ph Ph Ar = H3 C OS O 8 Scheme 3 Reaction of oxazolone 2 with p-phenylenediamine under different moles NO NS H2N NSAcOH H2NAcOHN O NPh H2N CHA3NcOCHH3 A r CHN H2ANcOH N NO NS Ph 9 Ph 10 Ph 1 1 N Scheme 5 Reaction of oxazolone 2 with thiosemicarbazide HS CH3NO2 HN O Ar NCCH2COOEt A r CH N Ph O O Scheme 6 Reaction of oxazolone 2 with secondary amines and thiophenol HN NH HN Ar CH O N O Ph 2 Ar= H3C O S O O H Ar N 18 N O O Ph Ar S N 19 NO2 N O Ph 22 O O Ph O NO2 N O Ph 23 O CH3CH2NO2 CH3COCH2COOEt Scheme 7 Reaction of oxazolone 2 with active methylene compounds 3.2 Antioxidant and anticorrosive additives 3.2.1 Evaluation of the prepared compounds as antioxidant additives for the tested lubricating oil As mentioned in the literature survey, air oxidation of aliphatic hydrocarbons proceeds by a series of free radical reactions as shown by the following scheme: Initiation: RH + O2 + OOH Propagation: R + O2 ROO RO + OH Termination: RO + R RO + RO The principle requirement for the majority of antioxidants is the presence of a labile hydrogen in their chemical structure or the presence of sulphur or phosphorous. It was stated that, the antioxidant molecule reacts with the peroxy radicals which form during oxidation and leads to the formation of inactive products as shown in the following scheme: ROO Followed by: or: ROO + A. where, AH is the antioxidant molecule and A is an antioxidant radical. Thus, as the labile hydrogen atoms increase, the To verify the effectiveness of the synthesized compounds as antioxidants, we prepared different solutions by adding 0.1 g of the selected compound to 1 L of the additivefree tested lubricating oil, then the lubricating oil with and without additives was subjected to severe oxidation at 155 for 36 h. Samples were taken at regular intervals of 3 h for testing their oxidation stability, which is expressed in terms of the total acid number (TAN) according to ASTMD 3242, and recorded their UV spectra and then compared them with the lubricating oil sample free from additives. The results showed that, in the absence of additives, the oxidation products increased with time. When the prepared additives 2-23 were added to the tested , the oxidation products increased at a rate much lower than that without additives, as shown in Figs. 1-4 and Table 2. The highest antioxidant activity was observed in the presence of 11-15 compounds due to the presence of some antioxidant groups in each of them. Compound 14, which were the most effective antioxidant additive have many antioxidant moieties, such as imidazolone and pyrazolone moieties, and some antioxidant groups such as N=N and NH groups, while, compound 15 contains imidazolone and thiotriazole moieties. On the other hand, compounds 11-13 exhibited the highest antioxidant activity because they contain thiazole, benzothiazole, and pyrazole moieties, respectively, beside the imidazolone moiety in each of them. 3.2.2 Evaluation of the prepared compounds as corrosion inhibitors for the tested lubricating oil Once more, the prepared compounds were tested as corrosion inhibitors for the corresponding lubricating oil using three different strips of copper, iron and aluminum with an area of 1 cm2. The results showed a loss in the weight of metal strips for oil without additives. While in the presence of the compounds 2-23, higher corrosion inhibition was Without additives Compound 2 Compound 3 Compound 4 Compound 5 Compound 6 12 11 lpe 10 m sa 9 ram 8 g rpe 7 HO 6 K g 5 m ,N 4 A T 3 2 12 11 0 5 10 15 25 30 35 40 observed, as shown in Table (3). 3.2.3 Mechanism of corrosion inhibition In lubricating oil, compounds 2-23 exist as neutral molecules, in general, the mode of adsorption could be considered. The neutral form may be adsorbed on the metal surface via a chemisorption mechanism, involving the displacement of oil molecules from the metal surface and the sharing electrons between the N, O and S atoms and metal. In addition, lone-pair electrons of N and O atoms in the investigated compounds 2-23 may combine with freshly generated M2+ or M3+ ions on metal surface, forming metal inhibitor complexes. In case of aluminum as metal the equations will be as follows: Inh. + M2+ [Inh.]n+ + M2+ M= Fe and Cu 2+ 3+ Inh. + Al3+ These complexes might be adsorbed onto the metal surface by van der Waal’s forces to form protective films. On the other hand, the surface coordination is through the nitrogen atoms. It can be concluded that the mode of adsorption depends on the affinity of the metal towards the were found to adsorb benzene rings in a flat orientation. Thus, it is reasonable to assume that the tested inhibitors are adsorbed in a flat orientation through the N- and O-atoms. It was found that, the prepared compounds (2-23) showed good corrosion inhibition for all the metals used. This could be explained by the presence of heterocyclic moieties in their structures. Also, in the presence of NH, C=N groups and sulfur atom which may react with these metals to form the corresponding sulphides. 3.2.4 Effect of concentration For the compound that gave the highest antioxidant find the optimum concentration recommended to be used. Thus, three different concentrations of additive 15, namely 0.01, 0.05 and 0.1 g, for 1 L lubricating oil were used. The obtained results showed that, increasing the additive concentration led to decrease of oxidative products, indicating that that concentration of 0.1 g for 1 L oil is the more effective concentration to be used for additives 15 (Fig. 5). 3.2.5 Measurement of surface tension of lubricating oil after oxidation Surface tension was measured for lubricating oil with and without additives after heating for 36 h at 155 °C with air in order to determine the detergency effect of additives. As shown in Table (4), we can see that, the surface tension decreased for the lubricating oil in the presence of additives after oxidation compared to that of the additive-free oil. This means that, in presence of compounds 2-23, the need of oil for detergency additives are decreased in comparison with other additives. 3.2.6 Thermal stability of the prepared antioxidant additives Some of the highly effective antioxidant additives, namely additives 11-15, were subjected to thermal analysis using 12 11 le10 p m9 a s m8 a r rg 7 e p 6 H KO 5 g ,m4 AN 3 T 2 1 12 11 le10 p m 9 a s m 8 a rg 7 r pe 6 H O 5 K g 4 m ,N 3 A T 2 1 0 5 10 15 25 30 35 40 stage of decomposition began at 185.1 °C for compound 11 and at 241.2 °C for compound 12, and ended at 251.1 °C and 272.2 °C with weight loss of 11.2% and 16.4%, respectively. Compounds 13-15 at 165.5 °C, 188.7 °C, 199.1 °C, and ended them at 237.5 °C, 245.5 °C, 275.3 °C with weight loss of 11.7%, 13.3% and 10.0%, respectively. 3.2.7 A comparison of the oxidation stability between the tested oil containing the prepared products and lubricating oil containing a commercial additive The oxidation stability of the tested lubricating oil containing the highly efficient prepared antioxidants (0.1 ) is compared with that of the lubricating oil containing a commercial antioxidant additive purchased from the local market. The results obtained after 36 h oxidation at 155 °C with air rate 10 L h are shown in Fig. 6. It can be seen that the lubricating oil containing the compounds 11-15 showed better oxidation stability than the commercial lubricating oil. Without additives Commercial oil Compound 11 Compound 12 Compound 13 Compound 14 Compound 15 15 Surface tension Additive used Lubricating oil before oxidation Oil without additives after oxidation 41.5 45.0 4 Conclusion Newly synthesized imidazolone derivatives seem to be interesting for antioxidant and anticorrosive studies. The present investigation offers rapid and effective new procedures for the synthesis of novel imidazolone derivatives incorporating sulfonate moiety. It is clear that incorporation of aryl sulfonate, oxazolone and imidazolone moieties in the same molecule provide high antioxidant and anticorrosive characteristics. On the other hand, incorporation of pyridine, thiazole, benzothiazole and pyrazole rings into imidazolone compounds was crucial for antioxidant and anticorrosive characteristics as in case of compounds 9-14. Amer F A , Hassan H M , Moawad E B , et al. 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Ahmed El-Mekabaty, Osman M. O. Habib, Hussein M. Hassan, Evelin B. Moawad. Synthesis and evaluation of some new oxazolones and imidazolones as antioxidant additives for Egyptian lubricating oils, Petroleum Science, 2012, 389-399, DOI: 10.1007/s12182-012-0223-8