About the metallic corrosion inhibition of some azomethines of cyclohexylamine series

Journal of Chemistry, Vol. 43 (3), P. 379 - 383, 2005<br /> <br /> <br /> ABOUT THE METALLIC CORROSION INHIBITION OF SOME<br /> AZOMETHINES OF CYCLOHEXYLAMINE SERIES<br /> Received 25th-March-2004<br /> Dang Nhu Tai, Nguyen Minh Thao, Nguyen Dinh Thanh, Nguyen Duc Minh<br /> Faculty of Chemistry, Hanoi University of Science<br /> <br /> <br /> Summary<br /> The appropriate conditions have been found for syntheses of a series of azomethines using the<br /> reaction between cyclohexylamine and different aromatic aldehydes. The structures of products<br /> have been determined by the data of IR- and 1H-NMR-spectra. All obtained azomethines have<br /> metallic inhibition corrosion capacities on CT-3 steel and aluminum in different levels. The<br /> influences of structures to their metallic inhibition corrosion capacities have been discussed.<br /> <br /> <br /> I - Introduction internal reference TMS (at the Lab of Structural<br /> Analysis Institute of Chemistry-the National<br /> In the present years, the azomethines have Center of Natural Science and Technology). The<br /> been studied widely due to their metallic aluminum samples for this case are aluminum<br /> inhibition corrosion aside from useful properties plates containing 0.3% - 0.9% Mn, 0.5% Fe,<br /> [1]. However, there are only two patents [3, 4] 3.8% - 4.9 % Cu, 0.3% Zn, 0.2% Ti, 0.1% Ni,<br /> about the synthesis and the study on inhibition 93.1% - 95% Al. The steel CT-3 samples<br /> corrosion on metals of azomethines containing containing 0.15% C, 0.42% Mn, 0.037% S,<br /> hexamethylenediamine component with 0.024% P, Si (trace) and ~99.369% Fe. The<br /> cinnamaldehyde and p-tolualdehyde. metallic corrosion inhibition properties have<br /> For searching the new compounds having been determined using the methods described in<br /> high inhibition corrosion capacities on metals, the articles [2].<br /> we have synthesized an azomethine series from Synthesis of Azomethines of<br /> cyclohexylamine and different substituted Cyclohexylamine (General Method)<br /> benzaldehydes and investigated their inhibition<br /> corrosion capacities on different metals (CT-3 An equivalent molar mixture of cyclo-<br /> steel, aluminum ...). hexylamine (0.1 mol) and different aromatic<br /> aldehyde (0.1 mol.) in 50 - 100 ml. of toluene<br /> II - Experimental was heating under reflux and with a water<br /> separator. After separating about 1.8 ml. of<br /> IR-spectra were recorded on NICOLET-760 water, the reaction mixture was remained to<br /> Spectrometer in form of mixing with KBr and cool to room temperature. Filter the separated<br /> using reflex-measure method at the Petrol- solid precipitate, and dried in air (in particular,<br /> Chemical Center (Hanoi University of Science, azomethine VII from cyclohexylamine and<br /> VNU). 1H-NMR spectra were recorded on salicylaldehyde was the oil). Recrystallized<br /> BRUKER AVANCE Spectrometer (German) at from ethanol or ethanol-water (1 : 1 v/v). The<br /> 500 MHz, solvent was DMSO-d6, with the results were showed in table 1.<br /> <br /> 379<br />  III - Results and Discussion were synthesized from cyclohexylamine and<br /> different aromatic aldehydes in toluene in<br /> The azomethines of cyclohexylamine series following reaction:<br /> -H2O<br /> ArCH=O + H2N ArCH N<br /> <br /> <br /> (I-VIII)<br /> where, Ar are p-nitrophenyl (I), m-nitrophenyl (II), phenyl (III), p-methoxyphenyl (IV),<br /> 3,4-dioxymethylenephenyl (V), p-dimethylaminophenyl (VI), o-hydroxyphenyl (VII) and indolyl-3 (VIII).<br /> <br /> A reaction mixture was consisted of reaction to take place gently and the products<br /> cyclohexylamine and different aromatic obtained in crystals, otherwise some oil<br /> aldehydes in molar ratio 1 : 1 in toluene. The products shall be obtained. The obtained<br /> reactions have been carried out by heating under products are solids with sharp melting points<br /> reflux with separation of water in the present of and high productivities (43-85%). The results<br /> the appropriate catalyst. This catalyst allows the are represented in table 1.<br /> Table 1: Azomethines of Cyclohexylamine I-VIII<br /> IR spectra, cm-1<br /> Azomethine m.p., oC Yield, %<br /> CH=N Other group<br /> I 89 - 90 32 1639 1516,1337 (NO2)<br /> II 51 - 52 16 1639 1521,1337 (NO2)<br /> III 167 - 168 15 1633 -<br /> IV 159 - 160 20 1644 1250 (C O C)<br /> V 63 - 64 62 1654 1252 (C O C)<br /> VI 87 - 88 59 1624 -<br /> VII Oil 80 1628 3058 (OH)<br /> VIII 111 - 112 98 1624 3385 (NH)<br /> <br /> In their IR spectra, there are the proved the presence of link group `>C=N in<br /> characteristic absorption bands with medium the azomethine molecules. In addition, the<br /> intensities in region 1635 to 1649 cm-1 in IR different functional groups also give their<br /> spectra and they were due to sp2 hybrid characteristic absorption bands in spectra (see<br /> nitrogen-carbon bond stretching vibration. This table 1).<br /> Table 2: The metallic corrosion inhibition capacities of azomethines I-VIII on CT-3 steel and Al<br /> CT-3 steel Aluminum<br /> 5 5<br /> No Substituent .10 , .10 ,<br /> Z, % Z, %<br /> g/cm2.min g/cm2.min<br /> 0 5.0257 1.0000 0.00 132.7636 1.0000 0.00<br /> I p-NO2 1.7678 0.3518 64.82 2.7324 0.0206 97.94<br /> II m-NO2 2.2700 0.4517 54.84 2.4129 0.0182 98.18<br /> III H 3.1100 0.6188 38.12 30.1351 0.2270 77.30<br /> IV p-OCH3 2.5351 0.5044 49.56 2.7907 0.0210 97.90<br /> V 3,4-O2CH2 2.5763 0.5126 48.74 46.9177 0.3534 64.66<br /> VI p-N(CH3)2 1.9592 0.3898 61.02 38.9015 0.2930 70.70<br /> VII o-OH 3.2171 0.6401 33.99 40.6328 0.3061 69.39<br /> VIII Indolyl-3 0.8430 0.1677 83.23 52.2706 0.3937 60.63<br /> 380<br />  Proton nuclear resonance spectrum of ppm (2H,3-Hcycl and 2H,5-Hcycl); 1.56 and 1.11<br /> azomethine III (Brucker Avance Spectrometer at ppm (2H,4-Hcycl).<br /> 500 MHz, solvent DMSO-d6) was presented as Thus, from data of IR- and 1H-NMR-spectra<br /> following: 8.10 ppm (1H, CH=N); 7.87 ppm of azomethine III it could be sure that the<br /> (2H,2-Har and 6-Har); 7.33 ppm (3H,3-Har, 4- structures of azomethines of cyclohexylamine<br /> Har and 5-Har); 2.91 ppm (1H,1-Hcycl.); 1.94 series have been determined and agreed with<br /> and 1.70 ppm (2H,2-Hcycl and 2H,6-Hcycl); 1.30 their provided structural formulas.<br /> <br /> Table 3: The charge densities on atom of parent skeleton of azomethine molecules I-VIII<br /> (calculated by using AM1 method)<br /> Azomethines<br /> Atom<br /> I II III IV V VI VII<br /> C1 -0.0479 -0.0447 -0.0432 -0.0419 -0.0535 -0.0419 -0.0489<br /> C2 -0.1451 -0.1422 -0.1421 -0.1420 -0.1486 -0.1418 -0.1460<br /> C3 -0.1575 -0.1590 -0.1586 -0.1586 -0.1565 -0.1584 -0.1572<br /> C4 -0.1587 -0.1578 -0.1570 -0.1569 -0.1565 -0.1567 -0.1581<br /> C5 -0.1519 -0.1538 -0.1534 -0.1536 -0.1574 -0.1536 -0.1515<br /> C6 -0.1837 -0.1709 -0.1705 -0.1696 -0.1441 -0.1685 -0.1833<br /> N7 -0.1656 -0.1717 -0.1799 -0.1867 -0.1691 -0.1892 -0.1684<br /> C8 -0.0465 -0.0379 -0.0300 -0.0224 -0.0255 -0.0183 -0.0405<br /> C9 -0.0161 -0.0670 -0.0649 -0.1017 -0.1046 -0.1131 -0.1380<br /> C10 -0.1279 -0.0556 -0.1127 -0.0813 -0.0936 -0.0752 -0.0576<br /> C11 -0.0751 -0.1374 -0.1387 -0.1653 0.0073 -0.2000 -0.1724<br /> C12 -0.1235 -0.0590 -0.1167 0.0924 0.0200 0.0975 -0.0878<br /> C13 -0.0764 -0.1488 -0.1412 -0.2162 -0.1168 -0.2042 -0.1637<br /> C14 -0.1026 -0.0495 -0.0858 -0.0495 -0.1112 -0.0487 0.0960<br /> <br /> Table 4: The Surface Areas of Molecule of Azomethines I-VIII<br /> Nonplanar Van der Solvent-<br /> Hammett’s Polarizability<br /> No. Substituent Angle (o) Waals Accessible*<br /> Sigma (Å3)<br /> surface (Å2) (Å2)<br /> I p-NO2 0.78 0.94 263.51 457.99 25.28<br /> II m-NO2 0.71 7.60 262.09 460.79 25.28<br /> III H 0.00 6.98 237.24 429.68 23.44<br /> IV p-OCH3 -0.27 4.46 268.05 471.02 25.91<br /> V 3,4-O2CH2 -0.34 9.90 258.61 452.55 25.77<br /> VI p-N(CH3)2 -0.83 0.40 290.68 498.74 28.46<br /> VII o-OH - 37.06 245.48 431.92 24.08<br /> *<br /> Solvent Probe Radius is 1.40 Å<br /> <br /> The corrosion inhibition capacities of these all the synthesized azomethines from<br /> compounds have been investigated using the cyclohexylamine and aromatic aldehydes have<br /> immersion method in 2M HCl solution. The the metallic corrosion inhibition capacity for<br /> obtained results are presented in table 2. Thus, CT-3 steel and aluminum in different levels.<br /> <br /> 381<br /> While azomethine which contained the indole- azomethines in which the aldehyde components<br /> 3-aldehyde component had the highest corrosion were m-nitrobenzaldehyde, p-nitrobenzaldehyde<br /> inhibition capacity for CT-3 steel (Z = 83.23%), and p-anisaldehyde had the protection capacity<br /> the other azomethines had higher corrosion Z as following: 98.18, 97.94 and 97.90%,<br /> inhibition capacity for aluminum, for example, respectively.<br /> <br /> <br /> <br /> <br /> I, = 0.94o II, = 7.60o III, = 6.98o IV, = 4.46o<br /> <br /> <br /> <br /> <br /> V, = 9.90o VI, = 0.40o VII, = 37.06o VIII, = 2.31o<br /> Figure 1: Geometry of some azomethines I-VIII optimized by using AM1 quantum chemistry<br /> method<br /> 70<br /> 3.3<br /> H<br /> 3.1 p-N(CH3)2 p-NO2<br /> -1<br /> P(CT-3).10 , g/cm .min<br /> <br /> <br /> <br /> <br /> 2.9 60<br /> -2<br /> <br /> <br /> <br /> <br /> 3,4-O2CH2 2.7 m-NO2<br /> p-OCH3<br /> Z (%)<br /> <br /> <br /> <br /> <br /> 2.5<br /> p-OCH3 m-NO2 50<br /> 5<br /> <br /> <br /> <br /> <br /> 2.3 3,4-O2CH2<br /> 2.1<br /> 40<br /> 1.9 H<br /> p-N(CH3)2<br /> 1.7<br /> p-NO2<br /> 1.5 30<br /> -1 -0.5 0 0.5 1 -1 -0.5 0 0.5 1<br /> Hammett's Hammett's<br /> A B<br /> Figure 2. Relationships of the corrosion rate P (A) and inhibition effects Z% (B) with the<br /> substituent Hammett’s constants<br /> <br /> Figure 2 presented the relationships between capacity Z. And on the contrary, azomethine<br /> the corrosion rate P and Hammett’s substituent molecules were more nonplanar (with the large<br /> constants . It showed that azomethine I had the nonplanar angle) had smaller protection<br /> highest corrosion rate and the lowest protection capacity Z. Especially, azomethine molecule VII<br /> capacity. From table 4 and figure 1 one could with the hydroxyl at the ortho-position of<br /> show that azomethines I-VII were nonplanar benzene ring had smallest protection capacity Z,<br /> conjugation system, and it should seem that the because this substituent caused to azomethine<br /> corrosion inhibition capacity certainly related molecule to be less planar. The nonplanar angle<br /> with planarity of azomethine molecule which in this case was 37.06o. Starting from that<br /> could be specify nonplanar angle [5]. The phenomenon, it would be seemed that the<br /> azomethine molecules were more planar (with protection effect of azomethine was physico-<br /> the small nonplanar angle) had higher protection chemical process: azomethine molecules were<br /> <br /> 382<br /> absorbed on the metal surface and protected There were some correlation relationships<br /> metal from the corrosion medium (see figure 3). between the corrosion rate P and the other<br /> 110 physicochemical properties of azomethine<br /> 100 molecule (for example, electron density (charge<br /> Inhibition Effect Z%<br /> <br /> <br /> <br /> <br /> 90 density) on atom, Van der Waals surface,<br /> 80 solvent-accessible surface, polarizability,…).<br /> 70 The electron densities on atom have been<br /> 60 computed using the quantum mechanics method<br /> 50 (AM1 method) (see table 3). It showed that the<br /> 40 charge densities on atom, Van der Waals<br /> 30 surfaces, solvent-accessible surfaces,<br /> 0 10 20 30 40 polarizabilities had remarkable influence on the<br /> Nonplanar Angle (degree) corrosion rates P (see table 4). These<br /> Figure 3: Relationships of the inhibition effects relationships were presented in the following<br /> Z% with the nonplanar angles expression:<br /> <br /> = 1.832x10-3 + 4.173x10-3xC2 + 7.518x10-3xC4 - 1.643x10-4xC10<br /> CT-3 steel<br /> + 2.065x10-4xC11 - 2.252x10-5xC12 + 2.326x10-4xC14.<br /> -3 -3 -2<br /> Al = 2.070x10 - 0.244xC2 + 0.243xC4 + 4.420x10 xC10 - 1.010x10 xC11<br /> -3 -3<br /> - 2.206x10 xC12 - 6.046x10 xC14.<br /> If the Wan der Waals surfaces of azomethine molecule were counted, then we have the following<br /> equations:<br /> -4 -3 -5 -4<br /> CT-3 steel = -1.355x10 - 1.396x10 xC3 - 1.065x10 xC5 - 1.025x10 xC9<br /> -5 -6 -7<br /> - 3.949x10 xC10 + 2.173x10 xC12 - 2.836x 10 xSVDW.<br /> -2<br /> Al = -3.255x10 - 9.100x10-2xC3 - 8.401x10-2xC5 - 1.173x10-2xC9<br /> - 8.308x10-3xC10 - 4.276x10-3xC12 + 1.405x10-5xSVDW.<br /> If the polarizability of azomethine molecule were counted, then we have the following equations:<br /> -4 -3 -3 -5<br /> CT-3 steel = 9.081x10 + 2.628x10 xC3 + 4.918x10 xC4 - 1.831x10 xC10<br /> - 4.596x10-6xC12 + 4.915x10-5xC14 - 2.627x 10-6xPPolarizability.<br /> -2 -3<br /> Al = 6.987x10 + 0.107xC3 + 0.354xC4 - 1.232x10 x C10<br /> - 3.043x10 xC12 + 2.349x10 xC14 + 1.138x10-4xPPolarizability.<br /> -3 -3<br /> <br /> <br /> <br /> <br /> IV - Conclusion References<br /> <br /> A series of eight azomethines has been 1. M. N. Desai, M. M. Pandya, G. V. Shan.<br /> synthesized from cyclohexylamine and different Indian J. Tech., Vol. 10, P. 292 - 294 (1981).<br /> aromatic aldehydes. The structures of products 2. Dang Nhu Tai, Nguyen Dinh Thanh, Tran<br /> have been determined by the data of IR- and 1H- Dinh Phong. Book of Abstracts of the 8th<br /> Eurasia Conference on Chemical Sciences,<br /> NMR-spectra. All obtained azomethines have P. 272, Oct. 21-24 (2003).<br /> metallic inhibition corrosion capacities on CT-3 3. E. Phillips, A. Braig. US Patent 5.120.356<br /> steel and aluminum in different levels. (1992).<br /> 4. A. Braig, E. Phillips. US Patent 5.288.315<br /> This publication is completed with financial (1994).<br /> support from the National Basic Research 5. Nguyen Dinh Thanh. PhD's thesis, Hanoi<br /> Program in Natural Sciences. (1986).<br /> <br /> 383<br /> 384<br />