Faculty of Natural Sciences and Technology RAPPORT. Felleslab, TKP 4105 og TKP 4110

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1 NTNU Norwegian Universiy of Science and Technology Faculy of Naural Sciences and Technology Deparmen of Chemical Engineering RAPPORT Felleslab, TKP 4105 og TKP Tiel: Kineic Sudy of Ehyl Iodide and NaOH in Versjon: bach reacor Sed: Trondheim Forfaere: Anders Leirpoll & Ufør i iden: Kasper Linnesad Kl. 13:00-17:00 Veileder: Andreas Lillebø Anall sider: 13 Hovedrapp: 9 Bilag: 3 Absrac The reacion rae of ehyl iodide ( ) and sodium hydroxide ( ) was sudied in a sirred bach reacor using differen sarconcenraions of reacans. The reacion was carried ou using dimehylsulfoxide ( ) and waer ( ) as solvens, under a nirogen ( ) amosphere a. The mean reacion rae consans were deermined o be and for a firs and second order reacion respecively. The reacion was deermined o be of second order using argumens from organic chemisry raher han he experimenal daa which was inconclusive, mos likely because of large uncerainies. Jeg erklærer a arbeide er ufør selvsendig og i samsvar med NTNUs eksamensreglemen. Dao og underskrifer: Address Locaion Tel Sem Sælands vei 4 NO-7491 Trondheim Fax Org. no. NO

2 i Table of Conens 1 Inroducion Theory Reacion mechanism Kineics Calculaion of amouns of reacans and solvens Experimenal Resuls Firs order Second Order Discussion Conclusion... 8

3 1 1 Inroducion This experimen wa c rried u p r f he fe e b for he courses TKP4105 and TKP 4110 a NTNU during fall The undersanding of kineics and raes of reacions is imporan o a chemical engineer, and esing of hese in he lab, using differen parameers is essenial in fine-uning of reacors. The purpose of his exercise is o change he reacion condiions o see heir effec on reacion parameers. 2 Theory 2.1 Reacion mechanism Ehyl iodide reacs wih he hydroxide ion according o Reacion mechanism 1. This is a ypical bimolecular nucleophilic subsiuion reacion [1]. In his case he hydroxide ion acs as a nucleophile, and is subsiuing wih he iodide anion by donaing elecrons o he carbon aom which has a parial posiive charge. Simulaneously he carbon-iodide bond breaks leaving he produc and a free iodide anion. Reacion mechanism 1: The nucleophile,, is donaing elecrons o he carbon aom, a he same ime as he carbon iodide bond breaks hus creaing a ransiion sae. The ransiion sae is hen convered o he produc. 2.2 Kineics To deermine he reacion rae consan, he following equaion is used [2] (2.1) Where is concenraion of componen, is ime and is he reacion rae of componen. If he reacion is of firs order [2] d d Where is he reacion rae consan. Inegraing from a, o a d d (2.2) (2.3) ( ) Where is he sar concenraion of componen. Ploing ( ) agains, gives a linear curve wih slope. If he reacion is of second order [2] This could also be wrien as d d (2.4)

4 2 d d Bu in his experimen he concenraion of he wo reacans is he same. Inegraing from a, o a (2.5) d d (2.6) Ploing as a funcion of ime gives a linear curve wih slope. 3 Calculaion of amouns of reacans and solvens Volume,, equals mass,, divided by densiy, Mass can be subsiued by he number of moles,, imes molar mass, Then he oal volume,, can be found. I is assumed ha he volume of ehyl iodide and sodium hydroxide are negligible (3.1) (3.2) (3.3) The relaion beween number of moles of dimehyl sulfoxide (DMSO from here on), number of moles of waer, is and (3.4) Here i is assumed ha he number of moles of sodium hydroxide and ehyl iodide are negligible. The mole raio is given by he mole fracion of DMSO which in his experimen is 0.4. If he equaion for oal volume is rearranged for, i can be wrien as (3.5) The relaion beween he number of moles and volume of each reacan and solven is hen given by (3.2). This gives he volume of waer, as (3.6) The volume of, is given by When volumes of and are found, volume of sodium hydroxide, is found hrough he sar concenraion and he undilued soluion concenraion, (3.7)

5 3 (3.8) Finally, he volume of ehyl iodide, i molar mass and densiy, is found from he number of moles of sodium hydroxide, (3.9) In hese calculaions all excess volumes are negleced, meaning ha he enhalpy of mixing is zero. 4 Experimenal In his experimen, he reacion beween ehyl iodide ( ) and sodium hydroxide ( ) was o be sudied a differen reacion condiions. The reacion ook place in a bach reacor wih an iner amosphere. Three experimens were performed, wih varying concenraions of reacans, ehyl iodide, and sodium hydroxide, while concenraion of solven, dimehyl sulfoxide, ( from hereon) was lef unchanged. Table 1: The v ri b e v ue f r he hree experi e provided by he insrucor, here is emperaure, is he concenraion of hydroxide ions and is he mole fracion of DMSO Experimen 1 Experimen 2 Experimen 3 T T T [ ] [ ] [ ] In Table 1 concenraions given by he supervisor are shown. Wih a oal volume of 350 ml, he amouns of all reacans and solvens can be calculaed, shown earlier, resuling in Table 2. Table 2: The amoun of solvens and reacans used in he hree experimens, an example of he calculaions is shown in (3.6), (3.7), (3.8) and (3.9). Compound Volume Experimen 1 Experimen 2 Experimen 3 NaOH (1M) DMSO EI , waer and sodium hydroxide were added o he reacor, mixed, and lef o sabilize. Erlenmeyer flasks were prepared in ice bah, wih disilled waer ( ) and phenolphhalein ( dr p ). The firs sample ( ) was aken from he reacor a firs, hen he sopwach was sared as ehyl iodide was added o he reacor. Samples were aken wih varying inervals, frequenly a firs, and more infrequenly owards he end. The samples were iraed agains unil color change. Amoun of reaced was calculaed.

6 ln(c o /C) C EI [mol/l] 4 5 Resuls Experimen 1 Experimen 2 Experimen [s] Figure 1: The concenraion of ehyl iodide ploed agains ime for each of he experimens. The daa for he plo is presened in Table 5, Table 6 and Table 7 in 7Appendix A Firs order The plos of ( ) versus ime,, are given in Figure 2, Figure 3 and Figure 4, for experimen 1,2 and 3 respecively. Linear regression performed wih Microsof Excel is shown, giving he rae consan,, as he curves slope y = x R² = [s] Figure 2: Plo of ( ) versus ime,, for experimen 1, giving he rae consan,, as he curves slope. The daa for he plo is presened in Table 5 in 7Appendix A -

7 ln(c 0 /C) ln(c o /C) y = x R² = [s] Figure 3: Plo of ( ) versus ime,, for experimen 2, giving he rae consan,, as he curves slope. The daa for he plo is presened in Table 6 in 7Appendix A y = x R² = [s] Figure 4: Plo of ( ) versus ime,, for experimen 3, giving he rae consan,, as he curves slope. The daa for he plo is presened in Table 7 in 7Appendix A -. The reacion consans for each experimen are displayed in Table 8 in 7Appendix A -, and heir mean value is 5.2 Second Order The plos of versus ime,, are given in Figure 5, Figure 6 and Figure 7 for experimen 1, 2 and 3 respecively. Linear regression performed wih Microsof Excel is shown, giving he rae consan,, as he curves slope.

8 1/C 1/C y = x R² = [s] Figure 5: Plo of versus ime,, for experimen 1, giving he rae consan,, as he curves slope. The daa for he plo is presened in Table 5 in 7Appendix A y = 0.02x R² = [s] Figure 6: Plo of versus ime,, for experimen 2, giving he rae consan,, as he curves slope. The daa for he plo is presened in Table 6 in 7Appendix A -.

9 1/C y = x R² = [s] Figure 7: Plo of versus ime,, for experimen 3, giving he rae consan,, as he curves slope. The daa for he plo is presened in Table 7 in 7Appendix A -. The reacion consans for each experimen are displayed in Table 9 in 7Appendix A -, and heir mean value is 6 Discussion As shown in Figure 2, Figure 3 and Figure 4 he plo of agains ime yield linear lines wih coefficiens of deerminaion ranging from 0.97 o This is a clear indicaion ha he reacion rae is of he firs order. On he oher hand hough, Figure 5, Figure 6 and Figure 7 which show he plo of as a funcion of ime also yield linear lines wih coefficiens of deerminaion ranging from 0.97 o This, and he reacion mechanism, gives a srong inclinaion ha he reacion is of he second order. In Reacion mechanism 1 boh he reacans are he par of he rae deermining sep which suppors he claim ha he reacion mechanism is of second order. An alernae possibiliy is ha he reacion migh occur wih wo differen reacion mechanisms, one by nucleophilic bimolecular subsiuion and he oher by nucleophilic unimolecular subsiuion which is a firs order reacion. However his is highly unlikely, due o he fac ha DMSO is an aproic polar solven which highly promoes nucleophilic bimolecular reacions. An addiional facor ha promoes he nucleophilic bimolecular subsiuion is ha he hydroxide ion is a very srong nucleophile and he iodide anion is a good leaving group [1]. A possible reason ha he reacion rae looks like i is of he firs order are he uncerainies. There is a fair amoun of uncerainy in he sar concenraion due o he use of inaccurae graduaed cylinders and assumpions in he calculaion of he volumes. The uncerainy in he concenraion in he differen samples also carries some uncerainy, bu i is believed ha his uncerainy is negligible in comparison since hey were done very meiculously. The bigges uncerainy is mos likely in he ime measuremen considering ha he reacion sill occurs during he pipeing, hence making i difficul o do accurae measuremens. The reacion rae consans for he firs order reacions vary considerably for each of he hree experimens as can be seen in Table 8 in Appendix A - This is mainly because of he large uncerainies menioned earlier, since he emperaure was held consan a for all of he experimens. The same argumens can be used for he second order reacion rae consans

10 8 shown in Table 9 in 7Appendix A -. An alernae explanaion is ha he firs experimen, which deviae he mos, was conduced a a lower emperaure. This may have occurred because he waer bah may no have had ime o reach he correc emperaure. The conversion, which is calculaed in Table 10 in 7Appendix A - afer ime of sream (TOS) equal o 1000 seconds and is subsanially lower for he firs experimen, also suppors his saemen. The reason ha he conversion a TOS is higher for experimen 2 han experimen 3 is mos likely due o he same reasons, ha he solvens emperaure had no had enough ime o sabilize. The reacion was assumed o be compleely irreversible a all imes in he derivaion of he rae laws. This is a very good approximaion when he concenraion of he produc is low; on he conrary i is an inadequae approximaion a higher produc concenraion closer o equilibrium [1]. In hese experimens he produc concenraion did no reach a subsanial level, and consequenly he oher uncerainies play a much bigger role. The acivaion energy was no calculaed since he reacion has o be carried ou a differen emperaures o have sufficien daa. In Figure 1 he concenraion of ehyl iodide is ploed agains ime, and i is clear ha experimen 1, which had he lowes iniial concenraion, had he leas change in concenraion. Experimen 2 and 3 look more similar, bu i is eviden ha he reacion progressed a a higher rae in experimen 3 for. This is an indicaion ha he reacion rae increase wih increasing reacan concenraion, as expeced. 7 Conclusion The mean reacion rae consans were deermined o be and for a firs and second order reacion respecively. The reacion was deermined o be of second order using argumens from organic chemisry raher han he experimenal daa which was inconclusive mos likely because of large uncerainies, especially a wha ime each sample were sampled. I was esablished ha higher iniial concenraions of he reacans lead o higher reacion raes, which was anicipaed.

11 9 References [1] J. McMurry, Organic Chemisry, 8h red., Belmon: Brooks/Cole, 2012, pp [2] H. S. Fogler, Elemens of Chemical Reacion Engineering, vol. IV, Wesford, Massachuses: Pearson Educaion, 2010, pp [3] G. A. o. T. Findlay, SI Chemical Daa, vol. VI, Milon: John Wiley and Sons Ausralia, Ld, Lis of symbols and abbreviaions Symbol Uni Descripion Concenraion of componen Sar concenraion of componen DMSO EI mol Dimehyl sulfoxide Ehyl iodide Reacion rae consan Molecular weigh of componen Mass of componen The number of moles of componen Coefficien of deerminaion Reacion rae of componen Temperaure Time TOS s Time of sream, when Volume of componen Toal volume Molefracion of componen c Densiy of componen

12 A-1 Appendix A - Daa The densiies and molecular weighs of he compounds are shown in Table 3. Table 3: The densiies and he molecular weighs of he compounds used in he calculaion of he volume needed of each reacan and solven. Compound Densiy [3] Molecular weigh [3] Dimehyl sulfoxide Waer Ehyl iodide Volumes calculaed from given sar-fracions are shown in Table 4. Table 4: The volume of each componen calculaed as shown in (3.6), (3.7), (3.8) and (3.9). Compound Volume Experimen 1 Experimen 2 Experimen 3 NaOH 1M DMSO EI Daa for Figure 2 and Figure 5 are shown in Table 5. Table 5: The daa used for Figure 2 and Figure 5 Sample # Time Volume HCl Concenraion of EI Daa for Figure 3 and Figure 6 are shown in Table 6. Table 6: The daa used for Figure 3and Figure 6 Sample # Time Volume HCl Concenraion of EI

13 A-2 Sample # Time Volume HCl Concenraion of EI Daa for Figure 4 and Figure 7 are shown in Table 7. Table 7: The daa used for Figure 4, Figure 2 and Figure 7 Sample # Time Volume HCl Concenraion of EI The reacion rae consan for he firs order reacions, are presened in Table 8. Table 8: The reacion rae consan for he firs order reacions, mean of all he experimens. Experimen # Mean for each experimen are shown ogeher wih he The reacion rae consan for he second order reacions, are presened in Table 9. Table 9: The reacion rae consan for he second order reacions, mean of all he experimens. Experimen # Mean In a bach reacor he concenraion of he reacing specie is given as [2] for each experimen are shown ogeher wih he ( ) (A.1) where is he concenraion of componen ; is he sar concenraion of componen ; is he conversion of componen Solving for he conversion

14 A-3 This equaion is used in Table 10 o calculae he conversion of ehyl iodide. Table 10: The conversion of ehyl iodide calculaed a via (A.2). The concenraions were calculaed from he linear regressions shown in Figure 5, Figure 6 and Figure 7. Experimen # (A.2)