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The conversion velocity of the cis- to the trans- form of decahydronaphthalene in the presence of aluminum… Yip, C.W. 1946

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THE CONVERSION VELOCITY OF THE C I S -TO THE TRANS- FORM OF DECAHYDRONAPHTHALENE IN THE PRESENCE OF ALUMINUM CHLORIDE A t h e s i s submit ted i n p a r t i a l f u l f i l l m e n t of the requirements of the course i n Chemical E n g i n e e r i n g l e a d i n g to the degree o f Master of A p p l i e d Science The U n i v e r s i t y of B r i t i s h Columbia C. W, Y i p September, 1946 ACKNOWLEDGEMENT The author wishes to guidance o f D r . W. E . Seyer of under whose d i r e c t i o n the work acknowledge the he lp and the Department o f Chemis t ry has been c a r r i e d ou t . TABLE OF CONTENTS Page 1. I n t r o d u c t i o n 1 2. Isomers o f Decahydronaphthalene 2 3. I s o m e r i z a t i o n o f Decahydronaphthalene i n the Presence o f Aluminum C h l o r i d e 3 4 . Role o f Aluminum C h l o r i d e 6 A . True C a t a l y s t 6 B . In termedia te Compound 8 3. E x p e r i m e n t a l 10 A . Apparatus 10 B . M a t e r i a l s 12 C . Procedure 13 6. R e s u l t s 13 A . Convers ion at D i f f e r e n t Temperatures 13 B . Convers ion U s i n g D i f f e r e n t Amounts o f Aluminum C h l o r i d e 19 7. Treatment o f the R e s u l t s 21 A . Convers ion K i n e t i c 21 B . Energy o f A c t i v a t i o n 24 8. D i s c u s s i o n of the R e s u l t s 28 THE CONVERSION TELOCITY OF THE C I S -TO THE TRANS- FORM OF DECAHYDRONAPHTHALENE IN THE PRESENCE OF ALUMINUM CHLORIDE 1. INTRODUCTION For the past cen tu ry , many new chemica l i n d u s t r i e s have been developed from the r e sea rch i n hydrocarbons; con-sequen t ly , more and more emphasis w i l l be p l a c e d upon the hydrocarbon s t r u c t u r e s and processes f o r o b t a i n i n g s e l e c t e d i n d i v i d u a l hydrocarbons . Many experiments have been conduct-ed to change the a v a i l a b l e hydrocarbons i n t o more d e s i r a b l e types merely by the process of i s o m e r i z a t i o n . A t p re sen t , the q u a n i t a t i v e measurement on the v e l o c i t y of c a t a l y t i c i s o m e r i z a t i o n i s ve ry l i m i t e d and p r a c t i c a l l y a l l the work done has been i n the s imple homo-geneous gas phase. The t h e o r i e s of c a t a l y t i c r e a c t i o n s , which take p l ace at s o l i d sur faces and i n l i q u i d phase, have not yet been completed. I f these t h e o r i e s are more 1 2 f u l l y developed, the petroleum i n d u s t r i e s w i l l make great advancement i n the f i e l d of c a t a l y t i c c r a c k i n g o f l i q u i d hydrocarbons by s o l i d c a t a l y s t s . The objec t of t h i s t h e s i s i s t o c o r r e l a t e the exper imenta l data w i t h the present t h e o r i e s on the convers ion v e l o c i t y of the c i s - to the t r a n s - form of decahydronaphthalene i n the presence of aluminum c h l o r i d e . 2 . ISOMERS OF DECAHYDRONAPHTHALENE Decahydronaphthalene, commerc ia l ly known as d e c a l i n , i s an b i c y c l o p a r a f f i n w i t h the chemica l formula o f C l o H ( 6 . A c c o r d i n g to M o h r \ there are two i somer i c forms of deca-hydronaphthalene, which appears to s tand i n a c i s - and t r a n s -2 r e l a t i o n s h i p . Mohr s t a t ed tha t s e v e r a l of Sachse ' s i somer i c s t r a i n - f r e e s t r u c t u r e s of decahydronaphthalene cou ld be conver ted from one i n t o another by temporary s t r a i n s r e s u l t -i n g from molecu la r c o l l i s i o n s . With t h i s i d e a , he reduced s e v e r a l p o s s i b l e geometric isomers i n t o j u s t two fundamental forms of decahydronaphthalene. J . P r . Chem., 98, 313 (1918). 2 B e r . , 23, 1363 (1890). Z . P h y s i k a l Chem., 10, 203 (1892). Wightmair has also done some work on decahydro-naphthalene. He proposed that the structures of decahydro-naphthalene are the combinations of two cyclohexane s t r u c t -ures. This proposal reduced the p o s s i b i l i t y of isomers into only two forms, and the transformation of the two funda-mental forms must be accomplished by the rupturing of the carbon to carbon bonds. }j_ ISOMERIZATION OF DECAHYDRONAPHTHALENE IN THE PRESENCE OF ALUMINUM CHLORIDE The isomerization of b i c y c l o p a r a f f i n s has been observed in only two direc t i o n s , namely: (a) conversion of the c i s - to the trans-form (b) change i n the r i n g s i z e . The isomerization of decahydronaphthalene i n the presence of aluminum chloride has been studied extensively 7 J . Chem. Soc., 127, 142J ( 1 9 2 5 ) . 4 E g l o f f , H u l l a , and Komarewsky, " Isomerization of Pure Hydrocarbons ", Reinhold Publishing Corporation, 1942, pp 112-121. 4 by Z e l i n s k y and T u r o v a - P o l l a k ^ . C i s - decahydronaphthalene, when t r e a t e d w i t h a t e c h n i c a l grade of aluminum c h l o r i d e ( c o n c e n t r a t i o n 28.6% by weight) at room temperature f o r 22 hours , gave an 85% y i e l d o f the t r a n s - i somer . Fu r the r s tud ie s^ showed that the c i s - decahydronaphthalene i n the presence of the t e c h n i c a l grade of aluminum c h l o r i d e (con-c e n t r a t i o n 24.3%) f o r 14 hours at 100 ° C , gave an 42.2f. y i e l d of the t r a n s - form and 30f° o f the lower b o i l i n g - p o i n t 6 0 t r ans fo rma t ion p r o d u c t s . A t h i g h temperatures 173-210 C , c i s - decahydronaphthalene and aluminum c h l o r i d e gave an i n d i c a t i o n o f the t r a n s - form and a d i m e t h y l b i c y c l o ( 3 » 3 > 0 ) -octane as p roduc t s . * 7 Trans - decahydronaphthalene i n contac t w i t h aluminum c h l o r i d e ( c o n c e n t r a t i o n 24.4f 0) at 130 °C. gave cyclohexane, methylcyc lohexane , 1 ,3 ,3 - t r imethy lcyc lohexane , a n d l , 4 - d i m e t h y l b i c y c l o ( 3 , 3 » 0 ) o c t a n e . From these experiments we know that the i s o m e r i z a -t i o n of decahydronaphthalene i n the presence of aluminum c h l o r i d e at low temperatures i s of the c i s - t r a n s t ype , w h i l e at h igher temperatures i t i s o f the r i n g changetype. B e r . , 63B, 1299-1301 (1932). J . A p p l i e d Chem., ( U . S . S . R . ) , 7, 733-736 (1934). Jones & L i n s t e a d , J . Chem. S o c , 6l6, (1936). 6 4 . ROLE OF ALUMINUM CHLORIDE Reac t ions of pure hydrocarbons i n the presence of aluminum c h l o r i d e are f i n d i n g a p p l i c a t i o n i n the p r o -d u c t i o n of isomers of both h ighe r and lower hydrocarbons . 8 Many s t u d i e s have been made, but owing to a l a c k o f d e f i n -i t e knowledge of the exact r o l e of the aluminum c h l o r i d e i n t&e hydrocarbon r e a c t i o n s , the aluminum c h l o r i d e i s g e n e r a l l y looked upon as a c a t a l y s t i n many i s o m e r i z a t i o n p roces se s . From the s tandpoin t o f the mechanism of r e a c t i o n , i t i s the re fore i n t e r e s t i n g to know i f the aluminum c h l o r i d e func t ions as a t rue c a t a l y s t , as a component pa r t o f the r e a c t i o n , or as b o t h . A . TttJbE CATALYST I f aluminum c h l o r i d e behaves l i k e a t rue c a t a l y s t , i t does not i n i t i a t e r e a c t i o n , but has an a c c e l e r a t i n g e f f ec t E g l o f f , H u l l a , and Komarewsky, " I s o m e r i z a t i o n of Pure Hydrocarbons R e i n h o l d P u b l i s h i n g C o r p o r a t i o n , 1942. 7 when p h y s i c a l l y combined wi th 1 c i s - decahydronaphthalene, which may r e s u l t i n the format ion of the t r a n s - form. The mechanism i s represen ted by the equat ion : C i s •+ A l C l j Trans •+ AICI3 The v e l o c i t y o f t h i s r e a c t i o n w i l l be g iven by the equa t ion : - dC - k(A)(C) (1) dt where dC i s the v e l o c i t y of c o n v e r s i o n , k i s the s p e c i f i c dt v e l o c i t y cons tan t , (A) and (C) are the concen t r a t ions o f aluminum c h l o r i d e and c i s - decahydronaphthalene, r e s p e c t -i v e l y . One o f the gene ra l p r o p e r t i e s of a c a t a l y s t i s the a b i l i t y of t a k i n g pa r t i n a r e a c t i o n over and over aga in by means of s e l f - g e n e r a t i o n ^ ; thus the c a t a l y s t i s unchanged on comple t ion of the r e a c t i o n . The v e l o c i t y equat ion (1), which desc r ibes the r a t e of the c o n v e r s i o n , i s o f a second order r a t e r e a c t i o n and may reduce to one of a f i r s t order r a t e r e a c t i o n because the c o n c e n t r a t i o n of the aluminum c h l o r i d e remains a constant v a l u e . Thus equat ion (1) can be expressed as : - dC = K(C) (2) dt where K i s a new v e l o c i t y constant equal to k ( A ) , (A) and (C) are the concen t ra t ions of aluminum c h l o r i d e and c i s -I p a t i e f f , B e r . , 34, 396 (1901) 34, 3379 (1901). 8 decahydronaphthalene, r e s p e c t i v e l y . I t i s c l e a r from the equat ion (2) tha t a l l t rue c a t a l y t i c i s o m e r i z a t i o n can be represen ted by a f i r s t order r a t e r e a c t i o n . INTERMEDIATE COMPOUND The a c c e l e r a t i o n o f a chemica l r e a c t i o n by a c a t a l y s t through the a l t e r a t e fo rmat ion and decomposi t ion of compounds by the a c t i o n between the c a t a l y s t and the r eac t an t s i s one o f the chemica l views o f c a t a l y s i s . These in te rmedia te compounds are s u f f i c i e n t l y l a b i l e to decompose r e a d i l y , y i e l d i n g the r e a c t i o n products and the regenera ted c a t a l y s t . C i s - decahydronaphthalene and aluminum c h l o r i d e may r eac t and form a complex in t e rmed ia t e compound which decomposes i n t o the t r a n s - form and regenerates the aluminum c h l o r i d e . The mechanism of t h i s in te rmedia te compound format ion i s represen ted by two chemica l equa t ions : C i s + A1C1 , — C i s - A l C l , (3) C i s - A l C l 5 Trans -t- A l C l ^ (4) where C i s - A l C l ^ r ep resen t s the in t e rmed ia t e compound. The v e l o c i t y of the fo rmat ion o f the C i s - A l C l ^ , equat ion (3), can be represented by the equa t ion : - dC = k (A)(C) (5) dt I f the r e v e r s i b i l i t y of the fo rmat ion comes i n t o c o n s i d e r -a t i o n , then equat ion (J?) should be: 9 - dC = k ^ A H O - k 2(AC) (6) dt where k.. and k are the respective forward and reverse 1 2 v e l o c i t y constants; and (A), (C) , and (AC) are the concent-rations of the aluminum chloride, the c i s - decahydronaphtha-lene, and the intermediate compound, respectively. Since anhydrous aluminum chloride i s a very active compound, the formation of the intermediate compound i s alway i n the forward d i r e c t i o n ; i n other words, k^ i s extremely small compared with k^ and can be neglected. Hence equation (6) can be reduced to equation (5) i n which the rate of formation i s t h e o r e t i c a l l y of second order. The v e l o c i t y of decomposition of the intermediate compound i s always a f i r s t order rate reaction and can be represented as: - dC =- K(AC) (7) dt We f i n d i n practice that most reactions, e s p e c i c a l l y c a t a l y t i c reactions, are multi-stage ones. It i s obvious, i n the c o l l e c t i v e processes, the slowest reaction i s the "velocity-determining" ra t e . I f we assume that the intermediate Tapid , compound formation, equation (2), i s v e r y N the v e l o c i t y rate of the o v e r a l l reaction i s controlled by the decomposition, equation ( 4 ) , The o v e r a l l conversion rate of the c i s - to the trans- form of decahydronaphthalene i n the presence of aluminum chloride w i l l be expressed simply as in equation (7). 10 We conclude from the chemical k i n e t i c s of the c i s - decahydronaphthalene and aluminum chloride reaction that the rate should be of f i r s t order no matter which mechanism of reaction i s followed, i . e . , whether i t takes part as a pure catalyst or enters into intermediate com-pound formation. 5. EXPERIMENTAL The conversion rate of the c i s - to the trans-form of decahydronaphthalene was studied at various temp-eratures between 0-4-5 C., and with d i f f e r e n t amounts of the aluminum chloride c a t a l y s t . The course of conversion was followed by observing the change i n the r e f r a c t i v e index. A^ _ APPARATUS The experimental arrangements are shown diagram-ma t i c a l l y i n F i g . 1. The reaction bulb A was made of pyrex glass tubing, 4 cm. i n diameter, 50 cm. long, and having a capacity of about 200 cc. At the top of bulb A were two openings: one f o r the s t i r r e r and one for the thermometer. A c a p i l l a r y tubing outlet was connected about 6 cm. from the bottom, so that samples of the decalin could be taken APPARATUS SET-UP out of the reaction bulb at any time while the s t i r r i n g was s t i l l i n progress. The reaction bulb A was immersed i n a constant temperature bath as shown i n F i g . 1. The bath consisted of a 130-watt knife blade heater, an e l e c t r i c a l l y . d r i v e n s t i r r e r , a liquid-mercury thermal regulator, and a rel a y . For bath temperatures above 20 °C., the bath was surrounded by rock-wool i n s u l a t i o n to prevent severe heat tr a n s f e r . For bath temperatures between 0-20 C,, ice replaced the rock-wool i n the in s u l a t i o n compartment. This i c e , i n conjunction with the heater and regulator, enabled the bath to be kept at the desired temperature. MATERIALS The decalin used i n t h i s research was prepared from Eastman Kodak Co. crude hydrogenated naphthalene. The c i s - and the trans- isomers were separated"1""*" by r e c t i f i c a t i o n i n a Stedman Column at 9 mm. absolute pressure, and p u r i f i e d by repeated c r y s t a l l i z a t i o n i n a dry-ice bath. The c i s - and the trans- isomers used had the index of r e f r a c t i o n of n£ 1.48089 and n D 1.4672, respectively. Anhydrous aluminum chloride of technical grade Seyer & Walker, J . A. C. S o c , 60, 2125 (1938). 13 was re-sublimed i n an atmosphere of nitrogen before using i t i n the experiments'. Cj_ PROCEDURE Before making an experiment, the reaction bulb was cleaned and dried. C i s - decahydronaphthalene and aluminum chloride were introduced into the bulb through the opening for the s t i r r e r . The content was s t i r r e d by a pyrex glass rod at a constant rate of 60 rpm. through-out the entire experiment. The course of conversion or isomerization of the c i s - to the trans- form of decahydronaphthalene was followed by observing the change i n the r e f r a c t i v e index of the decalin. A sample from the reaction bulb was drawn o f f with the aid of external nitrogen gas pressure which was applied through an opening near the top of the bulb. The external pressure forced the decalin to flow through the c a p i l l a r y outlet to a sample container. As soon as the r e f r a c t i v e index of each sample was measured, the sample was poured back into the reaction bulb through the thermo-meter opening. The r e f r a c t i v e indices were measured by a Hi l g e r P u l f r i c h Refractometer. It was found that the r e f r a c t i v e index was a l i n e a r function of the concentrations" 1"^. The rel a t i o n s h i p between the percent trans- isomer and the 14 r e f r a c t i v e index i s given by the equation: T = 12936 - 8734 n where T i s the percent trans- isomer and n i s the r e f r a c t i v e index for the D- l i n e at temperature of 20 °C. Solutions of the two isomers were prepared by weight and these solutions were measured. The re s u l t s are given i n Table 1. TABLE 1_ REFRACTIVE INDICES OF CIS-TRANS SOLUTIONS FOR D- LINE AT 20 °C. Cone, by Wt. f. Trans % c i s n 0 100 1.48113 10.03 89.93 1.47991 19.66 80.34 1.47890 29.69 70.31 1.47770 39.41 60.39 1.47667 49.88 30.12 1.47550 39.84 40.16 1.47437 69.72 30.28 1.47323 79.83 20.15 1.47207 89.77 10.23 1.47092 100 0 1.46968 15 6^  RESULTS A. CONVERSION AT DIFFERENT TEMPERATURES Using 70 gm. of c i s - decahydronaphthalene (98.0 fo purity) and 15 gm. of re-sublimed anhydrous aluminum chloride ( i . e . , cone. 17.6% by wt.), the conversion rate at the temperatures between 0-45 °C. i s observed and tabulated i n table 2. TABLE 2 CONVERSION OF THE CIS- TO THE TRANS- FORM OF DECAHYDRONAPHTHALENE IN THE PRESENCE OF ALUMINUM CHLORIDE (CONC. 17.6% BY WT.)  AT TEMPERATURES BETWEEN 0-45 °C. a. TEMPERATURE 0 °C. Time Angle of Refractive foTrans foCis Log f o0is hours Refraction index 0 64 21 1.48089 2.0 98.0 1.991 4 64 29 1.48028 7.0 93.0 1.968 9 64 38 I.47961 12.9 87.1 1.940 20 64 55 I.47836 24.2 75.8 I.880 32 65 16 1,47673 38.9 61.1 1.786 44 65 32 1.47553 50.1 49.9 1.698 56 65 43 1.47472 56.7 43.3 1.637 68 65 52 1.47405 62.6 37.4 1.573 80 ' 65 58 1.47363 66.3 33.7 1.528 92 66 04 1.47317 70.2 29.8 1.474 104 66 09 1.47280 73.4 26.6 1.425 115 66 15 1.47237 77.2 22.8 1.358 128 6621 1.47193 81.0 19.0 1.279 140 66 24 1.47171 82.9 17.1 1.233 155 66 28 1.47142 85.5 14.5 1.161 167 66 32 1.47114 88.0 12.0 1.080 176 66 37 1.47078 90.9 9.1 0.959 188 . 66 42 1.47042 93.9 6.1 0.785 200 66 45 1.47020 95.7 4.3 0.634 212 66 47 1.47006 97.0 3.0 0.477 224 66 49 1.46991 98.1 1.9 0.279 240 66. 52 1.46970 100 0 b. TEMPERATURE 10 C. Time Angle of Refractive foTrans %CIs Log %Cls Hours Refraction Index 0 64 21 1.47089 2.0 98.0 1.991 3 64 42 1.47929 15.9 84.1 1.925 8 64 52 1.47853 22.7 77.3 1.888 11 65 01 1.47785 28.4 71.6 1.853 17 23 65 28 1.47583 46.9 53.1 1.725 36 65 50 1.47420 61.3 38.7 1.588 48 66 03 1.47324 69.7 30.3 1.481 60 66 16 1.47229 77.9 22.1 1.344 72 66 25 1.47164 83.3 16.5 1.218 84 66 34 1.47098 89.3 10.7 1.029 96 66 44 1.47027 95.1 4.9 0.690 110 66 50 1.46984 98.5 1.5 0.176 c. TEMPERATURE 25 C . Time Angle of Refractive foTrans foCis Log %G±s Hours Refraction Index  0 64 21 I.48089 2.0 98.0 1.991 1 64 31 1.48012 8.3 91.7 1.962 2 64 40 1.47944 14.5 85.5 1.932 3 64 43 1.47921 16.7 83.3 1.921 4 64 49 1.47876 20.7 79.3 1.899 5 64 55 1.47806 26.7 73.3 I.865 13 65 33 1.47546 49.9 50.1 1.700 16 65 43 1.47472 56.8 43.2 I.636 26 65 58 1.47321 69.7 31.3 1.496 31 66 10 1.47273 74.0 26.0 1.415 36 66 17 1.47222 78.5 21.5 1.332 42 66 25 1.47164 83.6 16.4 1.215 48 66 32 1.47112 87.8 12.2 1.086 18 55 66 36 1.47085 90.3 9.7 0.987 62 66 41 1.47049 93.3 6.7 0.826 66 66 43 1.47034 94.6 5.4 0.732 70 66 45 1.47020 96.5 3.5 0.544 80 66 52 1.46970 100 0 a. TEMPERATURE 35°C. Time Angle of Refractive foTrans f.Cis Log f.Cis Hours Refraction Index 0 64 21 1.48089 2.0 98.0 1.991 1 64 47 1.47891 19.6 84.4 1.905 2 , 65 01 1.47786 28.4 71.6 1.855 3 65 13 1.47696 36.7 63.3 1.801 5 65 21 1.47636 47.2 52.8 1.723 8 65 47 1.47442 59.4 40.6 1.609 11 65 54 1.47390 63.9 3 6.1 1.558 14 66 11 1.47266 74.7 25.3 1.403 • 18 66 21 1.47193 81.0 19.0 1.279 24 66 37 1.47078 90.9 9.1 0.959 27 66 44 1.47027 95.1 4.9 O.690 29 66 47 1.47006 97.0 3.0 0.477 32 66 52 1.46970 100 0 19 e. TEMPERATURE 45 C . Time Hours Angle of Refraction Refractive f BTrans Index f 9Cis Log foCis 0 64 21 1.48089 2.0 98.0 1.991 1 65 05 1.47756 31.0 69.0 1.839 2 65 23 1.47611 44 .4 55 .6 1.745 3 65 37 1.47516 52.9 47 .1 1.673 4 65 51 1.47413 61.9 38.1 1.581 5 66 02 1.47331 69.0 31.0 1.491 7 66 20 1.47200 80.4 19.6 1.292 9 66 35 1.47092 89.8 10.2 1.009 11 66 45 1.47020 95.7 4 .3 0.634 12 66 52 1.46970 100 0 CONVERSION USING DIFFERENT AMOUNTS OF ALUMINUM CHLORIDE The rate of conversion of the c i s - to the trans-form of decahydronaphthalene as observed with d i f f e r e n t amounts of aluminum chloride at temperature of 25°C. i s shown i n Table 3. TABLE 3 CONVERSION OF THE CIS- TO THE TRANS- FORM OF DECAHYDRONAPHTHALENE IN THE PRESENCE DIFFERENT AMOUNTS OF ALUMINUM CHLORIDE AT CONSTANT TEMPERATURE OF 25 C. £U ALUMINUM CHLORIDE 17 . 6% BY WT. Time Angle of Refractive iTrans foCis Log %Cis hours Refraction Index 0 0 64 21 1.48089 2.0 98.0 1.991 4 64 49 1.47876 20.7 79.3 1.899 16 65 43 1.47476 56.8 43.2 1.634 36 66 17 1.47222 78.5 21.5 1.332 48 66 32 1.47114 87.8 12.2 1.086 66 66 43 1.47049 94.6 5.4 0.732 ALUMINUM CHLORIDE 30.0% BY WT. Time Angle of Refractive %Trans % Cis Log % C i s Hours REfraction Index . . . 0 64 21 1.48089 2.0 98.0 1.991 4 65 53 1.47398 63.2 36.8 1.566 8 66 29 1.47135 86.1 13.9 1.143 10 66 46 1.47013 96.3 3.7 O.568 21 c. ALUMINUM CHLORIDE 48.1% BY WT. Time Hours Angle of Refraction Refractive %Trans Index %Cis Log % C i s 0 64 21 1.48089 2.0 98.0 1.991 2 65 18 I.47658 40.6 59.4 1.774 4 65 52 1.47405 62.6 37.4 1.573 8 66 21 I.47193 81.0 19.0 1.279 7.L TREATMENT OF THE RESULTS  CONVERSION KINETIC The percent of c i s - decahydronaphthalene converted to the trans- form as plotted against time from Table 2. (fiy Log (%Cis) concentration was plotted against the time i n order to obtain a graphical picture of the rate of t h i s reaction as shown i n F i g . 3. These values of log (%Cis) concentration are found to l i e on a straight l i n e except toward the end of each conversion (approx. 90%) where a sl i g h t dip i n each curve occurs. The straight l i n e r e l a t i o n -ship i n F i g . 3 i s i n complete agreement with the require-ments of a f i r s t order rate reaction. The v e l o c i t y of a f i r s t order reaction i s given under normal conditions, by the equation: - dC = K(C) (8) dt where C i s the concentration of the reactant and K i s the v e l o c i t y constant or the s p e c i f i c reaction r a t e . The d i f f -e r e n t i a l equation (8) which describes the rate of a react-ion of the f i r s t order can be integrated to the expression: 0 = C 0 e " K t (9) In 0 - - Kt (10) Co log C = l o g C 0 - 0.434-3 Kt, (11) where C Q i s the i n i t i a l concentration (for t=0) and C i s the concentration of the reactant at any time t . In F i g . 3» the values of log(f 0 cis) concentration are plotted against the time, the slopes of these l i n e s representing the v e l o c i t y constants K of the conversion. The r e l a t i o n of the v e l o c i t y constant K ( s e c . - 1 ) of the conversion and the absolute temperature i s tabulated i n Table 4. ENERGY OF ACTIVATION An empirical equation, proposed by Arrhenius, expresses very s a t i s f a c t o r i l y the r e l a t i o n between the s p e c i f i c reaction rate K and the absolute temperature T. This equation i s d InK A dT R T (12) 25 and the integrated expression i s In K = constant - A R~T (13) assuming A i s a constant. From equation (13), we see that i f In K i s plotted against 1_ , we should get a straight l i n e T of slope - A . I f R i s expressed i n the usual way (1.986 R c a l o r i e s per degree), the value of A w i l l be given i n ca l o r i e s . TABLE 4 CONVERSION VELOCITY CONSTANT (SEC." 1)  AND ABSOLUTE TEMPERATURE Temp. °C. Slope K'^seeV log K Temp. °A i 0 -.00539 6.53x10' -7 -6.19 273 .00366 10 -.0110 1.32x10 -6 -5.92 283 .00353 25 -.0198 2.38x10' -6 -5.62 298 .00336 35 -.0457 5.53x10' -6 -5.26 308 .00325 45 -.0993 1.20x10' -5 -4.92 318 .00314 Application of the k i n e t i c theories and s t a t i s t -i c a l mechanics leads to a simple interpretation of the constant A i n equations (12) and (13) . This constant, which we may c a l l the energy of a c t i v a t i o n , represents the energy 27 necessary to activate an average molecule i n order to produce reaction. The values obtained f o r log K are plotted against values for the r e c i p r o c a l of the absolute temperature, as shown in. F i g . 4. A straight l i n e r e l a t i o n s h i p r e s u l t s , and may expressed by log K = constant - 6120(2.30?) (14) T Comparison of. equation (14) with equation (13) gives us a value for A, the energy of ac t i v a t i o n , for the conversion of the c i s - to the trans- form of decahydronaphthalene i n the presence of aluminum chloride. The data obtained indicate that the energy of ac t i v a t i o n i s equal to 28,000 c a l o r i e s . TABLE 3 CONVERSION VELOCITY CONSTANT (SEC." 1)  AND CONCENTRATION OF ALUMINUM CHLORIDE AT 25 °C. Cone, by wt. ~T percent K(sec." )  17.6 30.0 48.1 2.38 x 10"° 1.20 x 1.0"5 1.20 x 10~$ 8. DISCUSSION OF THE RESULTS The low energy of ac t i v a t i o n (28,000 calories) obtained i n the isomerization of the c i s - to the trans-form of decahydronaphthalene i n the presence of aluminum chloride would indicate' that the process of isomerization not was caused by the rupturing of the carbon to carbon bonds. The energy required to rupture a carbon to carbon bond has been found to be i n the neighbourhood of 56,000 c a l -o r i e s . A yellow color appears when aluminum chloride comes i n contact with c i s - decahydronaphthalene, and as the action of isomerization proceeds the yellow color disappears on near-completion of the conversion. This v a r i a t i o n i n color would seem to indicate that there are some changes i n the structure of the aluminum chloride and c i s - decahydronaphthalene. The formation of an i n t e r -mediate compound i s indicated by the yellow color. The intermediate compound l a t e r decomposes giving the trans-isomer and aluminum chloride again. This i s indicated by the disappearance of the colo r a t i o n . C i s - decahydronaphthalene on standing at room temperature i s a comparatively stable compound; however, i n the presence of aluminum chloride, i t 'is r a p i d l y con-verted into the trans- isomer. There are many cases i n which hydrocarbons undergo reactions i n the presence of aluminum chloride. As the amounts of aluminum chloride i s increased, the v e l o c i t y constant K approaches a maximum value of 1.20 x 10"^  seel The re l a t i o n s h i p between the v e l o c i t y constant K and various amounts of aluminum chlor-ide i s shown i n Table 5. The e f f e c t of aluminum chloride on c i s - decahydronaphthalene could be one of a physical nature; that i s , the weakening of the bond strengths of th i s c i s - isomer by aluminum chloride. I f t h i s weakening has taken place, less energy of ac t i v a t i o n would be re-quired to convert the c i s - to the trans- form of deca-hydronaphthalene • The k i n e t i c s of the isomerization of decahydro-naphthalene i n the presence of aluminum chloride are not easy to explain, for we are dealing with heterogeneous c a t a l y s i s . The v e l o c i t y rate of the reaction i s a function of many variables, such as temperature, concentration of c i s - decahydronaphthalene, concentration of the aluminum chloride, surface area of contact, and rate of s t i r r i n g . A l l these variables were kept constant except the temp-erature, and the rate of isomerization was found to be approximately of f i r s t order. The deviation of the l i n e a r r e l a t i o n s h i p of log 30 {% cis) concentration and time i n most of the curves at the beginning of the conversion, as shown i n F i g . 3» can be explained by the consecutive reactions of the process; that i s , the formation and decomposition of the intermediate compound of c i s - decahydronaphthalene and aluminum chloride. At low temperature, the formation of the intermediate com-pound affected the o v e r a l l v e l o c i t y of conversion. At higher temperatures t h i s e f f e c t i s not so pronounced because the intermediate compound forms so quickly that the o v e r a l l v e l o c i t y w i l l not be affected. This deviation also decreases with higher concentrations of aluminum chloride because there i s enough aluminum chloride present to form the intermediate compound r a p i d l y . The sharp deviation at the end of the conversion; that i s , the discontinuity of the l i n e a r r e l a t i o n s h i p i n the curves, as shown i n F i g . 3> may be caused by the transformation of the converted trans- decahydronaphthalene by the aluminum chloride into lower boiling-point products. The i n d i c a t i o n of the transformation was observed by the change i n r e f r a c t i v e index when a sample of pure trans-decahydronaphthalene was placed i n contact with aluminum chloride. This transformation of the trans- isomer would cause a side reaction which w i l l a f f e c t the o v e r a l l conversion rate. Thus the deviation from f i r s t order rate at the f i n a l stage of the conversion i s caused by a side reaction. 

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