RD-R SUCRS YRLSSTMEAUEDPNEC FTE11 ACTIVATION ENERGV(U) CHEMICAL RESEARCH AND DEVELOPMENT CENTER ABERDEEN PROVING GROUND MD J R WARD APR 85

Transcription

1 RD-R SUCRS YRLSSTMEAUEDPNEC FTE11 ACTIVATION ENERGV(U) CHEMICAL RESEARCH AND DEVELOPMENT CENTER ABERDEEN PROVING GROUND MD J R WARD APR 85 UNCLASSIFIED CRDC-TR F/G 7/3 N

2 MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU Or STANDARDS-1963-A -7I

3 f~itl~ ri AT (".(IFFI NMI NI r XVIF N';I IVM" CRDC-TR SUCROSE HYDROLYSIS-TEMPERATURE DEPENDENCE OF THE ACTIVATION ENERGY by J. Richard Ward, Ph.D. RESEARCH DIRECTORATE PS [~ April 1985 US Armty Armament, Munitions Chemical Command Aberdeen Proving Ground, Maryland *

4 Disclaimer The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorizing documents. Disposition For classified documents, follow the procedures in DOD R, Chapter IX, or DOD M, "Industrial Security Hanual,6 paragraph 19. For unclassified documents, destroy by any method which precludes reconstruction of the document i " Distribution Statement Approved for public release; distribution unlimited.

5 UNCLA SIFIED - SECURIrY CLASSIFICATION OF THIS PAGE la REPORT SECURITY CLASSIFICATION UNCLAS SI FIED REPORT DOCUMENTATION PAGE Ib. RESTRICTIVE MARKINGS 2a SECURITY CLASSIFICATION AUTHORITY 3 DISTRIBUTION /AVAILABIUITY OF REPORT Approved for public release; distribution 2b DECLASSIFICATION /DOWNGRADING SCHEDULE unlimited. 4 PERFORMING ORGANIZATION REPORT NUMBER(S) S. MONITORING ORGANIZATION REPORT NUMBER(S) CRDC-TR a NAME OF PERFORMING ORGANIZATION 6b OFFICE SYMBOL 7a. NAME OF MONITORING ORGANIZATION (if applicable) CRDC SMCCR-RSC-C 6. ADDRESS (City, State, and ZIPCode) 7b. ADDRESS (City, State, and ZIP Code) Aberdeen Proving Ground, MD Ba. NAME OF FUNDING/ SPONSORING Bb. OFFICE SYMBOL 9. PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER ORGANIZATION (if applicable)' CRDC ISMCCR-RSC-C 8c. ADDRESS (City, State, and ZIPCode) 10. SOURCE OF FUNDING NUMBERS PROGRAM PROJECT TASK WORK UNIT ELEMENT NO. NO. NO. ACCESSION NO. Aberdeen Proving Ground, MD L A71A S 11 TITLE (include Security Classification) Sucrose Hydrolysis-Temperature Dependence of the Activation Energy 12 PERSONAL AUTHOR(S) J. Richard Ward, Ph.D. I a. TYPE OF REPORT 13b. TIME COVEEDO 14. DATE OF REPORT (Year, Month, Day) S. PAGE COUNT Technical FROM Oct TO Sep April SUPPLEMENTARY NOTATION 17 COSATI CODES i8. SUBJECT TERMS (Continue on reverse if necessary and identify by block number) FIELD GROUP SUB-GROUP Sucrose hydrolysis Kinetics Blandamer Heat capacity of activation. 19 ABSTRACT (Continue on reverse if necessary and identify by block number) Sucrose hydrolysis is often cited as one of the classic examples of a chemical reaction with a temperature-dependent activation energy. Two different investigators, Moelwyn-Hughes (polarimetry) and Leininger and Kilpatrick (dilatometry), both claimed that the energy of activation decreased with increasing temperature. A less-cited paper by Heldt and Purvis claimed that the energy of activation was temperature independent. More recently, Kubler and co-workers at Furman University remeasured sucrose hydrolysis polarimetrically with correction made for the mutarotation lag and also concluded that the energy of activation did not vary with temperature,.- -S 20 DISTRIBUTION/AVAILABILITY OF ABSTRACT 21. ABSTRACT SECURITY CLASSIFICATION [AUNCLASSIFIED/UNLIMITED 0 SAME AS RPT. 0 OTIC USERS UNCLASSIFIED 22a NAME OF RESPONSIBLE INDIVIDUAL 22b. TELEPHONE (Include Area Code) 2Zc. OFFICE SYMBOL BRENDA C. ECKSTEIN (301) SMCCR-SPS-IR DO FORM 1473, 84 MAR 63 APR edition may be used until exhausted. All other editions are obsolete. K SECURITY CLASSIFICATION OF THIS PAGE UNCLASSIFIED

6 UNCIASSIFIED SECURITY CLASSIPCATION OF THIS PAe 19. ABSTRACT (continued) Recent interest in the measurement and interpretation of heat capacities of activation has led to more rigorous methods of detecting temperature varient activation parameters. One such method by Blandamer, Robertson, and co-workers was applied to the sucrose hydrolysis data of Moelwyn-Hughes and Leininger and Kilpatrick. It was found that the data did not support the inclusion of a temperature-dependent activation energy. Blandamer's method applied to Kubler's data also confirms the absence of any need to include temperature-dependent activation parameter SECURITY...LAS.IFIC...O...F.. H.S...

7 PREFACE This work was performed under Project No. ll161101a71a, Research in Defense Sciences. The work was started in October 1983 and completed in September The use of trade names in this report does not constitute an official endorsement or approval of the use of such commercial hardware or software. This report may not be cited for purposes of advertisement. Reproduction of this document in whole or in part is prohibited except with permission of the Commander, US Army Chemical Research and Development Center, ATTN: SMCCR-SPS-IR, Aberdeen Proving Ground, MD However, the Defense Technical Information Center and the National Technical Information Service are authorized to reproduce the document for US Government purposes. This report has been approved for public release. fld/ S JU N B3

8 Blank 4

9 CONTENTS Page 2.* BLANDA?4ER'*S METHOD RESULTS AND DISCUSSION o o.o.o.. 8 Table LITERATURE CITED... o ~ o... *... o o LIST OF TABLES 1 Summary of Rate Coefficients for Inversion of M SucroseinO.57M HC... o Enthalpy of Activation Versus Temperature with Moelwyn-Hughes' Data Obtained Polarimetrically Activation Parameters from Moelwyn-Hughes' Results with AC* 0 O o Enthalpy of Activation Versus Temperature with Leininger and Kilpatrick's Data Activation Parameters for Inversion of M Sucrose in 0.57M HCl... o..... o... o

10 Blank 6

11 SUCROSE HYDROLYSIS-TEMPERATURE DEPENDENCE OF THE ACTIVATION ENERGY INTRODUCTION The hydrolysis of sucrose has a permanent place in the history 5 physical chemistry since it was the first reaction studied as a func- Dn of time. 1 In addition, as Oon and Kubler note, 2 over 1,000 articles sucrose hydrolysis appeared by Despite this intense and ng-standing interest, questions persist relative to the mechanism of e reaction, particularly with regard to the temperature dependence of e activation energy. Moelwyn-Hughesl (polarimetry) and Leininger and lpatrick 3 (dilatometry) contend that the activation energy decreases th increasing temperature. Recently, Moelwyn-Hughes' results have en cited as the first example of a temperature-dependent activation ergy. 4 However, in 1939, Heidt and Purvis 5 claimed that the activation ergy was temperature independent based on a direct analysis of the oducts' reactions. More recently, Kubler and co-workers 6 remeasured 5 e rate of sucrose hydrolysis polarimetrically, including a correction r the mutarotation of the products, and also monitored directly the oducts' rate of formation. These workers also contend that the tivation energy is not temperature dependent. Since World War II, many examples of temperature-dependent -tivation energies have been reported.,8 Concurrently, more rigorous thods have also been devised for detecting such temperature-dependent.- tivation parameters as opposed to the method both Moelwyn-Hughes and -,ininger and Kilpatrick used to determine the activation energies over,rious temperature intervals. In this article, the method proposed by Blandamer, Robertson, Ld co-workers 9 has been applied to Moelwyn-Hughes and Leininger and lpatrick's data to test their contention of a temperature-dependent :tivation energy for sucrose hydrolysis. BLANDAMER'S METHOD Blandamer's expression for computing thermodynamic parameters om the temperature dependence of rate data is k 0 T 1AO 1' CP*1 T k = -. exp 1- + [tn ( +- T o R To T R To/T 1 iere k = rate coefficient at temperature, T T = temperature 7, o.< i- '.'.- '...-i-i i.i-.-.i..-< ,

12 k o = rate coefficient at temperature, T o AHO* = enthalpy of activation at T o AC = heat capacity of activation Equation (1) is obtained by inte rating the vant-hoff isochore Peen temperatures T o and T assuming ACp independent of tempera- For a given set of k, T data pairs, one pair of k and T are set *. - :o and To, and the remaining values of k, T are used in a regression :quation (1) to find a value of AH* and AC * at T o. Another of k, T are set as the new ko, T o and vayues of AH* and AC * at new T o are obtained. The process is repeated until each value of k, i the data set has been assigned k o, T o yielding values of AH* AC p for each temperature, T. Any data set produces: (a) ACp* zero, AH* constant with temperature, (b) ACp* constant, AH* linearly dependent with temperature, (c) ACp temperature dependent. Ltion (1) was derived with the assumption that AC is temkture independent, so for conditions (a) or (b) above, the values X are thermodynamically correct. However, Equation (1) gives correct sign for temperature dependent ACp* although the ies so computed are not correct since the wrong equation is used,ompute AC * In order to find the values of AH* and AC P.. ition (1) is fit directly with a non-linear, least-squares program 1 0 )pposed to the linear form of Equation (1) offered by Blandamer. 9 To :her distinguish between conditions (a) and (b) above, the enthalpies ictivation so computed are fit versus temperature with a linear, ;t-squares version of the program to see if the slope differs from RESULTS AND DISCUSSION The rate coefficients for sucrose hydrolysis are listed in Le 1. These numbers were taken from Table 1 of Kubler's article :erence 6). With the exception of Moelwyn-Hughes, all kinetic runs? done with M sucrose in 0.57M HC1. The followin calculations were done on each k, T data set. ies of AH* and ACp7, along with their respective standard Lvations of the mean, were computed at each temperature, T, with ition (1). The values of AH*, so generated, were fit with a ear, least-squares subroutine of the Los Alamos program 0 to AH* = a + bt (2) 1 8

13 3 (VI 0n ON 4-4 * '0('4'0 - f' n 0 P 4.4- r. 4-) SLA) LO L. ",. o 0 D C)' M C) - 0 I"C).4J 4) 4- o ( 0 En LCa( 0P m = 44 V. 0o o 0 04 o ' - o <,> " 0 )o (, e n cn a is 0 U) C UJ A -' U,4 C.)o." S"""W,,.,..<.',.' IJ 04 " ol r,a.. U 0 0 fl C- 4 0-, D wo, C0 6 C.0 CJ N OD an O'. > I o- 4' a- ' a;. ' V. 0),- E- C4 4 (N ) -L-4 >, -4 0 C UUn 01 lw C0 IV (Nj N- m- m' (a 4.)L 4.0 0M. ' 4 w 4-i w U)' 4.0 S-0 U nn C) 4 C-.r)~ 4jO TO 0-0). o 0 0 -w u- -- ii ". 0. n %DO, " - -J.... w (D,-" r- m- -o , i. U , 4-C) '. * * * * *- E. L a., = -l(.u ) "4-Lf cno 0C OD 0 0) U 4 ) 0 LA LA %D0 LA) tv) 0 0 C> 0 ) >1 ()4-V c. C 40(I.. -- *0 4" ' 0 0 ( rd (U c0 L, ---- I(1 4". ( t C) -'1C -4 r. ) r 4-) (d W 44 0)La (Nt ' 0)'- '.0)~ 7-04I t- 0) 0-4)LA IQ 1L r-4u).- 44UP.> U) cn 0' to 0 OD CC 0 04.) D )0) L4 W f )C cu LA IV CD0 (D 0 0'.4M r 0 Cf0)00 U W E- * * 040Q) ~ - -) U4L LA - X' -I) W. a Er(0L -4-) 'M (N (~ ' -1 -I (N 0 0) M 0 m s., I4J L) >4 -z C z (.) r-) %~ =%w 0ON LA 4.0 -y M( -4. r ) r'j n LA LA 0o z. P-4 V ) LA C' 4-(1) 1C M : L)C -~ 4.0 0C Cv' Q ) In C( - C>1U~ t) 04 (fl-,4~l~0) I ~ai)r U~~~Q 4-C-0.440V IM 0 0, 0a t w a) l C0 LA 0) LA 0D LA 0DD4=0b 1 Cv' ( 04' ( n 1) (U. ri 0)4-40a%...., _.,..,....,..: + ::...-: :.] -:.;::.:i -. :.

14 idence intervals were computed with the "Student-t" statftic to if values of AC,* or b differed significantly from zero. For arcent confidenge levels, values of t corresponding to a = n-p degrees of freedom were used, where n is the number of points g fit, and p is the number of parameters being varied. 1 0 Finally, entropy of activation was computed with Kt AH* AS* k =-exp + (3) h RT e previously undefined parameters are K = Boltzmann's constant, and Planck's constant. Equation (3) presumes that ACp* is zero, and aring values of k computed with AH* and AS* with experimental es of k also tests whether AH* is temperature independent. The first calculations were done with Moelwyn-Hughes' data. e 2 illustrates the values of AH* and ACp* obtained. In general, ACp values do not differ from zero. Results from fitting AH* us T give a = kcal/mole and b = cal/mole -k, esting that AH* is Independent of temperature. Table 3 lists the lts of fitting K, T to Equation (3) to obtain AS. One sees that computed values agree well with the experimental values except the rimental values at the two lowest temperatures (15.45 and C) smaller than the computed values. Interestingly, if the mutarotation had been taken into account, the experimental values at these temtures would have been smaller. 6 This also coincides with Kubler's rk 6 that a plot of ln k versus 1/T for Moelwyn-Hughes' data was htly curved in the opposite direction to his own polarimetric uncorrected for mutarotation. Nonetheless, one concludes that wyn-hughes' data do not prove that AH* varies with temperature. The results of the next calculations which were made with inger and Kilpatrick's rate data 3 are summarized in Table 4. slope of a plot of AH* versus T, cal/mole -k also ests that a temperature-independent AHT is sufficient to represent inger and Kilpatrick's data. 3 Table 5 lists the values of AH* and AS* computed with inger and Kilpatrick's results, illustrating that the experimental computed values of k agree within a few percent except for the value.0 C which differs by 7 percent. Comparing Leininger and Kilpatrick's lts with AH* and AS* computed with Heidt and Purvis' results, Kubler's polarimetric data illustrates that the fitted value of k.0 C corresponds with Heidt and Purvis' measured value, and that the es of AH* and AS* are identical to those computed with Kubler's Again, one concludes that Leininger and Kilpatrick's data do not ort a temperature-dependent AH*. 10

15 I~~~0 eno Ll4-14 % (Y N M NOLLAN'- ON (n~t~ 00 w.j * m %Ds Q CDV N OD4 q r- ('4 W ull 4) 43 GONU 4 0 C 0 0-0n CA Zv~- q D N.. 44m l%04 0 V ('4 '-I 0. N O ' 0~.~D.,Ia 4. M.. % ( I)4. V. f~ ~ O ~ N4 >~- -4I en %0D ; - 4. ('4a LaO 0 & C14 %D44)otn -4 - cu I(% 1-44 (44I 0.4A. j4 --0 '(~D ~ i n. c to %0 (1 l % L)( i00 a)s tocp 444J %NV)Dr CN ON C'4 E =4% a I I 4.J."I r. I N L r. (4'a4) gu C4N ('i-v) e0 0 0 U, goc 0 4JJ.0. * ~ * * I 0 4)~ I.- v04l. ()- U, I.V 4 r 44i N M-eI~' C) 0 n - U )44.0 W& co 04 1 ~ j -N X 4 I- N (P I 4 #- to (-I 0o ~ ~ ~ ~ ~ I F40f 0 * ~ ~ 00 N (D0 M(v 0 0 ti 0) 0 43 a Uv 4.) %,~ 4-) 0) NMV4 4-- M q3l. A I Ln r- MM Ln wu v 111

16 Table 3. Activation Parameters From Moelwyn-Hughes' Results with AC 0 T, *C kobs, S-1 x 105 kfitu S- 1x AH* = kcal/mole AS* = cal/mole-k 12

17 I-a CD m -4 E D.. 4'N fn W r D-0 4 &A 0 v (D Q' 0 %- m M* OD r N - L I *. *4.D a 0. a en10 O D W D 0% CD Q 40CIA Ia00 %,~ N 0 N% 0% fn IM 44 - D.I..0 m% r' IA 0D 0 m%d N 0 %D LM N 4.).a04 '.4 M VN V al r- %o t4 w a% %a 0; 04.1 M0 - " i 41 a1 o fn) - %D (n t 0 Q r- 0 La.) - en- %DPa 0 C4 0% - o a,.,i -I In.,. Fn I - Pal r-.x -4) 0 0.N %0% D m In4.a)1 -n IA LA NP I 0 N z.0a; a * a 0 a4 a 44 f to II P4 > Go a aa >.* LAa 4 F to 1 4) 0% a,% 04, 41 V a a a. n in ai U) Pl 1'- ID (~) LA 13 ~~4.

18 N ~ O0 ~ C C - ~ ~ cvnd%0c, ~ r C14 N 4-4 LAd C) 0 C.CD C>4 C' N. (n- 44 m C) 0~ C %D.0 7~' 07 a LLA O C: A -- %'DA ' a%0 0n - 1 ma 0 LAM - - %0 C' C'4 4-4J 44 Q4 -~ I 0 I ON % M %4e)n N,1-44M L ) CDC a) in ) C;~~ ~ ~ C; 4 CO A ;4.g); 4. d 0ILeA% N - - t 14 VI 44 -

19 L.~~~~,' For completeness, similar computations were done to Kubler's data and to Heidt and Purvis' results. In both instances, the fit of AH* versus T shows that the slope, b, is zero, and AH* is temperature independent, in accordance with each investigator's contention. 4. CONCLUSION Blandamer and Robertson's equation for determining heat capacities of activation was applied to Moelwyn-Hughes' and to Leininger and Kilpatrick's data on sucrose hydrolysis. There was no evidence for a finite heat capacity of activation in either case

20 Blank 161

21 LITERATURE CITED 1. Moelwyn-Hughes, E. A. Kinetics of Reactions in Solution. 2nd Edition. p 1. Oxford University Press Don, S. M., and Kubler, D. G. Hydrolysis of Aldal Acetals. J. Org. Chem. 47, (1982). 3. Leininger, P. M., and Kilpatrick, M. The Inversion of Sucrose. J. Am. Chem. Soc. 60, (1939). 4. Perlmutter-Hayman, B. The Temperature-Dependence of Ea. Prog. Inorganic Chem. 20, (1976). 5. Heidt, L. J., and Purvis, C. B. The Inversion of Sucrose. J. Am. Chem. Soc. 62, (1939). 6. Buchanan, S., Kubler, D. G., Meigs, C., Owens, M., and Talbman, A. Energy of Activation and Temperature for the Hydrolysis of Sucrose. Intl. J. Chem. Kinetics 15, (1983). 7. Kohnstam, G. Heat Capacities of Activation and Their Uses in Mechanistic Studies. Adv. Phys. Org. Chem. 5, (1967). 8. Kanerva, L. T., Euranto, E. K., and Cleve, N. J. On the Accuracy and Significance in Determination of the Temperature Dependence of Activation Energy in Neutral Ester Hydrolysis and Solvolytic Substitution Reactions. Acta. Chemical Scand. B. 37, (1983). 9. Blandamer, M. J., Robertson, R. E., Scott, J. M. W., and Vrielink, A. "Evidence for the Inclusion of Intermediates in the Hydrolysis of Tertiary, Secondary, and Primary Substrates. J. Am. Chem. Soc. 102, (1980). 10. Moore, R. H., and Ziegler, R. K. Los Alamos Scientific Laboratory Report LA The Solution of the General Least-Squares Problem with Special Reference to High-Speed Computers. March Laitinen, H. A. Chemical Analysis. Chapter 26. McGraw-Hill, New York,

22 FILMED 7-85 DTIC