Journal of Scientific & Industri ::ti Research Vol. 60, April 200 I , p. 348

Note

Reaction Kinetics of Para chlorophenol Table I - Reaction kineti cs of PCP vs NaOH (by titrati on)

and Sodiumhydroxide

M Natarajan, P Nalini , S S Dawn , D Mary and K Balu Department of Chemical Engineering.

Alagappa College of Technology.

Anna Univers ity, Chennai 600025.

Received: 03 M ay 2000; accepted OS January 200 I:

Sodium phenoxide is one of the important raw matcrials uscd in the manufacture of clofibratc, a product of mcdicinal va luc. Rcacti on between p-chlorophenol and sodium hydroxidc is carried out at at­mospheric conditions to yield sodium phcnox idc. It i ~ obscrved ex­perimentally that the rcaction is second ordcr and the rate constant is

e. timatcd as 12.51 x 10" Llmol/min.

Introduction Clofibrate is a antihyper lipidaemic agent. It is

most effecti ve in lowering the concentrati on of very low density lipoproteins and plasma tri g lyce ri des. The drug causes inhibition of cholestero l synthes is and increased faeca l exc retion of sterols. Clofibrate is manufactured from reacting p-chlorophenoxy iso­butyric ac id (PCPIBA) which, in turn , is produced from several raw materials . One of the raw materi­a ls is sodium phenoxide obtained by reaction of p­chlorophenol (PCP) and sodium hydrox ide. The ki­

netics of PCP with NaOH is in vest igated.

Reaction Kinetics Equimolar (0. 1M) cone. of PCP and NaOH are

prepared and the progress of the reac ti on is mea­sured by collecting a small quantity (I Oml) of reac­tion mixture at frequent intervals and titrating the

collected samples against hyd rochloric acid. The re­sults are reported in Table I .

For a second order reaction , the diffe re nti a l form t

of rate expression is : c/xlc/I=K(a-x) * (a-x), .. . ( I )

wherex= amollnt of PCPNa formed at time "f" and a = initial concentration of reacting mixture.

Time Volume of HCI Rate constant (in mi n) (inml ) ( in Llmol/min)

0 9

1.5 7.7 0.0 125n60 I

3 6.8 n.01198257

4.5 6 0.0 12~'+568

6 5.5 o.n 117)\.+5 I

7.5 5 n.o II )\51)\5

9 4.6 0011 X0891

10.5 4.2 0.01209373

12 3.9 0.01210826

13.5 3.7 n.n 1178957

15 3.4 0.0 11200.+.+

Average K 0.0120.+715

The integrated form of Eq. ( I ) is:

K =.1/ {II * (a-.I) * I){. . .. (2)

If V is the vo lume of HCL consumed initiall y "

and V is the volume of HCL consumed after time I

" I " then,

v" (X a and V, (X (II-X).

Hence V" - V, (XII - (a-x) = x

Eg . 2 is rearranged as:

K={V" - v,/ / { II" *11, * I J.

. (3)

. ('+)

The estimated K va lues for diffe rent time periods are presented in Table 1. The rate constant is fo und to be constant throughout the course of reaction and the average va lue is taken fo r estimating K. The rate constant is 12.51 x IO-'Umol/min .

Results and Discussion Reaction kinetics ofp-ch iorophenol w ith sod ium

hydroxide is studied at room temperature. It is ob­served experimentally that the reaction is second order and the rate constant is esti mated as: 12.51 x 1 0-JUmol/min .

Reference

Octave Levenspeil , Chemical Reaclion Engineering (Wiley East­ern Pri vate Limited, New Delhi ) 1983.