INDIAN J. CHEM., VOL. 1+A, SEPTEMBER 1976

TABLE 3 - VALUES OF 1\0' 1\0'" AND a (A) AT DIFFERENT TEMPERATURESFOR LITHIUM ACETATEIN WATER ANDAQUEOUSMETHYL ACETATE OBTAINED FROMTHE TEST OF THE FUOSS-ONSAGER-SKINNEREQUATION

Temp. 1\0 (ohm " cm-) 1\0 (ohrrr" cm-) 1\0'1 a (A)(0C) "Vater Aq.-methyl

acetate Water Aq.-methyl Vlater Aq.-methy\acetate acetate

+0 121'9 128·+ 0·80 1-06 H 1·7+5 130·2 135·5 0·78 0·99 1·6 1·950 133·2 1+3'6 0·73 0·95 2·2 2·0

The data in Table 3 reveal that the limitingequivalent conductances obtained by Onsager ex-trapolation method and Fuoss-Onsager-Skinnerequation differ slightly for solution in water, but forsolutions in aq.-methyl acetate, there is largedifference in 1'1.0 values. This large difference maybe due to the fact that (a) the Fuoss-Onsager-Skinnerconductance equation takes into account the pointsat higher concentrations also whereas these pointsshow deviations from simple Onsager plots and (b)manual extrapolation in Onsager plots may be thesource of error.

The structural effects on the conductance of ionsin aqueous solutions are derived by a comparisonof their Walden-products in aqueous and non-aqueoussolutions at different temperatures-v-". From theTable 3, it is clear that as the temperature increasesthe Walden-product goes on decreasing. The Ao'YJversus t plots are almost linear for both the solutionsand have negative temperature coefficient. Thenegative temperature coefficient' suggests that thelithium acetate acts as a structure-breaker both inwater and in aq.-methyl acetate. The slight in-crease in the ion size parameter a (A) with tempera-ture for lithium acetate in water and aqueousmethyl acetate may be interpreted? as an indica-tion "of the structure-breaking tendency of theelectrolyte in a solvent.

The structure-breaking capacity of lithium acetatein water and aqueous methyl acetate is also sup-ported from the viscosity measurementst",

One of the authors (p.e.v.) is thankful to eSIR,New Delhi, for the award of a junior researchfellowship.

References1. MAcINNES, D. A., The principles of electrochemistry

(Dover, New York). 1967, 327; 360.2. Fuoss, R. M., ONSAGER, L. & SKINNER, J. F., J. pbys.

Chem. Ithaca, 69 (1965), 2581.3. TIMMERMANS, 1., Physico-chemical constants of pure

organic compounds, Vol. I (Elsevier, New York), 1950,+13.

+. LANGE, N. A., Handbook of chemistry (McGraw-Hill,New York). 1967, 1221.

5. SHOEMAKER,D. P. & GARLAND, C. W., Experiments inphysical chemistry (McGraw-Hili, New York), 1967,131.

6. BLOKHRA, R. L. & SEHGAL,Y. P., Indian J. Chem., 14A(1976), 162.

7. BLOKHRA,R. L. & PARMAR,M. L., J. electroanal, Chem.,57 (197+), 117.

8. BLOKHRA,R. L. & SEHGAL,Y. P., J. electroanal. Chem.,62 (1975), 381.

9. BLOKHRA, R. L. & SEHGAL, Y. P., Z. phys. Chem., 93(197+), 155.

698

10. Fuoss, R. M. & KRAUSS, C. A., J. Am. chem, Soc., 55(1933), 1019; 2387.

11. BJERRUM, N., Det. Kgl. Danske Viden, 9 (1926), 2.12. BLOKHRA,R. L. & SEHGAL, Y. P., Indian J. Chem., 12

(197+), 998.13. BLOKHRA,R. L. & PARMAR,M. L., J. electroanal. Chem.,

59 (1975), 226.1+. KAY, R. L. & EVANS, D. F., J. phys. Chem, Ithaca, 70

(1966), 366; 2325.15. KAY, R. L., CUNNINGHAM,G. P. & EVANS, D. F.,

Hydrogen bonded solvent systems, edited by A. K.Govington & J. Jones (Taylor & Francis, London),1968, 2+9.

16. BLOKHRA, R. L. & VERMA, P. C., Electrocbim, Acta,(in press).

Study of Hydrolysis Kinetics & Lactone-Acid-Salt Equilibria of 'Y-D-Mannonoiactone

S. K. DUTTA· & SUVA BRATO Rov]Department of Pharmacy, Jadavpur University

Calcutta 700032

Received 2 August 1975; accepted 31 January 1976

Specific rate constant (hH) for the hydrolysis of "(-D-

mannonolactone in aqueous solution has been deter-mined conductometrically, the values at 25° and 37°are 2·04 and 5·37 x 10-6 see? respectively. Activationenergy (Ea=14·73 kcal mote<) has been found from theArrhenius plot. The overall equilibrium constant (Keq)for the hydrolysis of the lactone, hA for mannonic acidand the equilibrium constant kL for the hydrlysis of thelactone have been determined from pH and opticalrotation measurements and are found to be 2·48±0·10x 10-5, 1·60±0·16 X10-' and 0·18 respectively. Lactoni-zation constants hI for mannonic acid at 25° and 37°are 1·34 and 2·98 x 10-5 see= respectively.

THE hydrolysis kinetics of industria lly importantaldonolactone ..;, viz. n-glucono-Svlactonc-, lac-

tobiono-Sdactone'', maltobiono-Svlactone'', cello-biono-Svlactone- and Y-D-galactonolactone 6 havebeen reported earlier, but such data on Y-D-manno-no lactone are wanting. A systematic study ofthe hydrolysis kinetics of this lactone and lactone-acid-salt equilibria are reported in this note.

Y-D-A1annonolactone - n-Mannose (45 g) waselectrolytically oxidized in the presence of NaHC03(25 g) and 1% sodium bromide in 800 m) water

·To whom correspondences are to be directed.t Abstracted from a dissertation submitted by Suva Brato

Roy, Department of Pharmacy, Jadavpur University,Calcutta 32, in part fulfilment of Masters degree of Pharmacyrequirements.

-5'0

SLOPE, 3'182010'Eo'14'73Keel/mol.

37'

iI

-~::------------ - - ---!- - - - - ----N-b'03'L""'O---~3'':"::IO-----::3:L..'2'''"O--'-----.f.3'3:;----'---:;'3'4

,1fT"IO

Fig, 1 - Arrhenius plot for determination of E» for extra-polated values of kH at 25° and 37°

by passing 1 amp current for 14 ,hr (percentageof oxidation of the sugar, approximately 90%).The volume of water was reduced to 50 ml byevaporating on a water-bath and sodium rnanno-nate crystallized out by a~dition o.f met~am)l.The salt was filtered off. dissolved in rrumrm ..mvolume of water and recrystallized by the additionof methanol, which was finally purified by recrystal-lization from aq. methanol; m.p, 170°.

The salt was dissolved in minimum volume ofwater and passed through cation e~ch2.n~e resin(Amberlite IR 120) to give mannornc acid. Theacid was concentrated to a syrup on a water-bath,dissolved in 95% ethanol by little warming andkept at room temperature to give white needl~-shaped crystals of 'Y'-D-mannonohctone; m.p. 150-51 .

Purity was checked by paper chromatography(solvent-pyridine-ethyl acetate-water, 2: 8: ~ ,v/v/v)which gave single spots. RG 0·11 and U'12 torsodium mannonate and Y-n-mannonolactone res-p&~~. . ..'

Conductance was measured usmg a Philips conducti-vity bridge model PR 9500. The PH measurementswere made on a Beckman PH meter model H2.Optical rotations were m~2.sured on a ~i!ger micr<~-optic photoelectric polarimeter of preci.ron 0·005 .A 2 dm polarimeter tube was used for all measure-ments.

Kinetics of hydrolysis of 'Y'-n-mannonolactonein water was studied coriductometrically. A knownamount of lactone was placed in a fixed volumeof water equilibrated at 40°, 50° and 60.° re':I?ec-tivelv and changes in conductance WIth timemeasured. The kH values at 40°, 50° and 60°were calculated from the relation kH= 2'303/tlog (Ca-Co)/(Ca-Ct) (where Co. Ct and C,a are theconductances at times 0, t and oc respectively) andfound to be 0'675, 1·38 and 2·77 X 10-5 respectively.Arrhenius plot of log kH versus liT W8.Slinea (Fig. 1)which when extrapolated to 25° and 3.1° gave kHvalues of 2·04 and 5·37 X 10-6 respectively. Al.»the value of energy of activatio~ Ea has been cal-culated from the slope of Arrhenius plot and foundto be 14'73 kcal mole'".

~OTES

TABLE 1 - VALUES FOR LACTONE-ACID-SALT EQUILIBRIUMCONSTANT (Keg) AND DISSOCIATION CONSTANT (kA) OF

MANNONIC ACID

[Lactone] pH Keq x 10' Optical KAXlot(211) rotation

0·0995 2·80 2·56 1·765° 1·740·0999 2·80 2·55 1·770° 1·510·0999 2-80 2·55 1·770° 1·510·0998 2·82 2·28 1·770° 1·460·1004 2·81 2·40 1·780° 1,430·0998 2-80 2·56 1·770° 1·92

Mean 2'48±0'10 Mean 1-60±0'16

The hvdrolvsis of 'Y'-D-mannonolactone (M) inwater can be expressed by relation (1)M+HzO~HMH4~H++MH4 ... (1)

rnannomc mannonateacid ion

The equilibrium constant (Keq) is given by Eq, (2)[H+]{MH4J [H+] [MH,]

Keq = [HMH,J+[M] = C.-[H+J ... (2)

where [MJ= equilibrium concentration of unhydro-lysed lactone and [HMH,J = equilibrium concen-tration of undis sociated mannonic acid and C.=[initial lactone].

The values of Keq determined PH -metricallyare given in Table 1.The dissociation constant is given by Eq. (3)

[H+] [MH-]kA = [HMH

41' ... (3)

The kA value" for mannonic acid at different pHand optical rotation are given in Table 2. Thespecific rotation [ocJ~ for 'Y'-D-mannonolactone, man-noic acid and sodium mannonate have been foundto be +51°±O'So, +44·85±O·OSo and -8·00±0·5°respectively and molar rotations (2 dm-tube) are+18·16°, +17'58° and -3·49° respectively.

Dividing Eq, (3) by Eq. (2) and rearranging theequilibrium express ion for hydrolysis of lactoneis

kL = [HMH4J = Keq = 0.18 ... (4)[M] KA-·Keq

which is in good agreement with the observationof Carter et al.6•

Lactonization constant kl' of rnannonic acid isgiven by the expression

kl = kH = 1·34 X 10-5 sec-1 at 25° andkL

2·98 X 10-5 see'? at 37° ... (5)

References1. SAWYER. D. T. & BAGGER, J. B., J. Am. chem, Soc., 81

(1959). 5303.2. DUTTA. S. K & MUKHERJEE. S. K, Indian]. Chem., 9

(1971). 229.3. DUTTA, S. K, Indian]. Chem., 11 (1973), 240.4. DUTTA, S. K, Indian]. Chem., 13 (1975),192.5. DUTTA, S. K, Indian J. Chem., 13 (1975), 980.6. CARTER, S. R., HAWORTH. W. N. & ROBINSON, R. A.,

J. chem, Soc., (1930), 2125.

699