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Indian Journal of ChemistryVol. 25A. March 1986. pp, 302-304
Amphoteric Exchangers: Weakly Acidic &Weakly Basic
Exchangers obtained byCondensation of Resorcinol,
/3-Resors-aldehyde and 8-Hydroxyquinoline withEpichlorohydrin using
Pyrrolidine as
Cross-linkers
MUKESH PATEL & R N KAPADIA"Department of Chemistry, Faculty
of Science.M.S. University of Baroda. Baroda-390 002
Received 6 March 1985; recised 24June 1985;accepted 18July
1985
Some new amphoteric exchangers have been synthesised
bycondensing resorcinol. 8-hydroxyquinoline and
P-resorsaldehydewith epichlorohydrin using pyrrolidine as a
cross-linker andcharacterised by their various physico-chemical
properties.
Amphoteric exchangers are interesting from the view-point of (i)
basic chemistry specially in analyticalseparation and (ii)
industrial applications such as inwater treatment. We report herein
the synthesis ofamphoteric exchangers obtained from the
systemsepichlorohydrin-resorcinol-pyrrolidine. [EP(res-ol)Py],
epichlorohydrin-8-hydroxyquinoline-pyrroli-dine [EP(8-0H-Q)PY] and
epichlorohydrin-P-resorsaldehyde-pyrrolidine
[EP(/3-res-aldehyde)PY].
A solution of epichlorohydrin (0.6 mol)
andresorcinoI/8-hydroxyquinoline//3-resorsaldehyde (0.05mol) in
toluene (75 ml) was vigorously stirred at 0 to5"C. To the cooled
mixture. pyrrolidine (0.05 mol) wasadded slowly with constant
stirring, left overnight andrefluxed on a sand-bath for 25 to 30
hr. The productformed was washed with pet. ether. benzene
followedby acetone to remove unreacted monomers and lowmolecular
weight products and cured in an oven below90"C. The cured hard mass
was then crushed to - 60 to+ I00 mesh size as needed. All the
resins werecharacterised by the methods described in litera-ture'
-7.
The polymeric resins synthesised presently haveaverage physical
stability and are resistant towards 3Nacids and alkalis. Though
during polycondensation
under mild reaction and curing conditions cross-linking is
possible by the formation of - CH2 -linkages. on the basis of
analytical data (Table I)structures 0- III) for [Eptres-ollpy],
[Ep(8-0 H -Q )Py]and [Ep(/3-res-aldehyde)Py]. respectively) may
beproposed. Low moisture content of the resins(Table 2) reveal
fairly good degree of cross-linking.Cation and anion exchange
capacities have beendetermined at pH 12 and I. respectively. The
totalanion exchange capacities of these exchangers arehigher than
the corresponding cation exchangecapacities (Table 2). The total
capacities of theseexchangers are low due to involvement of
weaklyacidic and weakly basic groups. The copper exchangecapacities
of these exchangers follow the order: [EP(/3-res-aldehyde)Py] >
[EP(res-ol)Py] > [EP(8-0H-Q)Py]'
The true densities of H .,.-forrns of resins are low ascompared
to those of the OH - -Iorms. The columndensities of both H + and OH
- forms of the resins arelow. The large void volume fractions
(Table 2) indicatehigher porosity of the resins. This results in
fasterdiffusion of ions during ion exchange and hence tohigher rate
of exchange.
The rates of exchange for these amphoteric resins arevery high.
It is observed that 500/;. of the capacity isobserved in 20 min.
The rates of cation exchange(Fig.IA) of these resins follow the
order: [EP(res-aldehyde)Py] > [EP(res-ol)Py] =
[EP(8-0H-Q)Py].The rates of anion exchange (Fig. I B) of these
resinsfollow the order: [EP(res-oI)Py] > [EP(8-0H-Q)py] ~
[EP(res-aldehyde)Py].
From the pH titration behaviour (Fig. 2) it is clearthat
depending upon the pH of the solution these resinscan be used as
cation exchangers or anion exchangersand hence they are amphoteric
in nature. The data inTable 2 reveal that the pKo values for the
resins aresimilar to those of hydroxyl group indicating
weaklyacidic nature of the matrix. The pKb value arecharacteristic
of bases of medium strength. Theisoelectric points for these resins
are comparable tothose of amino acids.
Table 1 - Analytical Data of Amphoteric Resins
Resin Formula Found (%) Calc. (%)(Structure)
C H N C H N
[EP(res-ol)PY](I) C,.H2.O.N.3H2O 55.6 8.0 4.0 55.2 8.6
4.0[EPI8-0H-Q)PY](II) CSlH'80"N).4H2O 62.6 8.4 4.3 62.9 8.6 4.2[E
P(res-aldehyde)p Y](III) C"H8202,N2·4H20 59.0 6.5 2.0 59.4 6.3
2.0
302
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NOTES
-+---{A Br--t-
®OH (Hz014 OH n
0= -ECH2-CH(OH l-CH2~/® = -ECH2-CHCOH)-CH2*
Table 2 - Physicochemical Characteristics of Ion Exchange
ResinsProperty [EP(res-ol)PY] [EP(8-0H-Q)PY]
[EP(res-aldehyde)PY]
Total capacity" (a) 1.70 1.90 2.06(meq/g) (b) 0.86 0.75 1.90%
Moisture" (a) 7.2 8.46 8.43
(b) 10.19 9.04 11.510.1 0.00 0.26Cu-exchange
capacity (meqJg)pK.pKbIsoelectric pointTrue density"(dres) (g/cm
']Apparent density"(g/ml)Void vol. fraction"
9.453.876.66
(a) 1.15(b) 1.47(a) 0.27(b) 0.258(a) 0.766(b) 0.824(a) 0.92(b)
2.24(a) 0.22(b) 0.40
Cone. of ionogenicgroup (Cr)"Vol. capacity"(rneq/litre)
9.393.786.591.121.590.3230.3030.7120.8000.772.750.220.53
9.394.096.741.101.550.300.270.7270.8261.912.830.520.49
• (a) Values refer to anion exchange capacities (OH - form);
and(b)to cation exchange capacities (H + -form).
Table 3 - Swelling of Resins as Cation Exchangers in Various
Solvents
Resin % Swelling in·
Water Acetic acid DMF Dioxan THF
[EP(res-oI)pY] 6 76 5 0 0(20) (100) (5.5) (IOj (0)
[EP(8-0H-Q)PY] 0 85 36 12 10(25) (80) (10) (10) (15)
[EP(Res-aldehydejPY] 10 25 0 62 0(0) (95) (25) (0) (0)
• Values in parentheses refer to the resins as anion exchangers.
In alcohol, pet. ether benzene and acetone no swelling is
observed.
303
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INDIAN J. CHEM., VOL. 2SA, MARCH 1986
2-0
18 EPI ~·aldehyde) py1·6
1.4 CAliON EXCHANGE FIG A1·2
EPI RES)PY
E PI 8'OH'O) PY
EsE::: 01.U Ict. 02 [EP(8-0H-Q)Py(1.08)] >
[EP(res-aldehyde)Py (0.86)]. While as anionexchangers the
decreasing order of their stabilities is:[EP(res-aldehyde)Py
(4.55)] > [EP(res-oI)PY (3.86)]> [EP(8-0H-Q)Py (2.86)].
It is observed that the polar solvents produce moreextensive
swelling than the non-polar hydrocarbonsand larger the porosity
higher is the swelling (Table 3).
References1 Kunin R, Elements of ion exchange, edited by R E
Kriger
(Huntington. New York). 1971 pp. 163.2 Kunin R.lon exchange
resins. edited by Robert E Kriger (Wiley,
New York), 1958 pp 325, 337, 345.3 Krishnaswamy N & Trivedi
P B, Indian} Technol, 13 (1975) 39.4 Parikh S 0, Chelaung polymers,
Ph D Thesis. M.S. University of
Baroda. Baroda. 1977.5 Krishnaswamy N & Dasare B D.} scient
ind Res. 21 D (1962) 438.6 HelfTerich F. Ion exchange (McGraw Hill,
New York), 1962.7 Dorfner K. Ion exchangers. edited by Andree Fe
Coers tAnn Arbor
Science Publishers. Michigan). 1972 pp. 51.
