IR@NEIST - North East Institute of Science and Technology (CSIR)

BORAH , H N

BORUAH , R C

SANDHU , J S

Microwave-induced One-pot Synthesis of
N-carboxyalkyl Maleimides and Phthalimides$
Harsha N. Borah, Romesh C. Boruah and Jagir S. Sandhu*
Organic Chemistry Division, Regional Research Laboratory, Jorhat-6, Assam 785006, India
Maleic and phthalic anhydride condenses with amino acids and alkylamines under microwave irradiation to afford
N-substituted maleimides and phthalimides in excellent yields.
Maleimides constitute an important class of chemically and
biologically significant compounds.1 Reagents containing a
maleimido ligand tethered to an active ester group are in
high demand in modern chemistry and biotechnology.2
In addition, N-alkylphthalimides have received renewed
interest as a source of functionalized b-lactams.3 In general,
most methods of cyclic imide synthesis involve Lewis-acid-
mediated condensation of an amine with maleic anhydride
or n-alkylation of maleimide using Mitsunobo reaction
conditions.4 Maleimide-linked esters are prepared by cyclo-
condensation of maleimino acids in the presence of acetic
anhydride and sodium acetate or from N-(ethoxy-
carbonyl)maleimide and amino acids.5 However, these
methods have limitations of general applicability owing
to low yield, extensive by-product formation and harsh
reaction conditions.6
There has been a growing interest in the use of microwave
irradiation for heating in organic synthesis.7 This results
in better selectivity, rate enhancement and reduction of
thermally degradative products when compared with
conventional heating. In addition, microwave-mediated syn-
thesis without a solvent oers advantages for reducing
hazardous explosions and the removal of high boiling
aprotic solvents from the reaction mixture.8 Recently micro-
wave irradiation has been utilized for N-alkylation of
phthalimide in dry media under phase-transfer catalysis.9
Although the synthesis of N-arylmaleimides proceeds in
excellent yields, the synthesis of N-alkylmaleimides under
identical conditions is less satisfactory.10 In this report we
describe a microwave-induced fast synthesis of potentially
biologically active carboxyalkyl maleimides in a one-pot
reaction by condensing functionalized amines with maleic
anhydrides.
Equimolecular amounts of maleic anhydride (1) and
amino acid (3, R2=H, Me, Ph; R3=CO2H, CO2Me) were
placed in an open Erlenmeyer flask and heated in a domestic
microwave oven for an appropiate time (Table 1) to
obtain N-carboxyalkyl maleimides (4–6) in excellent yields
(90–96%). Under identical conditions phthalic anhydride (2)
reacted with alkylamine (3, R2=H, R3=Ph) and amino
acids (3, R2=H, R3=CO2H) aording N-substituted
phthalimides (9 and 10, respectively) in 89–95% yields.
Interestingly, our procedure of microwave heating excludes
polymerization.6 Further, alkylamines (3, R2=H, R3=Ph,
vinyl) eciently undergo one-pot condensation with 1 and
2, aording 7 and 8, respectively. All the products were
identified by spectral and microanalytical analysis.
In conclusion we have described a microwave-mediated
facile and fast synthesis of N-carboxyalkyl- and N-alkyl-
maleimides that may be biologically active. The reported
one-pot procedure is economical because of its high selec-
tivity, solvent-less condition and absence of dehydrating
agent.
Experimental
Mps were uncorrected and recorded on a Buchi apparatus.
IR spectra were obtained on a Perkin-Elmer 237B and 580B infra-
red spectrometer in KBr discs. The 1H NMR spectra were recorded
on Varian T-60 and JEOL JNM FX90Q spectrometers using Me4Si
as internal standard (d/ppm). Mass spectra were recorded on
a AEIMS-30 spectrometer at 70 eV. Microanalytical data were per-
formed on a Perkin-Elmer Series II 2400 instrument. Reactions
were conducted in a commercial microwave oven model ER 5054 D
of Microwave Products (India) Ltd.
General Procedure.—A mixture of either maleic anhydride (1) or
phthalic anhydride (2, 0.02 mol) and glycine (3, R2=H, R3=CO2H,
0.02 mol) was placed in an Erlenmeyer flask fitted with a loose top
cap and heated in a commercial microwave oven operating at
2450 MHz by setting the power range to medium high (70% of
total power). The reaction mixture turned red. After cooling, the
reaction mixture was extracted with chloroform (2 30 ml) and
wshed with cold water (2 10 ml), dried (Na2SO4), filtered and the
solvent removed.
N-Carboxymethylmaleimide 4: yield 94%, mp 112–13 8C; max/
cmÿ1 (KBr) 3050, 1710; dH (CDCl3) 6.70 (s, 2 H, olefinic), 3.75 (s, 2
H, methylene); m/z 111 (MÿCO2) (Found: 46.5; H, 3.15; N, 9.1.
C6H5NO4 requires C, 46.44; H, 3.25; N, 9.01%).
N-(a-Carboxyethyl )maleimide 5: yield 90%, mp 97–98 8C; max/
cmÿ1 (KBr) 3060, 1710; dH (CD3COCD3) 6.85 (s, 2 H, olefinic),
3.80 (q, 1 H, methine), 2.1 (d, 3 H, methyl); m/z 125 (MÿCO2)
(Found: C, 49.8; H, 4.2; N, 8.2. C7H7NO4 requires C, 49.69; H,
4.17; N, 8.25%).
N-(a-Methoxycarbonylbenzyl )maleimide 6: yield 95%, mp 87–
89 8C (lit.4(c), 88 8C); max/cm
ÿ1 (KBr) 3010, 1725, 1710; dH (CDCl3)
7.25–8.25 (m, 5 H, aromatic), 6.90 (s, 2 H, olefinic), 4.85 (s, 1 H,
methylene), 3.75 (s, 3 H, ester methyl); m/z 221 (M).
N-Benzylmaleimide 7: yield 96%, mp 69–70 8C (lit.,4(c) 69.5–
70.5 8C); max/cm
ÿ1 (KBr) 3050, 1705; dH (CDCl3) 7.20–7.40 (m,
5 H, aromatic), 6.70 (s, 2 H, olefinic) 4.68 (s, 2 H, methylene); m/z
237 (M).
N-Allylmaleimide 8: yield 82%, mp 42–43 8C (lit.,4(c) 42.5–43 8C);
max/cm
ÿ1 (KBr) 3000, 1710; dH(CDCl3) 6.72 (s, 2 H, olefinic), 5.80
(m, 1 H, vinylc), 5.12–5.24 (m, 2 H, vinylic), 4.10 (dt, 2 H, J
5.6 Hz, vinylic); m/z 137 (M).
N-Benzylphthalimide 9: yield 89%, mp 119–20 8C (lit.,4(c) 118.5–
119.5 8C); max/cm
ÿ1 (KBr) 3060, 1700; dH (CDCl3) 7.65–7.88 (m, 4
H, aromatic), 7.20–7.45 (m, 5 H, aromatic), 4.80 (s, 2 H, olefinic);
m/z 237 (M).
N-Carboxymethylphthalimide 10: yield 95%, mp 110–11 8C; max/
cmÿ1 (KBr) 3040, 1720; dH (CD3COCD3) 7.60–7.95 (m, 4 H,
aromatic), 4.70 (s, 2 H, methylene); m/z 161 (MÿCO2). (Found:
C, 58.6, H, 3.3, N, 6.9. C10H7NO4 requires C, 58.52, H, 3.44,
N, 6.83%).
J. Chem. Research (S),
1998, 272–273$
$This is a Short Paper as defined in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).
*To receive any correspondence.
272 J. CHEM. RESEARCH (S), 1998
Received, 5th December 1997; Accepted, 19th January 1998
Paper E/7/07961C
References
1 J. E. T. Corrie, J. Chem. Soc., Perkin Trans 1, 1994, 2975.
2 T. Kitagawa, T. Kawasaki and H. Munechika, J. Biochem.,
1982, 92, 585.
3 D. D. Pietro, R. M. Borzilleri and S. M. Weinreb, J. Org.
Chem., 1994, 59, 5856.
4 (a) G. B. Gill, G. B. James, K. V. Oates and G. J. Pattenden,
J. Chem. Soc., Perkin Trans. 1, 1993, 2567; (b) M. A. Walker,
J. Org. Chem., 1995, 60, 5352; (c) P. Y. Reddy, S. Kondo,
T. Toru and Y. Ueno, J. Org. Chem., 1997, 62, 2652.
5 O. Nielsen and O. Buchardt, Synthesis, 1991, 819 and references
cited therein.
6 M. P. Stevens, J. Polym. Sci. Polym. Lett. Ed., 1984, 22, 467.
7 (a) R. Laurent, A. Leporterie, J. Dubac, J. Berlan, S. Lauverie
and F. M. Audhuy, J. Org. Chem., 1992, 57, 7099 and references
cited therein; (b) S. Caddick, Tetrahedron, 1995, 51, 10403.
8 (a) G. Bram, A. Loupy and D. Villemerin, in Solid Supports and
Catalysts in Organic Chemistry, Ellis Horwood, London, 1992;
(b) A. Boruah, M. Baruah, D. Prajapati and J. S. Sandhu,
Chem. Lett., 1996, 965.
9 D. Bogda and J. Pielichiowski, Synlett, 1996, 873.
10 (a) N. B. Metha, A. P. Phillips, F. F. Lui and R. E. Brooks,
J. Org. Chem., 1960, 25, 1012; (b) D. H. Rich, P. D. Gesellchen,
D. Paul, A. Tong, T. A. Cheung and C. K. Buckner, J. Med.
Chem., 1975, 18, 1004.
Table 1 Condensation of maleic and phthalic anhydrides with amines
Entry Substrate Product
Reaction time
(t/min)
Solvent of
crystallization
1 Glycine N-Carboxymethylmaleimide (4) 3 Water
2 Alanine N-(a-Carboxyethyl)maleimide (5) 3 Water
3 2-Phenylglycine methyl ester N-(a-Methoxycarbonylbenzyl)maleimide (6) 2 Methanol
4 Benzylamine N-Benzylmaleimide (7) 2 Chloroform
5 Allylamine N-Allylmaleimide (8) 2 Methanol
6 Benzylamine N-Benzylphthalimide (9) 3 Water
7 Glycine N-(Carboxymethyl)phthalimide (10) 3 Chloroform
J. CHEM. RESEARCH (S), 1998 273


Microwave induced one-pot synthesis of N-carboxyalkyl maleimides and phthalimides

SAIKIA , C N

GOSWAMI , T

ALI , F

Wood Science and Technology 31 (1997) 467-475 © Springer-Verlag 1997 
Evaluation of Pulp and Paper making 
characteristics of certain fast growing 
C. N. Saikia, T. Goswami, F. Ali 
plants 
Summary Four species of fast growing annual plant viz. Hibiscus sabdariffa, 
Crotalaria juncea, Tephrosia candida and Hibiscus cannabinus and a variety of 
reed, Neyraudia reynaudiana were evaluated in the laboratory for their pulp and 
paper making properties. Data on proximate chemical analysis of raw materials, 
unbleached and bleached pulp properties, morphological properties of fibres and 
physical strength properties of paper sheets were evaluated. The unbleached pulp 
yields were 44.90-53.20% with all the five plant materials, while bleached pulp 
yields varied from 39.80-50.60%. The average fibre lengths and diameters of the 
unbleached pulp obtained from the five plant species were within the range of 
0.75 mm-2.15 mm and 20-22 pm respectively. Paper hand sheets, made with 
bleached pulps (45 ° SR) obtained from the five plant species, gave burst indices 
2.75-3.92 kPa mZ/g, tear indices 3.73-9.61 m N mZ/g and tensile indices 37.27- 
47.81 N mg -1, indicating adequate strength properties for writing and printing 
type of paper. 
Introduction 
A global shortage of conventional pulpable raw material is visualised by the turn 
of this century (Anon, 1989). Search for new fibre crops has been underway 
during last three decades or so, to find and develop new fibre supplies for paper 
and cellulose industries. The most promising amongst he fibre bearing plants, 
some of which have already proven to be ideal for pulp and paper making, is the 
group of fast growing plant species. Many fast growing annual and perennial 
plants, have been identified, cultivated and studied for their suitability as alter- 
native source of raw material for paper industry (Nelson et al. 1966; Cunningham 
et al. 1970; Watson et al. 1976; Cunningham et al. 1978; Zarges et al. 1980; Mo- 
hanrao et al. 1982). Development of scientific ultivation technology for raising 
some of these fast growing annual and perennial plants, to give wood production, 
has helped to a great extent o fill the gap between demand and supply of pulpable 
467 
Received 9April 1996 
C. N. Saikia, T. G0swami, F. Ali 
Regional Research Laboratory 
Council of Scientific & Industrial Research 
Jorhat-785006, India 
Correspondence to:C. N. Saikia 
The authors thank Director, Regional Research Laboratory 
(CSIR), Jorhat, India, for his kind permission to publish this 
paper. The authors also wish to thank B. N. Tosh, JPF for his 
assistance. 
468 
raw materials. Paper industry in India, is also facing a grave raw material crisis 
today. Depletion of forest areas in the country has badly hit the supply of fibrous 
raw material to the industry. Great importance has, therefore, been given to raise 
fast growing plant species. The potentiality of some of the fast growing plants for 
use as raw material for paper and cellulose industries has also been studied 
(Durra, Fotedar 1979; Mohanrao et al. 1982; Kulkarni et al. 1985; Sarma et al. 1990; 
Saikia et al. 1991). 
The annual plants like Hibiscus sabdariffa, Crotalaria juncea, Tephrosia 
candida and Hibiscus cannabinus can be grown in the temperate and tropical 
climates and these have long been cultivated in many parts of India. Under agro- 
climatic conditions of Assam, India, all these annual plants attain luxuriant 
growth. These annual plants have been cultivated in the experimental farm of 
Regional Research Laboratory (RRL) and experiments were conducted to deter- 
mine various parameters of growth and biomass yields to optimise cultivation 
technology and silvicultural methods to get the best output under local conditions 
(Sarma 1990; R&D Report 1991). Neyraudia reynaudiana is one of the many 
varieties of reeds that grows in abundance in the forests of Northern Eastern part 
of India. It belongs to the family Poaceae and is a fast growing perennial grass, 
with thick, terete, smooth and shinning culms (Bor 1984). 
The present work was undertaken to evaluate the suitability of the above plant 
materials as pulp and paper making raw materials. 
Experimental 
Raw materials 
Fully matured annual plants were obtained from the experimental farm of RRL, 
Jorhat, Assam, India. The reed was collected from a forest near Jorhat. The plant 
materials were first cleaned and the sample along with bark was cut into 
2.5 x 1.5 cm chips. The chips were air dried (moisture 12%) before use. 
Evaluation of raw materials, pulp and paper sheets 
Proximate chemical analyses 
The proximate chemical analyses of the raw material were carried out as per 
TAPPI standard methods (Tappi, 1980). For this purpose, air dried chips were 
made into powder and screened through a40 BS sieve. Powder (-40 and +80) was 
taken for analysis. The results are recorded in Table 1. 
Pulping and bleaching 
Kraft pulping was carried out in a 10 L electrically heated rotary stainless teel 
reactor, with temperature controlled system. The oven dry (O.D.) chips (1000 g) 
were charged into the digester along with required amount of chemical solution at 
a material to liquor ratio 1 : 4. The cooking was done with 16.5% active alkali 
(NaOH + Na2S) on OD raw materials, keeping sulphidity at 20%. The chips were 
cooked at a controlled temperature of 163 + 2 °C for 3 h (including 45 min to 
raise the temperature to maximum). After the cooking, the pulp was washed 
thoroughly with deionised water and the unbleached pulp thus obtained was 
analysed for characteristic properties (Table 1). 
The unbleached pulp was bleached by using hypochlorite alkali extraction - 
hypochlorite (HEH) sequence, with approximately 5.50-6% total chlorine con- 
sumption, to yield pulp of 78-81% brightness. 
Fibre morphology 
The length (L), diameter (D), wall thickness (W) and lumen diameter (d) of well 
digested pulp fibre were determined under a Dokuval photomicroscope (JEOL, 
Japan) at different magnifications. 
Brightness 
The brightness of the bleached pulp sheets was determined by using an EIL 
Reflectance Spectrophotometer and the results were expressed on the basis of 
MgO = 100. 
Infra-red (IR) spectra 
The IR spectra of the bleached pulp fibres were collected in a Perkin Elmer 297 
spectrometer from 4000 to 200 cm -1 with resolution of 2 cm -1 with a five times 
scan per sample. All spectra were measured with air as background and were 
background subtracted to make them directly comparable. 
Scanning electron microscopy 
Fibres were separated in the pulp samples and were mounted on specimen 
holders with the help of electroconductive tape. The samples were coated with 
gold in an Ion sputter coater (JFC 100, JEOL, Japan) in low vacuum with a layer of 
150-200 nm thick. The observation was made in a JEOL, JSM-35M-35CF electron 
microscope at an accelerating potential of 15 KV. Micrographs were taken at this 
potential. 
Papersheet formation 
The unbleached and bleached pulps were beaten in a laboratory valley beater to 
45 ° SR (Schopper Reigler) freeness at 1.57% consistency and standard sheets of 
60 + 1 gm -2 were made from the pulps in a British Standard laboratory hand 
sheet forming machine, followed by pressing and drying. 
469 
Table 1. Proximate chemical analysis of plant raw materials and evaluation of unbleached 
pulp properties (values in brackets) 
Parameters (%) Plant raw materials 
H. cannabinus H. sabdariffa T. candida C. juncea IV. reynaudiana 
Solubility in 
Cold water 3.55 3.97 3.10 4.70 5.75 
(1.85) (0.99) (1.97) (1.80) (1.08) 
Hot water 6.55 7.25 5.25 6.30 7.35 
(1.02) (1.12) (0.66) (0.59) (2.06) 
1% Alkali 34.20 30.40 22.70 28.58 32.58 
(9.16) (9.95) (4.00) (4.36) (6.88) 
Alcohol 7.85 4.80 5.01 3.20 2.64 
benzene (5.71) (3.75) (2.37) (2.22) (2.23) 
Lignin 17.33 17.92 21.05 20.50 22.15 
(4.02) (3.01) (4.76) (3.68) (3.70) 
Pentosan 18.10 18.35 19.57 17.80 20.65 
(14.52) (17.44) (14.45) (14.89) (15.90) 
Cross & Bevan 59.50 58.40 52.22 56.70 62.45 
Cellulose (85.14) (84.49) (85.82) (87.16) (81.44) 
Ash 2.25 1.15 1.30 1.85 2.35 
470 
Testing of paper sheets 
The dried paper sheets were conditioned at 65% relative humidity at 27 °C for 2 h 
and then tested for various physical properties. 
Results and discussion 
Table 1 gives the results obtained in the characterization f the plant raw mate- 
rims. The lignin and pentosan contents are found to be more in the reed plant in 
comparison to the annual plant species. So also, the cellulose contents. The cel- 
lulose contents of all the five species of plants were between 52.22-62.45%. The 
chemical compositions indicate their suitability as pulpable cellulosic materials. 
The optimum kraft pulping conditions were fixed up after carrying out di- 
gestions at different conditions of chemical concentrations, temperature and time 
periods. The unbleached pulp yields from all the species were between 44.90 and 
52.50% (Table 2). The results obtained in the evaluation of unbleached pulp 
characters are shown in brackets in Table 1. The lignin and pentosan contents 
and the solubility figures of the unbleached pulps are proportionately reduced in 
comparison to wood raw material. The cellulose contents of the pulps from all the 
plant raw materials vary from 81.44-87.16%, exhibiting suitability of the cellulose 
for paper making. 
The characteristic morphological properties of the bleached pulp fibres are 
given in Table 3. Hibiscus cannabinus and Hibiscus sabdariffa have long fibres in 
comparison to other three plant fibres. The average fibre lengths (L), varied from 
0.75 mm (T. candida) to 2.15 mm (H. cannabinus); the average fibre width (D) 
from 20.00 btm (T. cannabinus) to the 22.00 gm (H. sabdariffa); the average lu- 
men diameter (d) from 12.70 llm (N. reynaudiana) to 17.10 btm (H. cannabinus) 
and the cell wall thickness (W) from 3.90 ~tm (H. cannabinus) to 4.75 btm (T. 
candida). Thus, the Runkel ratio (2 W/d) and the shape factor (D2-d2/D2+d 2) 
varied from 0.47 (N. reynaudiana) to 0.63 (T. candida) and 0.23 (H. cannabinus) 
to 0.47 (N. reynaudiana) respectively. The fibre characteristics are collectively 
represented by Runkel ratio and shape factor. The paper formation and its 
strength properties are largely dependent on these properties. The results show 
that all the five species of plants are suitable for paper making. The classification 
of unbleached pulp fibres showed well-balanced fibre sizes as given in Table 4. 
Table 2. Analytical data on unbleached and bleached pulps 
Parameters Pulp from plant raw materials 
H. cannabinus H. sabdariffa T. candida C. juncea i'4. rwnaudiana 
Yield of unbleached 52.50 51.70 45.80 53.20 44.90 
pulp (%) 
Kappa Number (%) 25.00 23.50 19.90 16.60 22.10 
Yield of bleached 50.60 47.00 40.80 46.10 40.35 
pulp (%) 
Brightness of 81.70 80.50 78.90 80.10 80.00 
bleached pulp (%) 
CED Viscosity at 45.00 40.00 38.50 48.00 38.22 
27 ° (Cp) 
Degree of 387 328 325 475 322 
polymerization 
(DP) (average) 
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471 
Table 4. Bauer McNett Fibre classification 
Mesh Retention (%) Pulp from plant raw materials 
H. cannabinus H. sabdariffa C. juncea T. candida N. reynaudiana 
472 
+ 14 44.50 46.00 35.50 8.60 6.20 
-14,+30 20.75 18.70 22.60 7.80 8.10 
-30,+50 11.80 10.20 7.80 47.90 45.60 
-50,+100 3.85 5.10 3.50 26.30 22.70 
-100 19.10 20.00 29.50 15.20 17.40 
Figures 1-5 show the scanning electron micrographs of pulp fibres of H. can- 
nabinus (1), H. sabdariffa (2), C. juncea (3), T. candida (4) and N. reynaudiana 
(5). Some of the fibres of H. cannabinus are long cylindrical with distinct nodes, 
whereas, some are though long and cylindrical, but smaller in diameter. The fibres 
Figs. 1 and 2. SEM of pulp fibres of H. sabdariffa respectively. (×200) 
473 
Figs. 3 and 4. SEM of pulp fibres of C. juncea and T. candida respectively. (x200) 
Fig. 5. SEM of pulp fibres of N. reynaudiana (x200) 
474 
of H. sabdariffa are flat, rosette like and wavy, comparatively larger in diameter 
than that of H. cannabinus fibres. C. juncea has two types of fibres - some are flat 
and large in size and others are small and cylindrical. The fibres of T. candida are 
though fiat but uniform in size with no distinct nodes, whereas, the fibres of N. 
reynaudiana re narrow cylindrical and are mostly of uniform size. 
The Infra-red spectra of bleached pulps from all the five species of plant and 
that of bleached bamboo pulp were found to be identical. The region from 4000 to 
1900 cm -1 would be largely responsible for the O H and aliphetic C--H 
stretching frequencies (Liang, Marchessault 1959a; Higgins et al. 1961; Sao et al. 
1987; Stewart, Morrision 1992). The strong band at 1640 cm -1 was due to vi- 
bration of adsorbed water molecules in the non-crystalline r gion of the cellulose 
(Liang, Marchessault 1959a; Williams, Fleming 1976). The region between 1530 
and 670 cm -1 represented carbon-hydrogen vibrational modes of the glucose unit 
of the cellulose chain. The bands at 1365 cm -1 and 1315 cm -1 were due to CH 
deformation and CH 2 wagging frequencies and attributed to the xylan fractions in 
cellulose (Liang, Marchessault 1959b; Pray 1972). 
The physical strength properties of paper sheets, made out of unbleached and 
bleached pulps that were beaten to 45°SR are shown in Table 5. The data obtained 
for bulk densities (1.42-1.58 c/g), burst indices (3.82-5.19 kPa m2/g-X), tear in- 
dices (4.41-10.79 m N mi/g-1), tensile indices (51.68-63.26 N mg 1) and double 
folds (210-420) of the unbleached pulp sheets made from the pulp obtained from 
all the five species of plant, are found to be more or less comparable, although 
pulp sheets made from Crotalaria juncea and Hibiscus cannabinus how higher 
values of physical strength properties. So also, the physical strength properties of 
pulp sheets made from bleached pulp of all the five plant species exhibit that 
paper with adequate physical strength properties can be produced. 
It can, therefore, be concluded that the plant species under investigation would 
be ideal sources of raw material for pulp & paper industry. 
Table 5. Physical strength properties of paper sheets made from pulp obtained from dif- 
ferent plant raw materials 
Plant raw materials Bulk Burst Tear Tensile Folding 
density index index index endurance 
(cc/g) (kPa m2/g -1) (m N m2/g) (N mg -1) (double folds) 
Hibiscus cannabinus 
Ubps 1.58 5.19 
Bps 1.42 3.43 
Hibiscus abdariffa 
Ubps 1.52 4.90 
Bps 1.38 3.73 
Crotalariajuncea 
Ubps 1.47 5.09 
Bps 1.39 3.92 
Tephrosia candida 
Ubps 1.44 4.71 
Bps 1.35 3.43 
Neyraudia reynaudiana 
Ubps 1.42 3.82 
Bps 1.38 2.75 
10.79 60.31 350 
5.88 37.27 110 
11.77 62.03 320 
6.37 42.17 120 
10.79 63.26 420 
9.61 47.81 255 
5.69 57.62 300 
4.32 40.45 150 
4.41 51.68 210 
3.73 38.15 120 
Ubps = Unbleached pulp sheet 
Bps = Bleached pulp sheet 
References 
Anon. 1989: Strong growth predicted to year 2001. Pulp and Paper International. 31:46 
Bor. N. L. 1984: Flora of Assam, Vol. V, p 115, Govt. of Assam 
Cunningham, R. L; Clark, T. F.; Kwolek, W. F.; Wolf, I. A.; Jones, Q. 1970: A search for new 
fibre crops. XIII. Laboratory scale pulping studies. Tappi., 53(9): 1697-1700 
Cnnnlngham, R. L.; Clark, T. F.; Bagby, M. O. 1978: fibre. Tappi. 61(2):37-39 
Dutta, A. K.; Fotedar, A. K. 1979: Performances of some Kenaf varieties under Jammu 
conditions. Ippta, 16(4): 182-185 
Higgins, H. G.; Stewart, C. M.; Harrington, K. J. 1961: Infrared spectra of cellulose and 
related polysaccharides. J. polymer Sci., 51:59-84 
Kulkarni, A. G.; Mathur, R. M.; Naithani, S.; Agarwall, G. C.; Pant, R. 1985: Newsprint grade 
pulps from whole mesta plant of Sabdariffa hibiscus variety, part II, pilot plant studies on 
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475 


Evaluation of pulp and paper making characteristics of certain fast growing plants

DEY , N C

BHUYAN , J

HAQUE , I

Partial molar volumes and partial molar adiabatic compressibilities of potassium trioxalato complexes of Al(III),Fe(III),Co(III) and Cr(III) between 15 and 35 degree centigrade

Research carried out on sulphur in Assam coals are reviewed. It is intended to provide

a general overview with some recent advances on the forms of sulphur in these coals and their

desulphurization and recovery in the forms of elemental sulphur or useful compounds. Greater

emphasis is given on a new form of sulphur, i.e., secondary sulphur, in Assam coals. Studies on

sulphur in Assam coals would be potentially useful in coal utilization

BAROOAH , P K

BARUAH , M K

Sulfur in Assam Coal

MAHIUDDIN , S

Density, viscosity and electrical conductivity of XCH3CONH2 + (1-X)Ca(NO3)2 4.37 H2O from 253.15 to 348.15 K

SKIBO , E B

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Page 2 of 2The Journal of Organic Chemistry - Determination of the pKa Values for the Mitomycin C Redox Co...
4/24/2009http://pubs.acs.org/doi/pdf/10.1021/jo00112a051


Determination of pKa values for the mitomycin C redox couple by titration, pH rate profiles, and nernst-Clark Fits. studies of methanol elimination, carbocation formation, and carbocation/quinone method equilibrium

SAHU,  P O

SAIKIA , M M

The b-value before the 6th August, 1988, India- Myanmar border region earthquake - a case study

DUTTA , D K

SINGH , M M

290 Rh ~ carbonyl complexes with N and S ligands Transition Metal Chemistry, 19 (1994) 290-292 
Rhodium(I) carbonyl complexes with sulphur and nitrogen donor 
ligands 
Dipak K. Dutta* 
Inorganic Chemistry Division, Regional Research Laboratory, Jorhat 785 006, Assam, India 
Mono M. Singh 
Merrimack College, North Andover, Massachusetts 01845, USA 
Summary 
Rhodium(I) carbonyl complexes, namely [Rh(CO)2C1L ] 
where L = thiourea (Tu), 1,3-diphenyl-2-thiourea (DTu), 
dithizone (Dtz), indole (Id), 3-chloropyridine (Clpy), 3- 
hydroxypyridine (HOpy), 3-methylpyridine (Mepy), 2,5- 
dimethylpyridine (Me2py) or 2,5-dichloropyridine (C12py)] 
were prepared. [Rh(CO)2CI(Clpy)2 ] has also been isolated. 
In the (Tu) complex, v(C--S) occurs at ca. 710cm -1 
indicating the presence of a metal-sulphur bond. The 
carbonyl stretching frequencies in [Rh(CO)2C1L] and 
[Rh(CO)2C1L2] occur at ca. 2100 1990 and 1830- 
1800 cm-1, respectively. PPh3 reacts with the complexes 
to form trans-[Rh(CO)Cl(PPh3)2]. The complexes were 
characterized byelemental nalyses, conductivity measure- 
ments and by their i.r. spectra. 
Introduction 
Rhodium(I) complexes have gained much importance 
because of their applications in catalysis and biological 
activity. A limited number of rhodium(I) complexes with 
sulphur donor ligands are known. Most of the reported ~1-6) 
rhodium(I) carbonyl complexes having metal-sulphur 
bonds containing alkyl/aryl, sulphoxide/sulphide ligands. 
So far no attempt has been made to prepare these com- 
plexes with ligands such as thiourea. Bridge splitting of 
[(OC)2Rh(p-C1)2Rh(CO)2] with a considerable number 
of heterocyclic nitrogen ligands have been reported ~1. v-9), 
but a systematic study with some mono- and di-substituted 
heterocyclic nitrogen ligands has not been made hitherto. 
In this study, we report he synthesis and characterization 
of rhodium(I) carbonyl complexes containing thiourea 
(Tu), 1,3-diphenyl-2-thiourea (DTu), dithizone (Dtz), indole 
(ld), 3-chloropyridine (Clpy), 3-hydroxypyridine (HOpy), 
3-methylpyridine (Mepy), 2,5-dimethytpyridine (Me2py) 
or 2,5-dichloropyridine (C12py) ligands. 
Experimental 
RhC13"xH20 was obtained from Johnson Matthey. 
Analytically pure Tu, DTu, Dtz, Id, py and substituted 
pyridines (Aldrich) were used directly without further 
purification. All solvents were purified by standard methods 
before use. I.r. spectra were recorded on a Specord 75 IR 
spectrophotometer (4000-400 cm- 1). Conductivity mea- 
surements were carried out with the help of a Systronics 
type 303 conductivity meter. Carbon and hydrogen ele- 
mental analyses were performed by CSIRO, Australia. 
Rhodium analysis was done by a standard gravimetric 
method~10). 
All the complexes were prepared from [(OC)2Rh(#- 
* Author to whom all correspondence should be directed. 
C1)2Rh(CO)2], which was in turn prepared (11) by passing 
dry CO gas over RhC13.xH2 O at ca. 100 ~ C. 
[Rh(CO)zCl(Tu)] 
[(OC)2Rh(#-CI)2Rh(CO)2] (0.3 g) was dissolved in Me2CO 
(ca. 20 cm 3) and Tu (0.125 g) was then added very slowly 
with constant stirring. On removal of the solvent by 
evaporation under vacuum, abrown compound separated. 
It was washed with Me2CO and dried over fused CaC12 
in a desiccator. 
[RhCO )2CIL] ( L = DTu or Dtz ) 
[(OC)2Rh(#-C1)2Rh(CO)2 ] (0.2 g) in benzene (15 cm 3) was 
treated with DTu (0.24 g) or Dtz (0.28 g). The mixture was 
stirred thoroughly and evaporated under vacuum. The 
complexes thus obtained were washed with benzene and 
finally dried over fuscd CaC12 in a desiccator. 
[Rh(CO)2C1L ] (where L = Id, py, Clpy, HOpy, 
Mepy, Me2py and Cl2py )
[(OC)2Rh(#-CI)2Rh(CO)2] (0.2 g) in benzene (15 cm 3) was 
treated with a stoichiometric amount of the respective 
ligand with constant stirring. The solution was evaporated 
in vacuo and the solid mass was washed with benzene. The 
complexes thus obtained were dried over fused CaC12 in 
a desiccator. 
[ Rh( CO )2Cl( Clpy )2] 
[(OC)2Rh(#-C1)2Rh(CO)2] (0.2 g) in benzene (20 cm 3) was 
treated with about a four-fold excess (0.95 g) of Clpy under 
constant stirring. The solution was evaporated under 
vacuum and washed with benzene. The solid complex was 
dried over fused CaC12 in a desiccator. 
Results and discussion 
It was reported ~t2-2m that the bicovalent sulphur atoms 
in thioureas can act as donor atoms with a degree of 
n-acceptor property. Such a molecule therefore contains 
both sulphur and nitrogen donor atoms. It is well known 
that thiourea may coordinate in either of the following 
modes: 
S=C/NH2 _ /,NH2 
NH 2 S--C<" "NH 2 
(1) (2) 
Coordination through the nitrogen atom gives rise to 
structure (I), resulting in a relatively high C- -S  bond 
order ~t3). On the other hand, coordination through the 
0340 4285 9 1994 Chapman &Hall 


Rhodium (1) carbonyl complexes with sulphur and nitrogen donor ligands

BHUYAN , B R

Resource sharing amongst the special libraries at Jorhat in periodical acquisition, In-Librarianship & Information Technology, ed by A Buragohain & K N Baisya

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Page 2 of 3Journal of Medicinal Chemistry - A Comparison of the Cytotoxic and Physical Properties of Aziridin...
4/24/2009http://pubs.acs.org/doi/pdf/10.1021/jm00037a013


A comparison of the cytotoxic and physical properties of aziridinyl quinone derivatives based on pyrrolo[1,2-a] benzimidazole and pyrrolo[1,2-a]indole ring systems

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