Synthesis, biological evaluation and study of the effect of various N-substituents on the thermal stabilities of some new diethanolamine derivatives

Article abstract of DOI:10.14233/ajchem.2013.14543

Diethanolamine and its derivatives are of considerable interest in medicinal and other industrial products. A series of new diethanolamine derivatives has been synthesized and characterized by 1H NMR, 13C NMR, FTIR and mass spectrometry. All synthesized compounds have been tested for their in vitro antibacterial activity against pathogenic microorganisms Escherichia coli, Staphylococcus aureus, Micrococcus luteus, Pseudomonas aeruginosa, Bacillus subtilis, Pasteurrella mutocida, Rhizopus oryzae and Salmonella typhi. Among the tested compounds, compounds 2a, 2b, 2c, 3a and 4b have been found to be most potent members, which inhibited most of the pathogens used in the assay. Diethanolamine must posses tosyl or trifluoro groups in order to have good antimicrobial activities. All synthesized derivatives exhibited average FRAP activity and considerably good metal chelating activity and compound 2c showed excellent ABTS radical scavanging among all tested derivatives. Thermal stability and the effect of various N-protected groups on the thermal stability and degradation of selected diethanolamine derivatives (free flowing oils at room temperature and solid derivative 2a) has been studied by TGA and DSC analysis.

Full text of DOI:10.14233/ajchem.2013.14543

Asian Journal of Chemistry; Vol. 25, No. 13 (2013), 7297-7304
http://dx.doi.org/10.14233/ajchem.2013.14543
Synthesis, Biological Evaluation and Study of the Effect of Various N-Substituents
on the Thermal Stabilities of Some New Diethanolamine Derivatives
1,*
1
1
1
2
MUHAMMAD YAR , NAFEESA MUSHTAQ , SADIA AFZAL , ABDUL SAMAD KHAN , ISLAM ULLAH KHAN ,
3
3
4
5
MUHAMMAD NADEEM AKHTER , SEEMA ZAREEN , SOHAIL ANJUM SHAHZAD , ZULFIQAR ALI KHAN ,
5
6
7
7
SYED ALI RAZA NAQVI , NASIR MAHMOOD , LUBNA TAHIR and MUHAMMAD SALEEM
1Interdisciplinary Research Centre in Biomedical Materials, COMSATS Institute of Information Technology, Lahore, Pakistan
2Materials Chemistry Laboratory, Department of Chemistry, GC University Lahore, Pakistan
3Faculty of Industrial Science & Technology, Universiti Malaysia Pahang, Lebuhraya, Tun Razak 26300 Gambang, Kauntan, Malaysia
4Department of Chemistry, COMSATS Institute of Information Technology, Abbottabad-22060, Pakistan
5Department of Chemistry, Government College University, Faisalabad-38000, Pakistan
6Department of Allied Health Sciences and Chemical Pathology, University of Health Sciences, Lahore, Pakistan
7Pharmeceutical Section, Applied Chemistry Research Centre, PCSIR Laboratories Complex, Lahore, Pakistan
*Corresponding author: Fax: +92 42 235321090; Tel: +92 42 111001007; Ext.: 829; E-mail: drmyar@ciitlahore.edu.pk
(Received: 10 September 2012;
Accepted: 24 June 2013)
AJC-13695
Diethanolamine and its derivatives are of considerable interest in medicinal and other industrial products. A series of new diethanolamine
derivatives has been synthesized and characterized by 1H NMR, 13C NMR, FTIR and mass spectrometry. All synthesized compounds have
been tested for their in vitro antibacterial activity against pathogenic microorganisms Escherichia coli, Staphylococcus aureus, Micrococcus
luteus, Pseudomonas aeruginosa, Bacillus subtilis, Pasteurrella mutocida, Rhizopus oryzae and Salmonella typhi. Among the tested
compounds, compounds 2a, 2b, 2c, 3a and 4b have been found to be most potent members, which inhibited most of the pathogens used
in the assay. Diethanolamine must posses tosyl or trifluoro groups in order to have good antimicrobial activities.All synthesized derivatives
exhibited average FRAP activity and considerably good metal chelating activity and compound 2c showed excellent ABTS radical
scavanging among all tested derivatives. Thermal stability and the effect of various N-protected groups on the thermal stability and
degradation of selected diethanolamine derivatives (free flowing oils at room temperature and solid derivative 2a) has been studied by
TGA and DSC analysis.
Key Words: Diethanolamine, Antioxidant activity, Antibacterial, DSC, TGA.
high concern due to their fuel lubricity view point. However
there are limited TGA and DSC analysis performed for
diethanolamine and its derivatives to predict their thermal stabi-
lities. They have essential contribution to mantain required
lubricating properties11.
INTRODUCTION
Diethanolamine and its derivatives have wide applications
in pharmaceuticals, surfactants formation, polishers and cos-
metics industries. Diethanolamine has been used as interme-
diate in the rubber chemicals industry and as an emulsifier
and dispersing agent in various agricultural products1,2 and
also used in adhesives, cements, coatings, electroplating, printing
inks, paints, papers, petroleum, coal and polymer productions,
textile finishing and lubricants3. The use of lubricants is crucial
and plays an important role in our daily lives. The search for
new lubricants particularly liquid and stable at high temperature
is highly desired. TGA/DSC have successfully been utilized
for determination of physical properties and study of chemical
reactions4-8 and for investigation of thermal stabilities of comp-
ounds9,10. Diethanolamine derivatives have previously been in
The increasing resistance of pathogens to current antimi-
crobial agents is a dilemma and fungal infections are also
serious issue of concern12. Antioxidants are widely used and
have been investigated for direct and indirect prevention of
diseases such as cancer, diabetes mellitus, coronary heart
disease and even altitude sickness.Antioxidants have also been
used in food industry to prevent deterioration, nutritional losses
and as flavoring agents in various foods13. Diethanolamine and
its derivatives constitute an important class of heteroatom
compounds as they have attracted significant interest in medi-
cinal chemistry. Diethanolamine derivatives possess vibrant

7298 Yar et al.
Asian J. Chem.
spectrum of biological activities including antibacterial14,
anticancer15, local anesthetic16, antiplatelet aggregation17 and
antioxidant properties18 antituberculosis19. Such promising
biological potentials of diethanolamine and its derivatives have
prompted us to devise, synthesize and biologically evaluate a
new series of compounds with potent antimicrobial and anti-
oxidant potential and also to test their thermal properties.
uder vaccum, then water (15 mL) was added to residue and
extracted with ethyl acetate (3 × 30 mL). The organic layers
were combined, dried over anhydrous magnesium sulphate
and filtered. After evaporation of ethyl acetate under vaccum,
2b was obtained as colourless liquid (58 %); Rf 0.11 (1:1;
n-hexane and ethyl acetate); 1H NMR (500 MHz, CDCl3); 3.85
(4H, br s, CH2-O), 3.19 (4H, br s, CH2-N); 13C NMR (500
MHz; CDCl3) 157.4 (C), 115.8 (C), 49.7 (CH2), 49.5 (CH2),
59.4 (CH2), 59.0 (CH2).
EXPERIMENTAL
All the solvents were used as obtained, except THF and
Et2O were dried over sodium in benzophenone. TLC was
performed on silica coated aluminium plates (6F254, 0.2 mm).
IR spectra were recorded on a JASCO A-302 IR spectropho-
Phenyl bis(2-hydroxyethyl)carbamate (2c): Diethanol-
amine (1.0 g, 9.52 mmol) was added to a stirred solution of
NaHCO3 (0.79 g, 10.47 mmol) in water (10 mL). The solution
was further stirred at room temperature for 15 min. Then
phenoxylchloroformate (1.48 g, 9.52 mmol) was added drop
wise. The reaction mixture was further stirred for 5 h at room
temperature. The reaction mixture was extracted with ethyl
acetate (3 × 30 mL). The organic layers were combined, dried
over anhydrous magnesium sulphate and filtered. On evapo-
rating solvent, 2c was obtained as colourless liquid (51 %); Rf
1
tometer. H and 13C NMR spectra were recorded on Bruker
NMR 500 MHz and chemical shifts were calculated with refe-
rence to CDCl3 (7.25). Mass spectra were recorded on aVarian
MAT 312 double focusing spectrometer, connected to an IBM-
AT compatible PC computer system. Standard antioxidants
such as Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-
carboxylic acid), iron(II) sulphate, 2,4,6-tri(2-pyridyl)-s-triazine
(TPTZ), ferrozine, 2,2'-azinobis(3-ethylbenzothiazoline-6-
sulfonic acid) (ABTS) were purchased from Fluka (UK).
HPLC grade ethanol was purchased from Rathburn Chemicals
Ltd. (Walkerburn, Peebleshire, Scotland). Spectrophotometric
measurements were made on UV-1700 PharmaSpec. UV-visible
spectrophotometer, Shimadzu, Japan equipped with tempe-
rature control device.All the solutions were made in triplicate
and experiments were performed three times. The results
obtained were averaged. Thermogravimetric analysis (TGA)
and differential scanning microscopy (DSC) analyses of all
derivatives were carried out from 15-450 ºC at a heating rate
of 20 ºC min-1 in nitrogen atmosphere using SDT Q-600. Dried
alumina pan was used as a reference material and alumina
sample holder (90 µL) was employed for taking curves.
N,N-Bis(2-hydroxyethyl)-4-methylbenzenesulfon-
amide (2a): A solution of tosyl chloride (7.56 g, 0.03 mmol)
in CH2Cl2 (20 mL) was added slowely to a stirred solution of
diethanolamine (5 g, 0.04 mmol) in triethylamine (12.1 g, 0.12
mmol) at room temperature. The reaction mixture was further
stirred at room temperature for 4 h.After completion of reaction,
water (15 mL) was added in reaction mixture and extracted
with CH2Cl2 (3 × 15 mL). Organic layers were combined, dried
over anhydrous magnesium sulphate and filtered. The filterate
was concentrated under vaccum which afforded the titled 2a
as white crystaline solid (90 %); m.p. 92-94 ºC; Rf, 0.13 (1:1;
n-hexane and ethyl acetate); λmax (neat, νmax, cm-1): 3523-3241
(O-H), 3030-2925 (C-H, ar. and aliph.), 1595 (C-C Ar.), 1162
(S=O), 1087 (C-O), 714 (ar. C-S); 1H NMR (500 MHz, CDCl3),
7.70 (2H, d, J = 8.2, Ar-H), 7.33 (2H, d , J = 8.2, Ar-H), 3.86
(4H, t, J = 4.8, CH2OH), 3.26 (4H, t, J = 4.8, CH2-N), 2.43
(3H, s, CH3-Ar); 13C NMR (500 MHz; CDCl3) 143.7 (C), 135.2
(C), 129.83 (CH), 127.2 (CH), 62.2 (CH2O), 52.94 (CH2),
52.86 (CH2), 21.48 (CH3).
1
0.16 (1:1; n-hexane and ethyl acetate); H NMR (500 MHz,
CDCl3) 7.08-7.36 (5H, m, ArH), 3.81 (4H, t, J = 4.5, CH2O),
3.58 (4H, t, J = 4.5, CH2N); 13C NMR (500 MHz; CDCl3)
155.0 (C), 150.9 (C), 129.3 (CH) 125.4 (CH), 121.0 (CH),
60.8 (CH2), 60.3 (CH2), 52.2 (CH2), 52.1 (CH2).
N,N-Bis(2-hydroxyethyl)acetamide (2d): Acetic anhy-
dride (1.06 g, 10.47 mmol) was added to a stirred solution of
diethanolamine (1.0 g, 9.52 mmol) in water (10 mL). The
reaction mixture was stirred at room temperature for 3 h. The
reaction mixture was extracted with ethyl acetate (3 × 30 mL).
The organic layers were combined, dried over anhydrous
magnesium sulphate and filtered. On evaporating solvent, 2d
was obtained as yellowish liquid (47 %); 1H NMR (500 MHz,
CDCl3); 4.23 (2H, t, J = 6.0, CH2-O), 4.21 (2H, t, J = 6.0,
CH2-O), 3.62 (2H, t, J = 2.0, CH2-N), 3.61 (2H, t, J = 4.5,
CH2-N), 2.15 (3H, s, CH3).
2,2'-(Tosylazanediyl)bis(ethane-2,1-diyl)bis(4-methyl-
benzenesulfonate) (3a): Sodium hydride (154 mg, 3.85 mmol)
was added to a stirred solution of N,N-bis(2-hydroxyethyl)-
4-methylbenzene sulfonamide (2a) and tosyl chloride (0.6 g ,
3.24 mmol, 2.11 equiv.) in anhydrous CH2Cl2 (10 mL). The
reaction mixture was stirred at room temperature for 3 h. Then
reaction mixture was quenched with water (15 mL) and
extracted with CH2Cl2 (3 × 15 mL). The organic layers were
combined, dried over anhydrous MgSO4 and concentrated
under vaccum, 3a was obtained as white solid (65 %); Rf 0.20
(7:3; n-hexane and ethyl acetate): m.p. 81-82 ºC; (neat, νmax
,
cm-1): 3030-2923 (C-H, ar. and aliph.), 1595 (C-C Ar.), 1361
(S-O), 1162 (S=O), 1095 (C-O), 720-815 (ar. C-S); 1H NMR
(500 MHz, CDCl3) 7.26-7.76 (12H, m, ArH), 4.11 (4H, t, J =
6.0, CH2-O),3.37 (4H, t, J = 6.0, CH2-N), 2.44 (9H, s, CH3-
Ar); 13C NMR (500 MHz; CDCl3) 144.9 (C), 144.8 (C), 143.8
(C), 135.0 (C), 132.1(CH), 132.1 (CH), 129.7 (CH), 129.6
(CH), 129.4 (CH), 127.6 (CH), 126.9 (CH), 65.9 (CH2), 65.8
(CH2), 48.1 (CH2), 48.1 (CH2), 21.3 (CH3), 21.2 (CH3), 21.1 (CH3).
2-(N-(2-Hydroxyethyl)-4-methylphenylsulfonamido)-
ethyl 2-nitrobenzenesulfonate (3b): N-(2-Hydroxyethyl)-N-
(hydroxymethyl)-4-methylbenzene sulphonamide (2a) (100 mg,
0.386 mmol) was dissolved into dichloromethane (4 mL), then
2,2,2-Trifluoro-N,N-bis(2-hydroxyethyl)acetamide
(2b): Trifluroacetic anhydride (4.39 g, 20.94 mmol) was added
drop wise to a stirred solution of diethanolamine (2 g, 19.04
mmol) in THF (10 mL). The reaction mixture was further
stirred at room temperature for 6 h. The solvent was evaporated

Vol. 25, No. 13 (2013)
Synthesis and Thermal Stabilities of Some New Diethanolamine Derivatives 7299
aquous solution of sodium hydroxide (8 mL, 10 M) and 2-
nitrobenzene sulfonylchloride (25 mg, 0.11mmol) were added
to the reaction mixture. Then reaction mixture was refluxed
for 12 h, cooled to room temperature, quenched with water
(10 mL) and extracted with dichloromethane (3 × 10 mL).
The combined organic layers were passed over the anhydrous
magnesium sulphate, filtered and concentrated in vacuum to
afford the 2-(N-(2-hydroxyethyl)-4-methylphenylsulfon-
amido) ethyl 2-nitrobenzene sulfonate as white solid (86.5 %),
was washed with n-hexane to remove the excess benzene
sulfonyl chloride; Rf 0.37 (1:1; n-hexane and ethyl acetate);
m.p. 91-93 ºC; (neat, νmax, cm-1): 2852-3400 (C-H, ar. and
aliph.), 1595.6 (C-C Ar.), 1365 (S-O), 1162 (S=O), 1087 (C-
O), 731-795 (ar. C-S); 1H NMR (500 MHz, CDCl3) 7.30-8.15
(8H, m, ArH), 4.40 (2H, t, J = 6.0, CH2-O), 3.74 (2H, t, J =
4.5, CH2-O), 3.5 (2H, t, J = 6.0, CH2-N), 2.98 (2H, t, J = 4.5,
CH2-N), 2.43 (3H, s, CH3); MS m/z (EI) 444; HRMS calcd.
(%) for C17H20N2O8S2 (M+) 444.0661, obs. 444.0556.
10 M) was added and refluxed for 5 h. Reaction mixture was
quenched with water (20 mL) and extracted with dichloro-
methane (3 × 20 mL). The combined organic layers were dried
over anhydrous magnesium sulphate, filtered and concentrated
in vacuum to afford 3e as white solid (53 %); Rf 0.20 (7:3;
n-hexane and ethyl acetate); m.p. 61-63 ºC; (neat, νmax, cm-1):
3428-2926 (C-H), 1770 (C=O), 1597 (C-C), 1353 (S-O), 1176
1
(S=O), 1094 (C-O), 723-814 (C-S); H NMR (500 MHz,
CDCl3), 7.31-7.76 (8H, m,ArH), 4.11 (4H, t, J = 5.5, CH2-O),
3.37 (4H, t, J = 5.5, CH2-N), 2.46 (3H, s, CH3), 2.43 (3H, s,
CH3); MS m/z (EI) 455; HRMS calcd. (%) for C20H25NO7S2
(M+) 455.1072, obs. 455.1061.
2,2,2-Trifluoro-N,N-bis(2-(trifluoromethoxy)ethyl)
acetamide (4b): 2,2,2-Trifluoro-N,N-bis(2-hydroxyethyl)
acetamide (2b) (0.50 g, 2.49 mmol) was added to a stirred
solution of trifluoroaccetic acid (1.44 mL, 0.01 mmol) in THF
(10 mL). The reaction mixture was stirred at room tempera-
ture for 6 h.After the completion of reaction solvent was evapo-
rated on rotary evaporator, quenched with water and extracted
with ethyl acetate (3 × 20 mL). The obtained organic layers
were combined obtained, dried over anhydrous magnesium
sulphate, concentrated in vacuum to get 2,2,2-trifluoro-N,N-
bis(2-(trifluoromethoxy)ethyl)acetamide (4b) as clear yellow-
ish liquid of fuming nature (90 %); Rf 0.58 (1:1; n-hexane and
2,2'-(Tosylazanediyl)bis(ethane-2,1-diyl) dibenzene-
sulfinate (3c): N-(2-Hydroxyethyl)-N-(hydroxymethyl)-4-
methylbenzene sulphonamide (2a) (200 mg, 0.77 mmol), was
dissolved in dichloromethane (5 mL). Then benzene sulphonyl
chloride (0.33 mL, 1.62 mmol) and aquous solution of sodium
hydroxide (4 mL, 10 M) was added and the reaction mixture
was refluxed for 7 h. Then reaction was quenched with water
(20 mL) and extracted with dichloromethane (3 × 20 mL).
The combined organic layeres were passed over anhydrous
magnesium sulphate, filtered and concentrated in vacuum to
afford 2,2'-(tosylazanediyl)bis(ethane-2,1-diyl) dibenzene
sulfinate (3c) as white solid (96 %); Rf 0.65 (1:1; n-hexane
and ethyl acetate); m.p. 107-108 ºC; (neat, νmax, cm-1): 3411-
2924 (C-H), 1596 (C-C ), 1358 (S-O), 1169 (S=O), 1095 (C-
O), 730-810 ( C-S); 1H NMR (500 MHz, CDCl3), 7.56-7.89
(12H, m, ArH), 4.14 (4H, t, J = 6.0, CH2-O), 3.38 (4H, t, J =
6, CH2-N), 2.43 (3H, s, CH3); MS m/z (EI) 539; HRMS calcd.
(%) for C23H25NO8S3 (M+) 539.0742, obs. 539.0734.
1
ethyl acetate); H NMR (500 MHz, CDCl3), 4.4 (4H, m 2 ×
CH2-O), 3.65 (2H, t, J = 5.5, CH2-N), 3.49 (2H, t, J = 5.5,
CH2-N); MS m/z (EI) 393; HRMS calcd. (%) for C10H8F9NO5
(M+) 393.0259, obs. 393.0247.
N,N-Bis(2-azidoethyl)-4-methylbenzenesulfonamide
(5a): 2,2'-(Tosylazanediyl)bis(ethane-2,1-diyl)bis(4-
methylbenzenesulfonate) (3a) (2.0 g, 0.17 mmol ) was dissol-
ved in DMF (5 mL). Then sodium azide (24.07 mg, 0.37 mmol)
was added in the soultion and reaction mixture was heated at
80 ºC for 2 h. After this reaction mixture was quenched with
water (15 mL) and extracted with ethyl acetate (3 × 15 mL).
The combined organic layers were dried over anhydrous
magnesium sulphate and concentrated under vaccum to afford
N,N-bis(2-azidoethyl)-4-methylbenzenesulfonamide (5a) as
white solid (82 %); Rf 0.52 (1:1; n-hexane and ethyl acetate);
m.p. 75-77 ºC; (neat, νmax, cm-1): 3395-2924 (C-H), 2121
2,2'-(2,2,2-Trifluoroacetylazanediyl)bis(ethane-2,1-
diyl) bis(4 methylbenzenesulfonate) (3d): Tosyl chloride (2.0
g, 10.9 mmol) was added slowly to a stirred solution of 2,2,2-
trifluoro-N,N-bis(2-hydroxyethyl)acetamide (2b) (1.0 g, 4.97
mmol) in CH2Cl2 (15 mL). Then aquous NaOH solution (10
mL, 10 M) was added and refluxed for 5 h. Reaction mixture
was quenched with water (25 mL) and extracted with
dichloromethane (3 × 20 mL). The organic layers were com-
bined, dried over anhydrous magnesium sulphate, filtered and
concentrated in vaccum to afford 3d as white solid (60 %); Rf
0.21 (7:3; n-hexane and ethyl acetate); m.p. 47-49 ºC; (neat,
νmax, cm-1): 2927-3400 (C-H.),1767 (C=O), 1598 (C-C), 1357
(S-O), 1167 (S=O), 1095 (C-O), 734-815 (C-S); 1H NMR (500
MHz, CDCl3) 7.30-7.77 (8H, m,ArH) 4.11 (4H, t, J = 6,CH2O),
3.37 (4H, t, J = 6, CH2-N), 2.46 (3H, s, CH3), 2.43 (3H, s,
CH3); MS m/z (EI) 509; HRMS calcd. (%) for C23H25NO8S3
(M+) 509.0790, obs. 539.0779.
1
(N≡N), 1593 (C-C), 1160 (S=O), 707-812 (C-S); H NMR
(500 MHz, CDCl3) 7.26-7.72 (4H, m, Ar-H), 3.5 (2H, t, J =
6.0, CH2-N), 3.30 (4H, t, J = 6.0, CH2-N), 2.44 (3H, s, CH3-
Ar); 13C NMR (500 MHz; CDCl3) 144 (C), 135.7 (C), 129.9
(CH), 127.2 (CH), 50.7 (CH2), 48.9 (CH2), 21.5(CH3), 21.4
(CH3).
2-(N-(2-Azidoethyl)acetamido)ethyl 4-methyl benzene
sulfonate (5e): 2,2'-(Acetylazanediyl)bis(ethane-2,1-diyl)bis-
(4-methylbenzene sulfonate) (3e) (200 mg, 0.43 mmol) was
dissolved in DMF (5 mL). Then sodium azide (62.45 mg, 0.96
mmol, 2.2 equiv.) was added to the solution and reaction
mixture was heated at 80 ºC for 2 h. After this reaction mixture
was quenched with water (15 mL) and extracted with ethyl
acetate (3 × 15 mL). The combined organic layers were dried
over anhydrous magnesium sulphate and concentrated under
vaccumto afford N,N-bis(2-azidoethyl)acetamide (5e) as white
solid (71 %); m.p. 117-120 ºC; (neat, νmax, cm-1): 3388-2915
(C-H), 2124 (N≡N), 1627 (C=O); 1H NMR (500 MHz, CDCl3)
2,2'-(Acetylazanediyl)bis(ethane-2,1-diyl)bis(4-
methylbenzene sulfonate) (3e): Tosyl chloride (3.23 g, 17
mmol) was added slowly to a stirred soultion of N,N-bis(2-
hydroxyethyl)acetamide (2d) (1.0 g , 6.8 mmol) in CH2Cl2
(10 mL). Then aquous solution of sodium hydroxide (10 mL,

7300 Yar et al.
Asian J. Chem.
7.64-7.39 (4H, m, ArH), 3.73(2H, t, J = 5.0, CH2-O), 2.99
(2H, t, J = 5.0, CH2-N), 2.44 (3H, s, CH3), 1.256 (2H, t, J =
5.0, CH2-N), 0.92 (2H, t, J = 5.0, CH2-N=N); MS m/z (EI)
438; HRMS calcd. (%) for C18H22N4O5S2 (M+) 438.1032, obs.
438.1025.
Pseudomonas aeruginosa, Bacillus subtilis, Pasteurrella
mutocida Rhizopus oryzae and Salmonella typhi were used
for in vitro antibacterial activity. These bacterial strains were
obtained from Pakistan Council of Scientific and Industrial
Research (PCSIR) Lahore.
Antibacterial assay: Agar well diffusion method was
used to determine the antimicrobial activity22. The plates were
autoclaved for 5 h. We used nutrient agar 28 g/L of distilled
water. The media was poured in the petri dishes and allowed
to solidify. The well was dug in the media using a sterile borer.
The surface of the nutrient agar was inoculated by microbes
using a sterile coton swab. The samples were introduced into
respective wells. For each treatment, three replicates were
maintained. Dichloromethane and the reference antibacterial
and antifungal drug served as negative and positive controls,
respectively. The plates were incubated immediately at 37 ºC
for 24 h. The activity was determined by measuring the dia-
meter of the inhibition zone in millimeter. Growth inhibition
was calculated with reference to the positive control. Standard
deviation was also calculated.
Antioxidant activity
ABTS assay: ABTS radical cation was produced by a
reaction betweenABTS and potassium persulphate (7 and 2.45
mM final concentrations, respectively) and before its use the
mixture was allowed to stand in the dark at room temperature
for 12-16 h. To study the antioxidant activity of samples, the
ABTS stock solution was diluted with PBS buffer (pH 7.4) to
an absorbance of 0.70 0.02 at 734 nm and equilibrated at 30
ºC. After addition of 10 µL of sample to 2.99 mL of diluted
ABTS•+ solution (A = 0.700 0.020), the absorbance was
measured at 30 ºC with exactly 1 min intervals for 6 min.
Appropriate solvent blanks were run in each assay for accurate
readings. The percentage inhibition of absorbance was calcu-
lated by the following formula.
The percentage inhibition was calculated as follows;








1-A
Ao
Inhibition (%) =
×100
(1)








A
Inhibition (%) =
×100
(4)
A0
where, Ao is the absorbance at 734 nm of the negative control
andA is the absorbance at 734 nm of the mixture with sample.
Ferric reducing power (FRAP) assay: The reducing
capacity of derivatives was measured according to the reported
method20. Fresh FRAP solution was prepared by mixing 25
mL of 300 mM acetate buffer (pH 3.6), 2.5 mL of 10 mM
tripyridyl triazine (TPTZ) solution in 40 mM HCl solution
and 2.5 mL of 20 mM ferric chloride solution. The mixture
was incubated at 37 ºC throughout the monitoring period. 3000
µL of FRAP reagent was mixed with 100 µL of sample and
300 µL of distilled water. Absorbance was measured at 593
nm after 6 min.
A = Area of inhibition of sample compound, A0 = Area of
inhibition of standard drug (positive control) × 100.
RESULTS AND DISCUSSION
Diethanolamine was used as a precursor which contains
two hydroxyl groups and an amine group. All these groups
are susceptible to acylation, alkylation and sulfonamide
formation. Under mild reaction conditions in first step we were
able to selectively attach only one acyl or sulfonyl group to
nitrogen to synthesize 2a-2d, following acylation on two
hydroxyl groups of compound 2b gave 4b. Derivatives 3a-3e
were prepared from 2a-2d by reacting with different sulfonyl
chlorides in the presence of excess NaOH and 1:1 mixture of
dichloromethane and water. Compounds 3a and 3e yielded
azides 5a and 5e by reacting with sodium azide in the presence
of DMF. The reactions with azides were clean and completed
in 2 h (Scheme-I). Derivatives 2b-2d and 4b were isolated as
free flowing oils. We were able to easily synthesize 6 new
comounds (3b-3e, 4b and 5e).
Ao
Inhibition =
(2)
0.025
where, Ao is the absorbance taken at 593 nm.
Metal chelating assay: For metal chelating activity we
followed the method of Denis et al.21. Sample solution (10
mg/mL) was prepared. Then 100 µL of sample solution was
added to a solution of 50 µL FeSO4. The reaction was initiated
by the addition of ferrozine (200 µL). The total volume of
mixture was adjusted to 3650 µL with ethanol. Then, the
mixture was shaken vigorously and left at room temperature
for 10 min. Absorbance of the solution was then measured
spectrophotometrically at 562 nm. The percentage inhibition
of absorbance was calculated by the following formula.
Thermogravimetric analysis (TGA): One of the aim of
this study was to synthesize new potential lubricants from
diethanolamine. We were succesfull to prepare four free
flowing oils (2b-2d, 4b) which could be used as lubricants.
Thermal stabilities of compounds 2a-2d and 4b were studied
by TGA at heating rate of 20 ºC min-1 under nitrogen atmos-
phere. For illustration, TGA curves of 2a-2d and 4b at heating
rate of 20 ºC min-1 are shown in Fig. 1.






(A0 − A1)
Inhibition (%) =
×100
(3)
A0
It was observed that different N-substituents of diethanol-
amine has great influence on the thermal stabilities of products.
Compound 2a showed better thermal stability as compared to
other samples there was almost no weight loss until 200 ºC.
This is persumably due to the greater stability of tosyl group.
It is expected that tosyl group cleaves from nitrogen at 200 ºC
and then gradual thermal decomposition started as shown in
Fig. 1.


where, A0 is the absorbance of the solution without sample at
562 nm andA1 is the absorbance in the presence of the sample.
EDTA was used as a reference compound.
Antimicrobial activity
Test-microorganisms: Pathogenic microorganisms
Escherichia coli, Staphylococcus aureus, Micrococcus luteus,

Vol. 25, No. 13 (2013)
Synthesis and Thermal Stabilities of Some New Diethanolamine Derivatives 7301
OH
OH
OH
O
O
R3
diethanolamine derivatives 2a-2d and 4b to observe the effect
of temperature. It was observed by ANOVA results that
Excess NaOH
H
N
R1
N
R1
N
53-93 %
DCM: H2O
4 - 6 hours
OH
R2
except 4b and 2a there is insignificant difference among these
derivatives. Compound 2a showed comparitivly greater stability
among these derivatives. However in case of derivative 4b,
decomposition became significant in temperature range 15-
200 ºC.
2
3
1
2a (R1= Ts)
2b
2c (R1= PhOCO)
2d (R1= CH3CO)
(R1= CF3CO)
3a
(R1 = Ts ,R2, R3 = Ts)
3b (R1 = Ts , R2 = H ,R3 = NO2PhSO2)
3c (R1 = Ts ,R2=R3 = PhSO2)
3d
(R1 = CF3CO ,R2 = R3 = Ts)
3e (R1 = CH3CO ,R2 = R3 = Ts)
O
O
THF,
4 hr, r.t
F3
C
O
CF3
O
R4
Differential scanning calorimetry (DSC):The DSC thermo-
grams of 2a-2d and 4b are compared in Fig. 2. All derivatives
show first broad endothermic peak in their thermograms at
50-100 ºC which could be due to their phase change.
R1
N
4
O
R4
4b
(R1= CF3CO , R4 = CF3CO )
90 %
R5
3b, 3c, 3d, 3e, 4b and 5e are new compounds
2b
2d
2a
2c
4b
NaN3
3a,3e
R1
N
71-82 %
20
10
DMF, 80 °C, 2h
R6
5a (R5 = R6 = N3)
5e (R5 = N3,R6 = OTs)
0
Scheme-I: Synthetic pathway for diethanolamine derivatives
-10
-20
-30
-40
-50
-60
2a
2c
4b
2b
2d
120
100
80
60
40
20
0
00.
50
100
150
200 250
Temperature (ºC)
300
350
400
450
Fig. 2. DSC thermograms as heat flow (mW) versus temprature (ºC)
The compound 2a showed a glass transition at temperature
range Tg (20-60 ºC) and characteristic endothermic peak of
melting at Tm (95 ºC). There was no endothermic or exothermic
transition in temperature range of 115-250 ºC. This might be
due to the heat absorbed by 2a to increase its internal energy
that leads to an endothermic peak of boiling at 270 ºC followed
by final glass transition of decomposition at 325 ºC. The
compunds 2b, 2d and 4b showed their endothermic peak of
boiling at 200, 175 and 70 ºC respectively. The distinguished
endothermic peak at 185 ºC for compound 2c could be due to
the intermolecular cyclization and subsequent removal of
phenoxy group as shown in Fig. 3. It is important to note there
is no such intramolecular cyclization possiblity present in other
studied compounds.
00.
50
100
150
200 250
Temperature (ºC)
300
350
400
450
Fig. 1. Thermal decomposition as weight per cent loss (W %) and heat
flow (mW) versus temperature (T/ºC)
Thermal stability of 2b-2d was almost similar in which
initially presumably N substituent detaches, followed by the
decomposition of diethanolamine as shown in Fig. 1. Final
decomposition temperatures (225-300 ºC) were high that could
be due to loss of hydrogen bonding among hydroxyl groups
of diethanolamine23. The compound 4b have no hydroxyl
groups, therefore it was comparatively less stable among the
derivatives studied. In case of 4b significant thermal decom-
position occured at 40 ºC and completed almost at 225 ºC. For
comparative studies, activation energies, enthalpies and
entropies of derivatives 2a-2d and 4b were calculated (Table-
1) using graphical data obtained from thermogravimetric
analysis incorporated with curve-fitting software- the Battery
program24.
OH
O
O
OH
O
N
N
(5)
O
OH
Ph
Fig. 3. Intermolecular cyclization of derivative 2c
TABLE-1
ACTIVATION ENERGY, ENTHALPY, ENTROPY
AND ORDER OF REACTION OF 2a-2d AND 4b
Heat capacity Cp of 2a-2d and 4b was calculated by
following formula.
Activation
energy (J/mol)
Enthalpy
(J/mol)
Entropy
(J/mol.K)
Samples
{E×H×60}
Cp =
(6)
258727.88
9238.56
257065.08
7575.76
2691.64
-193.25
-145.07
686.86
2a
2b
2c
2d
4b
{M×Hr}
where Cp is heat capacity, E is cell calibration constant
(dimensionless) at a temperature of interest, H is heat flow
(mW), 60 is conversion constant for minute to seconds, M is
mass of sample and Hr is heating rate (ºC/min). The values of
Cp of 2a-2d and 4b have been measured for temperatures from
50-298 ºC (Fig. 4).
12898.57
82219.33
4040.54
11235.77
80556.53
2377.74
-268.69
Statistical analysis: Using one wayANOVA system, the
analysis of variance for thermal analysis was performed for

7302 Yar et al.
Asian J. Chem.
35
30
25
20
15
10
5
4b and 5e showed comparitively higher FRAP values than
other derivatives, may be due to the presnece of high electron
density as delocalisation in substituents of the derivatives.
While 2b, 2d and 3f exibited comparitively lower FRAP
values that can be attributed to the low electron density or
absence of aromaticity (Fig. 6).
2a
2b
2c
2d
4b
0
00.
50
100
150
200
250
300
Temperature (ºC)
Fig. 4. Heat capictiy of samples
Antioxidant activity
ABTS•+ radical cation decolurization assay: Antioxi-
dant ability of synthesized compounds was studied in com-
parison with reference compound, Trolox25.
Fig. 6. FRAP result
Diethanolamine derivatives (2a-5e) showed better ABTS
radical scanvanging than reactant diethanolamine as shown in
Fig. 5. These derivatives have TEAC value between 2.5-16
while precursor diethanolamine exibited 2.3 TEAC value. By
definition, Trolox has a TEAC of 1. As the TEAC of 2c is 16,
this shows that one molecule of 2c scavenges on average 16
times as much ABTS as Trolox. Among all derivatives 2c
showed excellent antioxidant activity that may be due to
phenolic moiety. Derivatives other than 2a and 3b showed
average scanvanging of ABTS radical cations while 2a and
3b showed comparitivly poor scanvanging.
Metal chelating activity: An important advantage of
antioxidants is their ability to chelate/deactivate transition
metals26, which possess the ability to catalyze hydroperoxide
decomposition and Fenton-type reactions. Chelating agents
may also serve as secondary antioxidants since they reduce
redox potential, thereby stabilizes the oxidized forms of metal
species. Therefore, the ion(II) chelating capacities of the
samples were screened (Fig. 7).
Metal chelating activity
120
100
80
60
40
20
0
Samples
Fig. 7. Metal chelating ativity
Ferrozine forms complexes with Fe2+. In the presence of
chelating agents, complex formation between ferrozine and
Fe2+ is disrupted, as a result red colour of the complex is
reduced which allows estimation of the chelating activity of
the co-existing chelator. Interestingly, all derivatives were
found to have metal chelating activity.
Fig. 5. ABTS radical scanvanging
FRAPAssay:The FRAP assay was carried out following
method developed by Benzie and Strain20. Any antioxidant
species with lower reduction potential than that of Fe(III) TPTZ
salt (0.7V) can reduce Fe3+-TPTZ to Fe2+ TPTZ. This reduction
is monitored spectrophotometrically at 593 nm. If a sample
contains reducing components intense blue colour is appeared.
The original method of Benzie and Strain uses a 4 min interval
but we noted that the reaction/colour change is in progress
even after 4 min interval. Therefore absorbance was measured
at a 6 min interval after addition of sample to TPTZ reagent
allowing the reaction to reach a steady state. The FRAP values
of the samples were measured in comparison with a calibra-
tion curve obtained using iron(II) sulphate as the standard
reductant.
As the reactive oxygen species (ROS) generation is asso-
ciated with redox active metal catalysis which involves chelating
of metal ion. Diethanolamine derivatives showed good result
in metal chelating activity as compared to ABTS assay and
FRAP assay. Diethanolamine derivatives considerably inter-
fered the formation of ferozine complex by capturing ferrous
ions.All derivatives except 2a, scanvenged ferrous ions before
its formation to ferrozine complex which may be due to the
presence of OH, protected alcohols and protected amine groups.
Comparitivly poor metal chelating activity of 2a may be
due to bulky group (mention group here in bracket) attached
with nitrogen which hindered chelate formation with ferrous
ions.
Diethanolamine and its derivatives showed FRAP values
in the range of 4-6. As graphical data showed that 2a, 2c, 3c,

Vol. 25, No. 13 (2013)
Synthesis and Thermal Stabilities of Some New Diethanolamine Derivatives 7303
Antimicrobial activity: All the compounds except 3d,
possessed antimicrobial activity against Escherichia coli,
Staphylococcus aureus, Micrococcus luteus, Bacillus subtilis,
Pasteurrella mutocida, Rhizopus oryzae, Salmonella typhi.
None of the compounds was active against Pseudomonas
aeruginosa (Table-2).
as well as on both oxygen imparted an astonishing strength to
the parent molecule. It not only strengthened antimicrobial
character of diethanolamine but also the mechanical behaviour
of the parent compound. The compound 2c performed an
average character. It added inhibition of some new organism
to the diethanolamine's antimicrobial spectra that were not
inhibited by diethanolamine before. This is attributed to
phenoxy addition to nitrogen. Benzene sulphonyl group at both
oxygen in 3c diminished the antimicrobial character of 2a,
this might be an inverse relationship of tosyl and benzene
sulfonyl group, this must be related to structure activity
relationship of the both groups.
The solvent dichloromethane (S1) is used as negative
control, in order to check the role of the solvent in inhibition.
The samples were dissolved in dichloromethane. Ciprofloxacin
(S2) was used as the standard antibacterial drug ketoconazole
(S3) was used as the standard antifungal drug. Diethanolamine
itself is a good antimicrobial agent and we expected synthesized
diethanolamine derivatives may be more potent.
The compound 3d showed no activity, it seems triflouro
group has played an antagonistic role in tosyl activity, although
independently 2b behaved an excellent microbial inhibitor.
Similarly in 3e, the acetyl group acted as an inhibitor for tosyl
attached at both oxygens. In 5a, the azide group was silent.
Overall synthesized derivatives showed satisfactory
results not only for gram positive, gram negative bacteria, but
also for the fungus Rhizopus oryzae used in the assay.
The compounds 2a, 2b, 2c, 3a and 4b inhibited most of
the pathogens used in the assay (Table-3). The broad antimi-
crobial activity of 2a and 3a might be related to the belonging
of compounds to sulfonamide class of antimicrobials, as tosyl
group has boosted the activity of diethanolamine. It is obvious
from results that trifluoro group improved the antimicrobial
strength of diethanolamine. Similary trifluoro group at nitrogen
TABLE-2
MEAN ZONE OF INHIBITION BY MICROORGANISMS
Mean zone of inhibition of microorganisms
Code
Escherichia
coli
Staphylococcus Micrococcus Pseudomonas
aureus
Bacillus
subtilis
Pasteurrella
mutocida
Rhizopus
oryzae
Salmonella
typhi
luteus
aeruginosa
11.5 0.707
10 1.414
10.5 0.707
–
–
–
–
10.5 0.707
15 1.414
19 1.414
2a
2b
2c
2d
3a
3b
3c
3d
3e
4b
5a
1
–
15 1.414
17.5 0.707
14 1.414
19 1.414
14 1.414
17 1.414
10 1.414
14.5 0.707
–
–
–
10.5 0.707
10.5 1.414
13 1.414
–
–
–
10.5 0.707
–
–
13 1.414
13.5 2.12
–
16 1.414
16 1.414
–
13 1.414
10.5 0.707
14 1.414
21 1.414
15 1.414
–
–
–
–
10.5 0.707
–
–
–
–
–
–
–
9
1.414
–
–
–
–
–
–
–
–
–
–
–
19 1.414
10.5 0.707
13 1.414
–
–
10.5 0.707
–
–
17 1.414
–
–
14 1.414
–
–
11.5 0.707
15.5 0.707
–
14 1.414
17 1.414
–
–
–
–
14.4 2.121
–
20 1.414
–
10.5 0.707 15.5 0.707
11 1.414
15
–
S1
S2
S3
–
–
–
–
–
–
30
30
22
30
22
30
22
30
22
30
22
30
22
30
22
22
TABLE-3
PERCENTAGE INHIBTION BY PATHOGENIC MICROBES
Inhibition by pathogenic microorganisms (%)
Code
Escherichia
coli
Staphylococcus Micrococcus Pseudomonas
Bacillus
subtilis
Pasteurrella
mutocida
Rhizopus
oryzae
Salmonella
typhi
aureus
33.33
50
luteus
aeruginosa
38.33
–
35
–
–
–
46.7
–
–
63.33
–
47
68
47
47
59
47
40
–
63.3
46.7
–
2a
2b
2c
2d
3a
3b
3c
3d
3e
4b
5a
1
58.33
48.33
35
56.66
–
33.33
–
–
–
–
43.33
35
0.45
46.7
–
–
53.33
50
53.33
–
–
43.3
–
70
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
35
–
–
–
–
–
63.33
35
38.33
–
51.7
–
–
56.7
–
46.7
–
63.6
65.4
50
–
56.7
–
–
43.3
–
–
66.7
–
–
35
–
51.7
–
51.7
–
S1
S2
S3
–
–
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100

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Asian J. Chem.
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thermal stabilities of free flowing oils 2b-2d and solid derivative
2a was 2a > 2c > 2d > 2b > 4b. Compounds 2a and 4b had
significant difference in thermal decompositional behaviour
while 2b-2d exhibited insignificant difference. The activation
energies of oils 2b-2d increased as function of thermal stability
of N-substitution at diethanolamine. All the compounds were
tested for their in vitro antimicrobial and antioxidant activities.
Regarding antioxidant activity all derivatives showed moderate-
to-good FRAP and ABTS result and considerably excellent
metal chelating activity and derivative 2c having phenoxyl
group exhibited excellent ABTS radical scavenging among
all derivatives. Studies showed that compounds 2a, 2b, 3a and
4b, having tosyl and triflouro group as a substituent were found
to be the most potent member against used microorganisms
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