CHAPTER-3 CHARACTERIZATION OF 3-[(8-HYDROXY QUINOLIN-5-

YL) AMINO METHYL]-5-ARYLOXY ACETYL-1,3,4-OXADIAZOLE-2(3H)-THIONE [RCC-1 TO RCC-6].

Chapter-3

49

Chapter-3

Characterization of 3-[(8-hydroxy quinolin-5-yl)

amino methyl]-5-aryloxy acetyl-1,3,4-oxadiazole-

2(3H)-thione [RCC-1 to RCC-6].

The present chapter deals with the characterization of 3-[(8-hydroxy quinolin-

5-yl) amino methyl]-5-aryloxy acetyl-1,3,4-oxadiazole-2(3H)-thione (i.e.RCC-1 to

RCC-6) derivatives described in Chapter 2 by,

(I) Elemental analysis

(II) IR, NMR and Mass spectral studies

(III) Hydroxyl group determination and

(IV) Oxidation

3.1 ELEMENTAL ANALYSIS.

The general properties of ligands RCC-1 to RCC-6 are:

Melting points (oC) of all the compounds were measured by capillary method.

All the mp’s are uncorrected.

The yields of all compounds reported are of crystallized. All solvents used

were distilled and dried. The purity of the compounds was checked by TLC.

Column chromatography was performed on silica gel (60-120 mesh).

All the ligands synthesized and described in an earlier chapter were analyzed

by their elemental contents. The C, H and N elements of all the samples were

measured by Elemental analyzer Thermofinigan flash1101 EA (Italy). The halogen

and sulfur contents as case may be determined by Carius method [1]. The method

was adopted as follow:

Chapter-3

50

100 mg of the sample was placed in a dried Carius tube (80 cm long, 1 cm

diameter). Then about 25 mg of silver nitrate (for halogen) or Barium Chloride (for

sulfur) was added. Finally 5 to 7 drops of fuming nitric acid were added and sealed

the tube and placed in a furnace for 6 hrs with maintaining the temperature 300 0C.

After cooling the tube was opened and the obtained precipitates of silver halide or

barium sulfur transferred into pre-weighted G-4 funnel and the precipitates weighed.

Finally the halogen or sulfur percentages were calculated. The C, H, and N

contents of all RCC-1 to RCC-6 derivatives are shown in Table 3.1. The data are

consistent with the predicted structures of ligands.

Chapter-3

51

Table 3.1 Characterization of Ligands RCC-1 to RCC-6.

Ligand No. Molecular

formula

Mol. Wt.

Gm/Mole

% Yield

RCC-1 C19H16N4O3S 380 70

RCC-2 C19H15N4O3SCl 414.5 78

RCC-3 C19H15N4O3SBr 459 70

RCC-4 C19H15N5O5S 425 74

RCC-5 C19H14N4O3SCl2 449 73

RCC-6 C23H18N4O3S 430 75

For, RCC-2 = %Cl = 8.56 (Cal.), 8.50 (Found)

RCC-3 = %Br = 17.42 (Cal.), 17.50 (Found)

RCC-5 = %Cl = 15.81 (Cal.), 15.80 (Found)

Ligand

No.

%C %H %N %S

Cal. Found Cal. Found Cal. Found Cal. Found

RCC-1 60.00 60.00 4.21 4.20 14.73 14.70 8.42 8.50

RCC-2 55.00 55.00 3.61 3.60 13.51 13.50 7.72 7.70

RCC-3 49.67 50.00 3.26 3.20 12.20 12.20 6.97 7.00

RCC-4 53.64 54.00 3.52 3.50 16.47 16.50 7.52 7.50

RCC-5 50.77 50.50 3.11 3.10 12.47 12.50 7.12 7.10

RCC-6 64.18 64.10 4.18 4.20 13.02 13.00 7.44 7.40

Chapter-3

52

3.2 INFRARED SPECTROSCOPY.

The atoms of a molecular behave as if they were connected by flexible

spizing, rather than by rigid bound resembling the connectors of a ball and stick

model. Their component parts can oscillate in different vibrational modes, designed

by such terms as rocking, scissoring, twisting, wagging and symmetrical and

asymmetrical stretching. When infra red radiation is passed through a sample of a

given compound, its molecules can absorb radiation of the energy (and frequency)

needed to bring about transitions between vibration of ground states and vibration of

excited states.

For example, a C-H bond, that vibrates 90 trillion times a second, must absorb

infrared radiation of just that frequency to jump to its first vibration excited state.

This absorption of energy at various frequencies can be detected by an infrared

spectrometer, which plots and amount of infrared radiation transmitted through the

sample as a function of the frequency (or wavelength) of the radiation. An infrared

spectrum consists of comparatively broad absorption bands rather than sharp peaks

such as those seen in NMR spectra. The bands are also usually “Inverted”-a deep

valley rather than a peak represents strong absorption.

Infrared spectroscopy is extremely useful [2-6] in qualitative analysis. It can

be used both to detect the presence of specific functional groups and other structural

features from band positions and intensities and to establish the identity of an

unknown compound with a known standard. The fingerprint region of the infrared

spectrum, (1250-670 cm-1, 8-15 lym) is best for showing that two substance are

identical, since the distinctive patterns found in this region are usually characterizes of

the whole molecule and not of isolated groups. Infrared spectra can also be used in

establishing the purity of compounds, monitoring reaction rates, measuring the

constructions of solubility, determining the structures of Chelate molecules, and

carrying out theoretical studies of hydrogen bonding in other phenomena.

Chapter-3

53

3.2.1 Experimental

Infrared scanning for the produced ligands was made in the range 4000-

600cm-1 in KBr. AR grade KBr was used for this purpose. It was first fused,

powdered and dried in vacuum. The absence of moisture in this dried KBr pellet was

checked by scanning and IR spectra of purified KBr. Then the pellet of KBr with

polymer was prepared as under.

A mixture of 4mg of pure dried sample and 1gm KBr powder was ground in a

mini ball mill for about 10 minutes. The resulting mixture was placed on the disc and

compressed at high pressure about 20,000 psi giving the transparent pellet. The IR

spectrum of this transparent pellet was scanned on Nicollet FTIR 760

spectrophotometer.

3.2.2 Results and discussion

The anticipated IR spectral frequencies of all the 3-[(8-hydroxy quinolin-5-yl)

amino methyl]-5-aryloxy acetyl-1,3,4-oxadiazole-2(3H)-thione ligands are given in

Table 3.2. The infrared spectra of selected ligands are shown in Figures 3.1 to 3.4.

The inspection of the infrared spectra of all the ligands reveals following.

Chapter-3

54

Table – 3.2 Anticipated IR spectral features for Ligands RCC-1 to RCC-6.

Sr.

No. Group IR frequencies (Cm-1)

1. -CH2- 2920, 2850, 1450

2. -NH- 3400

3. -OH of 8-hydroxy quinoline 3800-2700 broad

4. Aromatic 1600, 1500, 3030

5. 8-Hydroxy quinoline moiety 1575, 1560, 1470

6. C=S of Oxadiazole 1630

Chapter-3

55

Figure: 3.1 IR Spectrum of Ligand RCC-1

Chapter-3

56

Figure: 3.2 IR Spectrum of Ligand RCC-2

Chapter-3

57

Figure: 3.3 IR Spectrum of Ligand RCC-3

Chapter-3

58

Figure: 3.4 IR Spectrum of Ligand RCC-4

Chapter-3

59

(a) All the IR spectra comprise the broad band from 3800 to 2700 cm-1

with the inflections. The broad band is appeared due to phenolic

OH group of 8-hydroxy quinoline moiety.

(b) The inflections around 2920 cm-1 and 2850 cm-1 are attributed to

asymmetric and symmetric stretching vibration of -CH2 of

The supporting band at 1450 cm-1 is also appeared due to CH2 bending

vibrations.

(c) The bands around 1500 and 1600 cm-1 in the region of double bond are

appeared. Then might be raised from aromatic segment of 8-hydroxy

quinoline.

(d) The weak band around 3030 cm-1 might be due to aromatic C-H stretching

vibrations.

(e) The strong band around 3400 cm attributed to –NH- stretching vibrations.

(f) The other bands in the fingerprint region are appeared at their respective

position. The bands around 1220 and 1020 cm-1 are mainly due to C-N

bending vibrations while the C=N stretching vibration features is appeared

around 1690 and 1660 cm-1. The weak bands due to out of plane deformation

of 1, 2, 3 or 1,3 or 1,4-disubstituted benzene ring systems are appeared at 760,

860 and 810 cm-1 respectively.

Chapter-3

60

Table 3.3 IR Spectrum data of Ligands RCC-1 to RCC-6

Ligands Frequencies cm-1

-OH Aromatic 8-HQ Moiety -NH- -CH2-

RCC-1 2700-3800

1500

1600

3033

1470

1578

1630

3400

1448

2850

2920

RCC-2 2700-3800

1500

1600

3033

1470

1578

1630

3400

1448

2850

2920

RCC-3 2700-3800

1500

1600

3033

1470

1578

1630

3400

1448

2850

2920

RCC-4 2700-3800

1500

1600

3033

1470

1578

1630

3400

1448

2850

2920

RCC-5 2700-3800

1500

1600

3033

1470

1578

1630

3400

1448

2850

2920

RCC-6 2700-3800

1500

1600

3033

1470

1578

1630

3400

1448

2850

2920

Chapter-3

61

3.3 PROTON NUCLEAR MAGNETIC RESONANCE

SPECTROSCOPY:

Nuclear magnetic resonance (NMR) spectroscopy is supplementary technique

to IR spectroscopy to get details information about structure of organic compounds.

Most widely studied nucleus is proton and then the technique is called NMR

spectroscopy.

IR spectra give information about the functional group while NMR spectra

provide information about the exact nature of proton and its environment [7-9]. Thus

this technique is more useful in the elucidation of an organic compound. IR spectra of

isomers may appear same but their NMR spectra will markedly differ.

The phenomenon of nuclear magnetic resonance was first reported

independently in 1946 by two groups of physicists: Block, Hansen and Packard at

Stanford University detected a signal from the protons of water, and Purcell, Torrey

and Pound at Harvard University observed a signal from the protons in paraffin wax.

Block and Purcell were jointly awarded the Nobel Prize for physics in 1952 for this

discovery. Since that time, the advances in NMR techniques leading to wide spread

applications in various branches of science resulted in the Nobel Prize in chemistry in

1991. The applications of NMR in clinical, solid state and biophysical sciences are

really marvelous.

The proton magnetic resonance (NMR) spectroscopy is the most important

technique used for the characterization of organic compounds. It gives information

about the different kinds of protons in the molecule. In other words it tells one about

different kinds of environments of the hydrogen atoms in the molecule. PMR also

gives information about the number of protons of each type and the ratio of different

types of protons in the molecule.

It is well known that all nuclei carry a positive charge. In some nuclei this

charge ‘spins’ on the nuclear axis, and this circulation of nuclear charge generates a

Chapter-3

62

magnetic dipole along the axis. Thus, the nucleus behaves like a tiny bar magnet. The

angular momentum of the spinning charge is described in terms of spin number (I).

The magnitude of generated dipole is expressed in terms of nuclear magnetic moment

().

The spinning nucleus of a hydrogen atom (1H or proton) is the simplest and is

commonly encountered in organic compounds. The hydrogen nucleus has a magnetic

moment, = 2.79268 and its spin number (I) is + ½. Hence, in an applied external

magnetic field, its magnetic moment may have two possible orientations.

The orientations in which the magnetic moment is aligned with the applied

magnetic field is more stable (lower energy) than in which the magnetic moment is

aligned against the field (high energy). The energy required for flipping the proton

from its lower energy alignment to the higher energy alignment depends upon the

difference in energy (∆E) between the two states and is equal to h(∆E = h

In principle, the substance could be placed in a magnetic field of constant

strength, and then the spectrum can be obtained in the same way as an infrared or an

ultraviolet spectrum by passing radiation of steadily changing frequency through the

substance and observing the frequency at which radiations is absorbed. In practice,

however, it has been found to be more convenient to keep the radiation frequency

constant and vary the strength of the magnetic field. At some value of the field

strength the energy required to flip the proton matches the energy of the radiation,

absorption occurs and a signal is obtained. Such a spectrum is called a nuclear

magnetic resonance (NMR) spectrum.

Two types of NMR spectrometers are commonly encountered. They are:

a) Continuous wave (CW) NMR spectrometer

b) Fourier transform (FT) NMR spectrometer.

The CW-NMR spectrometer detects the resonance frequencies of nuclei in a

sample placed in a magnetic field by sweeping the frequency of RF radiation through

Chapter-3

63

a given range and directly recording the intensity of absorption as a function of

frequency. The spectrum is usually recorded and plotted simultaneously with a

recorder synchronized to the frequency of the RF source.

In FT-NMR spectroscopy, the sample is subjected to a high power short

duration pulse of RF radiation. This pulse of radiation contains a broad band of

frequencies and causes all the spin-active nuclei to resonate all at once at their Larmor

frequencies. Immediately following the pulse, the sample radiates a signal called free

induction decay (FID), which is modulated by all the frequencies of the nuclei excited

by the pulse. The signal detected as the nuclei return to equilibrium (intensity as a

function of time) is recorded, digitized and stored as an array of numbers in a

computer. Fourier transformation of the data affords a conventional (intensity as a

function of frequency) representation of the spectrum.

The first step in running NMR spectrum is the complete dissociation of a

requisite amount of the sample in the appropriate volume of a suitable NMR solvent.

Commonly used solvents are: CCl4, deuteron chloroform, deuteron DMSO, deuteron

methanol, deuteron water, deuteron benzene, trifluroacetic acid.

TMS is generally employed as internal standard for measuring the position of 1H, 13C, and 29Si in the NMR spectrum because it gives a single sharp peak, is

chemically inert and miscible with a large range of solvents, being a highly volatile,

can easily be removed if the sample has to be recovered, does not involve in

intramolecular association with the sample.

3.3.1 INTERPRETATION OF THE NMR SPECTRA:

It is not possible to prescribe a set of rules which is applicable on all

occasions. The amount of additional information available will most probably

determine the amount of information it is necessary to obtain from the NMR

spectrum. However, the following general procedure will form a useful initial

approach to the interpretation of most spectra.

Chapter-3

64

By making table of the chemical shifts of all the groups of absorptions in the

spectrum. In some cases it will not be possible to decide whether a particular group of

absorptions arises from separate sets of nuclei, or from a part of one complex

multiplet. In such cases it is probably best initially to include them under one group

and to note the spread of chemical shift values.

By measuring and recording the heights of the integration steps corresponding

to each group of absorptions. With overlapping groups of protons it may not be

possible to measure these exactly, in which case a range should be noted. Work out

possible proton ratios for the range of heights measured, by dividing by the lowest

height and multiplying as appropriate to give integral values.

By noting any obvious splitting of the absorptions in the table (e.g., doublet,

triplet, etc.). For spectra which appear to show first-order splitting, the coupling

constants of each multiplet should be determined by measuring the separation

between adjacent peaks in the multiplet. Any other recognizable patterns which are

not first order should be noted.

By noting any additional information such as the effect of shaking with D2O,

use of shift reagent, etc.

By considering both the relative intensities and the multiplicities of the

absorptions attempt to determine which groups of protons are coupled together. The

magnitude of the coupling constant may give indication of the nature of the proton

involved.

By relating the information to obtain other information available on the

compound under considerations.

Chapter-3

65

3.3.2 EXPERIMENTAL:

NMR spectra were recorded on Bruker NMR spectro-photometer. NMR

chemical shifts are recorded in value using TMS as an internal standard in

CDCl3/D6-DMSO. Typical NMR spectra are shown in figures 3.5 to 3.7. The NMR

data of all the ligands are covered in results and discussion.

3.3.3 RESULTS AND DISCUSSION:

The NMR spectra of all the ligands show the following common features,

while individual having additional signals are given below:

Chapter-3

66

Table 3.4 NMR Spectral data of Ligands RCC-1 to RCC-6

On the basis of structure of known reactants and their reactive sites, the

structures of all ligands shown are in chapter-2. The structures are confirmed by NMR

spectral data shown above and typical spectra shown in Figures: 3.5 to 3.7.

RCC-1 to

RCC-6

δ ppm 7.00 to 8.13 Multiplet, Quinoline and or

benzene rings

δ ppm 6.00-6.35 Singlet of phenolic OH

δ ppm 3.35-3.7 CH2 bridge of -CH2NH-

δ ppm 11.1-11.35 -NH-

δ ppm 3.7 – 3.8 -O-CH2- bridge

RCC-6 δ ppm 7.45 – 7.70

-Naphthyl

Chapter-3

67

Figure: 3.5 NMR Spectrum of Ligand RCC-1

Chapter-3

68

Figure: 3.6 NMR Spectrum of Ligand RCC-2

Chapter-3

69

Figure: 3.7 NMR Spectrum of Ligand RCC-3

Chapter-3

70

3.4 ESTIMATION OF NUMBER OF HYDROXYL (-OH) GROUPS IN LIGANDS RCC-1 TO RCC-6.

The structures of ligands were examined by estimation of number of

carboxylic–OH groups per mole of ligand. The non aqueous conductometric titration

was employed for -OH group estimation following the method reported in the

literature [10-13]. The titrant used for this non-aqueous titration was sodium

methanolate (NaOMe) in pyridine. The details procedure followed in titrations

described here for one of the selected ligand.

3.4.1 NON-AQUEOUS CONDUCTOMETRIC TITRATION. EXPERIMENTAL:

The ligand sample dried at 900C was finely powdered and used for non-

aqueous Conductometric titration. A weighed amount of ligand sample (50 mg) was

dissolved in 40 ml of anhydrous pyridine.

The solution was allowed to stand overnight for complete dissolution. This

ligand solution was transferred into conductance cell and it was then stirred

magnetically. The base sodium methoxide (0.1 N) in pyridine was added to the

conductance cell at regular interval of 0.01 ml of titrant beyond the stage of

equivalence. The conductance measurement after addition of each volume of titrant

base was carried out by following 2-3 minutes to lapse. During the titration the

temperature of solution was maintained constant about 250C when the point of

equivalence was exceeded; there it was a continuous increase in conductance on

addition of every additional aliquot of sodium methoxide indicating the stage of

complete neutralization of all the OH groups in the given amount of ligand sample.

The volume of base added is converted into millimoles of sodium methoxide required

for 100 gm of ligand. A plot of conductance against millimoles of sodium methoxide

per 100 gm of ligand sample was made as shown in figure 3.8. Inspection of such plot

revealed that was observed one break from the plot, the millimoles per 100 gm of

ligand sample corresponding to the break was noted and the numbers of OH groups

Chapter-3

71

were estimated. Each titration was reported twice as an independent experiments

using different amount of the ligand samples.

Figure – 3.8

Non Aqueous Conductometric Titration Curve for Ligand RCC-1

Estimations are agreed each other with 5% variation.

The No. of hydroxyl group per mole of ligand (X) was calculated as follow:

(X) = Millimoles of NaOMe per 100g of sample at the neutralization point (Y) X Mol. Wt of ligand (M) 100 X 103

Similarly, for all other ligands the values estimated for number of hydroxyl (-OH)

groups are reported in Table 3.5.

Chapter-3

72

3.4.2 RESULTS AND DISCUSSION:

The non-aqueous conductometric titration curves of each of the six ligands

have shown the presence of one break and the estimation of number of one –OH

group from the break has shown the values in the range of 0.98 to 1.10 indicating the

presence of one –OH groups. This is quite consistent with the proposed structure

shown in scheme-1.

Chapter-3

73

Table 3.5 Non-aqueous Conductometric titration of Ligands

Estimation of OH groups for RCC-1 to RCC-6

Solvent: - Anhydrous pyridine

Reagent :- 0.1 N sodium methanolate

Ligand

Molecular

weight

gm

Millimoles of NaOMe at

neutralization break per 100

gm of sample.

Estimated

No. of

–OH group

[RCC-1] 380 258 0.98

[RCC-2] 414.5 241 1.00

[RCC-3] 459 216 0.99

[RCC-4] 425 259 1.10

[RCC-5] 449 220 0.99

[RCC-6] 430 230 0.99

Chapter-3

74

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[1] S. Bance, Hand book of practical organic microanalysis, John willy and

sons N.Y. (1988).

[2] R.M. Silvestein, Spectrometric Identification of organic Compounds, 5th Edn.,

John Wiley, 123 (1991).

[3] Lyulin, O. M, Kurlovets, E. V, J. of quantitative spectroscopy & radiative

transfer, 113(17), 2167 (2012).

[4] A.I. Vogel, A Textbook of Quantitativ e Chemical Analysis Revised by J.

Bessett, R.C. Denny, J.H. Feffery and J. Mondhaus, EIBS, 5th Edn., London

(1996).

[5] G. Socrates;Infrared and Raman characteristics group’s frequencies: Table and

charts (2004).

[6] G. Peter, D. H. James; Fourier Transform Infrared Spectroscopy, 2nd Edition,

Wiley-Interscience (2007).

[7] D. N. Sathyanarayana, Introduction to Magnetic resonance spectroecopy

(Second edition) (2013).

[8] James Keeler, Understanding NMR Spectroscopy, Second edition (2010).

[9] Ray Freeman, A handbook of Nuclear magnetic resonance (1997)

[10] Petrenko, D.; Bulletin of the Moscow state regional university (Article), Issue

no. 1, 157 (2012).

[11] P. Patnaik, Dean’s Analytical Chemistry Handbook, 2nd edition, McGraw-Hill

(2004).

[12] S.K. Chatterjee and P.R. mitra, J. Polymer Sci., Part. A-1, 1299 (1970).

[13] S.K. Chatterjee and N.D. Gupta., J. Polymer Sci. Part A-1, 11, 1261 (1973).