Dependence of mesomorphism on molecular rigidity of chalconyl liquid crystals with two phenyl rings

Article abstract of DOI:10.1080/15421406.2016.1190502

A novel homologues series: RO-C₆H₄?CH=CH?CO?C₆H₄?OC₁₆H₃₃(n) (meta) of chalcones with two phenyl rings is synthesized and studied with a view to understanding and establishing the relationship between molecular structure and mesogenic behavior. The series consists of 13 homologues (C₁ to C₁₈). Mesomorphism commences from the second member of the series. C₂ to C₆ homologues are enantiotropicnematic and the rest of the homologues (C₇ to C₈) are monotropicnematic plus monotropicsmectic. C₁ homologue is nonmesogenic. Transition temperatures were determined by an optical polarizing microscope (POM) equipped with a heating stage. Textures of nematic and smectic phases are threaded, Schlieren or smectic-A, respectively, as judged directly from the heating top of microscopic observations. Thermal, analytical and spectral data confirms the molecular structures. Thermal stabilities for smectic and nematic are few (1 or 2°C) degrees and 72.6°C, respectively. The mesophase lengths are relatively shorter with low mesomorphic transition temperatures (44.0°C to 85.0°C).

Full text of DOI:10.1080/15421406.2016.1190502

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: http://www.tandfonline.com/loi/gmcl20
Dependence of mesomorphism on molecular
rigidity of chalconyl liquid crystals with two phenyl
rings
Vinay S. Sharma & R. B. Patel
To cite this article: Vinay S. Sharma & R. B. Patel (2016) Dependence of mesomorphism on
molecular rigidity of chalconyl liquid crystals with two phenyl rings, Molecular Crystals and
Liquid Crystals, 637:1, 19-27, DOI: 10.1080/15421406.2016.1190502
To link to this article: http://dx.doi.org/10.1080/15421406.2016.1190502
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Date: 11 November 2016, At: 00:17

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
, VOL. , –

http://dx.doi.org/./..
Dependence of mesomorphism on molecular rigidity of
chalconyl liquid crystals with two phenyl rings
Vinay S. Sharma and R. B. Patel
Chemistry Department, K. K. Shah Jarodwala Maninagar Science College, Gujarat University, Ahmedabad,
Gujarat, India
ABSTRACT
KEYWORDS
A novel homologues series: RO-C H ꢀCH=CHꢀCOꢀC H ꢀOC H (n)
Chalcones; liquid crystals;
monotropy; nematic; smectic
6
4
6
4
16 33
(
meta) of chalcones with two phenyl rings is synthesized and stud-
ied with a view to understanding and establishing the relationship
between molecular structure and mesogenic behavior. The series con-
sists of 13 homologues (C to C ). Mesomorphism commences from the
1
18
second member of the series. C to C homologues are enantiotrop-
2
6
icnematic and the rest of the homologues (C to C ) are monotrop-
7
8
icnematic plus monotropicsmectic. C homologue is nonmesogenic.
1
Transition temperatures were determined by an optical polarizing
microscope (POM) equipped with a heating stage. Textures of nematic
and smectic phases are threaded, Schlieren or smectic-A, respectively,
as judged directly from the heating top of microscopic observations.
Thermal, analytical and spectral data confirms the molecular struc-
tures. Thermal stabilities for smectic and nematic are few (1 or 2°C)
degrees and 72.6°C, respectively. The mesophase lengths are rela-
tively shorter with low mesomorphic transition temperatures (44.0°C to
85.0°C).
1
. Introduction
The combination of potency for thermotropic mesomorphism and biological activity as
antibacterial, antifungal, anticancer, antimalarial, etc. is rarely available. Therefore, the present
investigation was planned to synthesize chalcone derivatives which act as thermotropic liq-
uid crystals (LC) [1] and biologically active molecules [2]. Which are useful in the benefit of
mankind [3–7]. Present work is aimed to understand and establish the relationship between
thermotropic mesomorphism and molecular structure [8–12] excluding the study of applica-
tions of either thermotropic LC or biological activity. The present study concerns the syn-
thesis of novel LC substances as an homologous series, their characterizations, evaluation
of thermometric data and their interpretation in terms of molecular rigidity and flexibil-
ity [13–16]; including conclusions in relation with present novel work. Several homologous
series have been reported to date [17–23]. The novel compounds are compared with known
compounds.
CONTACT R. B. Patel
College, Gujarat University, Ahmedabad, Gujarat, India.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/gmcl.
 Taylor & Francis Group, LLC
roshanpatel@gmail.com
Chemistry Department, K. K. Shah Jarodwala Maninagar Science
©

20
V. S. SHARMA AND R. B. PATEL
Scheme . Synthetic route to the series.
2
. Experimental
2.1. Synthesis
Alkylation of 4-hydroxy benzaldehyde to give 4-n-alkoxy benzaldehyde was carried out by a
known method [24] and 3-n-alkoxy acetophenone was obtained by alkylation of 3-hydroxy
acetophenone by a known method [25].Thus, the chalconyl homologue derivatives (C) were
prepared by the usual established method [26] collected and filtered, washed with ethanol
solution dried and purified until constant transition temperatures obtained using an optical
polarizing microscope equipped with a heating stage. Alkyl halides, EtOH, KOH, 3-hydroxy
acetophenone, 4-hydroxy benzaldehyde, etc., required for synthesis were used as received
except solvents which were dried and distilled prior to use. The synthetic route to the series
is shown in Scheme-1.
2
.2. Characterization
Representative homologues of the series were characterized by elemental analysis, infrared
1
spectroscopy and H NMR spectra. IR spectra were recorded on a Perkin-Elmer spectrum
1
GX, H NMR spectra were recorded on a Bruker using CDCl as solvent. Microanalysis was
3
performed on a Perkin-Elmer PE 2400 CHN analyzer (Table 1). Texture of nematic phase
were determined by miscibility method (Table 2). Transition temperatures (Table 3) and LC
Table . Elemental analysis for () butoxy () decyloxy () dodecyloxy and () hexadecyloxy derivatives.
Elements % found
Elements % Calculated
Sr. No.
Molecular formula
C H O
C
H
C
H

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

  



C HO

C HO


C H O

  

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
21
Table . Texture of nematic phase of C , C , C , C by miscibility method.

  
Sr. No.
Homologue
Texture

C
Threaded
Droplets type
Schlieren



C
C
C
Droplets type
properties (Textures) were observed by using polarizing optical microscope (POM) equipped
with heating stage and digital camera.
3
. Analytical data
−1
3
.1. IR spectra in cm for pentoxy&decyloxy derivatives
Pentoxy :2914 (C–H str. of alkane), 2848 (C-H str. of –(CH -)n group of –OC H alkyl chain,
2
5
11
1
1
600–1660 (C=O str. of carbonyl carbon of chalconyl group), 1604 (C=C str. of alkene), 1510,
560 (C=C str. of aromatic ring), 999 (C–H bending of alkene), 1178 (C–O str. of ether link-
age), 1288, 1246 (C–O str. of carbonyl group), 776Polymethylene (-CH -) of –OC H , 678
2
16 33
Polymethylene (-CH -)n of –OC H 824(–C-H- def. m di-substituted-Para), IR data con-
2
5
11,
firms the molecular structure.
Decyloxy :2916 (C–H str. of alkane), 2850 (C–H str. of –(CH -)n group of –OC H group,
2
10 21
1
(
600–1660 (C=O str. of carbonyl group of chalconyl group), 1604(C=C str. of alkene), 1579
C=C str. of aromatic ring), 1004, (C-H bending of alkene), 1190 (C-O str. of ether link-
age), 1240, 1256 (C–O str. of carbonyl group), 776 Polymethylene (-CH -) of –OC H , 823
2
16 33
(–C-H- def. m di-substituted-Para), IR data confirms the molecular structure.
1
3
.2. HNMR spectra in CDCl in δ ppm for hexyloxy&octadecyloxy derivative
3
Hexyloxy: 0.88 (t, 6H, -CH of polymethylene –C H and –C H ), 1.79(p, 10H, CH -CH -
3
6
13
16 33
3
2
CH -CH -CH - of –OC H and –OC H ), 1.28 (m, 14H –CH -CH -CH - of –OC H and
2
2
2
6
13
16 33
2
2
2
6
13
–
OC H ), 1.31 (q, 8H, -CH -CH ), 4.06(t, 4H, -OCH -CH -), 7.59 (d, 2H, -CH=CH-), 7.43,
16
33
2
3
2
2
Table . Transition temperature in °C.
Transition temperatures in °C
Sr. no
R = n-alkyl group
Smectic
Nematic
Isotropic

C
C
C
C
C
C
C
C
C
C
C
C
C
—
—
—
—
—
—
.
.
.
.
.
(.)
(.)
(.)
(.)
(.)
(.)
(.)
.
.
.
.
.
.
.
.
.
.
.
.
.












—
(.)
(.)
(.)
(.)
(.)
(.)
(.)




(
) indicates monotropy.

2
2
V. S. SHARMA AND R. B. PATEL
Figure . Phase behaviors of series.
.28 & 7.83 (4H, meta substituted phenyl ring), 7.56 & 7.97 (4H, phenyl ring with alkoxy
7
chain). NMR data confirms the molecular structure.
Octadecyloxy: 0.88 (t, 6H, -CH of –C H and –C H ), 1.80(p, 10H, CH -CH -CH -
3
18 37
16 33
3
2
2
CH -CH -CH of -OC H and –OC H ), 1.28 (m, polymethylene 18H –CH -CH -CH -
2
2
2
18 37
16 33
2
2
2
of –OC H and –OC H ), 1.34 (q, 8H, -CH -CH ), 4.05(t, 4H, -OCH -CH -), 7.59 (d,
18
37
16 33
2
3
2
2
2
H, -CH=CH-),7.43, 7.28 &7.83 (4H, meta substituted phenyl ring), 7.56 & 7.97 (4H, phenyl
ring), 6.95 & 7.62 (4H, phenyl ring with alkoxy chain). NMR data confirms the molecular
structure.
4
. Results and discussion
-n-alkoxy benzaldehydes are nonmesomorphic but linking with metan-hexadecyloxyace
tophenone generates mesomorphic properties from the C to C homologues. The novel
4
2
18
homologues consist of two phenyl rings bonded through one central bridge –CH=CH–CO-
and exhibit mesomorphism.The C to C homologues are enantiotropicnematic whereas, and
2
6
the C to C homologues are monotropically nematogenic and also monotropically smecto-
7
18
genic. A phase diagram showing phase behaviors (Fig. 1) is obtained by plotting transition
temperatures against the number of carbon atoms present in n-alkyl chain “R” of left –OR
group and then on linking like or related points, transition curves Cr-N/I, N-I or I-N and
N-Sm are obtained. Cr-N/I transition curve adopted zigzag path of rising and falling with
overall descending tendency as series is ascended and behaved in normal manner. N-I or I-N
transition curve descended upto C homologue and then rises by about ten to twelve degree
7
and behaved in normal manner. Monotropic N-Sm transition curve rises, then falls at C12
homologues and then again ascended upto C18 member of a series, under discussion, Thus
N-Sm transition curve also behaved in normal manner. N-I/I-N and N-Sm transition curves
adopted very short and narrow odd–even effects for one or two homologues. Odd–even effects
for N-I and N-Sm transition curves are observed upto C and C homologues, respectively,
4
9
and then a single transition curves are followed for higher homologues of longer n-alkyl chain

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
23
Figure . POM image of (a) Sm C phase of C homologue monotropically at °C, (b) Nematic phase of C


homologue at °C during cooled condition.
“R” of –OR group. Thermal stability for smectic is few degree (1 or 2°C) but thermal sta-
bility fornematic is 72.6°C. Mesophase length ranges between 5.0 and 21.0°C. Normally the
sequence of appearing mesophase in ester or azoester series is first monotropy and then enan-
tiotropy, but; in case of presently invested chalconyl (-CH=CH–CO-) central group contain-
ing two phenyl ring consisted homologous series is appeared as first enantiotropy and then
monotropy which is reversal to normal behavior; due to presence of only chalconyl central
group. The variations in thermotropic mesomorphic properties from homologue to homo-
logue in the same series appeared, with changing value of “R” of –OR group.
The molecular length of 4-n-alkoxy benzaldehyde increases by linking 3-n-hexadecyloxy
acetophenone, which upgrades the molecular rigidity and flexibility to suitable and favorable
magnitudes of intermolecular cohesion and closeness to induce nematic and smectic phase in
enantiotropic or monotropic manner. The exhibition of smectogenic and nematogenic char-
acters are attributed to the corresponding molecular arrangements as sliding layered organi-
zation due to lamellar packing of molecules in preoccupied lattices of rigid crystals to induce
smectogenic property and the stastically parallel orientational order of molecules due to end
to end favorable intermolecular attractions and closeness as well as suitable magnitudes of
polar and polarizable nature of flexible end groups of laterally substituted group. Fig. 2 shows
the POM image of C10 homologue at its transition temperature during cooled condition at
4
4°C, while comp. C16 shows nematic mesophase at 56°C monotropically, respectively.
The presence of laterally substituted flexible longer n-alkoxy group (-OC H ) (n) widens
16
33
the molecular width which causes reduction in the magnitudes of attractions but suitable
to induce enantiotropic/monotropic mesophase or inducing mesophases reversibly or irre-
versibly. Meta substituted –OC H (n) group helps in building sliding layered molecular
16
33
arrangement on cooling the isotropic mass of a sample substance commencing from C to
7
C homologues in irreversible manner or in monotropic condition, and lowers the transition
18
temperatures upto 44.0°C. The exhibition of minor or shorter odd–even effects in mesogenic
transition curves of a phase diagram is due to the addition of methylene unit in n-alkyl chain
“
R” of –OR end group. The disappearance of odd–even effect from and beyond a homologue
to which curves for odd and even members are merging into each other for higher homologues
of longer n-alkyl chains “R” of –OR and–OC H (n) flexible groups which is attributed to the
16
33
coiling or bending or flexing or coupling of n-alkyl chain with the major axis of core struc-
ture of a molecule which causes resultant suitable magnitudes of intermolecular cohesion to

24
V. S. SHARMA AND R. B. PATEL
Figure . Structurally similar series.
induce mesophase or mesophases. The absence of mesogenic character in C homologue is
1
due to the low magnitudes of dispersion forces and low magnitudes of dipole-dipole inter-
actions. The changing trend in mesogenic properties from homologue to homologue in the
same series is attributed to the changing number of carbon atoms present in n-alkyl chain
“
R” of –OR group and unexpected status of n-alkyl chain or end groups of a molecule. The
reverse deviating effect from normal sequence of appearing monotropy and then enantiotropy
is attributed to the unexpected status of n-alkyl chains which affected molecular lengths from
homologue to homologue in the same series which alters molecular polarity and polarizabil-
ity. Some thermometric properties and degree of mesomorphism of presently investigated
homologous series-1 and a structurally similar homologous series-X [27] as shown in Fig. 3
are compared.
Figure 4 shows the space-filling model of energy minimized for series1 and series X respec-
tively. Homologous series-1 and X are identical with respect to two phenyl rings bonded
through –CH=CH–CO- which contributes the total rigidity of series-1 and the part of rigid-
ity of series-X to its total rigidity. However, they differ with respect to absence and presence of
–
C H -COO- unit of molecules of series-1 and X contributing to molecular rigidity as well as
6 4
tail ends –OC H (n) and –NO contributing to molecular flexibilities due to the differing
16
33
2
Figure . Space filling diagram of series  and X.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
25
Table . Thermal stability in°C
Series→
Series- (-OC H ) Absent
Series-X (-NO ) Presence



of -C H .COO-
of -.COO-


Sm-N or N-Sm or Sm-I
Commencement of smectic phase
–°C
.
(C –C )
(C - C )




C
.
(C – C )
C
N-I or I-N
Commencement of nematic phase
.
(C - C )
C
. to .
C C




C
Mesophaselength (Sm + N) in°C
.°C to .°C
C C
molecular polarity and polarizability. Thus, variations in mesogenicproperties and the degree
of mesomorphism will depend upon the magnitudes of differing features between series-1
and X. i.e. rigidity played by –C H -COO- and the flexibility varied due to –OC H (n)
6
4
16 33
and –NO lateral group of series-1 and X, together which operates the differing behaviours
2
between series-1 and X for the same homologue and homologue to homologue in the same
series.
Following Table 4 represents some thermometric properties in comparative manner as
under.
Above Table 3 shows the following.
•
Homologous series of present investigation −1 and X under comparative study are smec-
togenic plus nematogenic.
•
Sequential order of mesophase is as enantiotropy first (C to C ) and then monotropy
2
6
from C to C homologue in case of series-1, whereas monotropic transitions are absent
7
18
for analogous series-X. Its smectogenic and nematogenic transitions are enantiotropic.
Smectogenicmesophase commences from C and C homologue respectively for series-1
•
•
•
7
6
and X.
Nematogenicmesophase commences from C and C homologue respectively for series-
2
3
1
and X.
Thermal stabilities and mesophaselengths of series 1 are relatively much lower than cor-
responding analogous series-X chosen for comparison.
The exhibition of smectogenic and nematogenic characters by the chalconyl series-1 and a
chalconyl ester series-X is attributed to the optimum magnitudes of dispersion forces and opti-
mum magnitudes of dipole-dipole interactions controlling suitable magnitudes of anisotropic
forces of intermolecular cohesion and closeness to induce smectic plus nematic phase in either
reversible or irreversible manner. The early or late commencement of smectic and nematic
phase are depended upon the extent of noncoplanarity of a molecule. Homologous series 1
and X under comparison are equally noncoplanar due to meta substituted tail end groups
whose group polarity and polarizability differed and therefore the smectic and nematicme-
sophases commences by the difference of one homologue, i.e., C or C and C or C . The
7
6
2
3
lower values of thermal stabilities and mesophaselengths of series-1 as compared to series-
X are attributed to the weakening of the suitable magnitudes of inter molecular cohesion by
reducing molecular rigidity by –C H .COO- unit which is related with energy stored (ꢀH) by
6
4
a molecules of homologous series at the time of formation. Thus, it is obvious that a molecule
of same homologue from series to series having lower rigidity will resist, exposed thermal
vibrations at lower transition temperatures and will facilitate low degree of mesophaselengths
of and low thermal stabilities. Thus, lowering of molecular rigidity results in lowering of ther-
mal stabilities and simultaneously the degree of mesomorphism. The variations in mesogenic

26
V. S. SHARMA AND R. B. PATEL
properties for the same homologue from series to series are due to the changing tail end or lat-
eral group; its polarity and polarizability and overall molecular rigidity / flexibility keeping rest
of the molecular part unaltered, whereas, variations in mesogenic properties from homologue
to homologue in the same series is due the sequentially changing numbers of methylene unit
or units at n-alkyl chain ‘R’ of –OR keeping tail or lateral group unaltered throughout a series.
5
. Conclusions
•
Novel homologous series of only chalconyl (-CH=CH–CO-) central bridge as link-
ing group with side chain based two phenyl rings and two end or lateral groups are
predominantly nematogenic and partly smectogenic whose thermal stabilities and the
mesophaselengths are low and it is as low ordered melting type.Chalconyl group is
generally nematogenic and bioactive which is useful for devices to be operated at low
temperature or room temperature, as well as its bioactivity is very useful in agriculture
products of good quality by its antibacterial and antifungal activity. Here, in present arti-
cle, we successfully synthesized the homologous series which shows LC properties as
lower temperature as present demand.
•
The group efficiency order derived on the basis of (i) thermal stabilities (ii) commence-
ment of mesophase and (iii) upper and lower mesophaselengths for smectic and nematic
are as under.
(
i) Smectic:
-
NO > -OC H (n)
2 16 33
Nematic:
NO > -OC H (n)
ii) Smectic:
-
2
16 33
(
-
NO > -OC H (n)
2
16 33
Nematic:
OC H (n) > -NO
2
-
16
33
(
iii) Smectic / Nematic
-
NO > -OC H (n)
2
16 33
Acknowledgments
Authors acknowledge thanks to Dr. R. R. Shah, principal and management of K. K. Shah Jarodwala
Maninagar Science College, Ahmedabad. Authors are also thankful to Dr. A.V. Doshi, Ex-principal of
M.V.M. Science and Home Sci. College, Rajkot for his constant support, inspirations, valuable sugges-
tions and comments, as and when needed during the course of present investigation. Authors thank to
NFDD Centre for the analytical and spectral services.
References
[
[
1] Reintitzer, F. (1988). Monatshefte, 9, 421.
2] Griffin, R. J., Srinivasan, S., Bowman, K., Calvert, A. H., Curtin, N. J., Newell, D. R., Pemberton,
L. C., & Golding, B. T. (1988). J. Med. Chem., 41, 5256.
[
[
[
3] Kim, W. S., Elston, S. J., & Raynes, F. P. (2008). Displays, 29, 458–463.
4] Naruma, S. (2001). Display, 22, 1.
5] Calliste, C. A., Bail le, J.C., Trouilas, P., Poug, C., Chulia, A.J., & Duroux, L. J. (2001). Anticancer
Res., 21, 3949–3956.
6] Gaikwad, P., & Desai, T. (2013). IJPRR, 2(12), 40–52.
[

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
27
[
[
[
7] Fischer, P., & Finkelman, H. (1988). Prog. Colloid. Polym. Sci., 111, 127.
8] Henderson, P. A., Niemeyer, O., & Imrie, C. T. (2001). Liq. Cryst., 28, 463–472.
9] Imrie, C. T. (1999). Struct. Bond, 95, 149–192.
[
10] Brehmer, M., & Zentel, R. (1994). Mol. Cryst. Liq. Cryst., 243, 353.
[
11] Gray, G.W. (1962). Molecular Structures and Properties of Liquid Crystals, Academic Press: Lon-
don.
12] Imrie, C. T., & Luckhrust, G. R. (1988). In: Liquid Dimers and Oligomers in Handbook of Liquid
[
Crystal, Low Molecular Liquid Crystals, Vol. 2B, Demus, D., Goodby, J. W., Gray, G. W., Spiess, H.,
&
Vill, V. (Eds.), pp. 801–833. Wiley-VCH: Weinheim.
[
[
[
[
13] Hird, M., Toyne, K. J., Gray, G. W., Day, S. E., & McDonell, D. G. (1993). Liq. Cryst., 15, 123.
14] Marcos, M., Omenat, A., Serrano, J. L., & Ezcurra, A. (1992). Adv. Matter, 4, 285.
15] Hird, M., Toyne, K. J., Gray, G. W., & Day, S. E. (1993). Liq. Cryst., 14, 741.
16] Collings, P. J., & Hird, M. (1998). Introduction of Liquid Crystals Chemistry and Physics, Taylor and
Francis Ltd.: U.K.
[
[
[
17] Demus, D. (1988). Mol. Cryst. Liq. Cryst., 165, 45–84.
18] Demus, D. (1988). Liq. Cryst., 5, 75–110.
19] (i) Suthar, D. M., & Doshi, A. V. (2013). Mol. Cryst. Liq. Cryst., 575, 76–83. (iv)Bhoya, U. C., Vyas,
N. N., & Doshi, A. V. (2012). Mol, Cryst. Liq. Cryst., 552, 104–110.
[
20] Suthar, D. M., Doshi, A. A., & Doshi, A. V. (2013). Mol. Cryst. Liq. Cryst., 527, 51–58.
21] (a) Sharma, V. S., & Patel, R. B. (2015). ILCPA, Scipress Ltd., 60, 182–191. (b) Sharma, V. S., &
Patel, R. B. (2015). ILCPA, Scipress Ltd., 59, 115–123. (c) Sharma, V. S., Solanki, R. B., Patel, P. K.,
[
&
Patel, R. B. (2016). Mol. Cryst. Liq. Cryst., 625(1), 137–145.
[
[
[
[
[
22] Sharma, V. S., & Patel, R. B. (2015). ILCPA, Scipress Ltd., 58, 144–153.
23] Patel, B. H., & Doshi, A. V. (2015). Mol. Cryst. Liq. Cryst., 605, 61–69.
24] Hasan, A., Abbas, A., & Akhtar, M. N. (2011). Molecule, 16, 7789–7802.
25] Nikitin, K. V., & Andryukhova, N. P. (2004). Can. J. Chem., 82, 571–578.
26] Furniss, B. S., Hannford, A. J., Smith, P. W.G., & Tatchell, A. R. (Revisors). (1989). Vogel’s Textbook
th
of Practical Organic Chemistry (4 Edn.), Longmann Singapore Publishers Pvt. Ltd.: Singapore,
5
63–649.
[
27] Chaudhari, R. P., & Doshi, A. V. (2013). Mol. Cryst. Liq. Cryst., 570, 109–116.