Synthesis and mesomorphism of novel chalconyl esters with a lateral nitro group

Article abstract of DOI:10.1080/15421406.2016.1190500

A new chalconyl homologous novel series with lateral nitro group: 4-(3-4-(heptyloxy)phenyl) acryloyl-2^/-nitro phenyl 4′-alk oxy benzoate have been synthesized and all the members are differed by the terminal chain length C_nH_2n+1, where n = 1,2,3,4,5,6,7,8,10,12,14,16,18. Their transition temperatures and mesophase characteristics are studied with the help of polarizing optical microscope (POM). All 13 homolog of series except the C₁–C₄ are enantiotropically mesogenic. The molecular structures have been confirmed by the analytical techniques of NMR, IR, and elemental analysis.

Full text of DOI:10.1080/15421406.2016.1190500

Molecular Crystals and Liquid Crystals
ISSN: 1542-1406 (Print) 1563-5287 (Online) Journal homepage: http://www.tandfonline.com/loi/gmcl20
Synthesis and mesomorphism of novel chalconyl
esters with a lateral nitro group
B. B. Jain & R. B. Patel
To cite this article: B. B. Jain & R. B. Patel (2016) Synthesis and mesomorphism of novel
chalconyl esters with a lateral nitro group, Molecular Crystals and Liquid Crystals, 637:1, 1-9,
DOI: 10.1080/15421406.2016.1190500
To link to this article: http://dx.doi.org/10.1080/15421406.2016.1190500
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Date: 11 November 2016, At: 00:16

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
, VOL. , –

http://dx.doi.org/./..
Synthesis and mesomorphism of novel chalconyl esters
with a lateral nitro group
B. B. Jain and R. B. Patel
Chemistry Department, K. K. Shah Jarodwala Maninagar Science College, Gujarat University, Ahmedabad,
Gujarat, India
ABSTRACT
KEYWORDS
A new chalconyl homologous novel series with lateral nitro group: 4-(3-
Liquid Crystal; Smectic;
Nematic; Mesophase;
Chalconyl ester
/
ꢀ
4
-(heptyloxy)phenyl) acryloyl-2 -nitro phenyl 4 -alk oxy benzoate have
been synthesized and all the members are differed by the terminal
chain length C H , where n = 1,2,3,4,5,6,7,8,10,12,14,16,18. Their transi-
n
2n+1
tion temperatures and mesophase characteristics are studied with the
help of polarizing optical microscope (POM). All 13 homolog of series
except the C –C are enantiotropically mesogenic. The molecular struc-
1
4
tures have been confirmed by the analytical techniques of NMR, IR, and
elemental analysis.
GRAPHICAL ABSTRACT
Introduction
Materials with three phenyl ring and –CH=CH–COO– and –CO–CH=CH– central link-
age have been synthesized earlier now we attach a lateral nitro group in this structure and
study what effect come to the liquid crystal properties. The interest in the study of the liq-
uid crystalline (LC) [1] state of matter has attracted scientists and technologists because of its
dual character as to flow like an isotropic liquid and have to behave as rigid crystals. Some
LCs like chalconyl esters with lateral nitro group derivatives are thermotropically and biolog-
ically active materials which are useful for the manufacture of LC devices or pharmaceutical
preparation useful for curing of various physical disorder of human or animal bodies [2–10].
CONTACT R. B. Patel
lege, 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 Col-
©

2
B. B. JAIN AND R. B. PATEL
Present investigation is planned to synthesize novel LC material through homologous series
with a view to understand and establish the effects of molecular structure on thermotropic LC
properties, with reference to changing the tail group and its flexibility [11–14]. The aims and
object in view to study the effect of molecular structure and lateral group on LC properties and
LC behavior [15–20] as a result of molecular flexibility keeping molecular rigidity unaltered
throughout a series and changing flexibility from series to series for the same homolog at con-
stant rigidity. The novel homologous series contain three phenyl rings and bridged through
two central linkage (–CH=CH–COO and –CO–CH=CH–) as the rigid core and n-alkoxy
(
–OR), –OC H and nitro (NO ) as flexible units of a molecule.
7 15 2
Experimental
Synthesis
Trans 4-n-alkoxy cinnamic acids (A) were prepared by modified method [21,22]. α-3-
/
nitro 4-hydroxy benzoyl β-4 tetradecyloxy ethylene (B) was prepared by usual established
method [23]. Esters were synthesized by a literature method [24]. Thus, the Chalconyl – ester
homolog derivatives were decomposed, filtered, washed with solution of sodium bicarbon-
ate and sodium hydroxide followed by water dried and purified till constant transition tem-
peratures obtained using an optical polarizing microscope equipped with a heating stage.
Alkyl halides, 3-Nitro 4-hydroxybenzaldehyde, 3-hydroxy acetophenone, dicyclohexylcar-
bodimide, Dimethyl amino pyridine, DCM, Ethanol, Acetone required for synthesis were
used as received except solvents which were dried and distilled prior to use. The synthetic
route to a series is shown below in Scheme 1.
Characterization
Selected members of the novel homologous series were characterized by Elemental Analy-
1
sis, infrared spectroscopy, H NMR spectra. IR spectra were recorded by Perkin-Elmer spec-
1
trum GX, H NMR spectra (Table 1) were recorded on Bruker using CDCl as solvent.
3
Microanalysis (Table 2) was performed on a Perkin-Elmer PE2400 CHN analyzer. Transi-
tion temperature and LC properties (textures) were determined using an optical polarizing
microscopy equipped with a heating stage. Textures of nematic phase are determined by mis-
cibility method.
Analytical data
IR spectra in cm  for octyloxy & dodecyloxy derivatives
−
Octyloxy: 721Polymethylene (–CH –)n of –OC H , 831(–C–H– def. m di-substituted), 759
2
8
17
Polymethylene (–CH –) of –OC H , 952 (–C–H– def. hydrocarbon), 1112(–C–O–) Str,
2
7
15
1
165,1251 and 1379 (–C–O str in –(CH )n chain), 1458 (–C–H– def. in CH ), 1492 (nitro
2
2
group), 1518 (–C=C–)str, 1604 (–C=O group) 1710(–COO– ester group), 2848 and 2922
(
–C–H str in CH ).
3
Dodecyloxy: 718Polymethylene (–CH –)n of –OC H , 815(–C–H– def. m di-
2
12 25
substituted), 767 Polymethylene (–CH –) of –OC H , 952 (–C–H– def. hydrocarbon),
2
7
15
1
110(–C–O–) Str, 1377, 1165 and 1254(–C–O str in –(CH )n chain, 1465(–C–H– def. in
2
CH ),1495 (nitro group) 1516 (–C=C–)str, 1602 (–C=O group) 1712 (–COO– ester group),
2
2
848 and 2920 (–C–H str in CH ).
3

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
3
Scheme . Synthetic Route of Series.
HNMR spectra in CDCl in δ ppm for hexyloxy & decyloxy derivative


Hexyloxy: 0.86(t, –CH3 of –C H ), 1.1–1.5 (m, n-poly methylene groups of-
6
13
OC H ),1.75(m, n-poly methylene groups of –OC H ), 3.2–3.4 (s,-OCH –CH -ofOC H ),
6
13
7
15
2
2
7
15
4
.03 (s,-OCH –CH -of -OC H ), 6.8–7.2 (s,-CO–CH=CH), 8.12 (s, p-disubstituted phenyl
2
2
6
13
ring).
Table . Elmental analysis for heptyloxy, octyloxy, tetradecyloxy, and octadecyloxy derivatives.
%
Elements found
%Elements theoretical
H
Sr. No.
Molecular formula
C HON
C
H
N
C
N

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.





CH O N
 
C H O N
  
C H O N
  

4
B. B. JAIN AND R. B. PATEL
Table . Texture of nematic phase of C , C , C , C by miscibility method.

  
Sr. No.
Homolog
Texture

C
C
C
C
Threaded
Threaded
Schlieren
Schlieren



Decyloxy: 0.83 (t,–CH of –C H ), 1.3–1.6(m, n-poly methylene groups of-OC H ),
3
10 25
10 25
1
.77 (m, n-poly methylene groups of -OC H ), 3.4–3.6(s,-OCH –CH -ofOC H ), 4.12(s,-
7 15 2 2 7 15
OCH –CH -of OC H ), 6.9–7.4 (s,-CO–CH=CH),8.2 (s, p-disubstituted phenyl ring).
2
2
10 21
Result and discussion
Novel series of chalconyl derivatives with lateral nitro group have been synthesized by conden-
/
sation of trans 4-n-alkoxy cinnamic acids and α-3-nitro 4-hydroxy benzoyl β-4 tetradecyloxy
ethylene (m.p. : 69°C and yield : 64.54%). Series consist of thirteen (C –C ) homologs of
1
18
which C –C homologs are nonliquid crystals and C homolog is enantiotropically nemato-
1
4
5
genic without exhibition of smectic property and C –C homologs are enantiotropically
6
18
nematogenic and smectogenic. Transition and melting temperatures (Table 3) were deter-
mined through an optical polarizing microscopy (POM) equipped with a heating stage and
were plotted versus the number of carbon atoms present in n-alkyl chain R of left –OR group.
Transition curves, Cr-N/I and N-I were drawn by linking like or related transition points
as depicted in a phase diagram (Fig. 1) showing phase behaviors of series. Cr-Sm/N tran-
sition curve follow zigzag path of rising and falling with overall descending tendency and
behaved in normal manner. N-I transition curve initially descended from C to C through
5
8
C homolog and then ascended to C homolog through C and finally descended up to last
6
10
8
C homolog with exhibition of odd-even effect. Sm-N transition curve showing descending
18
Table . Transition temperature of homologous series.
Transition temperatures in C
Nematic
Sr.no
R = n-alkyl group
Smectic
Isotropic

C
C
C
C
C
C
C
C
C
C
C
C
C
—
—
—
—
—








—
—
—
























—















MOLECULAR CRYSTALS AND LIQUID CRYSTALS
5
Figure . Phase behavior of series.
tendency from C homolog up to C18 homolog. Thus, it behaves in normal manner. Odd-
5
even effect is observed between C to nearby C homologs and then it disappears from and
6
9
beyond C homolog for higher homologs of longer n-alkyl chain ‘R’ of –OR group. N-I tran-
9
sition curve of odd members occupy lower position then even members. Textures of nematic
phase are threaded or schlieren and smectic phase textures are smectic- A type are confirm
by polarizing optical microscope (POM) equipped with heating stage. Analytical, spectral,
and thermometric data supported the molecular structures of homologs. LC properties from
homolog to homolog in the same series varied keeping right terminal and geometrical shape
unchanged throughout the series, except number of changing number of methylene unit or
units.
The exhibition or inexhibition of mesomorphic property by a substance depends upon its
suitable or unsuitable magnitudes of anisotropic forces of intermolecular end-to-end and lat-
eral forces as a consequence of favorable or unfavorable molecular rigidity and flexibility. The
molecular rigidity remains unaltered throughout the series from homolog to homolog in the
same series; but, its molecular flexibility alters from homolog to homolog in the same series
due to changing number of methylene unit or units present in n-alkyl chain bonded to first
phenyl ring through oxygen atom. The combined effect of molecular rigidity and flexibility
of suitable magnitude induces mesomorphism in a substance to disalign the molecules and
resist exposed thermal vibrations on molecules under microscopic examination under float-
ing condition on the surface. The failure of exhibition by C –C homologs is attributed their
1
4
inability to resist exposed thermal vibrations due to unsuitable magnitudes of intermolec-
ular end-to-end and lateral attractions which abruptly breaks crystal lattices and smoothly
transform crystalline state to isotropic state without passing through LC state, due to low
dispersion forces and low magnitudes of dipole-dipole and electronic interactions between

6
B. B. JAIN AND R. B. PATEL
Figure . Structurally similar series.
instantaneous dipole produced by spontaneous oscillations of electron clouds of the molecules
leading to high crystallizing tendency. Thus, molecules of nonmesomorphs randomly ori-
ented in all possible directions with high order of disorder or uncontrolled movement. Such
molecules do not acquire monotropic LC state on cooling the isotropic mass. Thus, any sort
of mesomorphism either smectic or nematic is absent for C –C homologs. The commence-
1
4
ment of enantiotropic nematic mesophase formation from C homolog and enantiotropic
7
smectic mesophase from C to C homolog is attributed to disalignment of molecules at
6
18
an angle ninety or less than ninety degree which resisted exposed thermal vibrations by suit-
able magnitudes of end to end attractions, acquiring statistically parallel orientational order
of molecular arrangement under floating condition during microscopic examination for def-
inite range of temperature according to molecular permanent dipole moment, aromaticity,
molecular rigidity, flexibility, polarity, and polarizability. Thus, variations in mesomorphic
properties of a present novel series are compared with the structurally similar other known
homologous series as shown below in Fig. 2.
Homologous series 1 and A are identical with respect to three phenyl rings, two central
bridge linking middle. But they differ with respect to central phenyl ring series 1 have one
lateral nitro group and differ by right-handed end group –OC H and –OC H for series 1
7
15
14 29
and B, respectively. Homologous series 1 and B are identical with respect to three phenyl rings
and right handed end group –OC H but differ with respect to central phenyl ring series 1
7
15
have one lateral nitro group and central linkage –CH=CH–COO-, -CO–CH=CH– and –
COO, -CO–CH =CH– for series 1 and B, respectively. However, combine effect of molecular
rigidity plus flexibility vary for the same homolog from series to series and from homolog to
homolog in the same series. Following Table 4 represents some thermometric behaviors of
presently investigated novel chalconyl homologous series 1 and the series A [25] and B [26]
chosen for comparative study.
r
Homologous series 1 under comparative study are nematogenic and smectogenic, but
series A and B are nematogenic with absence of smectogenic property.
r
The mesogenic property commences from C (series1), C (series A), and C (series B)
5
5
6
homolog.
r
Thermal stability for nematic of series B and series A are less than series 1.
The total mesophase length ranges from minimum to maximum in increasing order
from series A to series B to series 1.
r
r
Thermal resistivity is poor for all the series under comparision except series 1.

MOLECULAR CRYSTALS AND LIQUID CRYSTALS
7
Table . Relative thermal stability in °C.
Series→

A
B
smectic-isotropic
Or
smectic-nematic
Commencement of Smectic phase
.
(
C –C )
 
C
_
_
_
_
Nematic-Isotropic
Commencement of Nematic phase
.
(
C
C –C )
 
.
.
(C –C )


C
(C –C )


C
Total upper and lower mesophase length range in °C C –Cj
–
i
C C

–
C C
C
–
C C
From above Table  it is clear that
Homologous series 1 and B are almost identical except the difference of seven methylene
units at the tail-end groups at right side of the molecules and one lateral nitro group at cen-
tral ring. Homologous series 1 and A are also almost identical but differ only with the central
linkage –COO and –CH=CH–COO and one lateral nitro group at central ring. Because of
one nitro group in series 1 its thermal stability is very higher than the series A and B because
nitro group increase the polarity of the homologous series and also series 1 shows nemato-
genic and smectogenic property, but series A and B do not show smectogenic property and
only shows nematogenic property because of absence of nitro group they have less polarity.
Enthalpy values (ꢀH) associated differs from homolog to homolog in the same series and
for the same homolog from series to series which plays role in the thermometric behavior of
series to series and the homolog to homolog. Thus, facilitation and stabilization of nematic
mesophase is more favored in case of series 1 as compared to series A and B. Thus, com-
mencement of nematic mesophase, mesophase length range, and the magnitudes of thermal
stability show positive or negative variations in mesogenic behaviors, from series to series for
the same homolog and homolog to homolog in the same series.
Conclusions
r
Present novel chalconyl ester series is nematogenic, smectogenic, and high-ordered melt-
ing type whose isotropic temperature vary between 160°C and 240°C.
Group efficiency order derived for nematic on the basis of
r
(
i) Thermal stability
(ii) Commencement of mesophase and

8
B. B. JAIN AND R. B. PATEL
(iii) Mesophase length range are as under
r
Molecular structure plays an important role in mesogenic behavior with reference to
changing tail-end group and lateral group.
Mesomorphism is very sensitive and susceptible to molecular structure.
Novel homolog of chalconyl ester derivatives with lateral nitro group may be useful in
the study of their biological activity lyotropically as antimalarial, anticancer, antibacterial
compounds.
Ester group of present novel investigation may be useful for the agricultural production
for the growth of quality and healthy fruits and flowers, potato, and potato-like material
as well as chalconyl group being biologically active and antibacterial and antifungal may
reduce the consumption of pesticides and insecticides.
Present study supported early views and raised reliability and credibility to the conclu-
sions drawn earlier.
r
r
r
r
Acknowledgments
Authors acknowledge thanks to Dr. R. R. Shah, principal of K. K. Shah Jarodwala Maninagar Science
College, Ahmedabad. Authors thank to NFDD Centre for the analytical and spectral services.
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