




































American International Journal of Humanities, Arts and Social Sciences  

Vol. 1, No. 1; 2019 

Published by American Center of Science and Education, USA 

 

17 

 

 

Preparation of Series Schiff Bases and Studying of their Liquid 

Crystalline Behavior 
 

 

 

Bari  Muhamd Islamallah 

Lasir Department   

College of Pharm Physical chemistry  
Pakistan 

 

 

Received: January 29, 2019      Accepted: February 3, 2019             Online Published: February 11, 2019        

 

 

Abstract  

Our study deals with   preparation   of two types of imine compounds differ in the type of terminal group, where one 

of them has a terminal carboxyl group COOH while the other contains methoxyOCH3 as a terminal group. In the 

first part of this research it was Identification by spectroscopy methods using infrared IR and nuclear magnetic 

resonance H NMR spectrum, besides elemental analysis shows the exact chemical structure of the expected 

synthesized compounds. In the second part was the study of liquid-crystalline behavior by polarized optical 

microscopy POM and differential scanning calorimetry DSC that showed a liquid crystal phase in the compounds 

that has odd number of carbon atoms in the terminal chain compounds in the first series, while the second series 

compounds showed liquid crystal phase in the   compounds that containing even number of atoms of carbon in the 

terminal chain. 

Keywords: Calom  , Pom 

 

INTRODUCTION 

heneazomet are a new phases of mater add to the three well-known phases  (solid, liquid and gas)[1].The differences 

between these three well-known states can be attributed to the temperature of the substance. Temperature is a 

measure of the randomness of the molecules and therefore the higher of temperature is the less order they exist. 

Increasing temperature will cause the transition from a solid to a liquid and then to a gas. However, Many materials 

exhibit more than a single transition when passing from solid to liquid, which proves the presence of one or more 

intermediate phases[2]. The new phases have mechanical, optical and structural properties between those of 

crystalline solid and the corresponding isotropic liquid. These phases are referred to as liquid crystalline phases[3,4]. 

Thermotropic liquid crystals is one of two types of liquid crystals (and the second is called lyotropic ) , Most 

thermotropic liquid crystals are rod-like molecules having a rigid core composed of two or more aromatic rings and 

one or more flexible terminal chains. 
 The liquid crystal mesogen must contain a side-chain to give a linear that required to the liquid crystalline 

behavior.Schiff base ( also known as imine CH=N ) is a linking group used to connect between core groups. It  has 

been received overwhelming response in liquid crystalsresearch ever since in 1970 where Kelker discovered the 4-

methoxylbenzylidene- 

4’-butylaniline (MBBA) which exhibit nematic phase at room temperature . 

 

In this our studies, Schiff base and alkyloxy terminal moieties are incorporated into a new series of homologous 

compounds with two different group in the other side of chain , 

4-(-alkoxybenzylideneamino)benzoic acid and 4-methoxy-N-(4-alkoxybenzylidene)aniline. 

 

Experimental: 

Preparation of N- (4-hydroxyphenyl) actamide 
1- 18.3 mL of concentration hydrochloric acid and , (0.22mol, 23.98 gm) of para-amino phenol were introduced in a 

beaker containing 500ml of distilled water. The mixture wasstirred until the amine completely passes in to solution . 



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2- To the resulting solution  25.6mL of acetic anhydride with  (three drops of H2SO4acidconcentration) were added 

and stirred and then immediately was poured in a solution of (33gm, 0.402mol) of crystallizedsodium acetate in 

100mL of water. The solution was stirred vigorously and cooled in ice. 

3- The N- (4-hydroxyphenyl) acetamide was filtered with suction washed with a little distilled water ,and dried upon 

filter paper in air melting point  was (169-170) C° . [5,6] 

 

Preparation of  N-Alkali bromides 
1-  In a round bottomed flask equipped with a separation  funnel and a condenser set downward for distillation, 

(71ml) of HBr acid (48%) and (16.5ml) of concentration H2SO4acid drop wise was added with stirring. 

2- After cooling(0.5mol) of appropriate alcohol was added in portions (the end  of the condenser was connected to 

an adapter dipping in to water contained in a 250ml flask, the later was surrounded by ice) then (2.5ml) of 

concentration H2SO4 acid was introduced gradually through the separation funnel and the mixture was distilled 

slowly until no more oily drops pass over . 

3- the organic layer was separated ,washed successively with water ,10 % Na2CO3solution and then with water 

,dried overanhydrous calcium chloride .it is used without further purification.[6]. 

 

Preparation of N-(4-methoxyphenyl) actamide 
1- (3.75gm, 0.025mol)of 4-actemido phenol were dissolved in 15mL of ethanol in aconical flask and with  added 
potassium hydroxide solution (1.85gm, 0.033mol),in a lest volume of (~ 1.5mL)by stirredmagnetic stirrer . 

2-A solutionofappropriate methane bromide (0.025mol) in 12.5mLdissolved in added ethanol, 

3-The  mixture heated  by using appropriate condenserfor more then one hour(then6mL distilled water added and the 

product was washed recrystallizefor ethanol,melting point (129C°), [7]. 

 

Prepare of 4-methoxy aniline  

1- In conical flask4 N- (actamide – methoxy  phenyl)(0.025mol) is dissolved in  (12.5ml) ethanol and heated  

2- Add to the mixture  (3.75ml) potassiumhydroxide solution (20M) .the mixture was heated for three hours, 

3- The solvent wasdistillation by using evaporator rotator. 

4- The product was extractof benzene then dried byanhydrous magnesium sulfate.  

5-The benzene was evaporatedbyrotary evaporator  , the product has a melting point 58C0 [5.6]. 

 

Prepare of 4-alkyloxy banzaldehayd 

1- (3.77gm)( 0.025mol,) of 4-hydroxy banzaldehayd dissolved in 15 mL of ethanol in aconical flask to the stirred 

solution  and slowlywas added solution of (0.033 mol) for KOH (1.85gm dissolved in less volume of water a (~ 

1.5mL )  

2-Then it was added of a solution of appropriate Alkyl bromide ( 0.025mol) in 12.5mL ethanol. 

3-The mixture was heated with stirring continued stir for more than one hour.6mL of water was added to mixture  

and then the product was extracted bypetroleum ether and  

4- Then washedthe extract with distillatedwater and the solvent was evaporated, the pure product was liquid yellow 

color , [7]. 

 

Prepare of Schiff bases:- 
We prepare two chain  schiff bases : 

The first chain :4-(4-alkoxybenzylideneamino)benzoic acid 

1-   equal moles number of 4- amino benzoic acidand 4-alkyloxy banzaldehayd dissolved inabsoluteethanol with 

three drops of glacialacetic acid  

2- the mixture was heated reflux for three hours,  

3- the mixture was cooled  and washed with a small amount of ethanol and then dried the resulting  

4.thecompoundwas purified by ethanol about three once . 

The second chain4-methoxy-N-(4-alkoxybenzylidene)aniline 

1-   equal moles number of 4- methoxy aniline and 4-alkyloxy banzaldehayd dissolved in absolute ethanol with three 

drops of glacialacetic acid  

2- the mixture was heated reflux for less than  hours,  
3- the mixture was cooled  and washed with a small amount of ethanol and then dried the resulting. 

4-  the compound was purified by ethanol about three once .[8] 



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Figure (1) infrared spectrum of the compound4-mehoxy actamide 

 

 

 

 

 
 

 

Figure (2) infrared spectrum of the compound 4-alkoxy aniline 

 

 

 
 

 

Figure (3) infrared spectrum of the compound4-alkoxy banzaldehayd 



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Table (1) chemical structures and melting point  , color and yield of the prepared compounds 

 
 

Results and Discussion         

Identificationof Prepared compound:- 

1-CHN analysis: all  data of  analysis  of  compounds  in  this table (2 

 

Table (2): physical properties of compounds&Elemental analysis 

 
 

 

 



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2- FT.IR-spectra :  which  gave  good  indicators  about  all  data  of  functional  groups  in  prepared  compounds  

 
Figure (4) infrared spectrum of the compound C5 

 

1. absorption bands  at 1118 due to a group -O-CH2-CH2 

2. absorption bands  at 1618 due to  imine group CH = N 

3. absorption bands  at 1737 due to the carbonyl group carboxylic 

4. absorption bands  at 2918 due to aliphatic CH  

5. absorption bands  at 2600-3198  due to OH of the carbonyl 

6. absorption bands  at 3032 due to aromatic CH 

 

 
Figure (5) infrared spectrum of the compound C7 

From  IR spectrum of a compound most important absorption bands  represent functional groups are: 

1. absorption band  at 1170 due to a group -O-CH2-CH2 

2. absorption band at  1630 belonged due to imine group CH = N 

3. absorption band at 1735 due to the carbonyl of carboxylic group  
4. absorption band at 2983 due to aliphatic CH  

5. Broadband absorption at 2574-3200  due to OH of Carbonyl group . 

 6. absorption band at 3034 due to aromatic CH 



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Figure (6) infrared spectrum of the compound M4 

1. absorption band at 1116 due to ether -O-CH2-CH2 

2. absorption band at 1154 due to ether -O- CH3 

3. absorption band at 1624 due to imine group CH = N 

4. absorption band at 2968 due to aliphatic CH  

5- absorption band at 3043 due to aromatic CH 
 

 
Figure (7) infrared spectrum of the compound M6 
 

1. absorption band at 1168 due to ether -O-CH2-CH2 

2. absorption band at 1618 due to  imine group CH = N 

3. absorption band at 1207 due to ether -O- CH3 

4. absorption band at 2912 due to aliphatic  CH  

5- absorption band at  3032 due to aromatic CH 

 



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3- HNMR  spectra :  all peaks  appeared  in  figures 

 
Figure (8), nuclear magnetic resonance spectrum of the compound C5 

 

1. peaks at (0.90-1.80)ppmdue to alkyl groups (CH3CH2 CH2 CH2)  

2. peaks at (6 2.5) ppmsolvent due to DMSO-d 

3. peaks at ( 3:41) ppmsolvent due to O-CH2 

4.peaks at (6.62-7.84)ppm due to  phenyl ring  
5. peaks at (8.41))ppm due to (CH = N) 

6. peaks at (13:28) ppm due to Carboxyl group  

 

References  

1- GehadG Mohamed, Mohamed MohamedOmar ,Ahmed Mohamed Hindy ," Metal Complexes of Schiff Bases: 

Preparation,Characterization, and Biological Activity", Turk. J Chem,  2006; 30 , 361- 382. 

2- O.lehmann,"Liquid Crystal" ,Ber 1908;41:3774  

3- Maier W. and Saupe A.; Saupe  "Eineeinfachemolekularetheorie des nematischenkristallinflussigenzustandes". Z. 

Naturforsch. A (in German)1958.13: 564-566  

4- G.W.Gray,"The Chemistry of Liquid Crystal ",Philosophical transaction of the society of London1983 

,series.A,Ch.1,p.77, 

5- S.T.,L.K. ,Ong,  S.T. Ong, G.Y. YeapandJ.P.W. Wong ., " Synthesis andmesomorphic properties of new Schiff 

base esterswith  different  alkyl  chains". Chin. Chem. Lett., 2009,  20: 767-770 

6-  Anthony S. Travis "Manufacture and uses of the anilines: A vast array of processes and products"  In 

ZviRappoport., The chemistry of Anilines 2007 Part 1. Wiley. p. 764. ISBN 978-0-470-87171-3 

7- A.I. Vogel , ''Practical Organic  Chem. Longman  "., FIFTH EDITION Group Ltd .,London , 1989 

8- G.W. Gray  ,M. Hird ,D.L. acq and K.I.Toyne ,"behavior of  organic compounds in  liquid  crystal  phase " , Mol. 

Cryst. Liq. Cryst., 1989; 172,165 

 

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open-access article distributed under the terms and conditions of the Creative Commons Attribution license 

(http://creativecommons.org/licenses/by/4.0/). 
 

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