Faculty of Resource Science and Technology - ir.unimas.my and Characterization of...kuning telah disintesis melalui kondensasi aldol dengan mencampurkan acetophenone dan 4-hydroxybenzaldehyde

Faculty of Resource Science and Technology

Synthesis and Characterization of Cyclophosphazene Bearing Chalcones

Derivatives

Prepared by,

Nurzafira Bt. Mahsir

Bachelor of Science with Honours

(Resource Chemistry)

2008

SYNTHESIS AND CHARACTERIZATION OF CYCLOPHOSPHAZENE

BEARING CHALCONES DERIVATIVES

NURZAFIRA BT. MAHSIR

This project is submitted in partial fulfillment of the requirements for the Degree of

Bachelor of Science with Honours (Chemistry Department)


UNIVERSITI MALAYSIA SARAWAK

2008

DECLARATION

No portion of the work referred to in this dissertation has been submitted in support of an

application for another degree of qualification of this or any other university or institution

of higher learning.

Nurzafira Bt. Mahsir

Chemistry Department


Universiti Malaysia Sarawak

ACKNOWLEDGEMENT

I wish to express my deepest gratitude and appreciation to Dr. Zainab Ngaini, my

supervisor, for spending countless hours clearing my doubts and problems upon doing

my project. Besides, I want to give special thanks to Norasyikin, Siti Muhaini and Chiew

Wang Se, postgraduates, who had guided me patiently and motivated me to reach greater

heights in research.

TABLE OF CONTENT

Content Page

Acknowledgement I

Table of Content II

Chapter 1: Introduction 1

Chapter 2: Literature Review 4

2.1 Chalcones

2.2 Synthesis of chalcones

2.3 Cyclophosphazene

Chapter 3: Material and Method 9

3.1 Synthesis of cyclophosphazene bearing C3-chalcone

3.1.1 Etherification of 4-hydroxybenzaldehyde

3.1.2 Synthesis of alkylated chalcone

3.1.3 Synthesis of mono-substituted cyclophosphazene

3.1.4 Synthesis of fully-substituted cyclophosphazene











Chapter 4: Results and Discussion 21

4.1 Physical properties: Melting point

4.2 Alkylation of benzaldehyde


4.4 Mono-substituted phosphazene compound

4.5 Hexa-substituted phosphazene compound

Chapter 5: Conclusion and Recommendation 29

Chapter 6: References 30

Chapter 7: Appendix 34

ABSTRACT

Chalcones is a type of compound which exists in plants, known to derive

from flavonoids. With recent technology, there are many chalcones derivatives have been

produced to improve its quality. Chalcones, yellow solid compounds was synthesized

through aldol condensation by reacting acetophenone and alkylated 4-

hydroxybenzaldehyde. Chalcones derivatives were then reacted with 1 mol

cyclophosphazene, to produce mono-substituted and 6 mol of cyclophosphazene to give

hexa-substituted phosphazene with chalcones derivatives. In spite of having various

applications in pharmaceutical and medicine field, this compound is important in the

technology of Liquid Crystal Displayed (LCDs) apparatus. This LCD quality can be

improved by introducing cyclicphosphazene structure into its structure with the hope to

give the flame retardant properties.

Key words: chalcones, cyclophosphazene, flame retardant.

ABSTRAK

Kalkon merupakan sejenis sebatian yang wujud dalam tumbuhan, diperolehi

daripada flavonoid. Dengan kemodenan teknologi masa kini, terdapat banyak terbitan

kalkon yang telah dihasilkan untuk memperbaiki kualitinya. Kalkon, sebatian pepejal

kuning telah disintesis melalui kondensasi aldol dengan mencampurkan acetophenone

dan 4-hydroxybenzaldehyde beralkil. Terbitan kalkon ini kemudiannya disintesis dengan

1 mol cyclophosphazene menghasilkan phosphazene berpenggantian mono- dan 6 mol

cyclophosphazene untuk menghasilkan phosphazene berpenggantian hexa- dengan

terbitan kalkon. Selain daripada mempunyai pelbagai aplikasi dalam bidang

farmaseutikal dan perubatan, sebatian ini juga turut mempunyai peranan penting dalam

teknologi alat-alatan Liquid Crystal Display (LCD). Kualiti LCD ini boleh

dipertingkatkan lagi dengan memperkenalkan sebatian cyclophosphazene dalam struktur

bahannya dengan harapan dapat memberikan sifat kalis api kepada sebatian berkenaan.

Kata kunci: kalkon, cyclophosphazene, kalis api.

CHAPTER 1: INTRODUCTION

This research involves the synthesis of chalcones derivative with

hexachlorocyclotriphosphazene, a type of cyclophosphazene to produce a compound with

flame retardant properties. Chalcones is a type of compound which has various

substituents attached to its 2 aromatic rings. Many chalcones have been found to have

biological properties especially in pharmaceutical and medicinal field. Generally,

chalcones can be synthesized through Claisen-schmidt reaction by reacting benzaldehyde

and acetophenone (Streitwieser, et. al. and Carey, 2007). Basic structure of chalcones is

shown below (Figure 1):

O

Figure 1: Basic structure of chalcone

Cyclophosphazene on the other hand is an inorganic-organic type of compound

which can produce thermally stable compounds (Weimin, 2005). The inorganic –P=N

backbone of the phosphazene has a flame resistant properties especially the one which

have halogen atoms attached to it (Lawson, 1989). It is known that phosphorous will

form char when it is burned. The coal coating formed will prevent oxygen from reacting

with the base causing further burning. Thus, it retards the flame. The structure of

hexachlorocyclotriphosphazene which will be used in this project is shown in Figure 2.

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N

PN

P

NP

Cl Cl

Cl Cl

ClCl

Figure 2: Structure of hexachlorocyclotriphosphazene

Chalcones-based can be synthesized to produce liquid crystal (Choi, et. al., 2004).

Liquid crystal is a compound which exhibits the properties which lies between liquid and

solid state. It has interesting mechanical properties, such as flexible strength and stiffness

as well as optical properties. The rigid properties is due to the aromatic units which are

aligned in linear structure and linked together while the flexibility is caused by the linear

aliphatic chain (Chung, et. al., 1989). This phenomenon can be demonstrated as in Figure

3. Its applications involve the usage in the displays of cameras, mobile phones, computer

screens and television sets (Premamoy, 1990).

Figure 3: Phenomenon of rigidity and flexibility of liquid crystal

- 2 -

A type of compound having flame retardant liquid crystal properties have been

synthesized which combine the properties of both chalcones and cyclophosphazene. The

phenolic group of chalcone attached to cyclophosphazenes was envisaged to give the

rigid properties. Whilst an alkyl group was attached to the chalcones derivatives which

give the flexibility properties that are useful in the applications of Liquid Crystal

Displayed (LCDs) apparatus. In combination with cyclophosphazene, which have the

flame retardant properties, the quality of product synthesized was envisaged to be

improved. Scheme 1 below shows the reaction between alkylated chalcones with

cyclophosphazene producing hexa-substituted cyclophosphazene. In the product

synthesized, chlorine atoms of cyclophosphazene were replaced by the chalcones

derivatives via substitution reaction for both mono-substituted and hexa-substituted.

Scheme 1: Proposed synthesis of cyclicphosphazene bearing chalcone derivatives.

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CHAPTER 2: LITERATURE REVIEW

2.1 Chalcones

Chalcones are important compound which are categorized under flavonoids

compound, known to contribute to the colors of plants. Most types of the compounds

have anti-inflammatory, such as asthma (Ni, et. al., 2007) and anti-oxidants properties

which make it very useful in the application of medical field (Streitwieser, et. al. and

Carey, 2007). It also have been proven that chalcone exhibit anti-malarial properties (Lee

and Elena, 2007). These biological properties of chalcones are due to the presence of both

α,β-unsaturation and an aromatic ring (Curti, et. al., 2007). It has also been found that

chalcones exhibit intermediate properties (between crystalline and amorphous) and

fluorescent behavior which increase the efficiency of solar cells (Chudgar and Shah,

1989).


The preparation of chalcones involves aldol condensation reaction where two

aromatic rings are combined by a 3-carbon at α,β-unsaturated carbonyl system

(Streitwieser, et. al. and Carey, 2007). The aldol reaction involves the addition of a

carbon nucleophile to a carbonyl group (Moloney, 1990 and Dixon and Pyne, 1992). In

detail, it is considered as Claisen-Schmidt reaction where benzaldehyde reacts with

acetophenone in the presence of heat and a base at room temperature or below (Aldol

(Claisen-Schmidt) condensation, 2007).

- 4 -

The Claisen-Schmidt condensation is a type of aldol condensation where an

aromatic aldehyde is condensed with an enolate of an aliphatic aldehyde or ketone to give

an α,β-unsaturated ketone. The steps involve electrophilic addition forming the

intermediate β-hydroxyl ketone, followed by dehydration (Mak, et. al., 2007).

Specifically, mixtures do not form because benzaldehydes have no α-hydrogens,

therefore no enolate can be formed. The benzophenone derivatives can form enolates, and

will react with the more electrophilic benzaldehyde (Streitwieser, et. al. and Carey,

2007). The reaction between benzaldehyde and acetophenone is shown in Scheme 2:

H

O O

CH3

O

+

Scheme 2: Formation of chalcones from the reaction between benzaldehyde and

acetophenone

- 5 -

2.3 Cyclophospazene

Compounds containing phosphazene are very useful in the application of

building, vehicles and electronic industries since it has flame retardant characteristics.

Phosphate plasticizers, for examples tritolyl phosphate and trixylyl phosphate are

additives which are being used in these applications (Premamoy, 1990). The combination

of phosphorus-containing compounds with organic polymers is important because it

provides fire retardant properties, enhances thermal stability and resistance to oxidation

by molecular oxygen (Hartle, et. al., 2000). The addition of phosphorus compounds is an

effective way to decrease the flammability of a system (Murray, 2006). This flame

retardants component plays a principle where it will decompose by absorbing heat. A

layer of fire retardant will be formed which coated the products, thus oxygen is prevented

from causing further burning (Premamoy, 1990). Therefore, phosphazene can be

classified as a protecting compound. There was a research done by Liu and his coworkers

(2001) which have proven that when phosphazene react with steel or aluminium

counterface, a protecting film containing organic compounds and phosphorous is formed.

Carriedo et. al. (2004) has stated that a type of cyclicphosphazene, spirocyclic

triphosphazene have properties that induce polymerization.

Hexachlorocyclotriphosphazene is being used as the flame retardant contributors because

chlorine atoms attached are easily being replaced by other substituents by nucleophilic

substitution and the substitution gives conformational stability (Carriedo et. al., 2004).

These substituents can be another halogen, aryl, alkyl, alcohol or an amine groups

(Murray, 2006). This is best described in the Scheme 3:

- 6 -

Scheme 3: Reaction of hexachlorocyclotriphosphazene with hydroxy compound and

amine

Allcock (1995) and his coworkers have done a research on photocrosslinkable

polyphosphazenes and their use as microencapsulation materials where properties of

phosphazenes as degree of hardness, hydrogel or organogel character, acidity and film

forming ability are controlled by the selection of organic cosubstituent groups that are

attached to the phosphazene ring. It has also been indicated that chalcones have high

photosensitivity which allows photocrosslinking efficiency.

The addition of substituents to the cyclicphosphazene is assisted by the presence

of hydroxy groups on the substituents, which help in the attachment to the

cyclophosphazene. Deprotonation of the hydroxy groups contributes to the attacking of

oxygen atoms of hydroxy groups to the chlorine atoms of cyclophosphazene. In other

words, it contributes to the solubility and etherification of compounds in specific solvent

(Premamoy, 1990).

- 7 -

Besides that, it has also been known that the chain flexibility is due to the linear

aliphatic chain (Premamoy, 1990). Calundann and his coworkers (1987) stated that alkyl

chains are needed to form liquid crystal phase.

- 8 -

CHAPTER 3: MATERIAL AND METHOD

3.1 Synthesis of cyclicphosphazene bearing C3-chalcone


O

H

H7C

3O

A mixture of 4-hydroxybenzadehyde (3.66 g, 0.03 mole), bromopropane (3.28 ml, 0.036

mole), TBAI (1.11 g, 0.003 mole), K2CO3 (4.98 g, 0.036 mole) and MEK (90 ml, 0.03

mole) was refluxed and stirred overnight. The solution was washed with DCM, filtered

and the solid was discarded. The filtrate was washed with distilled water in a separatory

funnel. Two layers formed were separated. Organic layer was added with MgSO4, filtered

and rotavap. The percentage of yield (oily yellow liquid) obtained is 92.61%, Rf = 0.50

(1:20 EtOAc: PET). 2968 C-H stretch, 1473 CH2 bending, 1314 CH3 group, 1693 C=C, 833-616

=C-H out of plane, 1602-1509 aromatic C=C, 1259-974 C-O.

- 9 -


OH O

O

Alkylated benzaldehyde and 4-hydroxyacetophenone were taken in a round bottom flask

and dissolved in methanol. Solution of KOH in minimum quantity of methanol was

added. The resultant mixtures were refluxed for 12 hours, excess of methanol was

removed and residue acidified with cold 2N HCl aqueous solution. Separated yellow

solid was filtered, washed with water and dried. The crude chalcones (yellow solid) were

further purified by recrystallization in 95% ethanol. Yield: 57%. Rf = 0.28 (1:3 THF:

Hexane). M.P: 161.5-164.0C. I.R. (cm-1

): 3058 O-H, 2924 C-H stretch, 1463 CH2 bending,

1342 CH3 group, 1644 C=C, 822-637 =C-H out of plane, 1587-1509 aromatic C=C, 1300-1011 C-O.

1H NMR (in acetone-d): 8.0453 (d, 2H, ArH), 7.7911 (t, 1H, olefinic H), 6.9723 (s, 1H,

Ar-OH), 6.88 (d, 4H, 4ArH), 3.9696 (t, 2H, Ar-O-CH2), 3.33-1.73 (m, 2H, CH2), 0.9680

(t, 3H, CH3). 13

C-NMR (in acetone-d): δ 206.5, 187.1, 162.0, 160.6, 142.7, 131.0, 130.6,

129.4, 127.4, 119.5, 115.3, 114.8, 69.2, 40.0, 39.8, 39.7, 39.5, 39.3, 39.2, 39.0, 30.7, 10.4.

- 10 -


N

PN

P

NP

Cl Cl

OR

ClCl

Cl

R= C6H4C(O)CH=CHC6H4OC3H7

Hexachlorocyclotriphosphazene (1g, 2.851410-3

mole), K2CO3 (5.74g), acetone (80ml)

and chalcones (0.80g, 2.851410-3

mole) was refluxed for about an hour. The ratio for

chalcones and hexachlorocyclotriphosphazene was 1:1. The solution was washed with

DCM, filtered and rotavap. Purification was done by CC using silica gel (60-120) and

DCM-Petroleum Ether as elutant in the ratio of 1:1 and further recrystallization by using

absolute ethanol. Yield (yellow solid): %. Rf = 0.61 (1:1 DCM: PET). I.R. (cm-1

): 2924

C-H stretch, 1462 CH2 bending, 1377 CH3 group, 1667-1599 C=C, 1014-723 =C-H out of plane, 1510

aromatic C=C, 1238-1014 C-O, 979 P-O-C, 1213 P-N-P.

- 11 -

3.1.4 Synthesis of hexa-substituted cyclophosphazene

N

PN

P

NP

RO OR

OR

OROR

RO


Hexachlorocyclotriphosphazene, K2CO3, acetone and chalcones was refluxed for about

an hour. The ratio for chalcones and hexachlorocyclotriphosphazene was 6:1. The

solution was washed with DCM, filtered and rotavap. Purification was done by

recrystallization with absolute ethanol. Yield (yellow whitish solid): 93.63%. Rf = 0.84

(1:2 THF: Hexane). M.P: 122.8-125.5C. I.R. (cm-1

): 2966 C-H stretch, 1471 CH2 bending,

1424 CH3 group, 1660-1598 C=C, 952-735 =C-H out of plane, 1511 aromatic C=C, 1258-1014 C-O,

952 P-O-C, 1206 P-N-P. 1H NMR (in CDCl3): 7.7884 (s, 2H, ArH), 7.4334 (d, 1H, olefinic

H), 7.4162 (d, 2H, 2ArH), 7.1849 (s, 1H, olefinic H), 6.9765 (s, 1H, Ar-OH), 6.8139 (d,

4H, 4ArH), 3.8696 (t, 2H, Ar-O-CH2), 2.09-1.73 (m, 2H, CH2), 0.9768 (t, 3H, CH3).

31P{

1H}-NMR: 9.0033 (s).

- 12 –

3.2 Synthesis of cyclicphosphazene bearing C4-chalcone


O

H

H9C

4O

A mixture of 4-hydroxybenzadehyde (9.76 g, 0.08 mole), bromobutane (10.32 ml, 0.096

mole), TBAI (2.96 g, 0.008 mole), K2CO3 (13.27 g, 0.096 mole) and MEK (240 ml, 0.08

mole) was refluxed and stirred overnight. The solution was washed with DCM, filtered

and the solid was discarded. The filtrate was washed with distilled water in a separatory

funnel. Two layers formed were separated. Organic layer was added with MgSO4, filtered

and rotavap. The percentage of yield (oily yellow liquid) obtained is 83.5%. Rf = 0.55

(1:3 Ethyl acetate: PET). 2959 C-H stretch, 1470 CH2 bending, 1394 CH3 group, 1694 C=C, 833-

617 =C-H out of plane, 1602-1509 aromatic C=C, 1312-1005 C-O.

- 13 -


OH O

O

Alkylated benzaldehyde (11.89g, 0.07 mole) and 4-hydroxyacetophenone (9.09g, 0.07

mole) were taken in a round bottom flask and dissolved in methanol (140 ml, 0.07mole).

Solution of KOH (14.14g, 0.252 mole) in minimum quantity of methanol was added. The

resultant mixtures were refluxed for 12 hours, excess of methanol was removed and

residue acidified with cold 2N HCl aqueous solution. Separated yellow solid was filtered,

washed with water and dried. The crude chalcones (yellow solid) were further purified by

recrystallization in 95% ethanol. Yield: %. Rf = 0.30 (1:2 THF: Hexane). M.P: 142.9-

144.4C. I.R. (cm-1

): O-H, 2957 C-H stretch, 1474 CH2 bending, 1339 CH3 group, 1643 C=C,

820-619 =C-H out of plane, 1587-1509 aromatic C=C, 1285-1003 C-O. ANAL: Calculated C,

77.03%; H, 7.09%; N, 0%. Found C, 76.26%; H, 6.83%; N, 0.32%.

- 14 -


N

PN

P

NP

Cl Cl

OR

ClCl

Cl


Hexachlorocyclotriphosphazene (1g, 2.851410-3

mole), K2CO3 (5.74g), acetone (80ml)

and chalcones (0.84g, 2.851410-3

mole) was refluxed for about an hour. The ratio for

chalcones and hexachlorocyclotriphosphazene was 1:1. The solution was washed with

DCM, filtered and rotavap. Purification was done by CC using silica gel (60-120) and

DCM-Petroleum Ether as elutant in the ratio 1:1 and further recrystallization by using

absolute ethanol. Rf = 0.67 (1:1 DCM: PET).

- 15 -

3.2.4 Synthesis of hexa-substituted cyclophosphazene

N

PN

P

NP

RO OR

OR

OROR

RO


Hexachlorocyclotriphosphazene (0.25g, 7.128610-4

mole), K2CO3 (1.435g), acetone (20

ml) and chalcones (1.27g, 4.277210-3

mole) was refluxed for about an hour. The ratio

for chalcones and hexachlorocyclotriphosphazene was 6:1. The solution was washed with

DCM, filtered and rotavap. Purification was done by recrystallization with absolute

ethanol. Yield (yellow whitish solid): %. Rf = 0.50 (1:2 THF: Hexane). M.P: 141.0-

143.8C. I.R. (cm-1

): 2958 C-H stretch, 1472 CH2 bending, 1423 CH3 group, 1660-1597 C=C,

951-675 =C-H out of plane, 1510 aromatic C=C, 1257-1014 C-O, 951 P-O-C, 1202 P-N-P. ANAL:

Calculated C, 71.82%; H, 6.30%; N, 2.21%. Found C, 69.44%; H, 5.81%; N, 2.27%.

- 16 -

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Faculty of Resource Science and Technology - ir.unimas.my and Characterization of...kuning telah disintesis melalui kondensasi aldol dengan mencampurkan acetophenone dan 4-hydroxybenzaldehyde