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)
Faculty of Resource Science and Technology 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
Faculty of Resource Science and Technology 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 3.2 Synthesis of cyclophosphazene bearing C4-chalcone
3.2.1 Etherification of 4-hydroxybenzaldehyde 3.2.2 Synthesis of alkylated chalcone
3.2.3 Synthesis of mono-substituted cyclophosphazene 3.2.4 Synthesis of fully-substituted cyclophosphazene
3.3 Synthesis of cyclophosphazene bearing C5-chalcone 3.3.1 Etherification of 4-hydroxybenzaldehyde 3.3.2 Synthesis of alkylated chalcone
3.3.3 Synthesis of mono-substituted cyclophosphazene 3.3.4 Synthesis of fully-substituted cyclophosphazene
Chapter 4: Results and Discussion 21 4.1 Physical properties: Melting point
4.2 Alkylation of benzaldehyde 4.3 Synthesis of chalcones
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
P N P P N Cl Cl
Cl Cl Cl Cl
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
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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).
2.2 Synthesis of chalcones
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).
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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
C H3
O
+
Scheme 2: Formation of chalcones from the reaction between benzaldehyde and acetophenone
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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:
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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).
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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.
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CHAPTER 3: MATERIAL AND METHOD
3.1 Synthesis of cyclicphosphazene bearing C3-chalcone 3.1.1 Etherification of 4-hydroxybenzaldehyde
O H
H7C3O
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.
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3.1.2 Synthesis of alkylated chalcone
O
H 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). 13C-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.
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3.1.3 Synthesis of mono-substituted cyclophosphazene
N P N P
P N Cl Cl
OR Cl Cl 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.
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3.1.4 Synthesis of hexa-substituted cyclophosphazene
N P N P
P N RO OR
OR OR OR RO
R= C6H4C(O)CH=CHC6H4OC3H7
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. 1
H 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).
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3.2 Synthesis of cyclicphosphazene bearing C4-chalcone 3.2.1 Etherification of 4-hydroxybenzaldehyde
O H
H9C4O
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.
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3.2.2 Synthesis of alkylated chalcone
O
H 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%.
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3.2.3 Synthesis of mono-substituted cyclophosphazene
N P N P
P N Cl Cl
OR Cl Cl Cl
R= C6H4C(O)CH=CHC6H4OC4H9
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).
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3.2.4 Synthesis of hexa-substituted cyclophosphazene
N P
N P P N RO OR
OR OR OR RO
R= C6H4C(O)CH=CHC6H4OC4H9
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%.
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