SYNTHESIS AND CHARACTERIZATION OF 1-(1-NAPHTHYL)-5- PHENYL-2,4-PENTADIEN-1-ONE FROM TRANS-CINNAMALDEHYDE AND 1-ACETONAPHTHONE

Chalcone analogues (1-(1-naphthyl)-5-phenyl-2,4-pentadiene-1-one) have been synthesized through an aldol condensation reaction between cinnamaldehyde and 1-acetylnaphthalene. The method used in this study is the stirrer method, with the reaction conducted at room temperature for 24 hours using a NaOH catalyst in H 2 O/ethanol (50%, v/v). The purity of the product was analyzed using thin-layer chromatography on silica gel plates with n-hexane: ethyl acetate (9:1) employed as the solvent. The resulting product obtained was 0.88 g with a yield of 61.97%. Structure Analysis and elucidation of the synthesized compounds were performed by measuring the vibrations of the functional groups using FTIR, LCMSMS analysis, and determining the 1 H and 13 C atoms by HNMR and CNMR analysis. The FTIR, LCMSMS, 1 H, and 13 C NMR analysis identified that the synthesized product as chalcone analogues, specifically 1-(1-naphthyl)-5- phenyl-2,4-pentadiene-1-one.


INTRODUCTION
Cinnamaldehyde is the main component of cinnamon oil, which contains approximately 50-70% and is extracted from the bark of the cinnamon tree [1,2]. The antibacterial properties of cinnamaldehyde have been thoroughly investigated for use in medications, food, and preservation [2]. However, there are limitations in applying cinnamaldehyde due to several drawbacks, such as its pungent smell and high volatility [2,3]. To overcome these issues and enhance the value of cinnamaldehyde, researchers have employed modified chemical approaches. Structurally, Cinnamaldehyde is a simple phenylpropanoid that contains unsaturated aromatic aldehyde groups, which can be modified to form chalcone analogues, known as bioactive compounds with medicinal significance [4].
Chalcone compound can be synthesized from an aldehyde with an aromatic ketone via an aldol condensation reaction [5]- [13]. Cinnamaldehyde which is an aromatic aldehyde when reacted with an aromatic ketone such as acetophenone can form a chalcone analog compound with the name cinnamylideneacetophenones.
An effective catalyst for this reaction is a base, specifically NaOH, which is a homogenous catalyst [14,15]. In addition, the reaction for the formation of chalcone analogues can also be catalyzed by a heterogeneous catalyst, for example, organobase Fe3O4/SiO2guanidine [ [20]. Due to the diversity of biological activities of chalcone compounds, many researchers have used chalcone as a structural model of the target compound, to explore the potential of chalcone with various structural variations.
In this study, cinnamaldehyde and 1acetonaphthone were utilized as the precursors for al Kimiya: Jurnal Ilmu Kimia dan Terapan p-ISSN: 2407-1897, e-ISSN: 2407-1927 Vol. 10, No. 1 (13)(14)(15)(16)(17)(18)(19), Juni 2023/Dzulhijah 1444 the synthesis of chalcone analogues. The use of this material is justified by the fact that 2acetylnaphthalene and different substituted acetophenones were the aromatic ketones employed in earlier investigations, which claimed to have already synthesized chalcone analogues from cinnamaldehyde [14] [15]. To the best of our knowledge, there have been no reports suggesting that an aromatic ketone variant in the form of 1acetylnaphthalene has ever been used as an aromatic ketone variant for cinnamaldehyde. So, the proposed structural model is a new structural model. To determine whether the synthesized substance matched the required target molecule, FTIR, MS, and NMR spectroscopic studies were used to characterize the compound [21]- [25] [26].

FTIR analysis was performed using a Thermo
Scientific-Nicolet iS50 FT-IR Spectrometer at the ILRC Laboratory, Universitas Indonesia. The Qtof LCMSMS analysis was carried out at the Indonesian National Police's Criminal Investigation Agency, Center for Forensic Laboratory, Sentul, Bogor. 1 H-NMR and 13 C-NMR analysis was carried out using the Bruker Avance Neo 500 MHz and 126 MHz Nuclear Magnetic Resonance Spectrometer at the ILRC Laboratory, Universitas Indonesia.

Synthesis of chalcone compound
In a 50 mL Erlenmeyer flask, the mixture containing 1-acetonaphthone (0.85 g, 5 mmol), ethanol (7.5 mL), and sodium hydroxide solution (0.40 g, 10 mmol, in 6 mL water/ethanol 1:1) was stirred at room temperature. trans-Cinnamaldehyde (0.66 g, 5 mmol) was then added to the mixture, and it was stirred for 24 h. After that, water (15 mL) was added to the mixture, and then it was extracted with ethyl acetate to wash with brine. The organic phase was dried over sodium sulfate. After the removal of the solvent, the desired product was obtained in good purity.

Scheme 1. Synthesis of the target compound.
The synthesis of chalcone analogues can be catalyzed by a base, generally, the base used is a homogeneous base catalyst, namely NaOH [14] [15] [27] and KOH [27]. The initial stage of this research was to find out how much yield was produced by the chalcone analog compound. The reaction conditions were carried out using 1acetylnaphthalene (5 mmol) and cinnamaldehyde (5 mmol), at room temperature, with absolute ethanol solvent, the catalyst used was 10 mmol (2 equivalents) for 24 hours. To find out whether the product has been formed, namely using the TLC test [28], [29]. The eluent ratio is hexane: ethyl (9:1). Figure 1 is the result of TLC of the starting compound with the product, where A is an acetylnaphthalene compound, B is a cinnamaldehyde compound and P is a product sample produced. The results of the TLC showed that the compound had been formed where the Rf of the synthesized compound was different from the initial compound. The 1-(1-naphthyl)-5-phenyl-2,4-pentadien-1-one compound was obtained after the evaporation process using a rotary evaporator because the product formed has a gel texture so it cannot be separated by ordinary filtering. To separate the product from the filtrate before being evaporated with a rotary evaporator, an extraction technique was used using a separating funnel by adding ethyl acetate to the synthesis product which had previously been added with distilled water. a b  The ethyl acetate fraction was then evaporated using a rotary evaporator. From the weighing results obtained a product weight of 0.88 g with a yield of 61.97%.

Characterization of The Target Compound
The FTIR spectrum shows a peak at wave number (ύ) 1610 cm -1 indicating the presence of a C=O group, the C=O group experiences a resonance effect due to the conjugated double bond in the chalcone analog compound. The presence of C=C is also indicated by a peak in the range of 1573 cm -1 . Absorption is specific for chalcone and can also be characterized by the presence of a peak in the 3051 cm-1 regions for C-H sp 2 vibrations, both from aromatic C-H and olefinic C-H. While a peak at wave number (ύ) 3417 cm -1 indicates the presence of an OH group, possibly from water vapor during measurement (Figure 3). The results of the analysis of the mass spectrum of the compound 1-(1-naphthyl)-5phenyl-2,4-pentadiene-1-one showed a molecular ion peak at m/z 285.1289 (M+H). The results of the LCMSMS data confirm that the compound synthesized matches the molecular formula C21H16O or matches the target compound ( Figure  4).  The H NMR spectrophotometer is used to detect the position of the proton nucleus. In addition, it can also be used to determine the number of protons bonded to carbon, nitrogen, or oxygen atoms. Proton positions are expressed in chemical shifts (δ) expressed in ppm, usually between 0 to 10 ppm. The greater the electron density (σ), the smaller the frequency, and the smaller the chemical shift of the proton (δ) [25]. 1 H-NMR analysis using chloroform solvent. The number of H atoms in the chalcone analog compound is 16, according to the data from the analysis.
In addition to measurements using 1 H-NMR, measurements were made using 13 C-NMR analysis for analysis of carbon shift values to serve as confirmatory data on the molecular structure of products produced using chloroform solvent. The number of C atoms in the chalcone analog compound is 21, but from the data synthesized it is known that there are 18 C atoms. This indicates the presence of equivalent C atoms. From the analysis data, confirmation of the proposed structure is shown in Table 1.
The 1 H-NMR spectrum of the chalcone analog showed a chemical shift at δ 7.03 (d, 1H); 7.56 ppm (m, 1H); 6.85 ppm (t, 1H); and 6.94 ppm (d, 1H), each compound exhibiting protons at positions C-2, C-3, C-4, and C-5. In unsaturated α,βketones, the proton adjacent to the carbonyl (Hα) will have a small δ (shielded) and Hβ will have a larger δ (deshielded) [24]. At positions C-2, C-3, C-4, and C-5, the biggest chemical shift is at position C-3 (Hβ). This can be explained because a resonance occurs in unsaturated α,β-ketones so that the carbon in Hβ (proton on C-3) is relatively more positive than the carbon in Hα (proton on C-2). As a result, the electron density of Hβ is smaller than the electron density of Hα. In addition, there is a geometric or spatial effect of the carbonyl on C-1, so that C-3 is more deshielded than C-2, C-4, and C-5. The chemical shift at δ 8.3058 ppm shows the proton at the position of the C-9' atom with a doublet peak, which is the highest peak. This is because, besides the anisotropic effect, there is also an aromatic effect so that the H in the C-9' position is deshielded. In the aromatic naphthalene ring, the aromatic compound is bonded to the C carbonyl group (ketone), because the C carbonyl group bonded to an aromatic compound attracts electrons, so three types of protons are obtained, namely H ortho, H meta, and H para with a chemical shift (δ) Ho > Hp > Hm. This can be explained because resonance occurs in aromatic compounds, the carbonyl group attracts electrons so that the ortho carbon is relatively more positive than the para carbon and the para carbon is more positive than the meta carbon. As a result, the electron density of H ortho is smaller than the electron density of H para, as well as the electron density of H para is smaller than the electron density of H meta [24].  The 13 C-NMR spectrum has a much wider chemical shift, namely 0-230 ppm, compared to 1 H-NMR which ranges from 0-10 ppm, sometimes up to 13-14 ppm (if there are hydrogen bonds) [24]. It is known that the chalcone analogues formed consist of alkene, aromatic, and carbonyl groups from ketones. Alkene and aromatic compounds generally have a chemical shift (δ) between 100-160 ppm, while carbonyls from ketones have a chemical shift between 190-230 ppm [24]. The 13 C-NMR spectrum of the chalcone derivative showed a chemical shift at δ 137.2 ppm and 136.0 ppm respectively to carbon C-1' and C-1''. It is known from the peak intensities during the chemical shift δ 137.2 ppm and 136.0 ppm, which have low intensities which indicate that the C in the chemical shift is quaternary C because there is no H directly bound to the C atom. The chemical shift at δ 195.9 ppm is the C carbonyl of a ketone (C=O). The chemical shift at δ 146.1 and 142.1 ppm indicated the presence of carbon at C-3 and C-5. The chemical shift at δ 126.9 and 125.7 ppm indicated the presence of carbon in C-2 and C-4. The chemical shift at δ 124.5-133.9 ppm indicated the presence of carbon in both aromatic rings. The number of C atoms in the chalcone analogous compound is 21, but from the analysis data, it is known that there are 18 C atoms. This indicates the presence of equivalent C atoms. The C atom is equivalent to C-2'' with C-6'' and C-3'; C-3'' with C-5''. The characterization results show that the resulting product is following the target compound. (Figure 5).

CONCLUSION
The chalcone analogue compound has been successfully synthesized using the starting materials in the form of cinnamaldehyde as an aromatic aldehyde and 1-acetylnaphthalene as an aromatic ketone with a yield of 61.97%. The results of the characterization of the compound using FTIR, LCMSMS, and NMR showed that the product formed corresponds to the expected target molecule, namely Compound 1-(1-naphthyl)-5phenyl-2,4-pentadiene-1-one.