STUDY OF CATALYTIC CYCLISATION OF (+)-CITRONELLAL WITH Zn/γ-ALUMINA AS CATALYST
The reaction of catalytic cyclisation of (+)-citronellal has been done using g-alumina and Zn/γ-alumina as catalysts. Zn/γ-alumina catalyst was prepared by impregnation of ZnBr2 into solid of γ-alumina in methanol as a solvent. The calcination process is performed on Muchalal reactor at 400 oC. The...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Universitas Gadjah Mada
2010-06-01
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| Series: | Indonesian Journal of Chemistry |
| Online Access: | https://jurnal.ugm.ac.id/ijc/article/view/21852 |
| Summary: | The reaction of catalytic cyclisation of (+)-citronellal has been done using g-alumina and Zn/γ-alumina as catalysts. Zn/γ-alumina catalyst was prepared by impregnation of ZnBr2 into solid of γ-alumina in methanol as a solvent. The calcination process is performed on Muchalal reactor at 400 oC. The reactions were carried out under nitrogen gas atmosphere by mixing 5 mL sample and 1.0 g catalyst at 90-95 oC for 3 hours. The product of reaction was analyzed using GC, FT-IR and GC-MS. The reaction of cyclization of (+)-citronellal with γ-alumina catalyst did not give targeted product as well as reaction with Zn/g-alumina catalyst. Whereas, the reactions with Zn/γ-alumina catalyst gave four compounds of isopulegol stereoisomer. Conversion of (-)-Isopulegol, (+)-Neoisopulegol, (+)-Isoisopulegol and (+)-Neoisoisopulegol were 64,29%, 18,80%, 9,20% and 3,32% respectively. For that reason, the transformation of (+)-sitronelal using Zn/γ-alumina was considered to be the best catalyst. A reaction mechanism is proposed where the (+)-citronellal molecule binds to a catalyst Lewis acid site via the aldehyde oxygen and the π-electrons of the double bond. Subsequent protonation of the aldehyde via a neighbouring Bronsted acid site initiates the cyclisation to isopulegol.
Keywords: catalytic cyclisation, impregnation, (+)-isopulegol |
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| ISSN: | 1411-9420 2460-1578 |