Sintesis asetal dimetilhidroksi sitronelal melalui oksimerkurasi-reduksi dengan garam merkuri asetat

MIHARJA, Muhammad Hidayat Jaya, Prof. Dr. (ret.) M. Muchalal, DEA

2010 | Tesis | S2 Ilmu Kimia

Telah dilakukan penelitian sintesis asetal dimetil hidroksi sitronelal sebagai zat antara molekul hidroksi sitronelal. Sintesis dilakukan melalui pembentukan asetal dimetil sitronelal yang selanjutnya diikuti reaksi oksimerkurasi–reduksi menghasilkan produk asetal dimetil hidroksi sitronelal. Sintesis asetal dimetil sitronelal dilakukan melalui reaksi adisi antara sitronelal dan metanol yang dikatalisis oleh gas HCl. Reaksi ini dilakukan pada temperatur 60 oC, pH 5 dan pH 3 dan rasio mol reaktan sitronelal dan metanol masing–masing 1:2 dan 1:4. Analisis struktur produk dilakukan menggunakan spektrofotometer inframerah dan kromatografi gas–spektrometer massa (GC– MS). Reaksi oksimerkurasi terhadap asetal dimetil sitronelal dilakukan pada temperatur 0 dan 25 oC selama 1 jam, sedangkan reduksi dilakukan secara simultan dengan NaBH4 pada temperatur yang sama selama 3 jam untuk mempelajari pengaruh temperatur dan durasi reaksi terhadap pembentukan produk asetal dimetil hidroksi sitronelal. Produk alkilmerkuri dari reaksi oksimerkurasi asetal dimetil sitronelal dianalisis dengan spektrofotometer inframerah, sedangkan produk asetal dimetil hidroksi sitronelal dianalisis dengan kromatografi gas– spektrometer massa (GC–MS). Sintesis asetal dimetil sitronelal mempunyai yield optimum 72% pada rasio mol 1:4 dan pH 3. Reaksi oksimerkurasi–reduksi terhadap asetal dimetil sitronelal menghasilkan produk asetal dimetil hidroksi sitronelal dengan yield optimum 20% dan total yield 18% pada temperatur 25 oC dan durasi reaksi 3 jam.

Synthesis of hydroxy citronellal dimethyl acetal as an intermediate of hydroxy citronellal has been performed. The synthesis was done through the formation of citronellal dimethyl acetal which was subsequently followed by the oxymercuration–reduction reaction to produce hydroxy citronellal dimethyl acetal. The synthesis of citronellal dimethyl acetal was carried out by addition reaction between citronellal and methanol catalyzed with HCl gas. This reaction was conducted at 60 oC, pH 5 and pH 3 and the mole ratio of reactants citronellal and methanol 1:2 and 1:4 respectively. The analysis of product structure was performed using infrared spectrophotometry (IR) and gas chromatography–mass spectrometry (GC–MS). Oxymercuration reaction of citronellal dimethyl acetal was carried out at 0 and 25 oC for 1 hour, while the reduction with NaBH4 was conducted simultaneously at the same temperature for 3 hours to study the effect on temperature and reaction duration on the formation of hydroxy citronellal dimethyl acetal. Alkylmercury products from the oxymercuration reaction of citronellal dimethyl acetal was analyzed with infrared spectrophotometry, while hydroxy citronellal dimethyl acetal was analyzed with gas chromatography–mass spectrometry (GC–MS). Citronellal dimethyl acetal synthesis had optimum yield of 72% at mole ratio of 1:4 and pH 3. Oxymercuration–reduction reaction of citronellal dimethyl acetal to produce hydroxy citronellal dimethyl acetal had optimum yield of 20% and total yield of 18% at 25 oC for 3 hours.

Kata Kunci : Asetal dimetil sitronelal,Reaksi oksimerkurasi,reduksi, citronellal dimethyl acetal, oxymercuration–reduction reaction