HRGC separation of hydroperoxides formed during the photosensitized oxidation of (R)—(+)-Limonene

✍ Scribed by Schieberle, P. ;Maier, W. ;Firl, J. ;Grosch, W.

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 501 KB
• Volume: 10
• Category: Article
• ISSN: 0935-6304
• DOI: 10.1002/jhrc.1240101102

✦ Synopsis

R) -(+)-Limonene was photooxidized in the presence of Rose Bengal as catalyst. After TLC isolation, the hydroperoxides formed were separated directly by HRGC and analyzed by MS (El; Cl). Each hydroperoxide isomer was then isolated by HPLC for structure determination which after reduction of the HOO group with sodium borohydride was performed by 'H-NMR and Six hydroperoxide isomers formed by oxidation of the endocyclic double bond were identified. The compounds eluted from the HRGC column in the following order (proportions are given in brackets) I (40.1 Oh) (1 S, 4R)-p-mentha-2,8-diene 1 -hydroperoxide; li (5.8%) (1 R, 4R)-p-mentha-2,8-diene 1 -hydroperoxide; 111 (20.6%) (2R, 4R)-pmentha-[l(7),8]-diene 2-hydroperoxide; IV (8.5Y0) (2R, 4R)-p-mentha-6,8-diene 2-hydroperoxide; V (4%) (2S, 4R)-p-mentha-6,8-diene 2-hydroperoxide; and Vl(21 .O%) (2S, 4R)-pmentha-[1(7),8]-diene 2-hydroperoxide.

Direct HRGC separation of the limonene hydroperoxides offers, inter alia, the possibility of determining their flavor qualities by HRGC/effluent sniffing. '3C-NMR.

Experimental

2.1 Chemicals and Reagents

(R)-(+)-Limonene and Rose Bengal were obtained from Aldrich (Steinheim, West Germany). Sodium borohydride and silica gel (KG 60) from Merck (Darmstadt, West