F.Reactions of Carotenoid Radicals 44小小小4小 140 1.Carotenoid radical cations (CAR 140 a)Reactions with nucleophiles 140 b)De-protonation 141 c)Reactions with amino acids and peptides 141 d)Reactions with porphyrins ................... 141 e)Reactions with other carotenoids 141 Association with the parent carotenoid 142 g)Reactions with oxygen 143 h)Miscellaneous reactions 143 2.Carotenoid radical anions(CAR) 144 a)Reactions with oxygen. 144 b)Reactions with porphyrins 144 e)Other carotenoids 145 3.Carotenoid neutral radicals 146 a)Unimolecular fragmentation reactions 146 b)Ionic dissociation.. 146 c)Reactions with oxygen 146 G.Antioxidant and Pro-oxidant Properties 147 H.Conclusion...... 150 References 150 Chapter 8:Structure and Properties of Carotenoid Cations Synnove Liaaen-Jensen and Bjart Frode Lutnces A.Introduction 155 B.Carotenoid Oxonium Ions................................ 157 1.Preparation and chemistry 157 2.Vis/NIR spectra 158 C.Delocalized Carotenoid Monocarbocations and Dicarbocations 158 1.Preparation ...... 158 2.Vis/NIR spectra and stability 159 3.Cyclic voltammetry 160 4.AMI calculations 160 5.NMR spectra and structure 160 6.Relation to the soliton model 162 7.Reactions with nucleophiles 163 x F. Reactions of Carotenoid Radicals …………………………………………. 140 1. Carotenoid radical cations (CAR+ ) …………………………………….. 140 a) Reactions with nucleophiles ………………………………………... 140 b) De-protonation ……………………………………………………… 141 c) Reactions with amino acids and peptides …………………………... 141 d) Reactions with porphyrins …………………………………………... 141 e) Reactions with other carotenoids …………………………………… 141 f) Association with the parent carotenoid …………………………….. 142 g) Reactions with oxygen ……………………………………………… 143 h) Miscellaneous reactions …………………………………………….. 143 2. Carotenoid radical anions (CAR ) ……………………………………... 144 a) Reactions with oxygen ………………………………………………. 144 b) Reactions with porphyrins ………………………………………….. 144 c) Other carotenoids …………………………………………………… 145 3. Carotenoid neutral radicals ……………………………………………... 146 a) Unimolecular fragmentation reactions ……………………………… 146 b) Ionic dissociation …………………………………………………… 146 c) Reactions with oxygen ……………………………………………… 146 G. Antioxidant and Pro-oxidant Properties …………………………………. 147 H. Conclusion ………………………………………………………………….. 150 References ……………………………………………………………………… 150 Chapter 8: Structure and Properties of Carotenoid Cations Synnøve Liaaen-Jensen and Bjart Frode Lutnæs A. Introduction ………………………………………………………………… 155 B. Carotenoid Oxonium Ions …………………………………………………. 157 1. Preparation and chemistry ………………………………………………. 157 2. Vis/NIR spectra …………………………………………………………. 158 C. Delocalized Carotenoid Monocarbocations and Dicarbocations ………... 158 1. Preparation ……………………………………………………………… 158 2. Vis/NIR spectra and stability …………………………………………… 159 3. Cyclic voltammetry …………………………………………………….. 160 4. AM1 calculations ……………………………………………………….. 160 5. NMR spectra and structure ……………………………………………... 160 6. Relation to the soliton model …………………………………………… 162 7. Reactions with nucleophiles ……………………………………………. 163