References. 3 Symbols .... 5 7 Key to Code Designations .. 1. Polyenes, Cyclopolyenes, Fulvenes, Fulvalenes, Radialenes 11. Odd Polyenes ... . 39 12. Even Polyenes ... . 40 13. Odd Cyclopolyenes . 41 14. Even Cyclopolyenes ([n] annulenes) .. . 43 15. Fulvenes ................... . 44 16. Fulvalenes ..................... . 45 17. Radialenes (Polykis-methylenecycloalkanes) 47 2. Cyclobutadienes 21. Benzocyclo bu tadienes 48 3. Benzenoid Hydrocarbons 31. Benzenoid Hydrocarbons 49 32. Arylmethyl Ions . 56 33. Vinylpolyacenes. 62 34. Quinodimethanes. 63 35. Phenylpolyenes . . . ..... . 64 36. Phenylaryls, Biaryls, and Polyphenyls 66 37. Arylphenylmethyl Ions ............. . 68 3S. a, w -Diphenylpolyenes ............ . 69 4. Cyclopentadienyl-like Compounds (Systems Containing Cyclopentadienyl Skeletons) 41. Benzocyclopentadienyl Ions . . . . . . . . . . . . . 71 42. Benzofulvenes ......... . . . . . . . . . . . . 74 43. Odd Cyclopentadienylpolyenes and Their Benzo Derivatives. . . . . . . . . . . . . . . . . . . . . . 76 . . 44. Odd a, w -Dicyclopentadlenylpolyenes and Their 79 Benzo Derivatives ... v vi CONTENTS 5. Cycloheptatrienyl-like Compounds (Systems Containing Cycloheptatrieny 1 Skeleton s) 51. Benzotropyls . . . . . . . . . . . . . . . . . . . . . . 80 . . . 52. Benzoheptaful venes ...................... 83 53. Polyenylcycloheptatrienyl and Vinylbenzotropyl Ions. 85 6. Bicyclic Systems 61. Benzopentalenes. 86 62. Benzazulenes .. 87 63. Benzoheptalenes 89 7. Tricyclic Systems 90 71. Cata-condensed Tricyclic Hydrocarbons. 72. Indacene-like Compounds ......... . 91 94 73. Peri-condensed Tricyclic Hydrocarbons. 74. Fluoranthene-like Compounds. 95 75. Benzacenaphthylenes .. 97 76. Fluoranthenopolyacenes 98 8. Tetracyclic Systems 99 81. Cata-condensed Tetracyc1ic Hydrocarbons.