Energy stabilisation

The requirements necessary for the occurrence of aromatic stabilisation, and character, in cyclic polyenes appear to be (a) that the molecule should be flat (to allow of cyclic overlap of p orbitals) and (b) that all the bonding orbitals should be completely filled. This latter condition is fulfilled in cyclic systems with 4n + 2n electrons (HuckeVs rule), and the arrangement that occurs by far the most commonly in aromatic compounds is when n = 1, i.e. that with 6n electrons. IO71 electrons (n = 2) are present in naphthalene [12, stabilisation energy, 255 kJ (61 kcal)mol-1], and I4n electrons (n = 3) in anthracene (13) and phenanthrene (14)—stabilisation energies, 352 and 380 kJ (84 and 91 kcal) mol- respectively ... 

The solvent effects on charge-transfer spectra between Me3Sn-NCS and I2 was investigated. Onsager s theory of dielectrics was used to estimate the stabilisation energy of excited states257. 

The concept of the hydrogen bond has a number of aspects in common with that of resonance (or electron delocalization) in molecular structures some of their qualitative effects were- well recognized before their present names were acquired and both phenomena are of very general occurrence. For their elucidation the same types of question have to be answered (i) What is the resultant electronic distribution and how can this be simply represented (ii) What stabilisation energy is achieved in particular systems in practice (id) Can this be calculated theoretically and so predicted for cases not yet directly measured ... 

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