Carbon, ground state energy

To allow for fluctuation of atomic electronegativities in response to the environment it has been proposed [120] that valence-state, rather than ground-state energies be used in Mulliken s formula to define orbital electronegativities. Despite common terminology, the valence state invoked here, is not the same as that of section 5.4, and refers to the improbable condition of an atom promoted to some hypothetical hybridized state. In the case of the carbon... 

The utility of thiol esters and carbonates as protecting groups is limited by their vulnerability to hydrolysis, The poor overlap between the non-bonded electrons on the sulfur atom (3p) and the n-system of the carbonyl (2p) precludes or diminishes resonance stabilisation of the type enjoyed by normal esters thereby raising their ground state energy, The carbonyl group of the thioester is more electrophilic than a normal ester and hence more reactive. Thiocarbonate derivatives are marginally more stable. The 5-benzoyl derivative of cysteine is 95% hydrolysed in 30 minutes with 2 M ammonia whereas the 5-benzyloxycarbonyl derivative is only 20% hydrolysed in 30 minutes under the same conditions.54... 

The question about the existence and the stability of pure carbon chain polymers has been repeatedly discussed in many papers. These polymers are called carbynes and are believed to consist of alternating triple and single bonds (polyynes) rather than of non alternating double bonds (polycumulenes) because of the lower ground state energy of the former. Thus, vibrational spectra of such materials are characterized by a more or less expressed structure around 2000 cm which is typical for the triple bond. A very efficient way to obtain such triple bonded carbon polymers nses an internal electrochemical reduction of fluorinated polymers such as poly(tetrafluoroethylene) (PTFE) or poly(tetrafluoroethylene/hexafluoropropylene) (FEP) by alkali metal amalgam according to the reaction... 

The upshot is that the ground-state energy E N) varies linearly between two adjacent integers, and has a derivative discontinuity at each integer. This discontinuity arises in part from the exchange-correlation energy (and entirely so in cases for which the integer does not fall on the boimdary of an electronic shell or subshell, e.g., for = 6 in the carbon atom but not for AT = 10 in the neon atom). 

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