Some remarks on the use of experimental bond lengths in the maximum overlap method

The hybridization in norbornane, ethane, acetylene, cyclo- propane, cyclobutane and cyclopentane has been reexamined by the maximum overlap calculations based on experimental bond lengths. The irregularity in the variations of the C—C bond lengths in small ring hydrocarbons is discussed and a qualitative agreement with the experimental bond lengths has been found. The results also indicate that the use of experimental molecular geometry is advantageous for the maximum overlap method

Semiempirical MNDO Study of Phenyl-sydnone and its Protonated Forms

The electronic and geometric structure of the phenylsydnone and its conjugated acids is investigated by the semiempirical MNDO method. A comparison of the interatomic bond distances and bond angles with available experimental data for the parent compound reveals only qualitative accordance. It appears that the MNDO method is unable to reproduce finer details of the molecular geometry of sydnones. The gross changes caused by protonation are described, however, in agreement with chemical intuition .and available experimental data. The variation in geometric parameters is interpreted in terms of rehybridization and :n-electron bond orders. The most stable conjugated acid is that with a proton bonded to the keto-oxygen in accordance with the highest electron density concentration

Vitamin C and Its Radicals: Tautomerism, Electronic Structure and Properties

The biological importance and activity of ascorbic acid and its radicals are briefly reviewed. The quantum mechanical calculations performed on these remarkable compounds are presented in some detail. Particular attention is devoted to structural and electronic features offered by the semiempirical MINDO/3 and MNDO schemes. By making use of the self-consistent charge (SCC-MO) method, the ESCA spectra of the ascorbic acid tautomers are predicted. It is found that the radical anion is more stable than each of the four AA tautomers. This is of importance because the unusual biological protective property of ascorbate against free radical damage is most likely related to the stability of its radical, Ortgins of the enhanced stability of the radical anion are analyzed by the energy partitioning technique

Semiempirical MNDO Study of Phenyl-sydnone and its Protonated Forms

The electronic and geometric structure of the phenylsydnone and its conjugated acids is investigated by the semiempirical MNDO method. A comparison of the interatomic bond distances and bond angles with available experimental data for the parent compound reveals only qualitative accordance. It appears that the MNDO method is unable to reproduce finer details of the molecular geometry of sydnones. The gross changes caused by protonation are described, however, in agreement with chemical intuition .and available experimental data. The variation in geometric parameters is interpreted in terms of rehybridization and :n-electron bond orders. The most stable conjugated acid is that with a proton bonded to the keto-oxygen in accordance with the highest electron density concentration

Neka pitanja o kreativnosti u digitalnom dobu

The subject of interest in this paper relates to the expression of creativity from childhood to adolescence in the society today, which many mirror as the digital age. Firstly, the paper presents a Developmental model of creativity developed in a research study focused on personal explicit theories of educational researchers. The model defines key descriptors and describes the manifestations of creativity from the preschool years all the way to the adulthood, when the individual joins the labour market. Secondly, the paper focuses onto the Digital Natives concept and attempts to describe the youngsters today taking into account research results from different settings. Thirdly, in the remaining part the manifestations of creativity from the model are associated with the characteristics of young people who were born in digital age in order to enhance understanding of creativity expression in digital age. Based on a thorough examination a list of questions and needed research studies about creativity of Digital Natives is presented, under the assumption that the digital media will only be further developed and their influence over the young generations will be even more copious. The concluding remark problematizes the notion on whether everybody may be regarded as creative in the digital age realm and if so how this changes the overall meaning of the concept of creativity?.Predmet interesovanja u ovom radu je izražavanje kreativnosti u detinjstvu i mladosti u našem vremenu koje mnogi vide kao digitalno doba. U radu se prvo predstavlja razvojni model kreativnosti koji je dobijen u istraživačkoj studiji o ličnim eksplicitnim teorijama kreativnosti istraživača koji proučavaju obrazovanje. Model definiše ključne deskriptore i opisuje manifestacije kreativnosti od predškolskog uzrasta do odraslog doba kada osoba počinje da radi. U drugom delu rada opisana je savremena mlada generacija na osnovu rezultata istraživanja iz različitih sredina i koncept Digitalni urođenici. U trećem delu rada, manifestacije kreativnosti iz modela dovode se u vezu s karakteristikama mladih koji su rođeni u digitalnom dobu u nameri da se bolje razume kreativno izražavanje u digitalnom dobu. Napravljena je lista pitanja i potrebnih istraživačkih studija o kreativnosti digitalaca, s pretpostavkom da će se digitalne tehnologije dalje razvijati i da će njihov uticaj na mlade rasti. Završni komentar odnosi se na pitanje da li bi svako mogao biti kreativan u digitalnom dobu, a ako se to desi, da li se menja značenje pojma kreativnost

Semiempirical Study of Intramolecular Hyclrogen Bond in 6-Hydroxy-2-formylfulvene and 9-Hydroxyphenalenone

It is shown that semiempirical MINDO/3, MNDO and AMI methods are very useful in discussing intramolecular hydrogen . bonding in sizeable systems. The present results indicate that intramolecular H-bonds in 6-hydroxy-2-formylfulvene and 9-hydroxyphenalenone are asymmetric, in fuU accordance with ESCA observations and DQCC measurements. The former molecule should exhibit a stronger H-bond. On the other hand, the barrier height for proton tunnelling is higher in the latter compound. Relative stabilities of various species are interpreted by employing the energy partitioning technique

On the Additivity of the Molecular Second Moments of Charge and Diamagnetic Susceptibility

It was shown that the application of the additivity rules [Chem. Phys. Letters 13 (1972) 571] may be very helpfull for the determination of the sign of the g tensor