Tetrahedron 

About: Tetrahedron is an academic journal published by Elsevier BV. The journal publishes majorly in the area(s): Cycloaddition & Enantioselective synthesis. It has an ISSN identifier of 0040-4020. Over the lifetime, 49679 publications have been published receiving 1328741 citations. The journal is also known as: 3-simplex & triangular pyramid.

Application of the pople-santry-segal CNDO method to the cyclopropylcarbinyl and cyclobutyl cation and to bicyclobutane

Abstract: The CNDO method has been applied to the cyclopropylcarbinyl and cyclobutyl cations, and has given results which are in very good accord with experimental data. A cross-ring interaction is calculated to be of importance with cyclobutyl derivatives, and agrees with the large difference in rate observed with equatorial and axial leaving groups. Some properties of bicyclobutane as well as the relative energies for some models of the activated complex for the thermal rearrangement of bicyclobutane have also been calculated and compared with experimental data. The CNDO method appears to have considerable promise in the investigation of the organic chemical phenomena.

Iterative partial equalization of orbital electronegativity – a rapid access to atomic charges

Abstract: A method is presented for the rapid calculation of atomic charges in σ-bonded and nonconjugated π-systems. Atoms are characterized by their orbital electronegativities. In the calculation only the connectivities of the atoms are considered. Thus only the topology of a molecule is of importance. Through an iterative procedure partial equalization of orbital electronegativity is obtained. Excellent correlations of the atomic charges with core electron binding energies and with acidity constants are observed. This establishes their value in predicting experimental data.

The relationship between proton-proton NMR coupling constants and substituent electronegativities—I : An empirical generalization of the karplus equation

Abstract: A new coupling constant-torsion angle relation for the three-bond 1H-1H spin-spin coupling constant is formulated. The relation includes a correction for the electronegativity of substituents. The correction term is written as a function of the electronegativity, the H-C-C-H torsion angle, and the orientation of each substituent relative to the coupled protons. A dataset consisting of 315 experimental coupling constants was used to derive six empirical parameters by means of an iterative least-squares minimization procedure. The precision of the proposed equation, expressed as the root-mean-square deviation (0.48 Hz), is superior to any hitherto reported. It is shown that separate treatment of CH2CH2, CH2CH and CHCH fragments even improves this precision. An application in the field of monosubstituted cyclohexanes is given.

Recent advances in olefin metathesis and its application in organic synthesis

Abstract: Recent advances in olefin metathesis, focusing on the areas of ring-closing olefin metathesis (RCM) and cross metathesis, are reviewed. Among numerous complexes which show catalytic activities in olefin metathesis, recently developed well-defined [Mo] and [Ru] catalyst systems have proven to be very efficient and tolerant of many functional groups. Examples of RCM are organized into the areas of medium or macrocyclizations, peptide chemistry, tandem ring-opening/ring-closing reactions, and RCM mediated rearrangements. Variation of substrates such as in polymer bound forms has been discussed. Applications of acyclic metathesis and ring-opening cross metathesis are also included.