Electronic effects of functional groups

A symmetry approach to the effect of temperature and substitution on Cope rearrangements has revealed that with increasing temperature the loss of symmetry can be considered as a collective variable which has a positive linear relationship with temperature. The results of an aromatic Cope rearrangement of a trans-l-aryl-2-ethenylcyclobutanecarbonitrile have been reported for the construction of the fused benzocyclooctene ring. The effects of gem-dimethyl substitution on the cyclopropane, alkene geometry, relative stereochemistry of the cyclopropane, and steric and electronic effects of functional groups on the thermal Cope rearrangement of divinylcyclopropanes have been reported (Scheme 10). " ... 

Resonance effects have been discussed earlier and involve the movement of electrons through a conjugated system. Unlike field and inductive effects, resonance effects decrease much more slowly with increasing distance. These effects often contribute more heavily to the overall electronic effects of functional groups than do polar effects. 

Be able to identify simple organic molecules from their H NMR spectra through the interpretation of their integrals (the number of hydrogens in each environment), chemical shifts (the effect of functional groups on the electron density of the molecule) and coupling patterns (the number of spin active nuclei on adjacent atoms)... 

Wishart JF, LaU-Ramnarine SI, Raju R, Scumpia A, Bellevue S, Ragbir R, Engel R. (2005) Effects of functional group substitution on electron spectra and solvation dynamics in a family of ionic liquids. Radiat Phys Chem 72 99-104. 

Optical absorption measurements indicate that the band gap of graphite oxide is within 2.4. 3 eV [64]. A detailed calculation has been performed to understand the effect of functional group, such as epoxide, hydroxyl, carbonyl, and their concentration to the optical properties of GO [65]. Their calculations predict a strong blue shift of the tt + <7 plasmon peak when the concentration of epoxides and hydroxyl groups in GO vary from 25 % to 75 %, while the n plasmon is less sensitive. Carbonyl groups present in the GO plane will create holes, which cause a red shift. Carbonyl holes significantly decreases the optical gap and opens the band gap, and they are useful for developing opto-electronic applications. 

The effects of functional groups on chemical activity and structure are also important considerations. In oxidative phosphorylation, for example, the addition of a phosphate (PO4) group can fundamentally change the three-dimensional structure of an enzyme or other protein. Since the function of these molecules is critically dependent upon their stereochemistry, this process can activate or deactivate a particular protein or enzyme to perform (or to not perform) some particular function. The particular arrangement of a molecule is determined, fundamentally, through a quantum mechanical analysis of the interactions among the electron clouds and the nuclei in the molecule. Such an analysis can be extremely complicated for even relatively small molecules, but there are less exacting techniques that can be applied to yield approximate results. 

Ong, S. P. Ceder, G., Investigation of the Effect of Functional Group Substitutions on the Gas-Phase Electron Affinities and Ionization Energies of Room-Temperature Ionic Liquids Ions Using Density Functional Theory. Electrochim. Acta 2010,55, 3804-3811. 

FIGURE 3.4 Deprotection of functional groups by reduction with sodium in liquid ammonia [du Vigneaud et al., 1930]. As in Figure 3.3, except reduction is effected by solvated electrons and protons are provided by water at the end of the reaction. Excess sodium is destroyed by NH4C1. This is a simplified presentation of the reaction. AH benzyl-based protectors as well as -Arg(N02)-, -Arg(Tos)-, and -His(Tos)- are sensitive to sodium in liquid ammonia. 

Like the monomers, the co-monomers are diols or diacids, and according to their functional groups, their reactions with TPA and EG follow the principal mechanisms outlined above. Very few data have been published on reactions with co-monomers, and it may be assumed that the same mechanisms and catalysis concepts should hold. Nevertheless, it has been observed that co-monomers influence the overall reaction rates significantly. In a typical batch process, the polycondensation time needed to prepare a polymer with an IV of 0.64 dL/g increases by about one third with co-monomer IPA and by about two thirds with co-monomer CHDM, in comparison to homo-PET. This may in part be due to the differing correlations between Pn and IV, but additionally a reduced reactivity due to steric and electronic effects or the influence of co-monomers on the mobility of functional groups seems probable. 

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