Molecules electron density around

For a proton, with its +1 charge, to separate from the molecule, the electron density around the oxygen should be as low as possible. This will weaken the O—H bond and favor ionization. The electron density around the oxygen atom is decreased when—... 

Amines are basic because they possess a pair of unshared electrons, which they can share with other atoms. These unshared electrons create an electron density around the nitrogen atom. The greater the electron density, the more basic the molecule. Groups that donate or supply electrons will increase the basicity of amines while groups that decrease the electron density around the nitrogen decrease the basicity of the molecule. For alkyl halides in the gas phase, the order of base strength is given below ... 

Shielding is just a combination of electron density in the vicinity of the nucleus and the ease of circulation of those electrons. For a proton, there is only one bond to the rest of the molecule, and the electron density around the proton is affected primarily by the electron-withdrawing effect of electronegative atoms that are nearby in the bonding network. For... 

The MEDLA method does not impose any size limitation on the fragments only the feasibilty of traditional ab initio calculations limits the actual size of the fragments and the size of the "coordination shell" around them in the small molecule imitating the actual surroundings within the target molecule. Electron densities of satisfactory accuracy have been obtained in all the test calculations. 

As the resolution of the Bragg reflection data is improved, it becomes possible to obtain information on the more minute details of electron density in a molecule. At high enough resolution information can be obtained on the redistribution of electron density (deformation density) around atoms when they combine to form a molecule. Electrons in molecules ma -form bonds or exist as lone pairs, thereby distorting the electron density around each atom and requiring a more complicated function to describe this overall electron density than normally used, in which it is treated as if it were spherically symmetrical (deformed to an ellipsoid in order to account for anisotropic displacements). This assumption is inherent in the use of spherically-symmetrical scattering factors although the elec-... 

Deformation density The difference between the electron density in a molecule, with all its distortions as a result of bonding, and the promolecule density, obtained by forming a molecule with spherical electron density around each atom (free atoms). This map contains effects caused both by the errors in the relative phases of Bragg reflections, experimental errors in the data, and inadequacies in the representations of the scattering factors of free atoms. 

As far as rel. (1) indicates, for one atomic species such as H, or one single precise frequency will be absorbed. However, the nuclei are shielded from an external magnetic field by their electron cloud. The electron density around each nucleus may vary from molecule to molecule [101], and this variation modifies the absorbed frequency as given by rel. (1). The difference in the absorbing frequency of a particular atom from a reference atom is called chemical shift. The result field Ho, which determines the resonance behavior of the nucleus, will be, therefore, different from the applied field Happi, and using a shielding parameter a t can be written ... 

---