Polarity, of a bond

An estimate of the polarity of a bond between two atoms may be obtained by reference to the electronegativity scale. The electronegativity values of some common elements are given in Table 5.1. The higher the value the greater the electronegativity. 

Electronic effects that modify the polarity of a bond have an influence on chemical shifts. If the position of a methyl group in an alkyl halide CH3-X is compared to that of methane, the shift in signal increases with the electronegativity of the halogen atom (Table 9.3). 

A measure of the polarity of a bond (or a molecule), proportional to the product of the charge separation times the bond length, (p. 10)... 

The product of the distance separating opposite charges of equal magnitude of the charge a measure of the polarity of a bond or molecule a measured dipole moment refers to the dipole moment of an entire molecule. 

The difference in EN between two elements can be used to predict the polarity of a bond. 

Polarity (Section 1.11) A characteristic that results from a dipole. The polarity of a bond is indicated by an arrow with the head of the arrow pointing toward the negative end of the dipole and the tail with a perpendicular line through it at the positive end of the dipole. The polarity of a bond can also be indicated by the symbols S and S. ... 

Bond polarities are intimately concerned with both physical and chemical properties. The polarity of bonds can lead to polarity of molecules, and thus profoundly affect melting point, boiling point, and solubility. The polarity of a bond determines the kind of reaction that can take place at that bond, and even affects reactivity at nearby bonds. 

Spreading out the charge over electron-withdrawing groups by the polarization of a bonds (inductive)... 

Both the degree and the direction of the polarization of a bond can be predicted by the electronegativity difference. The bonding electron pair is more likely to be found around the more electronegative atom. Carbon can be either partially plus, 6+, or... 

Unfortunately there is no unambiguous experimented method available for measuring the polarity of a bond and hence Eq. (7) cannot be tested ). 

Bond The polarity of a bond arises from the unequal sharing of electrons between atoms with... 

Another proposal advanced to explain the acid-strengthening effect of polar substituents holds that the electron-withdrawing effect is transmitted through the water molecules that surround the carboxylate ion rather than through successive polarization of a bonds. This is referred to as a field effect. Both field and inductive contributions to the polar effect tend to operate in the same direction, and it is believed that both are important. 

A molecule is polar if its centers of positive and negative charges do not coincide. A polar covalent molecule has at least one polar covalent bond. An imderstanding of the concept of electronegativity, the relative electron-attracting power of atoms in molecules, helps us to assess the polarity of a bond. 

What is the relationship between the polarity of a bond and the polarity of the molecule ... 

These Q- or U-values can be broken down into terms for the polarization of a-bonding, lone-pair and core electrons, but we find that the equation... 

Recall from Section 4.10 that effects that are transmitted by the polarization of a bonds are called inductive effects. 

The polarity of a bond depends on the difference between the electronegativity values of the atoms forming the bond. 

---