Nonpolar bonds

The two electrons in the H2 molecule are shared equally by the two nuclei. Stated another way, a bonding electron is as likely to be found in the vicinity of one nucleus as another. Bonds of this type are described as nonpolar. Nonpolar bonds are formed whenever the two atoms joined are identical, as in H2 and F2. 

Nonpolar bond A covalent bond in which the electrons are equally shared by two atoms, so there are no positive and negative ends, 182-183 Nonpolar molecule A molecule in which there is no separation of charge and hence no positive and negative poles, 183-185... 

A homonuclear diatomic molecule contains a nonpolar bond, since the electron pair between the two atoms is shared equally. Cl2 is an example of a homonuclear diatomic molecule. 

Both Cl2 and F2 are nonpolar molecules with nonpolar bonds. However, Cl2 is larger than F2, so it is easy to see... 

The capacity of nylon or the protein fibres to adsorb simple organic or inorganic acids is closely equivalent to their respective contents of accessible amino groups. More complex dye anions, however, differ in their affinity for these fibres owing to nonpolar bonding between the hydrophobic portions of the dye molecule (alkyl substituents and unsubstituted aryl... 

G. N. Lewis, W. C. Bray, and K. G. Falk developed theories of chemical valence addressing the problem of polar and nonpolar bonds. All were members of Noyes s MIT research group in the first decade of the 1900s, at a time when enthusiasm for the study of physics along with physical chemistry was at high tide in Noyes s laboratory. 

EHM has also been applied for the calculations of optimum coordination numbers 226> in hydrated alkali ions (Table 20). The affinities of alkali ions to NN -dimethylacetamide and methylacetate were estimated by Kostetsky et al. 227>, using the CNDO/2 procedure (Table 21). As long as the ions are constrained to lie in the peptide- or ester planes, correct trends are obtained, but relaxation of this constraint reveals serious discrepancies to ab initio calculations. The CNDO procedure artificially stabilizes structures with nonpolar bonding geometries,... 

In addition to insertions into polar X-H bonds by means of ylide intermediates, carbe-noids are capable of inserting into nonpolar bonds such as Si-H and C-H. The Si-H insertion by vinylcarbenoids has been developed as a novel method for the synthesis of allylsilanes 166 and 167 of defined geometry as illustrated in Eqs. (17) and (18) [28]. The alkene geometry of the vinyldiazoacetate is not altered during carbenoid formation or the subsequent Si-H insertion. 

The behavior of the nonpolar bonded phases, as well as the column packings based on crossbnked organic polymers of low polarity, however, differs from that of polar column packings and the classical solvent strength concept should be reevaluated. This is especially important for the alkyl bonded phases (Section 16.8.1). In this case, surface and interface adsorption of polymer species (Section 16.3.5) plays a less important role and macromolecules are mainly retained by the enthalpic partition (absorption) (Section 16.3.6). In order to ensure this kind of retention of polymer species, the mobile phase must push them into the solvated bonded phase. Therefore the interactions of mobile phase with both the bonded phase and (especially) with the sample macromolecules—that is, the solvent quality—extensively controls retention of latter species within the alkyl bonded phases. 

The bonded phases carrying polar groups such as -NH2, -OH, -CN, etc., which are separated from the packing surface by a spacer (usually the n-propyl groups) behave in an intermediate manner between the solid surfaces and the nonpolar bonded phases though the effect of polar end groups usually dominates (Sections 16.3.5 and 16.3.6). 

The greater the difference in electronegativity between two atoms, the more polar the bond is that forms between them. Imagine the electrons in the bond as being spread out into a cloud within the molecular orbital. In polar bonds, the cloud is denser in the vicinity of the more electronegative atom. In nonpolar bonds, like those formed between atoms of the Scime element, the cloud is evenly distributed between both atoms. Polar bonds have more ionic chciracter, whereas nonpolar bonds have more covalent character. Here s how to distinguish the chciracter of a bond ... 

Individual bonds have dipoles, which sum over all the bonds of a molecule (taking geometry into account) to create a molecular dipole. In addition to the permanent dipoles created by polar bonds, instantaneous dipoles can be temporarily created within nonpolar bonds and molecules. Both kinds of dipoles play important roles in the ways molecules interact ... 

Why doesn t it make sense to ask whether an element (like hydrogen or fluorine) engages in polar bonds versus nonpolar bonds ... 

You know whether an element engages in polar or nonpolar bonds only with respect to specific bonds with other elements. For example, hydrogen engages in... 

The example illustrates that enthalpy can be gained when nonpolar bonds, as commonly encountered in organic molecules, are broken and polar bonds, such as those in carbon dioxide and water, are formed. Reactions which involve the transfer of electrons between different chemical species are generally referred to as redox reactions. Such reactions form the basis for the energy production of all organisms. From this point of view we can consider organic compounds as energy sources. 

When the two atoms in a covalent bond have the same electronegativity, no dipole is formed (as is the case with H2) and the bond is classified as a nonpolar bond. When the electronegativities of the atoms differ, a dipole may form (as with HF) and the bond is classified as a polar bond. Just how polar a bond is depends on the difference between the electronegativity values of the two atoms—the greater the difference, the more polar the bond. 

Nonpolar bond A chemical bond that has no dipole. Polar bond A chemical bond that has a dipole. 

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