Polar single bonds

Methyl ethyl ether is a gas at room temperature (boiling point = 8 °C), but 1-propanol, shown in Figure 11-13. is a liquid (boiling point = 97 °C). The compounds have the same molecular formula, C3 Hg O, and each has a chain of four inner atoms, C—O—C—C and O—C—C—C. Consequently, the electron clouds of these two molecules are about the same size, and their dispersion forces are comparable. Each molecule has an s p -hybridized oxygen atom with two polar single bonds, so their dipolar forces should be similar. The very different boiling points of 1-propanol and methyl ethyl ether make it clear that dispersion and dipolar forces do not reveal the entire story of intermolecular attractions. 

With water, alcohols, amines and other compounds having a polar single bond, donor adducts react in the same way as free iminosilanes.I8-2425-33 For example24 ... 

Two models have been used to predict dissociation energies for heteronuclear diatomic transition metal molecules, the valence bond model (9), which proposes a polar single bond, and the atomic cell model (7). Their success when compared with experiment is indicated by the following examples ... 

The Knudsen effusion method In conjunction with mass spectrometrlc analysis has been used to determine the bond energies and appearance potentials of diatomic metals and small metallic clusters. The experimental bond energies are reported and Interpreted In terms of various empirical models of bonding, such as the Pauling model of a polar single bond, the empirical valence bond model for certain multiply-bonded dlatomlcs, the atomic cell model, and bond additivity concepts. The stability of positive Ions of metal molecules Is also discussed. 

The use of empirical models of bonding has been Invaluable for the interpretation of the experimental dissociation energies of diatomrLc Intermetallic molecules as well as for the prediction of the bond energies of new molecules. In the course of our work, conducted for over a decade, we have extended the applicability of the Pauling model of a polar single bond (31) and have developed new models such as the empirical valence bond model for certain multiple bonded transition metal molecules (32,33) and the atomic cell model (34). 

R. H. Crabtree and D.-H. Lee, Activation of Substrates with Non-Polar Single Bonds, ... 

Empirical models have been developed to predict the bond energies of metallic and intermetallic molecules, such as the following the Pauling model of a polar single bond [174], the valence bond model for certain multiply bonded metallic molecules by Brewer [175] and Gingerich [176], and the macroscopic atom or atomic cell model by Miedema and Gingerich [177]. 

Activation of Substrates with Non-Polar Single Bonds... 

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