Acceptor Molecular Fragments and the Question of Syn Anti Overlap

Donor and Acceptor Molecular Fragments and the Question of Syn vs. Anti Overlap 

In this part we employ the OEMO method in connection with bond MO s rather than delocalized MO s. There are three types of bond MO s n, pi and sigma. The interactions between bond MO s can be classified as follows  

In our subsequent discussions, we shall be using consistently hybrid lone pair AO s and hybrid bond MO s. The explicit forms of these orbitals are given below, for the case of any lone pair, located on atom Y, and the case of an X—H bond  

A hybrid orbital is drawn in Fig. 46a and is shown in its expanded form in Fig. 46b. 

An important point to be stressed before we proceed further with our analysis concerns the formal correspondence, of hybrid orbitals and delocalized group orbitals. For example, consider the model system HN=NH which can exist in a cis or a trans geometry. We can understand whether sigma interactions favor one or the other geometry be means of one of the following two approaches  

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