Intramolecular gauche interactions

It follows from the above X-ray data that betaines I and II have some structural peculiarities. Two main peculiarities are especially pronounced for betaines I. These compounds have the sterically strained gauche-conformation of the main chain due to the intramolecular Coulomb interaction of the cationic and anionic centers and noticeable distortions of the bond lengths in it. In Section 5 we discuss how these peculiarities of the betaine structure reflect their reactivity. 

Chair-like transition states minimizing gauche interactions between the substituents with metal nitrene insertion into the equatorial C-H bond are used to explain the stereochemical outcome. Such an intramolecular C-H amination with sulfamates was used in a few syntheses, including the total synthesis of (-l-)-sax-itoxin [66, 67]. 

Identify carbon atoms in the chair conformation of methylcyclohexane that have intramolecular interactions corresponding to those found in the gauche and anti conformations of butane. Which of the chair conformations has the greatest number of gauche interactions How many more If we assume, as in the case for butane, that the anti interaction is 3.8 kJ mol more favorable than gawc/ie, then what is the relative stability of the two chair conformations of methylcyclohexane Hint Identify the relative number of gauche interactions in the two conformations. 

Table 6. Total Lattice Sums for Trans and Gauche Conformations in PET and Contributions from Intramolecular Interactions...

Some other mechanisms will be discussed in later sections The Grant-Cheney formulation (88) of steric compression effects will appear in the context of y-gauche substituent effects (Section III-C), and hyperconjugative orbital interactions will be cited in interpretations of y-anti substituent (Section III-D) and intramolecular interaction effects (Section IV). 

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