Intramolecular attractions

Because the tertiary structure of a globular protein is delicately held together by weak intramolecular attractions, a modest change in temperature or pH is often enough to disrupt that structure and cause the protein to become denatured. Denaturation occurs under such mild conditions that the primary structure remains intact but the tertiary structure unfolds from a specific globular shape to a randomly looped chain (Figure 26.7). 

However, there is an optimum size for pendant groups with respect to decreasing Tg. Because of intramolecular attraction between large pendant... 

The negative signs are physically reasonable because these additional parameters would be expected to be associated with increased intramolecular attractions. The authors provided no measure of intercorrelation indeed, one might expect some correlation of a, the average molecular polarizability, with the presence of C=0, COOH, NO2, and CN groups. The counting descriptors are not QM quantities their inclusion is not philosophically satisfying, but they do improve the fit. 

According to Simons and Smiths the molar volume at the b.p. is given by log Vm=ciM+K where M=mol. wt., JSTis a universal constant, 1 427, and a is a constant for any particular series, which is related to the intramolecular attractive forces. 

Figure 6 shows three possibilities that can result when cleaning a contaminant from a smooth substrate surface. The top model shows the desired result of cleaning which occurs when the solubility of a contaminant is high enough to overcome any chemical or physical sorption mechanisms which bind it to the surfrice. Possibility I can occur when the contaminant is not sufficiently soluble in the SCF and has high intramolecular attraction which results in high surface tension. In other words, the contaminant likes itself better than the SCF or the substrate surface and subsequently forms beads on the surface. Possibility II can happen when > p. The contaminant is partially solvated by the SCF but sorption to the substrate surface prevents complete contaminant removal. 

Crystallization is the most important method for the purification of solid organic compounds. A crystalline organic substance is made up of a three-dimensional array of molecules held together primarily by van der Waals forces. These intramolecular attractions are fairly weak most organic solids melt in the range of room temperature to 250°C. 

The intra- and intermolecular interaction between cationic center and tt-electron system have attracted many chemists and much knowledge on the interaction has been accumulated (1). In 1975, we intended to apply such a kind of interaction to cyclopolymerization. Thus, it is expected that the transition state leading to a strained cyclic unit in the polymerization could be stabilized by the intramolecular attractive interaction between cationic growing-end and ir-system There had been few examples of cyclopolymerizations giving strained units. A paracyclophane unit was employed as a strained cyclic unit in the polymer main chain. In Table I are summarized some cyclophanes with their strain energies. 

The reason why only the cationic polymerization of St-C3 St produced the cyclopolymer containing [3.3]paracyclophane units would be due to the formation of (4n + 2)ir-system with fulfilling the necessity of orbital symmetry (second order conservation rule of orbital symmetry) and the intramolecular attractive interaction of the styryl group (a donor) and the cation (an acceptor) (5). 

Hydrogen bonding A strong inter- or intramolecular attraction that occurs between hydrogen and oxygen atoms. 

It seems fair to say that, in general, intermolecular noncovalent interactions, of whatever type, receive more attention than do intramolecular ones. However the latter can also be very important. For instance, intramolecular attractions are responsible for chlorotrinitromethane, C1-C(N02)3, having the shortest C(sp )-Cl bond ever observed crystallographically [36]. Another intramolecular interaction is a key factor in the remarkable increase in detonation sensitivity that occurs when the central carbon in the explosive PETN (2) is replaced by a silicon (3) [37]. 

In the temperature region near to or less than the 0 temperature, it is no longer valid to use a pseudo-potential, and the detailed structure of the segmental interaction matters. For example, polymers in dilute solutions collapse well below the temperature due to the intramolecular attractive force. The radius of gyration of a fully collapsed polymer depends on the hard core radius bf, of the segment, and will be written as... 

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