Functional groups steric interactions

In some systems, such as lake and river waters, the suspended inorganic particles may be coated by biological polymers, termed humic substances, which prevent flocculation by either steric or electrostatic mechanisms. These can also interact with added inorganic salts (31) that can neutralize charged functional groups on these polymers. 

When formation of either the five- or six-membered ring was possible for N-chloroamine 37, only the five-membered ring was conducive under the Hofmann-Ldffler-Freytag reaction conditions, forming exclusively 6-ethyl-6-aza-bicyclo[3.2.1]-octane (38). No 2-ethyl-2-aza-bicyclo[2.2.2]-octane (39) was observed. On the other hand, 2-methyl-2-aza-bicyclo[2,2.2]octan-6-one (41) was installed by UV irradiation of a solution of A -chloroamine 40 in TFA. Ironically, when the ketone functionality on 40 was protected as its ethylene ketal group, the resultant steric interactions completely prohibited the classic Hofmann-Loffler-Freytag reaction. 

This relatively new class of CSPs incorporates glycopeptides attached covalently to silica gel. These CSPs can be used in the normal phase, reversed phase, and polar organic modes in LC [62]. Various functional groups on the macrocyclic antibiotic molecule provide opportunities for tt-tt complexation, hydrogen bonding, and steric interactions between the analyte and the chiral selector. Association of the analyte... 

Thus, in spite of its lack of reactivity, iodine reacts chemically with unsaturated compounds, whereby the silica gel of the TLC layer can sometimes be assigned a catalytic role [11, 12]. Irreversible oxidations and electrophilic substitution and addition reactions have been observed on the interaction of iodine with tertiary nitrogen compounds such reactions possibly depend on particular steric relationships or are favored by particular functional groups [13, 14]. 

Step 3. Correction factors are responsible for deviations from simple group additivity. In most cases correction factors reflect internal (electronic, steric and H-bonding) interactions between polar functional groups. Figure 14.2 describes them as two-way arrows between any two functional groups, thereby reflecting the bidirectional nature of interactions (interaction between the ith and jth fragments separated by the kth type of skeleton) as expressed in ... 

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