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Supramolecular Chemistry

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Published in: Chemistry | IIT JEE Mains
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Supramolecular Chemistry

Akhilesh K / Lucknow

4 years of teaching experience

Qualification: M.Sc (NIT Rourkela - 2019)

Teaches: All Subjects, English, Mathematics, Science, Chemistry, Physics, Algebra, IIT JEE Mains, AIPMT, NEET

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  1. Supramolecular Chemistry Formation of new chemical structures by the assembly of molecular subunits bound together by non-covalent interactions. Host-guest chemistry The use of supramolecular assemblies as host for chemical reactivity, is emerging as an important way to study how the binding of molecules into the cavity can mediate their chemical reactivity.
  2. The emergence of supramolecular chemistry has had a profound effect on how efficiently chemists prepare structures of different sizes and shapes with dimension in the range of 1 to 100 nm using spontaneous secondary interactions such as hydrogen bonding, dipoledipole, charge transfer, van der Waals, and p-p stacking interactions
  3. Challenges The challenge is to synthetically create nanostructures with such precision and specificity as seen in biological systems by cleverly incorporating complementary recognition sites in the molecular components for secondary interactions.
  4. This challenge is only met by first understanding how molecular self-assembly in biological systems to generate well-defined aggregates and operates then transferring the knowledge learned from biological systems to chemical synthesis.
  5. DNA, perhaps the best known self-assembling structure in biological systems, exists in a double helical form Hydrogen bonding interaction Involving acidic hydrogen atoms (hydrogen bonding donor), oxygen (hydrogen bonding acceptor), and nitrogen atoms (hydrogen bonding acceptor) of the purine and pyrimidine bases (2.9 ± 0.1 Å)
  6. sugar cytosine (C) sugar guanine (G) (2.9 ± 0.1 Å) sugar O thymine (T) sugar adenine (A)
  7. 1) Electrostatic or coulomb energy (A ECOU) 2) Exchange repulsion 3) Polarization energy (AEPOL) 4) Charge-transfer energy or covalent bonding (AECHT) 5) Dispersion forces (AEDIS). Leonard J. Prins, Peter Timmerman, Angew. Chem. Int. Ed., 2001, 40, 2382-2426
  8. Hydrogen bond H-bond donor X = O, N, S, perhaps C H-bond acceptor X H Y = anything vvith Ione pair (e.g. O, S again) Range 4- 120 kJ mol-I Strength depends an (a) acidity of HI-I, (b) basicity of Y Exact nature of H-bonds controversial - covalent or electrostatic? Probably covalent when strong and electrostatic when weak.
  9. H-bonds prefer to be linear, along line of Ione pair
  10. Na01-I Crown Ethers ao
  11. Ionophore antibiotics Valinomycin Valinomycin Nonactin Clever, complicated molecules from nature; bind cations and kill bacteria
  12. Valinomycin is a dodecadepsipeptide antibiotic, obtained from the cells of several Streptomyces strains, among which "S. tsusimaensis" and "S. fulvissimus". Valinomycin o Hydrophobic
  13. Others, a 0 0 o 0 O 1 2-crovv n-4 total atarns in ring 1 5-crovv n-5 nurnber of axygens 0 1 8-crown-6 dibenzo-1 8-crow n-6
  14. Binds K + in MeOH with K a = 1.3 X 106 1 a-crow n-6 Mea linear analogue Binds in MeOH with = 200
  15. ?] ? 1 2-??-??•• ?) ? ? ? Lag .k.a ???? 1 2-cravqn-4 1 5-crawm-5 1 ?-?????-? 17 3.2 4.4 1 5-crow ?-5 3.4 1 8-crow ?-6 Cavity r-"ametek' (?) 1 2-cravm-4 1 5-c.ravm-5 1 ?-?????-? lonic diameters : Na+ = 1.9 ? ? = 2.7 ? ?? for 15-crown-5 + Na+ = 1740 Wt1 in ????, but only 6 Wt1 in waten
  16. high dilution, base high diluti on, base Similarly [2.2 .2]cryptand [2.21 ]cryptand
  17. 0 0 0 0 0 ? 2 2.2]cryptand 2.1]cryptand ? ag Ka in MeOH —l 1 Z CC' 7 [2.2.I]cryptand [2.2.2]cnjptand 1 ? ?

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